Issue Solved - engine bucking/surging at partial throttle - TCCoA Forums

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post #1 of 21 (permalink) Old 02-16-2016, 04:17 PM Thread Starter
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Issue Solved - engine bucking/surging at partial throttle

One of the other issues I should solve before my next race (but isn't 100% necessary since performance isn't compromised at WOT) is the surgy throttle response

* As it stands today, it's very very hard to get the car to be stable at say 1500RPM. This isn't a problem on the track but becomes an issue when you want to putter around the pits and not get flagged for speeding (the current coping mechanism is to goose the throttle, slip the poor clutch, let the car move, and then push the clutch back in).

* I also notice that when cold, the car has a hard time idling by itself without the driver revving it a bit.

Here's the current setup:
- 5.0 engine: GT40 heads, GT40 intake, stock MAF, e303 cam, recent honing 20 over, new pistons, new rings, and new hydraulic lifters. Stock 19# injectors.
- No EGR (plug threaded into intake manifold).
- No smog pump
- No thermostat (restrictor ring). A thermostat stuck closed killed our first engine. Never again.
- Stock exhaust manifolds, DIY downpipes w/ the O2 bungs, Y pipe underneath trans, 3" pipe going straight back through a cherry bomb + a flowmaster. No cats because racecar.
- ECU: I had a QH tune all setup but when I got my car together before the race day, we noticed that the car was idling way too rough even with the timing set at 10 degrees. We also had a hard time getting reading the variables from the QH (which you can normally do when the car is running. It woudl start datalogging and then stop abruptly). We swapped in the backup stock ECU (also W3D) because we knew it would work with this current engine setup and raced with it (other issues to solve).
- CEL is on (I suspect it's the lack of EGR) but I cannot read the code with my EECV reader for some reason.
- IACV was making a random ticking noise so I replaced it with a backup one that doesn't seem to click.
- At WOT, I'm reading 0.98-1.04 lambda. a little lean but i'm not seeing any knocks on my aftermarket knock sensor (again, I love my gauges).
- All in all, a mild engine (re)built for reliability (bigger bearing clearances). If I had to be generous, I'd say we were making 250HP max.
Questions
- What should I check which could cause this issue? IACV? TPS?
- Is there something else I should check?
- I know I need to do some more testing to see if its the ECU and or the QH that is causing issues. I've been told that a wierd connection between the ECU and the QH could cause this issue? Is this more likely to be a problem with the ECU-QH plug, the QH module itself, or did my primary ECU go bad?

UPDATE 2/6/2017: I found the root cause. See below
Issue Solved - engine bucking/surging at partial throttle

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Last edited by S4gunn; 02-07-2017 at 03:13 PM.
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post #2 of 21 (permalink) Old 02-16-2016, 04:55 PM
No, Mr. Lemmywinks, No!!!

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First up, I'd put a vacuum gauge on it.

Second, something is up with the wiring if neither EEC would readout.

The TB may be liberally coated with oil, unless you are running a separator.

If you open the TB, and there's crap, there's your idle prob, along with probably a new IAC needed.

After you check the other things, run the car with the vacuum gauge connected, ,and as you change the throttle, look for a throttle or vacuum dependent leak into the plenum; the vacuum will change or fall off at a steady throttle setting, and the engine will want to race/die.
(had a section of intake manifold gasket cause this on my 63 Tbird; it was 3 pieces on purpose, lol.)

The butterfly being crapped up will cause a bunch of grief; clean it and the TB. (even tho the sticker says that will void your warranty...)

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
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post #3 of 21 (permalink) Old 02-16-2016, 05:02 PM Thread Starter
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Originally Posted by Grog6 View Post
First up, I'd put a vacuum gauge on it.

Second, something is up with the wiring if neither EEC would readout.

The TB may be liberally coated with oil, unless you are running a separator.

If you open the TB, and there's crap, there's your idle prob, along with probably a new IAC needed.

After you check the other things, run the car with the vacuum gauge connected, ,and as you change the throttle, look for a throttle or vacuum dependent leak into the plenum; the vacuum will change or fall off at a steady throttle setting, and the engine will want to race/die.
(had a section of intake manifold gasket cause this on my 63 Tbird; it was 3 pieces on purpose, lol.)

The butterfly being crapped up will cause a bunch of grief; clean it and the TB. (even tho the sticker says that will void your warranty...)
1) Thanks for the tip on the vacuum. I think in the hunt for the dropped socket (long story but my friend dropped a socket into the engine and even after pulling off the intake manifolds + pan, it took us pulling it out to finally dislodge it from the crank), we did re-use the intake manifold gaskets.

2) I'll check the TB cleanliness but I do have a HF separator on the PCV line. This whole car is one big voided warranty so I'm not worried about that.

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post #4 of 21 (permalink) Old 02-16-2016, 05:08 PM
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Wow you changed the look of your car again. Is there any full size pics?
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post #5 of 21 (permalink) Old 02-16-2016, 05:26 PM
No, Mr. Lemmywinks, No!!!

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Quote:
Originally Posted by S4gunn View Post
1) Thanks for the tip on the vacuum. I think in the hunt for the dropped socket (long story but my friend dropped a socket into the engine and even after pulling off the intake manifolds + pan, it took us pulling it out to finally dislodge it from the crank), we did re-use the intake manifold gaskets.

2) I'll check the TB cleanliness but I do have a HF separator on the PCV line. This whole car is one big voided warranty so I'm not worried about that.
If I reuse gaskets, I always break one more rule. (at least, lol)

Ultra Black RTV is wonderful for gluing old gaskets back in place.

If it overheats and disintegrates, the babbit is gone from your bearings, lol.

When I do a replacement intake gasket in my cars, it gets glued in with Black. I ain't doin' that **** twice. (and usually a pi mod at the same time...)

All the cars I bought later in their life have had pitted head surfaces at the intakes. I scrape it out and backfill it with black.
Thankfully, the PI gasket sits in a different spot, and will seal better.

Sh*t doesn't leak, as long as the surfaces are clean and non oily.

You can't really use RTV on a head gasket, for very long.
But I've used it with copper gaskets on air-cooled 2-stroke dirt bikes.
It will last a race or 2; sometimes, that's just enough.
****, it was going to break anyway, right?

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
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post #6 of 21 (permalink) Old 02-16-2016, 05:31 PM Thread Starter
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Quote:
Originally Posted by Grog6 View Post
If I reuse gaskets, I always break one more rule. (at least, lol)

Ultra Black RTV is wonderful for gluing old gaskets back in place.

If it overheats and disintegrates, the babbit is gone from your bearings, lol.

When I do a replacement intake gasket in my cars, it gets glued in with Black. I ain't doin' that **** twice. (and usually a pi mod at the same time...)

All the cars I bought later in their life have had pitted head surfaces at the intakes. I scrape it out and backfill it with black.
Thankfully, the PI gasket sits in a different spot, and will seal better.

Sh*t doesn't leak, as long as the surfaces are clean and non oily.
My thinking was that the engine had never been run on the new gaskets (torqued down once). We just had to remove the intake manifold to go spelunking for the 10mm socket that was lost inside the block. The real lesson was that even if it works 3 times, spend the $20 and get the proper oil pump priming tool even if your janky shaved socket+jbweld+extension tool. Also, if you have the tool, use it.

That socket that took 3 months of my life trying to find (finally resigned to just pulling the engine again to get it out) still lives in my garage as a reminder of WHAT NOT TO DO.

-g

Q: For the 5.0 guys, is there a specific number I should see on the vacuum gauge or am I just looking for the lack of response depending on throttle load?

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post #7 of 21 (permalink) Old 02-16-2016, 05:45 PM
No, Mr. Lemmywinks, No!!!

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Originally Posted by S4gunn View Post
...
That socket that took 3 months of my life trying to find (finally resigned to just pulling the engine again to get it out) still lives in my garage as a reminder of WHAT NOT TO DO.

-g

Q: For the 5.0 guys, is there a specific number I should see on the vacuum gauge or am I just looking for the lack of response depending on throttle load?
There's no specific value; as low as possible gives some indication of condition of the engine.

I see ~20" hg on the cougar at idle; it has issues, but that's not too out of line with other motors I've done work to.

If there's NO restriction anywhere, it Should go to 0" hg vacuum at wot; that means all the restriction is at the valves.

That will never happen actually, just because of the reflected pulses from the closing valves.

Be sure to measure a bigger line; small lines with lots of flow can give false readings.


When you thumb the butterfly, you should see the vacuum drop.

Opening it slightly and holding it steady, should increase the rpm level to match the airflow; strange responses while holding it slightly elevated are likely vacuum leak related, wherever they are.

A friend with an unlighted propane torch can carefully hit selected areas, to see if the idle changes; testing at different rpm levels is recommended.
This used at different RPMs is good at finding leaks, if you don't blow up by finding spark leaks.

Don't use starter fluid for this; that's bad, m'kay? Richard Pryor bad.

The best thing is to use safety-wise is a cigar and a leaf blower in the intake, with the car not running, but most of the rpm dependent leaks won't show.


EDIT: Is the EEC tuned to ignore ALL of the deletes?

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.

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Last edited by Grog6; 02-16-2016 at 06:12 PM.
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post #8 of 21 (permalink) Old 02-17-2016, 06:06 AM
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How old is the battery on the QH unit?

If all else fails get a bigger hammer!

93 SC Tbird
MPII w/ Plenum,90mm MAF, 85mm TB, 40# Injectors, 255 lph FP, Double IC w/fan, SCT Chip (Tuned by Jerry),3/4" Raised Top, F52-TT TC, SilverFox AOD 550, SPT-R VB
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post #9 of 21 (permalink) Old 02-17-2016, 06:55 PM Thread Starter
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Quote:
Originally Posted by Grog6 View Post
There's no specific value; as low as possible gives some indication of condition of the engine.

I see ~20" hg on the cougar at idle; it has issues, but that's not too out of line with other motors I've done work to.

If there's NO restriction anywhere, it Should go to 0" hg vacuum at wot; that means all the restriction is at the valves.

That will never happen actually, just because of the reflected pulses from the closing valves.

Be sure to measure a bigger line; small lines with lots of flow can give false readings.


When you thumb the butterfly, you should see the vacuum drop.

Opening it slightly and holding it steady, should increase the rpm level to match the airflow; strange responses while holding it slightly elevated are likely vacuum leak related, wherever they are.

A friend with an unlighted propane torch can carefully hit selected areas, to see if the idle changes; testing at different rpm levels is recommended.
This used at different RPMs is good at finding leaks, if you don't blow up by finding spark leaks.

Don't use starter fluid for this; that's bad, m'kay? Richard Pryor bad.

The best thing is to use safety-wise is a cigar and a leaf blower in the intake, with the car not running, but most of the rpm dependent leaks won't show.


EDIT: Is the EEC tuned to ignore ALL of the deletes?
Thanks for the tip on the battery Bowez since this didn't occur to me at all.
The battery could be original since I bought the QH unit used on eBay (got a helluva deal since it was a bundle with a 2.3T Tbird ECU for $200 and I was able to resell the 2.3T ECU for ~$140.

I took a look back and I actually developed two tunes besides the stock one I read out:
1) One turns off the EGR scalars and sets the rev limiter as planned.
2) The second tune actually messes with the timing tables and this is the one that i had loaded.
I also remember looking at the suggestions for baseline timing from Decipha in his "T4M2" page but I honestly don't know if I tweaked something here.

According to my spreadhseet notes, I may have
a) "bumped spark to 29 deg at 75% load for >=2500RPM" in FN901 aka Spark Temporary Load Increase

in addition to
b) leaning out table (0.82 => 0.85) @ 90% load for RPM >2000RPM"
in the table FN1360 "Fuel Stabilized Table"

When I get back to the tuning portion of this car, I 'll start with the baseline tune again (scalars only). I can easily compare it to the stock tune to see wht I have changed. I wonder if messing with FN901 caused some of the misfiring issues I saw.

-g

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post #10 of 21 (permalink) Old 02-18-2016, 01:07 AM Thread Starter
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Originally Posted by bowez View Post
How old is the battery on the QH unit?
Good call on this one Bowez. I didn't ahve much time to mess around in the garage but I did test the QH battery. It measured <1V on this battery so it's good and dead. I've ordered a replacement from Moates.net
-g

FYI: I didn't know this but the MOATES was designed as a debug tool and not somethign you leave in the car. The battery comes into play when the car just sits there.

Since battery life is estimated from 2.5-10yrs, my board of 2009 mfg was probably due for a dead battery sometime soon.
http://support.moates.net/quarterhorse-battery-life/

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post #11 of 21 (permalink) Old 02-18-2016, 06:14 AM
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If memory serves Moates basically says not to use QH as a permanent computer but use a chip-burner like Jaybird. Battery issue are a much bigger problem on racecars than on street cars

If all else fails get a bigger hammer!

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post #12 of 21 (permalink) Old 02-18-2016, 01:41 PM Thread Starter
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Originally Posted by bowez View Post
If memory serves Moates basically says not to use QH as a permanent computer but use a chip-burner like Jaybird. Battery issue are a much bigger problem on racecars than on street cars
I've read that as well. I do like being able to see my computed load and injector duty cycle on the fly though. In the long term though, my teammate is building up an e30 with a 302 swap. Instead of him buying a second QH module to do his tuning, we will probably trade the tbird's QH module for a Jaybird+F3 setup.

After thinking things over this morning, I contacted QH to see if they could cancel my battery order so I could just replace it with a coin holder.

Moates support seems to be fantastic:
If I was willing to ship them the board, they offered to update it to the current spec: install a coin battery holder AND update the board to allow it to get the keepalive voltage from the car's battery vs not just relying 100% on the coin battery for free.

I'm shipping my QH board back to them tomorrow. Even if it takes a month, that's fine with me.

-g

PS. It seems they are doing R&D now on a future QH board that will use non volatile mem. Apparently, the supply of Xilinx/whatever chips they are using on the current QH board design have been EOL for a while now so most of the supply has dried up.

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post #13 of 21 (permalink) Old 02-18-2016, 04:04 PM
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Glad to here they going to use keep alive voltage form the car's battery, with that a properly sized cap would work for most battery disconnects, though non volatile memory is a better solution (though more expensive).

If all else fails get a bigger hammer!

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MPII w/ Plenum,90mm MAF, 85mm TB, 40# Injectors, 255 lph FP, Double IC w/fan, SCT Chip (Tuned by Jerry),3/4" Raised Top, F52-TT TC, SilverFox AOD 550, SPT-R VB
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post #14 of 21 (permalink) Old 02-07-2017, 01:10 AM Thread Starter
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All:
It's been nearly a year but I'm prepping my racecar for my next (annual) lemons race in March. One of my teammates came in this weekend after finishing our first DIY alignment (I had to think back to my HS trig as well to calculate total toe) and finishing up a brake overhaul, I decided to tackle the surgey idle we experienced at our last race. While the car felt smooth at WOT, it would buck a little bit at partial throttle in the pits (as described above). FWIW, one of my teammates also felt that the car felt a little down on it's power at the end of day 2 but that could have been chalked up to driver fatigue and/or getting used to how the car drove (laptimes generally improve over the course of the race weekend given how many laps we'll do on the track + the field opening up).

Well, we found our problem. For other's benefit, here's what we did:

Test 1: Vacuum test
- Measured 10 HG/in at idle. When you open the throttle, it would respond quickly and went up to 20 HG/in.
- MadMikey says this was a bit low since an e303 cam should be from 14-18 HG/in in his experience so it merited further testing. At this point, we thought it was a vacuum leak.

Test 2: Looking for a vacuum leak
- Originally I tried an unlit propane torch but we didn't see a rise in RPMs even with my tank fully open and aimed at a vacuum opening. Instead, we used the brake parts cleaner sprayed on the various gaskets.
- Results: nothing found. I was hoping it would have been an intake gasket leak.

Test 3: Compression Test
- Most cyl had 110-115 PSI (within 10%) but #2 and #3 were at 50PSi and 85PSI respectively.
- I seem to recall compression testing and getting more like 145PSI so this had me a little torried.
- The two cylinders with significantly lower compression ratings was a definite red flag.
- Squirting oil into the problem cylinders didn't improve the test numbers so the issue wasn't (likely) with the rings.

- Possible root causes at this point: blown head gasket or valve issue.

Test 4: Pressure test
- This one I have MadMikey to fully thank for suggesting this test. The idea is to inject air into the cylinder when it's at TDC and then look to see where it is leaking. Possibilities include a spark plug hole in an adjacent cylinder (because of a head gasket leak), into the oil pan (BHG), into the oil pan (rings), or finally into the intake or exhaust tracts (valves).
another (head gasket
- Since we knew the problem was at the heads now, the goal was to figure out the exact point of failure. We went ahead and took the upper/lower intake off. We also took off the exhaust manifolds to directly expose the exhaust ports to the outside air.
- Our compression test tool had a hose that screwed into the spark plug hole and could then be attached to an air compressor. NOTE: We did had to remove a shrader valve (a one way valve) at the end of the hose that screwed into the spark plug hole though. This allowed the test gauge to maintain pressure a certain pressure until you pushed the button on the gauge to release it.
- We moved the problem cylinder to TDC to make sure the piston was fully raised.
- After pumping up the air compressor's tank, we raised the operating PSi from 0PSI to ~40PSI and then listened to the engine to see where the air would go.
- We found that for the two problem cylinders, we were hearing compressed air escaping into the intake tract. This meant that the intake valves weren't fully seating and exhaust gases were being reintroduced into the intake tract. THAT caused all of the initial bucking experienced at low RPMS as the whole air/fuel mix would be different.
- Just to confirm things, we removed the rocker arms so the valves should have been stuck shut and tapped them with a rubber mallet to fully seat. Air was still leaking.


CONCLUSION: valves not seating were the root cause of our performance/throttle issues.
- At this point, we realized that we needed to pull the heads and take them into a shop.
- Once the heads were off a car, we shined a bright LED into the suspect intake tracts and you could see a little light leaking out from the edge of the problem valves. FWIW, no issues were seen with the head gaskets (you couldn't see any spots where exhaust had eaten into the ring around the cylinders.)
- We also inspected the block and the cylinder walls show no signs of scoring or and point where the valves hit the piston heads (whew -- they have reliefs on them but I still have flat top pistons). For now, I'm not expecting to do any further block work (other than draining the oil).
- Off to the machine shop they go for valve work and to confirm that it's not cracked (magnafluxing) and properly flat. The machinist might need to replace the valves if they are bent, regrind the valve seats, or replace the valve seals. Either way, the shop will do this work.
- I realize now that in the first race when I first rebuilt the V8, the engine got really, really hot (insufficient cooling system at the time). This probably warped some of these valve stems or messed up the valve seat.
- When i rebuilt the engine the last time, the heads were allegedly "checked out" but I probably should paid to have the heads inspected more closely and more thoroughly gone over.
- While we were able to finish our last race on the same engine we started with, we clearly haven't been able to go between races without opening up our engine yet At least our suspension is totally baller now (I can jump on the fender and the cars nose barely goes down. Jumping up and down on the fender makes the car barely move. It's not going to be comfy to drive it on the track but it's gonna be fun).
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post #15 of 21 (permalink) Old 02-07-2017, 03:52 PM
No, Mr. Lemmywinks, No!!!

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Sounds like a fun day in the shop.

For some reason I thought you had a 4.6...

Way easier to work on heads with no chains, lol.

We used to lap valves on the bikes between races; seats were softer in the 70's tho.

My bikes didn't have valves in the head, just reed valves in the intakes; but I used to help other people too.

Good thing to find out Now; that's the kind of thing that leaks more as it heats up, and it leaks more, and it heats up...

Nothing* is worse than feeling all the power go, just as everyone passes you.

*Well, I still have mixed feelings about once finishing second, upside down and backwards... at about 80, lol.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.

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post #16 of 21 (permalink) Old 02-07-2017, 04:18 PM Thread Starter
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Sounds like a fun day in the shop.

For some reason I thought you had a 4.6...
Way easier to work on heads with no chains, lol.
We used to lap valves on the bikes between races; seats were softer in the 70's tho.
My bikes didn't have valves in the head, just reed valves in the intakes; but I used to help other people too.
Good thing to find out Now; that's the kind of thing that leaks more as it heats up, and it leaks more, and it heats up...
Nothing* is worse than feeling all the power go, just as everyone passes you.
*Well, I still have mixed feelings about once finishing second, upside down and backwards... at about 80, lol.
1) 4.6L is easier to work on? Really? While I could believe the cams might be easier to swap, doesn't the wider heads make it much harder to do things like swap plugs/ install/replace exhaust manifolds? Also, from what I've read, rebuild costs are higher.

2) I know nothing about bikes but pulling the heads between races just to lap the valves doesn't sound like fun on a 302 given that I will need. At some point, I might just have to accept that rebuilding my tbird engine is a fact of life and just bite the bullet to buy a set of ARP studs.

3) As far as the car, the car still ran pretty well and was still faster than 50% of the field even in its current condition (which is all you really need in endurance racing -- the rest is about keeping there car out there doing laps. Any more HP and you will be wasting gas => more frequent refills => lost time). What worried me was the unequal loads I was putting on the engine with most cylinders at 110-115 PSI but two of them on the pass side only at 50PSI/85PSI. Since those cylinders weren't "pulling their weight", I suspect the main bearings were starting to wear unevenly. Catching this issue before our next race (which means 8-10hrs of continuous track time per day) probably saved us from doing a full rebuild (vs top end) sooner than expected. How soon? I'm not sure.

After this next race, if all goes well, we will have a good question: do we just leave things as-is and keep this engine in the car or do I do a full rebuild of my spare engine (which I haven't touched)? Doing a full rebuild would give us the peace of mind knowing our new spare will be fully race proven (GOOD), give me something to do in the time between races (OK), but also cost money (hrm).
I guess it all depends on if i decide it's worth having someone port our E7 heads (an option) or if I find another set of GT40 heads at a reasonable (aka Junkyard) price.

-g

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post #17 of 21 (permalink) Old 02-07-2017, 06:02 PM
No, Mr. Lemmywinks, No!!!

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1) 4.6L is easier to work on? Really? While I could believe the cams might be easier to swap, doesn't the wider heads make it much harder to do things like swap plugs/ install/replace exhaust manifolds? Also, from what I've read, rebuild costs are higher.

2) I know nothing about bikes but pulling the heads between races just to lap the valves doesn't sound like fun on a 302 given that I will need. At some point, I might just have to accept that rebuilding my tbird engine is a fact of life and just bite the bullet to buy a set of ARP studs.

3) As far as the car, the car still ran pretty well and was still faster than 50% of the field even in its current condition (which is all you really need in endurance racing -- the rest is about keeping there car out there doing laps. Any more HP and you will be wasting gas => more frequent refills => lost time). What worried me was the unequal loads I was putting on the engine with most cylinders at 110-115 PSI but two of them on the pass side only at 50PSI/85PSI. Since those cylinders weren't "pulling their weight", I suspect the main bearings were starting to wear unevenly. Catching this issue before our next race (which means 8-10hrs of continuous track time per day) probably saved us from doing a full rebuild (vs top end) sooner than expected. How soon? I'm not sure.

After this next race, if all goes well, we will have a good question: do we just leave things as-is and keep this engine in the car or do I do a full rebuild of my spare engine (which I haven't touched)? Doing a full rebuild would give us the peace of mind knowing our new spare will be fully race proven (GOOD), give me something to do in the time between races (OK), but also cost money (hrm).
I guess it all depends on if i decide it's worth having someone port our E7 heads (an option) or if I find another set of GT40 heads at a reasonable (aka Junkyard) price.

-g
No, you misunderstood, your engine is Much easier to deal with.

I rebuilt my old 390 V8 every 60k; it never cost more than ~$100. (70's-80's)

It HAD to be rebuilt; by then it would be making noise everywhere, lol.

As a contrast, my DOHC build is exorbitant; well into the 2k range by now. But I've had 3 sets of heads, 2 cranks, and three sets of pistons.


I wouldn't pull apart a V8 to lap valves, but it was done in the 60's; I've seen pix.

The Carbed bikes I helped work on were known to lean out and eat valves, so you didn't dare not take it apart.

I've taken a dirt bike apart, and found that I finished with no rings at all.
My '78 IT would break the rings into ~10mm pieces, and shoot them out the exhaust port at about 14k.
They'll run over ~2k rpms, but you can't start it if it dies.

As far as the last paragraph:

Your spare engine:

I'd Flip it over, yank the pan, and look at the cylinders first, looking for score marks.

Look at all the rod and crank bearings' edges; don't disassemble them, just look at the metal you can see closely with a magnifier and a good light.

See if any of the bearings are discolored, sticking out, missing pieces, etc.

If they are suspect, I'd pull all the caps, and see what the mains look like; you might as well look at the rod bearings too.

That's the "Crap, I have to do something" moment; but if you don't see anything, and if it all looks good, I wouldn't touch any bolts except the oilpan bolts, lol.

It wouldn't hurt to do the same test to the spare that you did to the installed engine; that way you feel better.

Is your starter mounted to the engine or tranny? if engine, you can do a compression test on a stand.

We're pulling for you!
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post #18 of 21 (permalink) Old 02-07-2017, 06:19 PM Thread Starter
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...
I rebuilt my old 390 V8 every 60k; it never cost more than ~$100. (70's-80's)
...
I'd Flip it over, yank the pan, and look at the cylinders first, looking for score marks.
$100 in 1985 = $222 in 2016
$100 in 1970 = $615 in 2016

Parts for the 390 are probably similar in cost/complexity to the 302 (read: dirt cheap) but out of curiosity, what is your labor rate for machine work in TN? In CA, esp the Bay Area, it's pretty damn expensive (like everything else -- esp since not many people do it).
How much to grind a crank? Bore out a block? Balance a rotating mass?

---
FWIW, the starter is mounted to the transmission but since I have an assembly together on a cradle, I could test compression like you suggest fairly easily. If the numbers look bad, your idea about doing an engine bearing inspection is a good next step.

I was already planning on rebuilding the spare M5R2 anyway (2nd gear synchros are gone) so if I'm going to pull the engine and trans apart (both are mounted to a shopping cart frame), I might as well consider looking at the bearings instead of sticking my head in the ground.

I have thought about building a fully working engine stand w/ ECU + cooling system but that's in the future. While I wouldn't need a dash harness (can always use a Quarterhorse -> PC setup to read gauges), I would need the harness that connects the engine harness plugs to the ECU. IIRC, one of my 5.0 harnesses is in the tbird and the other one I sold to Mad Mikey b/c it had some specific plugs for a digital dash.

-g

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post #19 of 21 (permalink) Old 02-07-2017, 07:23 PM
No, Mr. Lemmywinks, No!!!

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Quote:
Originally Posted by S4gunn View Post
$100 in 1985 = $222 in 2016
$100 in 1970 = $615 in 2016

Parts for the 390 are probably similar in cost/complexity to the 302 (read: dirt cheap) but out of curiosity, what is your labor rate for machine work in TN? In CA, esp the Bay Area, it's pretty damn expensive (like everything else -- esp since not many people do it).
How much to grind a crank? Bore out a block? Balance a rotating mass?


-g
Shop Labor rate here is generally $100 hour, last I checked. Mechanics are $85, and want book on everything.

I could get a 350 chevy completely rebuilt and assembled for less than a grand with good parts, but Fords are a problem here.

I was quoted $150 to line bore the mains, and hone the cylinders last year; none of the 4.6 engines I've torn down were worn more than 0.001".
At this point, I with I hadn't disassembled the short blocks, they were fine.

The DOHC had stuck IMRCs and the intake was full of crud, and the 2v I stuffed a valve into a piston; both head problems, much like yours.

My experience with the 4.6 is why I say "Look, but don't touch" unless you see something suspicious.

Woodman posted a good "look over thread" awhile back; he lost oil pressure and killed one.

His process was good tho; if you see what he saw, you have to go that route, but if you Don't see anything, you'll feel better for having looked.

The ARP bolts are expensive, but you can keep them forever, pretty much.

People reuse the stock ones, IDK how I feel about doing that.
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post #20 of 21 (permalink) Old 02-07-2017, 08:32 PM
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Shop Labor rate here is generally $100 hour, last I checked. Mechanics are $85, and want book on everything.

I could get a 350 chevy completely rebuilt and assembled for less than a grand with good parts, but Fords are a problem here.

I was quoted $150 to line bore the mains, and hone the cylinders last year; none of the 4.6 engines I've torn down were worn more than 0.001".
At this point, I with I hadn't disassembled the short blocks, they were fine.

The DOHC had stuck IMRCs and the intake was full of crud, and the 2v I stuffed a valve into a piston; both head problems, much like yours.

My experience with the 4.6 is why I say "Look, but don't touch" unless you see something suspicious.

Woodman posted a good "look over thread" awhile back; he lost oil pressure and killed one.

His process was good tho; if you see what he saw, you have to go that route, but if you Don't see anything, you'll feel better for having looked.

The ARP bolts are expensive, but you can keep them forever, pretty much.

People reuse the stock ones, IDK how I feel about doing that.
Thanks for the pat on the back!

FWIW, on my "new" motor, a 180K Explorer block, with the heads off you can still see the cross hatching in the cylinder bores, and with the oil pan off you can see the bearings all at least "look" good. So I'll bolt my pan up, put my heads on, and run it.
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post #21 of 21 (permalink) Old 04-03-2017, 03:20 PM Thread Starter
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One more comment for others looking to solve bucking/surging issues. After diagnosing and solving the leaky valve issues, we did find putting around the pits the day before our 7th race that there was still some bucking/surging.

We decide the day before the race to swap out the MAF for a spare and VOILA! bucking issues addressed.
It's totally drivable in the pits (<10MPH) without constantly slipping the clutch or having F1 level pedal control.

-g

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