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post #1 of 14 (permalink) Old 08-20-2007, 11:17 PM Thread Starter
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Bunch of questions...

'lo, everyone. I'm new (obviously).

>insert cricket chirps>

Er, so hi. I've a few questions about my ol thunderchicken...I'm wanting to get the best gas mileage out of it that I possibly can. So the following are things I want to do;

First of all, the engine's piston rings are gone to the point that it's burning too much oil to idle while in gear. This little problem came out of the woodwork so to speak, of course, right after I had someone replace the head gaskets. So I'm planning on saying "screw it", salvaging the newly-shaved heads along with anything else good on/in the engine, and buying a freshly-remanned one from a company on eBay for $1200 (including shipping)(here). Is it a decent price to (hopefully) have no further worries?
And on the same note, how much would it cost to have it broken in and tuned on a dyno?

I've been thinking about swapping the old AOD for a manual...how difficult and expensive would it be, and would it be better than staying with the AOD and stuffing 4R70W internals/wide-ratio gearset in it? And if the latter, how much can I expect to pay...
(there's an article around here that shows how to do an auto-to-manual swap, but I can't find it :\)

Also, it would be nice to swap out the rear gears for something favoring fuel economy over acceleration...what years can I swap from, and just how low can the 3.8 reasonably handle?

Headers. Oreilly's site has some listed for this engine and body, but no prices and I don't know exactly what pair to get. Hopefully, they aren't too expensive. Additionally, I want to slap dual exhausts on, but I can't seem to find any premade kits. If someone could point me to a site that makes stuff like this for my year of engine, that'd be great...
On the other hand, a decent muffler shop could likely make me a custom set of pipes, eh? But I'm not so sure what to do with the cats; I don't want the CEL to be constantly on due to the missing third cat, but I don't want to by another cat for the second pipe, either. It'd be nice to get rid of the big cat and stay with the small cats. If it weren't for my wanting to do my part and all that rot, I'd take all three of them out...

The mechanical fan has got to go. I can grab an electric fan from most any later model t-bird as long as I find a suitable controller for it, right?


Eh, it's getting late...there's more, but I'm tired. Any pointers would be very much appreciated

Last edited by wrk; 08-20-2007 at 11:27 PM.
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post #2 of 14 (permalink) Old 08-21-2007, 07:32 AM
 
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the manual swap is in the tech articles, http://tccoa.com/articles/tranny/index.html# then click auto to manual from there
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post #3 of 14 (permalink) Old 08-23-2007, 02:45 AM Thread Starter
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I was actually hoping for instructions...all that tells me is what I'll need. Not that I'm not appreciative, knowing what parts are required is half the battle
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post #4 of 14 (permalink) Old 08-23-2007, 08:59 AM
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first do a compression test on all cylinders to see which ones are actually bad. you may have bad valve seals, which leads to burning oil.

re-ringing an engine is fairly easy, but getting to it is the hard part. that price is insane. i wouldnt buy an engine thats already assembled. if you are going to re-ring your engine, you obviously have to pull it, so you might as well reuse your current engine. have a machine shop thoroughly inspect your block and perform the necessary work.

for rear gears, what do you have now? there should be an axle code on the door jamb sticker under "ax".

for headers, get the 96/7 3.8 tbird headers. im not too sure if you use the same heads as an mn12. they may also hit your steering shaft. i dont know of anyone with a v6 fox here that has swapped headers. maybe you could be the guinea pig to see if the 96/7s will fit. for the rest of your exhaust, gotta go custom. i know of no premade kits. go with 2.25" piping.

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post #5 of 14 (permalink) Old 08-23-2007, 01:18 PM Thread Starter
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I've replaced the valve seals...figured it was about the cheapest thing I could do, since a set of seals came with my head gasket set.
But I'll see about doing a compression test, no money right now to go rent a kit to do it, but one of my neighbors might have something.

I thought the price a bit high, myself, but I don't know of anywhere local that will do this extensive of work. Furthermore, I won't be in the area to arrange anything (work is going to take me a bit far away), thus the appeal of having an engine that I can have shipped here and a guy I know drop it right in. Guess it can't hurt to call around a bit though, see if anyone'll do it.

According to the sticker, the rear axle code is "Y". That same sticker also says my '88 is an '87, so I kind of wonder about its accuracy :P

I would have thought replacing the old, restrictive exhaust manifolds would be the one of the first steps to getting better performance from the V6...kind of surprised to hear that nobody has done it...well, the Oreilly site says that several sets will fit, I'll just nab some of those part numbers and see if they match up with the years you mentioned. Better to check around a bit rather than dump x hundred dollars on something that won't fit, eh?

Also considering buying a set of roller rockers. Will they help enough to offset the cost?
And will underdrive pulleys from the later years work with this thing? I've not seen them for any earlier than 1990 engines.
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post #6 of 14 (permalink) Old 08-23-2007, 02:01 PM
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talk to rod, racecougar on here. im pretty sure he's in missouri, but unsure where exactly.

code y is a 3.08 open differential. get an 8.8 rear end and swap in some 3.73s, install some kind of shift kit, and you will have a fun car to drive. i think the jump to 3.73s will cause computer problems. maybe someone can shed more light on this issue.

headers will give you a small gain, unless you redo the entire exhaust. then again, you probably wont notice much of a gain until you start throwing aftermarket intakes, cams, heads, etc on your engine. i would hop onto foxtbirdcougarforums.com or something like that. ill bet you can find some better answers over there.

like headers, roller rockers will give you a small gain. underdrives do help, but i dont know of any sets for a v6 fox. imo, its not worth it to mod a v6. better to save up for a 5.0. they are dirt cheap nowadays. you can probably pick up an entire engine with accessories for $300.

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post #7 of 14 (permalink) Old 08-23-2007, 02:08 PM
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He does not have a computer controlled transmission so I do not think the change in the rear end gear ratio will cause problems.

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post #8 of 14 (permalink) Old 08-23-2007, 02:12 PM
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yeah, i know but i thought i remember reading here that, even for an aod, more than two steps (3.08 to 3.27 to 3.55 to 3.73) in gearing will cause issues. ill see if i can dig up that thread.

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post #9 of 14 (permalink) Old 08-23-2007, 04:47 PM Thread Starter
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Found lots of good info over at http://www.coolcats.net/tech/

Keep in mind I'm looking more for fuel economy rather than acceleration...a daily driver, if you will. Otherwise, I probably would just go for the 5.0.
It looks more like I'll be getting 2.73 gears, if possible. As far as computer difficulties, the only problem I've heard about in swapping rear ends is the speedometer gear needing changed...which, of course, isn't related to the computer at all. Let me know if you find something though, it's good to know these problems before having them ruin a day.

I do plan on going "true" dual exhaust at some point, probably once I get some headers since...well, obviously the stock exhaust system won't match up anymore

Hopefully a combination of the exhaust modifications, electric cooling fan, rockers, rear end, manual tranny/modified automatic will net me a few more mpg. Aiming for 20city/30 highway in the end, at least...wouldn't be all that bad for a 19 year old, v6-equipped 3800lb car. 'course, getting to that will likely take more than these few mods. Le sigh.

Last edited by wrk; 08-23-2007 at 04:53 PM.
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post #10 of 14 (permalink) Old 08-28-2007, 03:24 PM Thread Starter
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Right well, in case anyone's curious, I've decided to go with 2.73 rear gears and a Borg-Warner T56 with 2.66/1.78/1.30/1.00/0.74/0.50 gear ratios. This'll allow me to run the car just above idle going 55mph (though me sticking to 55 is pretty rare). Though it's more likely I'd only use 6th going 65mph+, or on flat lower-speed highways, so as to retain *some* hill-climbing ability and not lug the engine too awful much.

Quote:
Originally Posted by big mike View Post
talk to rod, racecougar on here. im pretty sure he's in missouri, but unsure where exactly.
I take it he's a mechanic? I'll get ahold of him when I have a minute, barely have time to finish this post.

One last thing. I have the fully-digital instrument cluster. Anyone know how to get the speedometer to display above 85mph?
Edit: nevermind, found out how.

Last edited by wrk; 08-28-2007 at 06:33 PM.
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post #11 of 14 (permalink) Old 08-29-2007, 07:11 AM
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One thing to remember that it's not just about rpm at a certain speed, load has a lot to do with fuel economy. Often going to too steep of a gear will actually hurt your fuel economy.

IMHO, the best way to pick/design a drivetrain (transmission, gear ratio, etc.) is to dyno the engine and take a look at the hp/torque curve, determine where the majority of your cruising speed will be and then go from there.

I have seen it many times when someone went from something like 3.25's to 2.75's and actually hurt their gas mileage because the engine didn't have enough bottom end torque to maintain the speed without more throttle, which in turn burns more fuel. Think about the small engines in cars.

You could get a small commuter car for what you are going to spend on modifying a large car to get comparable gas mileage (IMHO).

Just $0.02 from someone that drives 110 miles a day and has done much research on fuel economy. (The price of a T-56 will buy you a lot of gas!!!)

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97 Ford Aspire (Slow, but getting 36 mpg (f'n Ethenol!! )
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post #12 of 14 (permalink) Old 08-30-2007, 02:30 AM Thread Starter
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I've been thinking about that, actually. According to Wikipedia (which is at least occasionally right), the engine puts out 215lbf-ft at around 1600rpm (or so, that's actually for the CFI version, but I'm sure the MPFI version is close) in stock form.

According to the calculator I found, the engine would be running at about [email protected] with the 2.73's and a .50 final drive...might be too far away from the powerband, eh?
BUT, I figure I can stick to using 6th when cruising on the freeway. Anything below 65mph, I'll use 5th to keep the engine around its ideal rpm. Thus is why the 6 speed is necessary...it's like having a two-stage overdrive system

(yea, I know, 5th and 6th count as overdrive anyway. I'm just that lame.)
(I also know the T-5 wouldn't be that much different. I've just always wanted a six-speed.)

You're going to tell me that "just because Wiki says those are the torque/rpm stats for that engine, it doesn't mean they apply to YOUR engine", aren't you. I do plan on getting the engine dyno'd to make sure, don't worry.
But, even after taking all that into consideration you still think it's a bad idea, I'll yield to someone more knowledgeable and try something different.

I could get a different car, sure. But this is my first car, she's a comfy car, and I think it would be cool to make a car this big get fairly good fuel economy. She's sat in the driveway for a year and a half, it's time for her to take to the roads again.
Anyway, T-birds are more stylish than any little economy car (though I really like my '90 Grand Am), and I like my digital gauges. After I'm done with it, it'll look even better...

On a final note, just how much will a T-56 with the above ratios run me, assuming I can find one at a salvage yard? Was planning on a few hundred dollars, but it sounds like it's going to be more than that...


"I"s used: 18...

Last edited by wrk; 08-30-2007 at 02:47 AM.
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post #13 of 14 (permalink) Old 08-30-2007, 06:35 AM
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Actually I like Wiki and have found that most of the time the info is pretty accurate.

I’m not saying it’s a good or bad idea as it’s your car and it is fun to work on them. I’m just presenting what I believe to be facts so you can make are more informed decision.

T-56 for a few hundred!?!?!? Well, I guess “30” 100's is a "few". IMHO, figure on about $3000 for everything for a T-56 swap once you're finished. That would include the transmission, clutch setup, pedal install, driveshaft, etc. (Will a T-56 bolt up to a 3.8L?)

Here’s something to think about when looking at modifications to get better fuel economy:
(I did this for a co-worker who commutes in a Dodge 4x4!!)

Assumptions:

Monthly miles driven: 600 (26 miles x 5 days x 4 weeks + 80 misc. miles)
Formula: Daily commute miles multiplied by 20 plus misc. weekends and trip milage
Dodge Truck: 15 mpg
Price per gallon: $2.75

Monthly cost @ 15 mpg: $110
Monthly cost @ 30 mpg: $55
Monthly cost @ 35 mpg: $47
Monthly cost @ 40 mpg: $41
Formula: Miles driven divided by mpg multiplied by 2.75

Monthly savings @ 30: $55
Monthly savings @ 35: $63
Monthly savings @ 40: $69
Formula: Current monthly cost minus new monthly cost

Months to recoup $1000 at 30 mpg: 18 months
Months to recoup $1000 at 35 mpg: 15.8 months
Months to recoup $1000 at 40 mpg: 14.5 months
Formula: $1000 divided by monthly savings

You can see that if you drop $4000 to improve you gas mileage, it is going to take a LONG time to recoup the money, which makes it not cost effective.

Shoot even at 110 miles a day, I can’t justify buying a better fuel efficient car vs. my Aspire.
Monthly miles driven: 2200 (110 miles x 5 days x 4 weeks)
1997 Ford Aspire: 35 mpg
Price per gallon: $2.75

Monthly cost @ 35 mpg: $173
Monthly cost @ 40 mpg: $151
Monthly cost @ 45 mpg: $134 (Diesels)
Monthly cost @ 55 mpg: $110 (Honda Insight)

Monthly savings @ 40: $21
Monthly savings @ 45: $39
Monthly savings @ 55: $63

Months to recoup $1000 at 30 mpg: 48 months
Months to recoup $1000 at 45 mpg: 26 months
Months to recoup $1000 at 55 mpg: 16 months


You’ll need to put in your own numbers to see how it applies to your situation. But if it takes $4000 to double your gas mileage, it may take years for you to see the payback. Simple cost/benefit analysis.

But again, just my .02. I hate to see people do a lot of work for an intended goal, but then not factor in the cost of said goal.

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post #14 of 14 (permalink) Old 08-30-2007, 10:17 PM Thread Starter
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Whenever I see something I know nothing about, Wiki gets pulled up. 'tis a rather useful site

$3000 for a tranny and associated hardware is insanity...I'd expect a lot less for a manual.
Did a little shopping around, cheapest I could find was $1200 or so from a company and a few hundred for one on eBay that "grinds when shifting 3-4". Surely I can find something for a decent price...this is Missouri, all our stuff is cheap o.O

Learned about the AOD to T-5(6) from http://www.coolcats.net/tech/advance...onversion.html .

This isn't ALL about gas mileage :P though that's a major part of it. I like my T-bird, it's a nice car...I just want to look down while cruising and see that I'm not eating copious amounts of gas driving it around. Nevermind how much it takes to get there.

How many people on this forum have dumped thousands into their cars to bring power levels up, when it would have been more cost-effective to simply buy something newer and go from there? What I'm doing isn't all that much different
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