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post #1 of 13 (permalink) Old 11-01-2014, 04:50 PM Thread Starter
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Head bolts

Maybe I am getting old, but I can't wrap my head around the instructions to put head bolts in on my 94 3.8l.

Are you supposed to literally put the first bolt in, tighten it, loosen it, then go to the next one and move through it like that in sequence?

Or do you put the first bolt in, tighten the first level, loosen, wait 15 minutes, tighten, loosen, wait... until the third time is finished? THEN MOVE to the next bolt?

I used to put all bolts in, tighten them to the first torque in sequence coming back around to the first one, tighten it again and go to the next one until I finished the rotation of 3 sets of tightening.

But as I read the instructions, we have to loosen each bolt and then come back to it and tighten, loosen and so on. Plus, you are supposed to wait 15 minutes between loosening to allow the metal to stretch before tightening again.

What it sounds like to me is you literally do ONE bolt at a time until it is finished, then move to the next bolt.

Can someone spell it out for this old mechanic?

1995 Lincoln Town Car Signature Series - 200k!
1994 Mercoury Cougar XR7 - 150k and still going.

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post #2 of 13 (permalink) Old 11-02-2014, 08:17 AM Thread Starter
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Despite what instructions I could find that were more specific, I am going to use common sense. I put all the bolts in the heads and will tighten and loosen them one at a time through the sequences and *maybe* wait 15 minutes between intervals.

Thanks all.

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1994 Mercoury Cougar XR7 - 150k and still going.

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post #3 of 13 (permalink) Old 11-02-2014, 10:52 AM
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Quote:
...tighten the bolts, in the sequence shown in the accompanying figure to:
a. 15 ft. lbs. (20 Nm)
b. 29 ft. lbs. (40 Nm)
c. 37 ft. lbs. (50 Nm)

Do NOT loosen more than one bolt at a time.

...loosen each bolt in the torque sequence, one at a time, 2-3 turns, then:
a. Tighten each long bolt to 11-18 ft. lbs. (15-25 Nm), then rotate an additional 90 degrees.
b. Tighten each short bolt to 7-15 ft. lbs. (10-20 Nm), then rotate an additional 90 degrees.
I can see how this can be interpreted different ways. I understand it as:

Tighten all bolts (in order) to the first spec.
Tighten all bolts (in order) to the next spec.
Tighten all bolts (in order) to the third spec.
Now with all bolts still torqued to 37, go to the first bolt and loosen, re-torque to final spec, plus 90 degrees. Then do the same with the second bolt. And so on.

The whole point is to get the gasket clamped down evenly. Whomever came up with these specs was trying to make damn sure that it was absolutely perfect, even if it seems like time-consuming overkill. There are various theories as to why the head-gaskets on these motors blow, one of which is possible incorrect torquing at the factory. Honestly, with that final 90 degree rotation, I'm not sure what the final torque is supposed to end up as.

1996 Thunderbird LX (4.6), previous daily driver

1995 Mustang GT (5.0), daily driver
1995 GMC C2500 (5.7), alternate daily driver

Last edited by Urambo Tauro; 11-02-2014 at 11:00 AM.
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post #4 of 13 (permalink) Old 11-02-2014, 11:39 AM Thread Starter
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Thanks UT for clearing up the confusion.

1995 Lincoln Town Car Signature Series - 200k!
1994 Mercoury Cougar XR7 - 150k and still going.

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post #5 of 13 (permalink) Old 11-02-2014, 12:16 PM
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You probably all ready know this, but just in case, and for other readers: Always use new torque to yield (stretch bolts). And dip the threads in motor oil before installation.

Tightening by angle rather than torque removes the error that is produced by friction in the threads. I would recommend using a torque gauge upon that last 90* rather than just turning the torque wrench. But, I'd double check that angle amount with manufacture specs. It is a 3.8 so there's no fault in being anally retentive.

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post #6 of 13 (permalink) Old 11-02-2014, 08:48 PM Thread Starter
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Unhappy

Quote:
Originally Posted by rushtonracing View Post
It is a 3.8 so there's no fault in being anally retentive.
I found this under "Specifications" in my 95 Ford CD:

3.8L Non-SC Engines

Tighten in numerical sequence in three steps as follows:

l 20 N-m(15 lb-ft) .

l 40 N-m (29 lb-ft).

l 50 N-m (37 lb-ft).In numerical sequence, loosen retaining bolts two to three revolutions and retighten bolt one at a time in the following manner:

a. Long bolts:

-- 15-25 N-m (11-18 lb-ft).

-- Tighten bolt an additional 85-95 degrees.

-- Go to next bolt in sequence.

b. Short bolts:

-- 10 N-m (7-15 lb-ft).

-- Tighten bolt an additional 85-95 degrees.

-- Go to next bolt in sequence.

3. Tighten in two steps:

a. 7-15 N-m maximum (5-11 lb-ft)

b. 30-40 N-m (22-30 lb-ft)

4. Tighten in numerical sequence in two steps:

a. 18 N-m (13 lb-ft)

b. 22 N-m (16 lb-ft)

5. Tighten in numerical sequence in three steps:

a. 10 N-m (8 lb-ft)

b. 20 N-m (15 lb-ft)

c. 32 N-m (24 lb-ft)

And it STILL Makes no sense to me.... (yes, that is all it says... )

1995 Lincoln Town Car Signature Series - 200k!
1994 Mercoury Cougar XR7 - 150k and still going.

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post #7 of 13 (permalink) Old 11-03-2014, 01:16 AM
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Have you surface checked the block?

Heads re-surfaced, pressure tested?

Before torquing, blow out all the bolt holes with an air gun with 90-110 psi of air. Use a tube type tip so you can reach down all the way into the bottom of the hole to blow out any debris.

Next, use a correct size and pitch bottoming tap (flat end at tip) to carefully chase the threads to clean them. Measure the depth of the hole, and mark it on the tap to know when you've reached the bottom, (note: long/short bolts). Yellow paint pen works the best. Marking will also speed up the process as you move from one hole to the next.

Dip/spray the tap first with a light oil (wd-40 is fine, yeah, it's technically a solvent) put some too in the hole, and work the tap down/up/down until you lightly bottom out. (If at any time you feel excessive interference stop. Remove the tap, blow tap, and hole to remove any debris.)

Remove tap, blow hole again, blow any debris stuck on the tap, and repeat until you are confident all debris are removed.

I cannot emphasize enough the importance of the above procedure.

Use a known calibrated torque wrench. Buy a new one if you question this. At work we calibrate ours at least once a yr. Tooling tells me they find one out of spec' every once in a while.

Easy to tell a 90* turn using a ratchet etc.. Still, I'd use an angle gauge for this motor.



94-95 Ford 3.8L Essex Only.

Dip head bolts in clean motor oil.

Tighten in numerical sequence in three steps as follows:

l 20 N-m(15 lb-ft) .

l 40 N-m (29 lb-ft).

l 50 N-m (37 lb-ft).

Wait 15 minutes


In numerical sequence, loosen retaining bolts two to three revolutions and re-tighten bolt one at a time in the following manner:

This means start back at number 1 bolt. Loosen just that bolt. Leave all the rest torqued to 37 ft. lbs. Once you have torqued that bolt to correct spec' tighten an additional 85-95 degrees. Then move on to next bolt in torque sequence regardless if it is long or short.

a. Long bolts:

-- Torque to 37 ft. lbs.

-- Tighten bolt an additional 85-95 degrees.

-- Go to next bolt in sequence.

b. Short bolts:

-- Torque to 15 ft. lbs.

-- Tighten bolt an additional 85-95 degrees.

-- Go to next bolt in sequence.

I had to do some research on this because of ambiguous findings. Found conflicting torque specs once you loosen the bolts, and re-torque before the additional 90* angle. Especially the long bolts.
I did find this chart's specs' repeated multiple times on other sites. Which leads me to believe the torque I specified is accurate.

http://www.allfordmustangs.com/Detailed/650.shtml

1995 Thunderbird LX 4.6l 97 Headlamps/Hood All Red Tails Muffler/Resonator Delete
2004 Tahoe 5.3 4x4
2008 Acadia Limited AWD

...still looking for a clean, low mileage, rust free 96/97 Thunderbird 4.6

Last edited by rushtonracing; 11-03-2014 at 03:22 AM.
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post #8 of 13 (permalink) Old 11-03-2014, 03:41 AM
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Or ditch all TTY bolts and be happier with studs.

-1996 Pearl White Thunderbird 4.6 Sport 4v with many mods:
Current Best: 13.583 @ 103.74 10/2014.
227hp/241tq measured on calibrated mustang dyno, tested at full vehicle simulation with inertia enabled, no number skewing.
-2001 White Ford F-250 Super Duty 6.8 V10, 4-door, 4x4, Limo Tint, BFG KO2's, Bilstein 7100 Remote Reservoir Race Bypass Shocks, 6" Spring lift, Kenwood Double Din, K&N Intake, FlowMaster Exhaust
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post #9 of 13 (permalink) Old 11-03-2014, 04:35 AM
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Quote:
Originally Posted by Chris_Murder View Post
Or ditch all TTY bolts and be happier with studs.

I agree. They offer less deterioration of clamping force over cold/heat cycles, and time. Plus, they're reusable. Check with parts provider/parts company for proper torque specs' and procedures.

While we're on the subject of parts. I will recommend to the original poster to use three layer head gaskets, even with the stock TTY bolts. Steal/copper/steal. Note too, machined heads may need a gasket shim to maintain stock compression.

1995 Thunderbird LX 4.6l 97 Headlamps/Hood All Red Tails Muffler/Resonator Delete
2004 Tahoe 5.3 4x4
2008 Acadia Limited AWD

...still looking for a clean, low mileage, rust free 96/97 Thunderbird 4.6
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post #10 of 13 (permalink) Old 11-03-2014, 08:50 AM Thread Starter
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Quote:
Originally Posted by rushtonracing View Post
Have you surface checked the block?

Heads re-surfaced, pressure tested?
Excellent advice, thank you Rush.

I have one question, can I redo the process after tightening all the bolts after the 90 deg process? I followed the process you suggested (before you wrote your post) but did not wait a full 15 min for each bolt before tightening the last time.

And no, I did not want to spend the money *again* to have the heads planed when I just did it done less than 20k ago. If the car was not a salvaged car, I would have had it done.

What I was so horrified about was when I was taking the engine apart, the left side lower bolts (short bolts) where not tight even though I used new bolts (I went over my records and found I did buy new bolts last time) and torqued per specs. And yes, I always clean out, tap out holes and clean and die the bolts (not new head bolts).

Next time this happens, if ever, the car is gone.

1995 Lincoln Town Car Signature Series - 200k!
1994 Mercoury Cougar XR7 - 150k and still going.

I've had too many other cars to mention...
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post #11 of 13 (permalink) Old 11-03-2014, 09:06 AM Thread Starter
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Quote:
Originally Posted by Chris_Murder View Post
Or ditch all TTY bolts and be happier with studs.
I'd be happier, maybe, but I would also be a lot more broke. When the price difference between head bolts and head studs is 5x, I think I'd rather buy more beer...

Thanks for the tip, if I ever get another 3.8l, I will remember that tip.

1995 Lincoln Town Car Signature Series - 200k!
1994 Mercoury Cougar XR7 - 150k and still going.

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post #12 of 13 (permalink) Old 11-03-2014, 09:12 AM Thread Starter
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Quote:
Originally Posted by rushtonracing View Post
I saw this web site before when I was looking for the process and this chart is just as confusing. What is it with the long bolts being 37 ft/lb and the short bolts being 15 ft/lb?

I read through my service manual and my service CD and neither really describe what they mean in the tightening process. Drives you nuts.

GET OUT AND VOTE TOMORROW!!!!

1995 Lincoln Town Car Signature Series - 200k!
1994 Mercoury Cougar XR7 - 150k and still going.

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post #13 of 13 (permalink) Old 11-03-2014, 12:22 PM
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Quote:
Originally Posted by white lincoln
I have one question, can I redo the process after tightening all the bolts after the 90 deg process? What is it with the long bolts being 37 ft/lb and the short bolts being 15 ft/lb?
No. Once the bolts are torqued to yield, and stretched, they cannot be re-torqued.

My only conclusion to the second question is that the shorter bolts have less material, so they apply the same amount of clamping force with less torque pre-load. But, this is purely conjecture on my part.

I do know that conventional head bolts are torqued to a point where they remain elastic. TTY bolts, on the hand, are torqued to point beyond elasticity into plastic transformation where they loose that elastic character, and remain stretched even after the load has been relieved. (Hence, why they cannot be reused.) This gives a more even clamping force than conventional bolts. The yield is that point beyond elasticity and into a given amount of plastic transformation.

The shorter bolt reaches that yield point "sooner" than a longer bolt with a longer shank, and more material. But, again, this statement may be in error.

1995 Thunderbird LX 4.6l 97 Headlamps/Hood All Red Tails Muffler/Resonator Delete
2004 Tahoe 5.3 4x4
2008 Acadia Limited AWD

...still looking for a clean, low mileage, rust free 96/97 Thunderbird 4.6
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