head bolt torque specifications
Thread Starter
Instructor
Joined: Apr 2011
Posts: 208
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From: Trophy Club Texas
head bolt torque specifications
I am looking to replace the head gaskets and all valve seals etc. on my 1991 l98 engine.
When torqueing down the head I see in the fsm the pattern to use and the torque specification of 67 ft lbs.
However, I read some people torque the head down in 2 or 3 passes. I.E. 30 ft lbs in sequence,then, 50 ft lbs in sequence, and finally 67 ft lbs in sequence.
Anyone who has done this successfully on an l98... Their insight is valued.
Also, I plan to get the heads machined so they are perfectly flat... How much additional can they shave from the head for better compression/performance? And will there be a need to reprogram the computer to compensate for the new compression?
When torqueing down the head I see in the fsm the pattern to use and the torque specification of 67 ft lbs.
However, I read some people torque the head down in 2 or 3 passes. I.E. 30 ft lbs in sequence,then, 50 ft lbs in sequence, and finally 67 ft lbs in sequence.
Anyone who has done this successfully on an l98... Their insight is valued.
Also, I plan to get the heads machined so they are perfectly flat... How much additional can they shave from the head for better compression/performance? And will there be a need to reprogram the computer to compensate for the new compression?
Last edited by Fredbird; Apr 25, 2012 at 02:06 PM. Reason: additional info.
Race Director
Joined: Jun 1999
Posts: 14,924
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From: Merritt Ils Fl
Your torquing procedure is correct. I do two additional steps, first I pull all bolts down until they are snug, slightly more than finger tight, insures the head is flat on the block. After my final torque I will run all the bolts twice more. I do not know if either of these are really necessary but I haven't lost a head gasket yet. Each time a head is milled the angle at which the intake manifold meets the head changes. I have heard .030 is the limit but am not sure. No, you will not need a tune due to the small increase in compression.
Le Mans Master
Joined: Mar 2001
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From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
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St. Jude Donor '12
One thing I do is after a few hours on the engine (couple of heat cool cycles) pull the valve covers and check the torque again.
Thread Starter
Instructor
Joined: Apr 2011
Posts: 208
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From: Trophy Club Texas
Is there an experience you've had which led to this suggestion or is this something you've heard?
I'm not trying to sound smart, just want more understanding before I do it.
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
I have never seen or heard of anyone doing that... The FSM doesn't even say anything about doing that.
Is there an experience you've had which led to this suggestion or is this something you've heard?
I'm not trying to sound smart, just want more understanding before I do it.
Is there an experience you've had which led to this suggestion or is this something you've heard?
I'm not trying to sound smart, just want more understanding before I do it.
Suckin' gas, haulin' ass.
Joined: Apr 2010
Posts: 1,100
Likes: 8
From: Newport News Virginia
I would definitely torque in steps. Start with something light like 20 ft-lbs, then go to 45, then the final, then go over them again at final torque a couple more times.
You don't want to have one bolt super tight and the rest just snug when you start torquing. It just doesn't seem right, at least in my opinion.
You don't want to have one bolt super tight and the rest just snug when you start torquing. It just doesn't seem right, at least in my opinion.
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
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Cruise-In IV Veteran
St. Jude Donor '12
its old school, but thats the way I learned and I still do it out of habit. The three times I've had the heads off and back on there might have been one head bolt that wasn't quite up to spec. So whats that one out of 60 bolts? Mine sees mostly road course use so the old method lets me sleep at night and not worry about it.Just brought it up cause its the way I do it.
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Melting Slicks
Joined: Dec 2009
Posts: 2,749
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From: Westmont Il.
I replaced the head gaskets on my '91 2 years and 20k mi. ago. Fel-Pro 1094 .015" thick steel shim, coated gasket compared to the .050" thick stock gasket. The stock 52k mi. heads were surfaced, and torqued in stages one time with new bolts. The block surface was good.
No problems so far and that includes about 40 trips down the 1/4 mi. and several road trips.
No problems so far and that includes about 40 trips down the 1/4 mi. and several road trips.
1st Gear
Joined: Jun 2019
Posts: 1
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I know this thread is old but couldnt help but notice the talk of re torque for heads. I would never advise this as most head bolts that are used are tty- torque to yield bolts. If you re torque after running the engine, in other words a heat cycle, you will weaken these bolts and could have head gasket failure down the road... Always best to follow manufacturers instructions.
