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Back off 1/4 or no on head retorque

  • Thread starter Thread starter doctorgonzo
  • Start date Start date
Man, all I did was a ask a simple question... the next thing you know it's a mechanical engineer nerd fest!
 
Shame to let a perfectly good thread die like this.:p

A question for the drag racers.

At what CR do you decide to fit larger studs and how much increase in torque on the nuts do you go to?

Does the increase in torque and heat generated on a high output air cooled engine affect the amount of natural expansion and cause some crushing of the aluminium cylinder surfaces? If so, how do you combat this?
 
I put the APE studs in ALL of the motors I have because once you start leaning on them the stock studs will give some. I would deem them mandatory on anything 12.0 to 1 or more but that is just me & I overbuild everything! Ray.
 
rapidray said:
I put the APE studs in ALL of the motors I have because once you start leaning on them the stock studs will give some. I would deem them mandatory on anything 12.0 to 1 or more but that is just me & I overbuild everything! Ray.
Click to expand...
I agree. The stock studs stretch.
 
Thanks for the info Ray. Do APE recommend increasing torque figures too?

With more rigid studs at higher torque, isn't there a tendency for the ali components (block deck, cylinders and head) to crush due to the greater resistance to natural expansion. Larger steel studs won't expand as fast as the ali parts that they are restraining. Head and base gaskets will give initially, but what happens after re-torque when an engine is continually heat cycled over a seasons racing.
 
The recommended torque spec for an 1100 or 1150 head with APE studs is 40-42 ft lbs. Stock is a lot less. Ray.
 
So...an update on the head "settling in" with my 8V 1000 engine using an Athena MLS head gasket and stock base gasket.

The head and cylinder were surfaced and the head tightened using a Snap-on dial type torque wrench. After only about 20 miles of run time the head bolts were checked and a number of them had loosened considerably - in the range of 15 ft-lbs.

Just checked them again after another 30 miles and a few of the bolts were loose again, but not as bad as before.

Guess the lesson here is if you are running an Athena MLS head gasket, check that puppy several times until things settle down. I'm setting the nuts at 30 ft-lbs too, instead of 27 like before.
 
Nessism said:
So...an update on the head "settling in" with my 8V 1000 engine using an Athena MLS head gasket and stock base gasket.

The head and cylinder were surfaced and the head tightened using a Snap-on dial type torque wrench. After only about 20 miles of run time the head bolts were checked and a number of them had loosened considerably - in the range of 15 ft-lbs.

Just checked them again after another 30 miles and a few of the bolts were loose again, but not as bad as before.

Guess the lesson here is if you are running an Athena MLS head gasket, check that puppy several times until things settle down. I'm setting the nuts at 30 ft-lbs too, instead of 27 like before.
Click to expand...
Wow! That substantial.
 
Nessism said:
So...an update on the head "settling in" with my 8V 1000 engine using an Athena MLS head gasket and stock base gasket.

The head and cylinder were surfaced and the head tightened using a Snap-on dial type torque wrench. After only about 20 miles of run time the head bolts were checked and a number of them had loosened considerably - in the range of 15 ft-lbs.

Just checked them again after another 30 miles and a few of the bolts were loose again, but not as bad as before.

Guess the lesson here is if you are running an Athena MLS head gasket, check that puppy several times until things settle down. I'm setting the nuts at 30 ft-lbs too, instead of 27 like before.
Click to expand...

Thanks for your timely update.

My 850 Cometic MLS head gasket got a re-torque at 100 kms and I found some give too. I further re-torqued at 800k kms. It won't see another re-torque until it's next valve adjustment. I will re-torque at all subsequent valve adjustments.

It did a track day 2 month ago without any oil leaks. That 0.002" proud sleeve mod is still working well after 4000 kms.;)
 
Last edited:
Nessism said:
So...an update on the head "settling in" with my 8V 1000 engine using an Athena MLS head gasket and stock base gasket.

The head and cylinder were surfaced and the head tightened using a Snap-on dial type torque wrench. After only about 20 miles of run time the head bolts were checked and a number of them had loosened considerably - in the range of 15 ft-lbs.

Just checked them again after another 30 miles and a few of the bolts were loose again, but not as bad as before.

Guess the lesson here is if you are running an Athena MLS head gasket, check that puppy several times until things settle down. I'm setting the nuts at 30 ft-lbs too, instead of 27 like before.
Click to expand...

Ed, did you back of the head nuts before retightening or just tighten them up to the proper settings.
Thanks.
 
Suzuki_Don said:
Ed, did you back of the head nuts before retightening or just tighten them up to the proper settings.
Thanks.
Click to expand...

The really loose ones could be made up but the tighter ones needed to be back off first in order to get an accurate torque reading.
 
chef1366 said:
I agree. The stock studs stretch.
Click to expand...



They are supposed to stretch. That is how a fastener works. Just like a rubber band. The whole point of torquing a bolt is getting it to the "stretched point,and with cylinder/head expansion, yet not getting to the yield point, which is the point of failure...when the little molecules start letting go of each others hands.

The proper way to stretch a bolt is to measure it static, and then stretched to it proper load specified by the manufacturer. Since this is impossible to do in most cylinder head bolt/stud applications, we use torque value, or torque angle as the Germans like. Either way works fine. The reason you need to lube the threads and especially the under head of the bolt head is to give the best "lab" results of proper stretch for that particular fastner.


Interesting the comitec gasket is looked down on in this application. I have used them on a bunch of FI BMW car engines with excellent results.


Go to ARPs website it is all explained in laymans terms.

I am okay with being a nerd. Also being corrected if I am wrong.:D

I always understood that the color you see is every other color than the one you see so it is refracted back, all the others are absorbed. :dunno
 
makr said:
Interesting the comitec gasket is looked down on in this application. I have used them on a bunch of FI BMW car engines with excellent results.
Click to expand...

The 16V 1100 1133-1166 Cometic Head Gaskets have a tooling issue are defective and leak.
 
chef1366 said:
This should be good for another 12 pages. :rolleyes:
Click to expand...

HEY BILL, Don't short change me !!!!!!!!!!!

Only 12 pages !!!

We've got to give ED something to do in his spare time (answering our novice questions)., We can't have him sitting at home getting bored can we.
 
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