Author Topic: Will head bolt length make any difference?  (Read 193 times)

Offline GR40

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Will head bolt length make any difference?
« on: April 10, 2019, 09:14:14 am »
So I just had some head work done to my engine (enlarged valves) and the shop that send me all the hardwear to reinstall the head send me shorter head bolts. The g40 engine has 95-96mm long and the ones I got are 92mm long. The probable reason for longer bolts on the g40 engine is the hicker head gasket, compared to the rest of the 8v vw engines. I needed the car on the road asap so I went and installed the head with the 92mm ones. Now my question is should I replace them with the proper longer ones or are they fine being 3mm shorter. The trick here is I am planning on making  more power now that I have bigger valves. Anyone has any experience on the matter?

Offline GR40

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Re: Will head bolt length make any difference?
« Reply #1 on: May 07, 2019, 09:11:19 pm »
Well I found the hard way not to use shorter head bolts. 6 or 7 pulls on the dyno and the head gasket let go. So to anyone wondering. Don' t use 92mm head bolts.

Offline Yoof

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Re: Will head bolt length make any difference?
« Reply #2 on: May 08, 2019, 06:09:26 pm »
From memory the G40 specific bolts are a higher tensile strength, so for a given torque they will stretch less (and thus have a greater clamping force).

 

Offline GR40

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Re: Will head bolt length make any difference?
« Reply #3 on: May 10, 2019, 10:40:10 am »
Yeap! Found out the hard way (head lifted on the dyno)! 8.8 hardness for the normal bolts 10.9 (900 N/mm² tensile strength) for the G40 ones! Now going for arp studs but having trouble finding any information on them. Any help would be much appreciated. Like part number etc. Also how to torque them. Talked to the guy who is the dealer for Greece and all he could find was studs listed as 8 valve volkswagen with hydraulic lifters M11 x 1,5 x 118. Hope they are the correct ones cause I already placed an order and it will take 10 days for them to get here!
« Last Edit: May 10, 2019, 11:06:17 am by GR40 »

Offline PeteG40

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Re: Will head bolt length make any difference?
« Reply #4 on: May 10, 2019, 04:24:17 pm »
I think ARP doesn't list studs for g40 -but that Maxrpm etc do- but they are just 8v golf ones I think - so you should be ok.

pete