Author Topic: Head gasket replacement  (Read 166 times)

Offline tmsmini

Head gasket replacement
« on: March 17, 2019, 11:05:04 AM »
I have seen several comments/suggestions on doing this when replacing a head gasket:


The Payen gasket has a sealant on the surface. When fitting a new gasket to ensure correct adhesion the engine should be run for 40seconds without any coolant, then allow the engine to cool, retorque the head and fill with coolant.
Head studs should be oiled when torquing and as advised above the head and block faces need to be flat.

55ft/lb oiled on A+ studs. If the block and head face are completely flat, clean the faces with methylated spirits and follow the procedure I outlined above.

Opinions?

Offline MiniDave

Re: Head gasket replacement
« Reply #1 on: March 17, 2019, 11:33:50 AM »
Who said to oil the threads and torque to 55?

I've always left the stud threads clean and dry, oiling them means you'll exceed the torque spec due to lack of friction....and I never torque to 55, 45 maybe 50 max.

I think if you torque to 55 with oil on the threads you'll stretch the studs, the head will be loose when it cools off and you'll blow the gasket eventually.

Just my opinion, from having had about 2 dozen of these heads off over the last 40 years....that's how I do it and I've never had one blow.

I make sure both surfaces are clean and dry and straight, install the head, torque in two steps - first to 30 lgs, then to 45 as above - run the engine till it's fully warmed up (with coolant in it). shut off and let cool overnight, then retorque the head and reset the valves. When I retorque, I break the nut loose, then tighten slowly and smoothly till I hit the torque spec.
« Last Edit: March 17, 2019, 11:42:02 AM by MiniDave »
1989 Cooper Racing Green
2009 Clubman S
2004 Audi Allroad 2.7 TT

Offline tmsmini

Re: Head gasket replacement
« Reply #2 on: March 17, 2019, 11:41:06 AM »
Oiling is the reason for the higher suggested torque setting?
ARP has some special lube they suggest using with their studs.
https://arpinstructions.com/generaltorque.html

I was more curious about the dry running to set the gasket.

Offline MiniDave

Re: Head gasket replacement
« Reply #3 on: March 17, 2019, 11:45:01 AM »
I doubt dry running will hurt anything, especially for 40 sec....but I've never bothered. Torque it, run it, let it cool, retorque.

55 was for 220K studs and their lube (which I've never used - but then I'm not building race motors - stock studs always worked fine for me), are anything but ARP studs that strong? and then only their top of the line ones. I've not had any issue with head gaskets blowing when installed and torqued correctly to 45.
« Last Edit: March 17, 2019, 11:47:01 AM by MiniDave »
1989 Cooper Racing Green
2009 Clubman S
2004 Audi Allroad 2.7 TT

Offline bikewiz

Re: Head gasket replacement
« Reply #4 on: March 17, 2019, 01:15:34 PM »
Not to side track the original question, but I'm curious as to what the ARP lube is. Are they saying the torque with the stud lubed only, not dry? As Dave says almost every torque value I've seen is dry, the Pocket Ref has a chart with percentage reduction when the threads are lubed with various substances. With that line of reasoning a dry ARP stud would actually have an even higher torque?

Offline tmsmini

Re: Head gasket replacement
« Reply #5 on: March 17, 2019, 08:10:33 PM »
I am not sure, but they have a seven page document to try to prove their point:
https://arp-bolts.com/p/arpultratorque.php

Looks like advertising/marketing stuff to me

I have just followed what the engine builder has told me in the past.

Offline MiniDave

Re: Head gasket replacement
« Reply #6 on: March 17, 2019, 08:37:02 PM »
Yes but I think that lube is for bolts that are supposed to stretch - one time use bolts.

I always learned to do them clean and dry, at least on these older engines.
1989 Cooper Racing Green
2009 Clubman S
2004 Audi Allroad 2.7 TT