View Poll Results: What issues have you had with your headgaskets?
Due to detonation?
14
60.87%
Due to headlift?
3
13.04%
Due to too much boost?
5
21.74%
Due to uneven block/head surfaces?
1
4.35%
Voters: 23. You may not vote on this poll
HEAD GASKET POLL???
07-13-2010, 09:10 AM
#16
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In reality I want a core sample of what issues all or any of the guys have had, what symptoms, what applications, what solutions. Adam is quite right in saying that in many cases it's what we think is going on without any absolute proof. We have felt it might be headlift based on what our headgaskets have looked like, plus no sign of detonation on the pistons or head...but I don't have my camera in there capturing proof of this happening. Hmm, we have some very small cameras, do you think it would be at all visible from the outside? Crazy idea...
07-13-2010, 09:46 AM
#18
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What do you see that has you under the wild hypothesis of the head lifting?
the science is heavily stacked against the head lifting.
the studs really don't stretch. What does happen if you look at the expansion rates of the materials is as it all gets hot the heads grows much more than the studs this compresses the gasket and distort's the head and block and then you have a gasket failure ..Formula V solved head gasket failure by necking down there head studs ...
I don't n think the seemingly off topic posts are really off topic at all I think its interesting that so often a tuning failure can be found .
I'd like to hear weather the careful tuners like john chris mike really think the head gasket is a trouble some weak link ...
the science is heavily stacked against the head lifting.
the studs really don't stretch. What does happen if you look at the expansion rates of the materials is as it all gets hot the heads grows much more than the studs this compresses the gasket and distort's the head and block and then you have a gasket failure ..Formula V solved head gasket failure by necking down there head studs ...
I don't n think the seemingly off topic posts are really off topic at all I think its interesting that so often a tuning failure can be found .
I'd like to hear weather the careful tuners like john chris mike really think the head gasket is a trouble some weak link ...
07-13-2010, 09:59 AM
#19
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[QUOTE=gt37vgt;7729163]Head lift ??? that is as unproven and theoretical as "hawking radiation"
QUOTE]
No longer theoretical, officially disproven.
But our cars rarely follow the laws of physics. We need string theory to explain most of the issues with our cars. LOL
Actually, most "causes" all lead back to heat as the root. No such thing as detonation/too much boost; just too much heat that lead to pre ignition.
QUOTE]
No longer theoretical, officially disproven.
But our cars rarely follow the laws of physics. We need string theory to explain most of the issues with our cars. LOL
Actually, most "causes" all lead back to heat as the root. No such thing as detonation/too much boost; just too much heat that lead to pre ignition.
"string theory" was the other phrase i was considering when writing that
07-13-2010, 11:58 AM
#21
Three Wheelin'
My car still has the stock HG after 22 years and 106k miles. Is it a smart idea to go ahead and change it before adding power? Maybe go ahead and drop the money for o-ringing the head and using a widefire gasket? The ultimate goal down the road will be a GT3076R or similar turbo, but that won't be for several years. In the meantime I'd be running 15-18psi on the stock K26/8, aiming for ~300RWHP.
07-13-2010, 04:23 PM
#23
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07-13-2010, 04:41 PM
#25
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My car still has the stock HG after 22 years and 106k miles. Is it a smart idea to go ahead and change it before adding power? Maybe go ahead and drop the money for o-ringing the head and using a widefire gasket? The ultimate goal down the road will be a GT3076R or similar turbo, but that won't be for several years. In the meantime I'd be running 15-18psi on the stock K26/8, aiming for ~300RWHP.
07-13-2010, 04:50 PM
#26
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But does that mean for sure it was due to head lift or the seal being comprimised via some other way other than head lift? i.e. the gasket itself, det, not 100% true deck, etc. Meaning, the tolerances at 20 psi are not as much of an issue as they are at 30psi.
07-13-2010, 09:35 PM
#27
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or does it simply mean it boiled a heap of water in the head being the hardest thermally loaded 944 head ever ??
So Chris you believe the head is lifting ? but shot down my M14 head stud thread in flames of cleverness ?
So Chris you believe the head is lifting ? but shot down my M14 head stud thread in flames of cleverness ?
07-14-2010, 04:09 AM
#28
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I know Tool and John had spoken about headlift in the past. Be nice to know their findings.
07-14-2010, 09:44 AM
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Yes!
Head lift is not cause (directly) by high boost, but by high cylinder pressures. High cylinder pressures are usually caused by detonation but can also be cause by very aggressive ignition advance (which usually causes detonation unless you are running some serious fuel).
A couple of notes about the video – according to Jim (Tool) he drove the car around after that video with no problems, if the head gasket had really let go that would not happen, if it was head lift for a short period then the head could reseat after lifting….I would not recommend doing that often!
The thermal loading on Tool’s head is nothing compared to a heat soaked endurance racing engine!
The coolant is puked out so fast/hard that I don’t think that localized overheating is a cause – if it were overheating it would not stop until well after the pull was complete. Also notice that he puking starts very after the boost comes on hard.
Tool did revise his timing and made more HP without puking coolant….more thermal load and no leaks!
maybe Jim could have used the 14mm studs….I don’t consider his 600 rwhp project to be ‘normal’! I could amend my comments on the 14mm head studs to say that 99.9% of 951’s won’t benefit from them…but that .1% that is running 110 octane, massive advance and high boost might just need them in order to complete a dyno pull!
I should include a disclaimer in my sig (maybe if I could do it in 2point type!) Just about all my views / opinions are based on the fact that I like road racing….not drag racing, not dyno numbers, not car shows…just road racing.
Head lift is not cause (directly) by high boost, but by high cylinder pressures. High cylinder pressures are usually caused by detonation but can also be cause by very aggressive ignition advance (which usually causes detonation unless you are running some serious fuel).
A couple of notes about the video – according to Jim (Tool) he drove the car around after that video with no problems, if the head gasket had really let go that would not happen, if it was head lift for a short period then the head could reseat after lifting….I would not recommend doing that often!
The coolant is puked out so fast/hard that I don’t think that localized overheating is a cause – if it were overheating it would not stop until well after the pull was complete. Also notice that he puking starts very after the boost comes on hard.
Tool did revise his timing and made more HP without puking coolant….more thermal load and no leaks!
maybe Jim could have used the 14mm studs….I don’t consider his 600 rwhp project to be ‘normal’! I could amend my comments on the 14mm head studs to say that 99.9% of 951’s won’t benefit from them…but that .1% that is running 110 octane, massive advance and high boost might just need them in order to complete a dyno pull! I should include a disclaimer in my sig (maybe if I could do it in 2point type!) Just about all my views / opinions are based on the fact that I like road racing….not drag racing, not dyno numbers, not car shows…just road racing.