can heads still lift under load without detonating?

[Fast4Ward]

wondering if say 10-15 lbs of boost would lift the head with zero knock. thnx.

 

[TurboDave]

Heads don't lift.
Head gaskets will blow out under certain conditions, too much boost for the octane available, too lean a mixture, etc.

But heads don't lift. Been hearing that term a lot lately on this board and can't for the life of me understand how or why is started lately.

 

[theCATman]

TurboDave...... I've wondered the same thing.

Can high boost (say 24+ PSI), without any detonation, blowout a head gasket?

 

[qwknuf6 jr]

Cyl heads DO lift under cyl presure even without detonation .
Would not normally cause a blown head gasket , with normal cyl presures , but the heads lift , gaskets scrub , ect ect ,
More head bolts , stiffer/thicker cyl heads will keep head lifting to a min.


Mark

 

[LOT]

Then maybe you can explain why

Heads don't lift.
Head gaskets will blow out under certain conditions, too much boost for the octane available, too lean a mixture, etc.

But heads don't lift. Been hearing that term a lot lately on this board and can't for the life of me understand how or why is started lately.

The fire ring is still intact but the tell tell signs of grooves in the graphite (detonation) behind the fire ring is present. How is the fire getting past the fire ring? Youv'e got the head pulled flat against the fire ring with 75-80 ft. lbs. or torque. I've seen more than one that way. Gasket is not blown but the graphite is being blown away --How?

 

[BlownV6]

Heads don't lift.
Head gaskets will blow out under certain conditions, too much boost for the octane available, too lean a mixture, etc.

But heads don't lift. Been hearing that term a lot lately on this board and can't for the life of me understand how or why is started lately.

Sorry Dave but I strongly disagree!! Heads do lift!! If the head bolt/studs in use are not of sufficent material and torqued to an adequate stretch value to withstand the cylinder pressure put against them they will stretch enough (lifting the head) that the gasket will leak and or move because of the lack of clamping force on the gasket. To the point I put 1/2" studs in my motor over the winter and have been over 60# of boost with no issues so far as far as head gasket seal. Last year with the 7/16 studs I couldnt make over 3-5 passes without torching a gasket.

So that raises the question , what kind of head bolts/studs are you using??
Mike

 

[TurboDave]

Sorry Dave but I strongly disagree!! Heads do lift!! If the head bolt/studs in use are not of sufficent material and torqued to an adequate stretch value to withstand the cylinder pressure put against them they will stretch enough (lifting the head) that the gasket will leak and or move because of the lack of clamping force on the gasket. To the point I put 1/2" studs in my motor over the winter and have been over 60# of boost with no issues so far as far as head gasket seal. Last year with the 7/16 studs I couldnt make over 3-5 passes without torching a gasket.

So that raises the question , what kind of head bolts/studs are you using??
Mike

That's not fair. You run Many times more boost than any of use even can fathom in our motors.
I still contend that in a "normal" turbo Buick motor NOT running torque to yield bolts, that we don't generate enough cylinder pressures to "lift" the heads. Most of us that have had the heads off for one reason or another will be running ARP fasteners as a replacement anyway, and with them properly torqued it shouldn't happen.

My heads don't lift. I run 21.5# of boost in 1st and 2nd with 21.5 deg of WOT timing. And 19.5-20# of boost in 3rd and 4th, with 19 deg of WOT timing.
No head lifting issues here, and MORE importantly no detonation.

I contend that 99% of all head gasket issues suffered here on the board are blown head gaskets, and that virtually all of those due to detonation, either as cummulative damage over time or a huge amount in short periods. Mostly a result of operator error (AKA bad tuning) or equipment failures that cause said detonation.

 

[KL Mallender]

Heads lifting or Gasket blowing?

It may be of interest to those still chasing the seal,
I believe the Power Source book stated that factory cast iron "yeilded" at like 30,000 psi and the higher nickle content blocks at 36,000 psi or something like that.

A 3.8 bore represents a 11.35 sq in surface area: /30,000 = 2643 psi cyl pressure
A 4.1 bore represents a 12.50 sq in surface area: /30,000 = 2400 psi cyl pressure

Approach that cylinder pressure and you relieve the clamping force of the cast iron in the non-reinforced areas and the gasket material is blown out of further duty,

Now returning to your regularly scheduled programing...............

Kevin.

 

[BlownV6]

Ok Im sorry for using mine as any kind of example in this situation. I was just pointing out that given a certain set of conditions that may provide suspect cylinder pressures this is a possibility. My question about what head bolts was directed at fast4ward. I will step off now!!! Mike

 

[LOT]

I agree with you

Ok Im sorry for using mine as any kind of example in this situation. I was just pointing out that given a certain set of conditions that may provide suspect cylinder pressures this is a possibility. My question about what head bolts was directed at fast4ward. I will step off now!!! Mike

@ least you tried.

 

[turboc87gn]

Ok so how much cylinder pressure will a tb motor see at say 25lbs of boost
?

 

[qwknuf6 jr]

My heads don't lift.

This is incorrect

Mark

 

[TurboDave]

This is incorrect

Mark

And you know this how???

 

[Cme2fly]

And you know this how???

Heads can lift without detonation. I have data logs that indicate zero knock and head gaskets are in pieces. My knock sensor works just fine. Boost average was 29lbs. 10.7 on the WB.

 

[TurboDave]

Heads can lift without detonation. I have data logs that indicate zero knock and head gaskets are in pieces. My knock sensor works just fine. Boost average was 29lbs. 10.7 on the WB.

I don't remember saying I run 29# of boost. So "quoting" my post and implying that your heads lift at 29 isn't a fair comparison either.

 

[qwknuf6 jr]

And you know this how???

Since you first posted stating that cyl heads do not lift , I will let you explain YOUR conclusions

 

[Cme2fly]

Heads don't lift.
Head gaskets will blow out under certain conditions, too much boost for the octane available, too lean a mixture, etc.

But heads don't lift. Been hearing that term a lot lately on this board and can't for the life of me understand how or why is started lately.

This was your statement..I have never lifted a head at 20lbs to be fair. My boost guage starts at 20lbs.

 

[SloGN]

The fire ring is still intact but the tell tell signs of grooves in the graphite (detonation) behind the fire ring is present. How is the fire getting past the fire ring? Youv'e got the head pulled flat against the fire ring with 75-80 ft. lbs. or torque. I've seen more than one that way. Gasket is not blown but the graphite is being blown away --How?

i have seen this before myself. I do believe that the heads do lift in some way or another. I generally see this happen on the center cylinder. I think that due to the 8 bolts per heads allow the head to flex and lift in that area.

On the older engine they had a problem with gaskets failing near the front and rear of the head near the oblong water port. the update to that was adding a bridge in that port to help stiffen up the head. This was done in the 84 and newer engines/heads. maybe it started on the even fire engines i can't remember.

 

[LOT]

To answer your ?

wondering if say 10-15 lbs of boost would lift the head with zero knock. thnx.

If everything is RIGHT---NO

 

[TurboDave]

Since you first posted stating that cyl heads do not lift , I will let you explain YOUR conclusions

No, I said, my heads don't lift at my tune and boost levels. You said, "that's incorrect". My question again is, how do you know this???