X-post - Heads are lifting at 1.4 bar of boost. What to do now? (Photos)

[Tippy]

Eating crow right now, as I thought lifting heads was a figment of ones imagination. Well, I have proof now.

Appears my heads are lifting from 1.4 bar of boost. Did not see this at 1.2 bar on 1st rebuild.

Been reading that flame rings aren't a guarantee??

If flame rings aren't a cure, what is?

Also, what is happening around the piston crowns?

[cliyde]

WOW, tippy! That's some serious boost'n. What compression are you running? Any potential the oil residual build up would cause compression to be higher than expected? Are you using a oil/air separator from crank case pressures and or recirculating back to intake? Curious where the build up is coming from.

[Tippy]

Originally Posted by cliyde

WOW, tippy! That's some serious boost'n. What compression are you running? Any potential the oil residual build up would cause compression to be higher than expected? Are you using a oil/air separator from crank case pressures and or recirculating back to intake? Curious where the build up is coming from.

7.5:1 CR. No oil/air separator, just normal system from the 3.2.

[JFairman]

We can see that you have the good 993 dilivar head studs. What did you torque them to before?
I've been told by a top Porsche engine builder you can torque those to 36 ft lbs in race motors and they won't break. I've never tried that with dilivar head studs but if you don't want to buy new ARP, Supertech, or Raceware head studs and torque them to 38ft lbs for ARP or whatever the others are supposed to be if they are used then I would try those 993 studs at 36 ft lbs with thread lubricant on the studs, nuts, and washer contact surfaces.
Good luck with it

[cliyde]

FWIW, I used the stock 930 oil/air separator and it was quite effective. May help with the excess oil ingestion, coating on pistons, and hemisphere area.

Tucked in on the right side, behind BOV. Hose leading from filler neck


Part #9

Originally Posted by Tippy

7.5:1 CR. No oil/air separator, just normal system from the 3.2.

[1979-930]

That is diesel engine cylinder pressure, almost 18:1, and the older 7.3L engines had head bounce issues when boosted to that level. As mentioned you need better studs that will resist the stretch. Can these engines be o-ring'd? I would think ARP 2000 studs and O-rings would hold up. If not you need to back down the boost.

Question. At what level to the stock rods and crankshaft become an issue with these engines?

[Tippy]

Originally Posted by JFairman

We can see that you have the good 993 dilivar head studs. What did you torque them to before?
I've been told by a top Porsche engine builder you can torque those to 36 ft lbs in race motors and they won't break. I've never tried that with dilivar head studs but if you don't want to buy new ARP, Supertech, or Raceware head studs and torque them to 38ft lbs for ARP or whatever the others are supposed to be if they are used then I would try those 993 studs at 36 ft lbs with thread lubricant on the studs, nuts, and washer contact surfaces.
Good luck with it

I torqued them to 3.2 specs, whatever that is?

Some given torque, then angle.

I did this dry, and remember they creaked a lot during torqueing. Sounded like they wanted to break any second!

I felt torque was well over 36ft/lbs!!

[JFairman]

Use some type of thread lube on them, or a drop or two of motor oil before tightening them.

[Tippy]

Originally Posted by JFairman

Use some type of thread lube on them, or a drop or two of motor oil before tightening them.

Yeah, that would have effected the run-on torque resulting in a lower overall torque.

[m42racer]

First off, head studs are not the problem. To expect the heads to seal at 1.4b manifold pressure without any sort of sealing system is your problem. Running pressures are more in the 200 -300b region. Thats what you are trying to seal.

Sure a better head stud will be better but it wont solve the problem. It will empty your wallet though. Better spent on a good sealing system. Call Performance Developments. They developed one years ago many have copied. Multi piece system that does work.

As for your question regarding the Pistons, best to look at the plugs. They will tell you what is going on inside the cylinder better than anything else.

[stownsen914]

Originally Posted by m42racer

Call Performance Developments. They developed one years ago many have copied. Multi piece system that does work.

Is that something different from ni-resist / fire rings?

[Tippy]

Originally Posted by stownsen914

Is that something different from ni-resist / fire rings?

Ditto

[stownsen914]

Found this from their web site Parts – performancedevelopments.com

"Sealing System – Head Gaskets multi ring sealing system for all 911, 930 and 993 engines. The dual ring system for the 996 and 997 Turbo engines use our proprietary Back up Ring along with custom Head Gaskets made especially for this system. A gas filled Garlock Ring is used to seal the Cylinder gases"

I wonder what that would look like on a 3.2 head.

[Tippy]

Originally Posted by m42racer

First off, head studs are not the problem. To expect the heads to seal at 1.4b manifold pressure without any sort of sealing system is your problem. Running pressures are more in the 200 -300b region. Thats what you are trying to seal.

Sure a better head stud will be better but it wont solve the problem. It will empty your wallet though. Better spent on a good sealing system. Call Performance Developments. They developed one years ago many have copied. Multi piece system that does work.

As for your question regarding the Pistons, best to look at the plugs. They will tell you what is going on inside the cylinder better than anything else.

Thanks for the source.

[stownsen914]

Originally Posted by Tippy

Thanks for the source.

No problem.

One thing just occurred to me - how big is your intercooler? I imagine it takes a pretty healthy sized one to keep temps in a reasonable range at 1.5+ bar.

[Tippy]

Originally Posted by stownsen914

No problem.

One thing just occurred to me - how big is your intercooler? I imagine it takes a pretty healthy sized one to keep temps in a reasonable range at 1.5+ bar.

It's a 3.5" core, 25" X 9". Treadstone states 1900CFM/1300HP.

It's make for V8 cars. I modified it.

[jsveb]

Crazy stuff

How about an aviation-style threaded cylinder-to-head.

I believe Capricorn/Perfectbore once made that.

[m42racer]

Ni-resist were stainless rings to stop the combustion from burning its way out. They floated in a groove. Didn't seal the gas pressure very well.

These are special Be Cu rings (multi) that are under different levels of crush. Best to call PD and get the full scope.

I remember they did lots of them back in the day.

[Porsche 935]

What made you pull it apart?

[Tippy]

Originally Posted by Porsche 935

What made you pull it apart?

Clutch started slipping. Then, I had oil leaks after about 100 miles after I rebuilt it the 1st time.

Figured, if I have it out, might as well reseal it.

Slid right off the slope....