Sealing 3.2L Cylinders with 3.0 Heads

[TomCounihan]

Hi Folks,

In one of Wayne's tech articles - he mentions the 3.2 cylinder is interchangeable with 3.0L cylinders, but offers the caviate that the 3.0 requires a gasket between cylinder and head and the 3.2 doesn't. The 3.2 cylinder has a slight slope, the 3.0 flat with a groove for gasket. Then suggests this difference is over-comable but goes no further.
In addition, I'm struggling to find the differences in the mating surface of the heads also - are both flat neutral, or does the 3.2 head have an inverse slope?

I've done a lot of digging here, maybe my search terms are wrong, But I would be hugely appreciative if folks could direct me on best practice to mate these parts with proper seal.

Warm Regards
Tom.

[Flat6pac]

The heads are basically interchangeable
Torque value changes from 25#ft to 15#ft+90 degrees sweep,
The head intakes are different heights so the reason for the double gaskets and insulator.
Bruce

[TomCounihan]

Thank you Bruce for the quick reply. Hugely appreciated!
Some clarifying questions if I may

Originally Posted by Flat6pac

The heads are basically interchangeable
Torque value changes from 25#ft to 15#ft+90 degrees sweep,

So metal to metal and torque as you recommended. Any sealant?
I'd be curious to know the theory behind the change in approach to Torque approach - can you enlighten me please?

Originally Posted by Flat6pac

The head intakes are different heights so the reason for the double gaskets and insulator.

Can you expand a little more on this sentence - not sure what the guidance is here?
It reads like an extra consideration I should factor in - but gaskets for where (cam housing?) and insulators I'm not sure what that is.

I re-read what I originally wrote and figured it could be read two ways - for clarity:
I have a 911 SC 3.0L 1978 - just in case my starting point may have been confusing. So its a basic 3.0 build with 3.2 cylinders sandwiched between the 3.0 case and 3.0 heads.
If I were to add that I'll either (a) use a stock Mahle 3.0 Piston or (b) go with something like a JE Piston - does that help color the job at hand? Does it make any difference to your reply?


Warm Regards
tom.

[dannobee]

Double gaskets and insulator sandwiched between the intake manifold and the head on the 3.2L.

[Eagledriver]

You don’t have to make any changes. The cylinders are compatible with your heads. Just no CE ring on the 3.2 cylinders. No sealant. It’s a good idea to have your heads resurfaced to ensure a good seal.

-Andy

[HaroldMHedge]

This thread should answer your question on using 3.2 cylinders in a 3.0 engine.

3.2 cylinders vs 3.0 sc cylinders?

Originally Posted by crashmy911

Why does my engine builder want me to use 3.2 cylinders in my 3.0 engine. They are both 95mm just want to know why?

[TomCounihan]

Great thread. One detail missing for me however - the torque.

Would I be correct in saying - for completeness - the permutations and torque values areas follows:


3.0 Case <-> 3.2 Cylinder <-> no gasket <-> 3.0 Heads = 25#ft (my config)
3.2 Case <-> 3.0 Cylinder <-> yes gasket <-> 3.2 Heads = 15#ft+90 degrees sweep

[Henry Schmidt]

Originally Posted by TomCounihan

Great thread. One detail missing for me however - the torque.

Would I be correct in saying - for completeness - the permutations and torque values areas follows:


3.0 Case <-> 3.2 Cylinder <-> no gasket <-> 3.0 Heads = 25#ft (my config)
3.2 Case <-> 3.0 Cylinder <-> yes gasket <-> 3.2 Heads = 15#ft+90 degrees sweep

Cylinder head torque is dependent upon your choice of head studs. Cylinders are irrelevant.
Porsche struggled with a way to make Dilavar head studs work. They failed miserably and yet, continued to try.

[HaroldMHedge]

Originally Posted by TomCounihan

Great thread. One detail missing for me however - the torque.

Would I be correct in saying - for completeness - the permutations and torque values areas follows:


3.0 Case <-> 3.2 Cylinder <-> no gasket <-> 3.0 Heads = 25#ft (my config)
3.2 Case <-> 3.0 Cylinder <-> yes gasket <-> 3.2 Heads = 15#ft+90 degrees sweep

I believe you have these backwards and the torque values are incorrect.

Check what Flat6pac (Bruce) says on the higher torque Post 2 of 3.2 cylinders vs 3.0 sc cylinders?.

Originally Posted by Flat6pac

Didn’t you just ask him...
The difference is the sealing systems, head gaskets
The 3.0 uses an aluminum seal ring to the head.
The 3.2 uses a tapered edge and more torque to seal the head.
A 3.2 short stroke cylinders need to be opened to 98mm which leaves little support for the 3.0 head gasket, the 3.2 cylinder is preferred for the application.
I’d still ask him

Bruce

TSB 8703 Tightening Procedure for Cylinder Heads, page 5, reviews torqueing of the Carrera heads, 911 cylinder heads up to 1983 Model Year and all 911 Turbos.



3.0 Case <-> 3.2 Cylinder <-> no gasket <-> 3.0 Heads
Step 1: Torque to 15 Nm (11 ft. lbs) in sequence.
Step 2: Torque nuts an additional 90 degrees.

I agree with Henry Schmidt that the Porsche head studs have issues.

I've used the Supertec Performance Cylinder Head Stud Kit on two different rebuilds and think they are the best solution.

Edit
After the initial posting, I realized I was guessing on which torque method had the higher final torque value. So to test it out, I used a M10 1.5 stud I torqued a nut to 11 ft lbs and then an additional 90 degrees using a deflector beam torque wrench. When 90 degrees was reached the beam torque wrench indicated about 85 ft lbs.

[TomCounihan]

Originally Posted by HaroldMHedge

I believe you have these backwards and the torque values are incorrect.

3.0 Case <-> 3.2 Cylinder <-> no gasket <-> 3.0 Heads
Step 1: Torque to 15 Nm (11 ft. lbs) in sequence.
Step 2: Torque nuts an additional 90 degrees.


Edit
After the initial posting, I realized I was guessing on which torque method had the higher final torque value. So to test it out, I used a M10 1.5 stud I torqued a nut to 11 ft lbs and then an additional 90 degrees using a deflector beam torque wrench. When 90 degrees was reached the beam torque wrench indicated about 85 ft lbs.

Thanks everyone - its clear now.
The penny dropped for me on this last email and my mis-reading was around the topic of 'higher torque' - I had originally assumed the 15Nm option to be less than the 25#ft option. That 90 deg sweep corrects that incorrect assumption I had.

Thanks Everyone. Case closed - excuse the pun.

Warm Regards
Tom.