2.4l Cylinder head CE ring/head gasket ID

[JKarow08]

Does anyone have a 2.4l CE ring laying around that they could check the ID on? I'm planning a 2.5l build with 86mm cylinders/pistons and I'm trying figure out if 2.7l heads will seal to 2.4l cylinders (overbored to 2.5l) with the chamfer on the 2.7 head combustion chamber. It looks like the OD on the chamfer is 89.2mm so if the CE ring ID is less than than it may not seal. Thanks in advance for the help!

-Josh

[JKarow08]

Nobody?

[PeteKz]

Send a PM to Henry Schmidt. He should know.

[Henry Schmidt]

The issue is not whether the CE ring will seal but with the late 2.7 head the chamfer will create a lip where the combustion will encounter a lip at the top of the cylinder.
Chmfer larger than the bore.
The Chamfer on the late 2.7 head is generally about 88mm (depending on who machined it last. Not all machine work/machinists are equal.
The early 2.7 (74, 2.7 RS) heads have no chamfer at the sealing surface and they are about 86mm.
The inside diameter of the CE groove in the AA 86 is 91mm.
That's all I have from memory. Others may have closer numbers..

[JKarow08]

Originally Posted by Henry Schmidt

The issue is not whether the CE ring will seal but with the late 2.7 head the chamfer will create a lip where the combustion will encounter a lip at the top of the cylinder.
Chmfer larger than the bore.
The Chamfer on the late 2.7 head is generally about 88mm (depending on who machined it last. Not all machine work/machinists are equal.
The early 2.7 (74, 2.7 RS) heads have no chamfer at the sealing surface and they are about 86mm.
The inside diameter of the CE groove in the AA 86 is 91mm.
That's all I have from memory. Others may have closer numbers..

Thanks SO much Henry! You are the first one that could shed some light on this. So it looks like early 2.7 heads would be perfect without additional matching being necessary, otherwise it is best to use 2.4 heads and have them chamfered. The heads I'm looking at have a 5-74 date but are chamfered, I'll have to have the seller measure them to see what the OD on the chamfer is. I'm assuming the attached pic are the later 2.7 heads?

[JKarow08]

As an FYI to everyone, 5-74 date 2.7s heads are indeed "late" 2.7 heads so they are a no-go for 86mm jugs unfortunately. The OD on the chamfer measured 88.81mm.

[kwikt 911]

[JKarow08]

Originally Posted by kwikt 911

Thanks!

[Henry Schmidt]

Originally Posted by kwikt 911

The important measurement is the groove cut in the cylinder not the ID of the CE ring. The CE ring dimensions can vary from manufacturer to manufacturer.

You were a gentleman to take the time to offer your measurement.
Cheers

[JKarow08]

Originally Posted by Henry Schmidt

The important measurement is the groove cut in the cylinder not the ID of the CE ring. The CE ring dimensions can vary from manufacturer to manufacturer.

You were a gentleman to take the time to offer your measurement.
Cheers

Interesting, I would have thought CE rings would have been machined to pretty exacting dimensions. The groove ID is what I was angling for, just assumed it would be more likely someone would have a CE ring easily accessible. With that said, it seems like John Walker also had a good point relating to 2.7 heads on 84/86mm bores...with an 89mm-ish head chamfer OD and a 91mm CE groove ID, that only leaves 1mm of inner sealing surface. I'm far from an expert, but I've read the inner sealing surface is what is most responsible for head sealing (CE ring is just for fluid), and I'd guess only 1mm of metal to metal seal is not sufficient, especially in higher compression builds. Thoughts?

And thank you both...gentlemen all around

[kwikt 911]

[kwikt 911]