Head Gaskets

[RinalStar93atx]

I am confused about this whole head gasket problem for 3.2 liter SHO's. They are in limited supply and thus very expensive. In a search I was doing on my own and from what I gathered I could just take a set of 3.0 heads and stick them on a 3.2 because they are interchangeable and have the exact same combustion chamber size. You would also get the benefit of having the mtx intake cams and be slightly better. I only ask because I recently came across a cheap 3.0 engine and scooped it up. So if you could put a 3.0 head on a 3.2 motor, then why not use a significantly cheaper 3.0 head gasket as well. I must be missing something somewhere. Someone please set the story straight.

 

[Mr Anonymous]

The head gasket difference has to do with the size of the bore of the cylinder in the block, not the combustion area on the head. 3.0 and 3.2 heads are basically identical. The minor differences in the heads are external. A 3.0 HG will not properly seal a 3.2 cylinder.

 

[Cobraii976]

I don't belive that! If the only diff is external then the 3.0 head gasket should fit the 3.2 and seal it. Seeing how I can use a stock 302 headgasket on an engine bored 60 over and still seal I don't see why the 3.0 would not seal on the 3.2. Anyone with me on this? Unless I'm totally missing something here and the SHO headgaskets fit perfectly to the size of the bore and leave no room for overbore..........Which I highly doubt. I'm guessing the biggest thing would be the 3.0 head gasket would bring the ring closer the bore on the 3.2

 

[revhardSHO]

I don't belive that! If the only diff is external then the 3.0 head gasket should fit the 3.2 and seal it. Seeing how I can use a stock 302 headgasket on an engine bored 60 over and still seal I don't see why the 3.0 would not seal on the 3.2. Anyone with me on this? Unless I'm totally missing something here and the SHO headgaskets fit perfectly to the size of the bore and leave no room for overbore..........Which I highly doubt. I'm guessing the biggest thing would be the 3.0 head gasket would bring the ring closer the bore on the 3.2

89mm vs. 92mm bore = you better believe it!

 

[Yamaha V6]

The SHO headgaskets are a precision piece, not something slapped together with gobs of clearance all around. The fire ring is pretty much right on the bore diameter on both of them.

I just sold my last set of 3.2L HG's, don't know if I can get any more (they're very expensive anyway), but midwest SHO has reported they're developing new ones for the V6 engines.

 

[shojuan]

I don't belive that! If the only diff is external then the 3.0 head gasket should fit the 3.2 and seal it.

So you think it's perfectly acceptable for the metal fire-ring on the 3.0 gasket to not be crushed between a 3.2 block and head but instead sticking several mm into the top of the cylinder?

 

[Mr Anonymous]

I don't belive that! <SNIP> Unless I'm totally missing something here and the SHO headgaskets fit perfectly to the size of the bore and leave no room for overbore..........<SNIP>

DING DING DING DING DING!!!

 

[RinalStar93atx]

You guys are giving seemingly conflicting information. This one thing you have seemed to agree on, a 3.0 head is definately directly interchangable to a 3.2 motor (except our exterior only mods).

Riddle me this, if the 3.0 head combustion chamber lines up perfectly with the bore on a 3.2 with out the head itself overhanging the top of the cylinder already then how is a gasket made for a 3.0 head going to perfectly fit a 3.0 head and thus it's combustion chamber but then overhang the top of the cylinder.

Potential issue that I foresee. The 3.0 head does overhang the top of 3.2 bore somewhat but this is ok because it is a solid hunk of metal and would not fall apart as a gasket might. And of course this all assures us that the pistons on these motors do not over rise above the decks surface. Otherwise we might have an issue with it hitting the 3.0 head that slightly hangs over the bore.

Maybe to really start clearing up some issues, someone with a 3.2 head gasket set could get together with someone who has a 3.0 head gasket, overlay them and see the differences and just tell us what you see.

 

[Yamaha V6]

Ok, I haven't taken measurements, but look at it this way:

3.0L
Piston Bore: 89mm
Cylinder Head Combustion Chamber dia: 89mm
Head Gasket Fire Ring Dia: 89mm

3.2L
Piston Bore: 92mm
Cylinder Head Combustion Chamber dia: 89mm
Head Gasket Fire Ring ID: 92mm

(The ring dia. is probably SLIGHTLY larger than 89mm, so when it's crushed, it extends inward to a finished dia. of 89mm).

If the fire ring on the head gasket is too small, the compression & combustion would blow through / by it, into the soft gasket material area, and blow out the gasket.

The cylinder head combustion chamber area diameter doesn't matter - go smaller than the piston (providing the piston choice is a flat-top, etc. & not domed to match the combustion chamber perfectly), it doesn't matter. You're looking at 1.5mm of flat cylinder head surface that extends over the fire ring & over the piston. Since the SHO piston is flat topped with recesses for the valves, and the valves, you're not into anything that's going to hurt the engine any - there's no water passages, etc that are going to be exposed, etc.

 

[Yamaha V6]

To answer your question about the HG comparison, I have. The 3.2L has an ID notch in it, on the outside. Aside from the fire ring diameter being larger as already mentioned, THAT'S IT. No other differences. The one KEY difference is the one that matters - the ring diameter is larger.

Assemble your engine with the 3.0L HG's, and let us know what happens at startup, at 100 miles, at 1000 miles, at 5000 miles & at 25000 miles. Personally, I think at startup & break-in up to the 100 miles, you're going to be blowing it out.

 

[AREA 91]

I have both 3.0 and 3.2 head gaskets. I overlaid them and can tell you that switching head gaskets is a no, no.

 

[RinalStar93atx]

Thanks Fred, that description sure well seals the deal on that one. Thanks all for entertaining my question. Don't worry I am not going to be doing head gaskets on my SHO anytime soon it only has 85k on it. By the way Fred, I should be getting it back by the end of the week from Ron's Automotive. I talked to him on saturday and he said that it should be a pretty beefy trans. Ill be sure to post how it is when i get it back. Thanks again.