3500 Graphite Head Gaskets

[mfuller]

You'll be fine.
While I might not be boosted, I'm running 3400 graphite HGs on my 1mm (.040") overbored 3400.

[3400-95-Modified]

OEM 04+ gaskets are graphite.

And I think with you studding the heads that will help prevent some failure of the gaskets. All the failures I had with my felpro's I was using stock stretch type head bolts.

[ForcedFirebird]

Yes, you will be safe. I built loner's turbo kit and he had your same combination (Ben's heads and cam) and he saw a couple boost spikes to 21psi, but ran it 12psi at the track. Ran a 12.9@113

[boscov6]

So based on all info gathered, 3400 block bored 0.030 with 3500 heads and boosted to 12 pounds MAX. Studded, I should be able to use the 3400 graphite gaskets and this will not affect the combustion side of the head?. Are the OEM gaskets graphite??. Sorry to be a pain but i want to get this right before I stud it and boost it. I have a ton in this thing and for a matter of a set of gaskets toi make it all go boom, I would rather ask as many questions as possible. The Cometics would have been a no brainer but I have a fresh bored bottom and everything ready to go except for studs, gaskets and injectors. I kinda want to drop this baby in the hole and see what it will do .

Thank you

[3400-95-Modified]

I guess what I am saying in a lot of words is that GM allows you to rebuild the motor and use stock gaskets lol.

They know its gotta happen some time... LOL

[ForcedFirebird]

The 3.4 and 3400 have a 3.622" bore and 3.75" gaskets. It would take more than .100" of over bore to breach the head gaskets. The 3500 has a 3.8" bore on the head gasket, again allowing almost a .100" overbore. Since most blocks are not designed to bore more than .080" over, the stock gaskets don't need to be bigger than .100" over stock bore to allow several rebuilds on stock gaskets.

I guess what I am saying in a lot of words is that GM allows you to rebuild the motor and use stock gaskets lol.

[3400-95-Modified]

Not sure... I have never used the HD aka Severe duty ones, and this will be my first year really abusing a set of GM ones with my nitrous, the standard Fel-Pro's didn't survive well on my last try. I've heard on other boards that some J-body guys are pushing 8+ psi with OEM graphite gaskets and they are holding up just fine. But as noted, I have not heard a word on the SD felpro ones. Maybe Ben has some more info on these since he has a "heavy duty" option listed in his store, granted its a kit though.

Call me crazy, but I cant find Severe Duty felpro gaskets even listed for the 3400's anymore... just the 3.1's

http://www.felpro-only.com/prod_apps/Fel-Pro_PTSD.pdf

Sounds like your best bet is OEM Graphite ones.

[boscov6]

Stock 3400 bore is 3.6, so 30 over should measure up at 3.630 I don't see how a stock 3400 head gasket wouldn't work, those are already .130 larger than the stock bore. Stock 3400 head gaskets should measure up at 3.730. The 3.720 bore you are stating for a 3500 would only be true if you were buying the Cometic 3500 MLS gaskets which do not exist anymore due to the screw up. As noted stock gaskets are at least .130 larger than stock bore.

And as I've always stated before I would use the correct head gasket for the block your using, as long as the fire ring does not overlap into the combustion chamber, and on a 3500 head, the 3400 gasket just fits around it so it will seal.

I'm running 3400 head gaskets on my stock 3400 bottom end with 3500 heads.

According to measurements I've seen, the stock 3500 bore is 3.7 so if I know someone who is using a stock 3400 head gasket on a stock bore 3500, then your 30 over is no where near larger than that bore.

I have not had much luck with Fel-Pro gaskets on my motors, but I was not using the HD ones which are supposedly graphite. I've now decided to stick with the OEM GM ones, 05 3400 ones to be exact.

This is awsome information, THANK YOU. This is a boosted application. Do you think the stock graphite GM gaskets are the way to go as well, or do you think that the Fel-Pro HD would be better under 8-12 pounds with studded heads?

I appreciate your input

[boscov6]

no fel-pro is not graphite. its just that i thought they would be good a for a non-boosted app.

Sorry, kinda left out that its a boosted app. 8-12 pounds

[3400-95-Modified]

Stock 3400 bore is 3.6, so 30 over should measure up at 3.630 I don't see how a stock 3400 head gasket wouldn't work, those are already .130 larger than the stock bore. Stock 3400 head gaskets should measure up at 3.730. The 3.720 bore you are stating for a 3500 would only be true if you were buying the Cometic 3500 MLS gaskets which do not exist anymore due to the screw up. As noted stock gaskets are at least .130 larger than stock bore.

And as I've always stated before I would use the correct head gasket for the block your using, as long as the fire ring does not overlap into the combustion chamber, and on a 3500 head, the 3400 gasket just fits around it so it will seal.

I'm running 3400 head gaskets on my stock 3400 bottom end with 3500 heads.

According to measurements I've seen, the stock 3500 bore is 3.7 so if I know someone who is using a stock 3400 head gasket on a stock bore 3500, then your 30 over is no where near larger than that bore.

I have not had much luck with Fel-Pro gaskets on my motors, but I was not using the HD ones which are supposedly graphite. I've now decided to stick with the OEM GM ones, 05 3400 ones to be exact.

[mickaz]

no fel-pro is not graphite. its just that i thought they would be good a for a non-boosted app.

[boscov6]

3400 Graphite head gaskets will fit a 3500 and actually bring the bore down to the size that the 3500 MLS gaskets were going to use. Eric aka Asylum Motorsports, is using a set of 05 graphite 3400 gaskets on his 3500 right now since he found the same thing as you... no chance to get just a set of head-gaskets for the 3500.

I am running a 3400 block bored .030 with 3500 heads. I need the 3.720 bore of a 3500 head gasket not the 3.642 bore of a 3400 head gasket. Thats the way I understand it

so the fel-pro are junk?

I am unaware of Fel Pro packaging just the 3500 graphite head gasket. Gotta part #??

Thanks for the feedback

[mickaz]

so the fel-pro are junk?

[3400-95-Modified]

3400 Graphite head gaskets will fit a 3500 and actually bring the bore down to the size that the 3500 MLS gaskets were going to use. Eric aka Asylum Motorsports, is using a set of 05 graphite 3400 gaskets on his 3500 right now since he found the same thing as you... no chance to get just a set of head-gaskets for the 3500.

[boscov6]

I havnt been able to find just the 3500 head gaskets. Only ones in a kit with a shit load of stuff I dont need. Anyone have a set they are willing to sell or trade? I have a 3400 UIM/LIM(plastic) set with valve seals seats bunch of O rings and the like, missing the oil pan and timing cover gaskets plus cash????
Thanks