Greg88

Hey guys,

I am trying to find a complete fel-pro gasket kit for my LT1. I don't know if I am not searching it right but I can't seem to find the right part number, specifically for a 355. Can anyone guide me in the correct direction?

Thanks,
Greg

Injuneer

You won't find a specific 355 kit. The only difference between a 350 and a 355 is the cylinder bore. The Fel Pro 1074 or 9966 PT head gaskets both have a 9.125" bore, will work with 4.000" or 4.030" cylinder bore.

Chimera96

Greg

You would need to buy specific gasket/seals vs a all inclusive kit.

I use FelPro which you can search for the various part #'s

pan gasket (blue in color)
Intake manifold, I like the "printo" series of FelPro
Timing Cover gasket/seal kit (about $12)
head gasket (depending on what thickness you want). The felpro 1074 (one I use) is .039 thick. Mr Gasket one is .029 thick. a stock GM aluminum head one is .050 IIRC). head gasket thickness is part of the equation for quench and compression ratio you need to determine what is best for your build based on pistons, block machining (piston +/- "x" in/out of the hole) and head work.

Greg88

Ok, I'll have a look into that! I guess maybe just purchasing single
Gaskets would be more work but then you know you have the correct one. I'll look into the kits as I am unsure what exact gasket I have at this point and want to keep the same thickness!

Chimera96

you really won't know what head gasket the PO put on until you pull the heads. Many went with the .029 thick one if just doing a head swap.

Also you can buy LT1 gasket kits but the "kit" may not have the head gasket thickness you want and they don't include "all" the gaskets & seals and some are off brand gaskets

That is why most just buy them individually. FelPro timing cover kit has several gaskets and seals needed for the timing cover. Rear main seals, egr, oil filter adapter, etc are all sold individually and most auto part stores carry them. I order the intake (FelPro "printle" and the FelPro .039 (or other brand/thickness) head gaskets from Summit.

Greg88

Is there a thread or a list that I can get to show me exactly what gaskets are needed for a complete engine? My engine is leaking oil like crazy so I was going to pull it and get someone to go over it! The oil is leaking bad on my exhaust ... assuming it's the rear main gasket.

Chimera96

No I don't have a list...

If you are pulling the motor you should have a Service Book like Haynes or the Factory Service Books but basically you need to have enough of a understanding of the motor to know what seals & gaskets you need.

One link for very good reference 411 is:

4th Gen LT1 F-Body Tech Aids

FelPro makes a variety of gasket/seal "combos" but when it comes to head gaskets I don't see "what" thickness or even what specific part # the head gasket in those "combo kits" is. They say fit camaro, roadmaster....one has iron heads the other aluminum. Both had different head gasket thickness. Impala/Roadmasters had .029 and the F-Body had aluminum heads with .050. You would likely want the .029 ones with your LE heads so you would want to confirm what thickness does come with any gasket kit.

For example:

Fel-Pro Gasket Sets | JEGS

Greg88

So I got my heads off. They are MLS gaskets, not sure if that means they are 0.039 or 0.021? The guy taking my engine apart said the heads were very very tight. He figured north of 100 lb/ft. Anyways, he is wondering what volume is? Unfortunately I can't help
Him. Does anyone else know this number?

Also he said the intake bolts were all loose because the threads were all stripped on the heads so they will need to be heli coiled.

And the crank bolt is stripped somehow. Would this HOPEFULLY be the bolt and not the crank??

Thanks for the help!

Injuneer

Did he try measuring the thickness of the old gaskets? Should provide rough indication.

Are you looking for combustion chamber cc's? Has to be measured, using a burette. There is some variability in factory cc's (often quoted as 54cc) and is there any evidence the heads may have been decked at some point? Only way to be sure is to measure.

Greg88

He measured them and are around .032 to .036. Heads are 60cc

Injuneer

With 60cc chambers, what was the calculated static compression ratio? Are the piston flat tops? Measuring the deck height, and calculating the CR should tell you which way to go with gasket thickness.

Greg88

From what I can calculate it's 10.25 currently.

Bore: 4.030
Stroke: 3.48
Head gasket: 0.035
Deck height: 0.030 (at top) almost 0.05 (at bottom)
Piston Volume CC - from what I gather they have a 5cc valve clearance relief. (Dished)
Combustion chamber Volume - I was told 60. My buddy did a quick check on one of the chambers and he said it was like 62-63. But I used 60 for these purposes.


They heads are pitted a bit from using dexcool. I might send them to a machine shop and get them cleaned up.

Any suggestions on finished # on CC? And then what gasket to use? Little disappointed with 10.2:1 .... and I was being generous!

Injuneer

Did you build this engine, or did you buy it from someone who previously built and ran it? AFR doesn't currently make a 190cc LT1 head. I think they did at least 15 years ago, if not more. AFR also offers their LT1 heads in both 65cc and 54cc. Sounds like someone started w/ the 65cc heads. Was the engine ever set up for forced induction? That is the only reason for using a 65cc head on an LT1.

You can only cut the heads so much, and then you get into trouble w/ the fit up of the intake manifold. Wonder if that's the cause of the stripped intake bolt threads?

Greg88

I bought the engine entirely from someone else. They started with a 65CC head and decked or milled them down to 60cc. The engine was never built for forced induction (as far as I know) I think maybe the previous owner scored a good deal on the heads and then just machined them down?

I don't know if that's the reason the threads are pulling out? To much cyclinder pressure?

Can you explain the "fit up" of the intake manifold!

Injuneer

When you mill the heads, it lowers the intake ports and the bolt holes. Now the manifold, which is wedged into the "V" made by the heads, doesn't seat correctly, with the ports and the bolt holes slightly above the matching items on the heads. You can get away with a small cut, but a thick cut can require that the faces of the intake manifolds are machined down to let the manifold sit lower in the "V". Nothing to do with cylinder pressure, strictly geometry.

Not sure how much they would have to take off the AFR's to reduce the chambers to 60cc. But thinner head gaskets also drop the heads down, increasing intake manifold misalignment. The milling plus thinner gasket, plus anything that was taken off the block surfaces are additive.

A buddy of mine, with nothing but pockets full of money, and a desire to go fast, bought a brand new 97 SS M6 convertible. Immediately started making serious mods. First choice of after market heads was a set of the AFR's. They were not very good. His set did have the 54cc chambers, but (according to a highly experienced shop) the way AFR decreased the cc's was to simply thicken up the chamber domes, and in doing so, shrouding the spark plug.

He tossed the AFR's almost immediately. Settled on a set of Lingenfelter CNC'd stock LT1 heads (this is late 1990's, when there was no LE or AI porting stock heads, just Craig Gallant). Made 900 flywheel HP with those (Vortech S/C 383 by that time), then found a set of the elusive Canfield heads, and pushed it to 1,125HP.

The milled 65's should not have the problem with the shrouded plugs, and maybe that is why someone chose to start with them and mill them, but it's still giving up too much CR.