How bad do Copper Head Gaskets leak on the street for a daily driver
 

I've researched conflicting information regarding copper head gaskets for an LT1 Gen II.

Cons:
- Always leak
- Different metals expand differently
- Over time the copper will electrolysize (sp?) to the aluminum heads

Pros:
- Ring the heads and they will never leak
- Lightly coat the copper head gasket with Hylomar

Your thoughts?

Thanks

never had a problem on our old 1800 hp rail

It may be possible to make them work, but what is the upside? If you have extreme cylinder pressures and a good hi-performance "conventional" gasket (eg. FelPro) isn't enough you can go with an MLS gasket. They are a little finicky, but nothing like copper. I'm am curious why you are thinking of copper? We use them on my buddys alcohol blown hemi due to strength considerations but that is a dry block. I have never seen them fully seal on a wet block - there is always some seepage. I guess if you did everything totally meticulously it might work.

Rich

The goal was to get the quench into the sweet spot 0.035 - 0.045. I'll be pulling my heads soon and check the deck height, but I understand stock decks on an LT1 typically are 0.025.

0.025" on the deck, plus
+ 0.016" on the copper head gasket, equals
0.041" for quench

I was only planning on pulling the heads. The best option would be to pull the block too and deck the bottom end to 0.00" and get a 0.039" Felpro. But I really don't want to strip the block... then I figure I'll upgrade the crank, pistons, rods... then I'll be out another $3,000.

This project was only a head & cam upgrade but it seems I may have to go further. ;)
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It's odd how asking questions brings up more questions but here's another:
Quench = Deck height + Gasket thickness

The idea is to get the valve within 0.035" - 0.045" to the piston head for turbulance. But there is no factor for milling the head. If a head is milled 0.010 or 0.060, the valve will be closer to the piston head in the latter. Right? As the deck of the head is slowly removed then that brings the valves closer to interference which should affect quench.

I thought the idea was to get the piston a certain distance to the combustion chamber.

And I don't think quench is critical enough to take the bottom end apart to deck the block.

I think you can use an Impala head gasket that is .028-.029" thick. It would get it a little closer to optimum quench.

I saw a Mr. Gasket for the LT1 that was a bit thinner.

MRG-5716 Mr. Gasket Ultra-Seal Head Gaskets
Head Gaskets, Ultra Seal, 4.100 in. Bore, .026 in. Compressed Thickness, Chevy, Small Block LT1, Pair

You can get MLS gaskets with any thickness center shim plate, just not sure if they make LT1 specific gaskets.


Kevin

SCE Titan ICS gaskets work perfectly on the street, never have seen them leak.

The Titan ICS has a bore of 4.060 and a compressed height of .043. That would be perfect once a block is decked. Without a decked block, the shortest reliable gasket seems to be the impala .029. There is a MLS at Summit Racing with an .026, but for .003 I would seem to be better with an Impala head gasket.

I searched Summit Racing for an Impala Head gasket and they do not list one for an LT1.

Also, I searched the Fel-Pro / Federal Mogul website and they didn't have any part numbers.

What is the P/N on the Impala gasket .029? Is it a GM part?

we used copper gaskets on our 3.8 turbo motor and made over 600hp athe wheels and never leaked. proper prep and good parts make the difference. i am using the mls gaskets with great success and love them for boosted apps. the key is proper prep with a very fine gasket surface.

Very fine gasket seal. So, I should tell the place that does my heads to be sure the surface is smooth.

I read on another website where he put 1200 grit compound paste on the head and moved it in a figure-8 over a flat steel surface. He claimed the end result was perfectly straight and near mirror finish. Is that overkill?

Probably, and anyway, how would you do that on the engine side?, and the average guy isn't going to have a big flat hard surface to be able to do that either.

I just used a light coat of Hylomar spray with my MLS head gaskets. Fills in any imperfections, never hardens, and won't leak.

be carefull some mls are dry fit only and have the coating on them. i believe the surface should be 160-240rms. do not quote me. your machinist or gasket maker would know. i use cometic by the way

The Cometics have a .001" coating of Viton on the top & bottom and nothing between the layers where the coolant can also seep from, but the Hylomar can be used with that, no problem. Some of the copper gaskets have a more generous .010" coating for less-than-perfect surfaces - I doubt anyone would feel the need to suppliment a .010" coating, but .001" has left a lot of guys with leaks.