I see Mr Gasket makes a .020 thick steel shim head gasket. I think it may be just the ticket for swapping 781's onto my 396. I plan on coating them well with copper coat before installing them. Any problem with using these on the street?

Rod,
GM used steel shim gaskets for many many years as the OEM gasket. They should be fine. Just make sure to read the instructions ... most of the MrG shim gaskets I have seen already have a coating on them and adding something else might actually hurt as far as sealing goes. Also .. shim gaskets really require a very smooth surface and do not like used surfaces that have not been resurfaced.

Thanks, Bill. My heads are fresh from the shop so hopefully my block still looks good when I get the old ones off. (It did last winter)

Spray or daub them down with either spray-can aluminum paint or Copper-Cote..

And you can if careful use a new fine cut bastard file to smooth both the head and block decks by using the holes as locating spots and very carefully filing down smooth. THE word is CAREFULLY!!

You will see the high's and low's as you very carefully remove the crud from them down to bare metal..

NOTE!!! THIS is a "feelly" AND a "see-e" thing here so don't go hog wild!!

pdq67

i have used the mr gasket steel shims for almost everything cheap way to add compression. they are the mrg-1131 part number which has no coating on them. i coat them with copper coat spray and install.

i have used them on undecked engines and heads and worked just fine. even my current 414 bbc has never had the block deck its still the same deck from 1970 and i have put alot of heads on this block without any fear of blowing one. the heads for the most part are decked almost everytime i go thru a set for what ever reason.

im not saying the decks shouldnt be straight im just saying there shouldnt be a huge concern that they are not a freshen deck. meaning you have to run out and do it to use them. as long as the decks are within reason of being flat i run them. i just never came across any that was so far out that it had to be done.

i also find that these head gasket show up as .018" thick after they are removed from a running engine. i have a few sets hanging on the wall and they just come out to that.

Doesn't FelPro have a coated steel shim gasket (.015") that doesn't require a fresh-cut deck?

Yes, for the small-blocks. Far as I know, it's Mr G or GM for steel shim big block gaskets. GM is the prefered choice because of the routing of the water passages. May require drilling holes in the deck of the block, though.

Mr. G gasket uses the old familiar 2 big holes at the back of the engine to route coolant into the head.

How well do the MR. G's shims seal with a 10:1 CR BBC?

Thanks!!

Can't say specifically about the Mr. G, but the GM ones were good enough for GM to use them on the old LS-6.

I used the GM steel shim #14015351 on my 10.88:1 496. DCR is 7.866:1 and it's working out great so far. smile.gif

---Chris

That's good to know. I need them to get my quench down to .040".

The heads are new, so no worries there. The block was decked the last time it was rebuilt (10k miles ago).

Hopefully I'll be good to go.

How well do the steel shim head gaskets work with a little bit of N2O?

Lets say 150-175HP shot.

I was not impressed with the quality of the MrG gaskets. The dowel holes did not line up properly and would have required filing one of the holes to fit. I went with the GM gaskets, but I'm still assembling the engine.

Didn't the 12.0 and 12.5 to 1 CR. L-88 motors use shims??

pdq67