Shims To Bump Compression

[Scoobum]

RJC sells shims that raises the compression ratio 4 points. Any other shims that are available readily to do the same thing? Seems to be a cheap and easy way to quicker spooling and better driveability. Steve...your site says they won't blow out...but they lose their sealing capability. Is this under constant high boost pressures...or is this with KR thrown into the equation? I believe it was a quote from Jim Beeler about the sealing. My engines never see any KR...so more compression with just a pair of shims sounds like good bang for the buck.

[Steve Wood]

My son's T appears to be seeping a little altho the water level has not gone down.  I say this because, at times, it seems to be putting pressure in the radiator on cold starts.  It started this after 18 years of hard running.  Did not do it yesterday so I am not sure. Runs perfectly under boost but it has pushed a little water out in spite of the radiator appearing to be full.

The consensus that I have heard is that the silicone glue that is used with them on our cars begins to lose its grip after a number of years.  Mine are the single 0.018 shims from GM that are no longer available.  I think the hot air cars used two of these on each side.  I have one on each side.

In all these years, I have never blown a HG.  Knock on wood.  I suspect that it would catastrophic if I did.

[Scoobum]

Funny you should mention the hot air cars. I was having a discussion with Joe last week who's my friend/engine builder about head gaskets. He uses the hot air gaskets...whic h are readily available up here. I'll likely go that route the next time around. Thanks for the input.

[Steve Wood]

Now that is really interesting.  Does he use the magic GE silicone industrial sealer that everyone tries to keep a secret down here?

[Scoobum]

No...they go on dry. Forgot to ask him what he uses for a torque spec with them using ARP studs.

[Steve Wood]

I am pretty sure the factory went on dry as well but they stacked two....

[Scoobum]

I am pretty sure the factory went on dry as well but they stacked two....

Steve, he said nothing about stacking. I'll call him tonite...if he has time. He's up the wazoo with marine engines at the moment.

[Steve Wood]

The factory stacked them on hot air cars.  I used a single

You probably remember that in the old days, the factory used a single shim on sbc and such.  We used to use aluminum paint on them right before we installed them

[Scoobum]

I've read about guys spraying gaskets with some sort of copper spray. I'll get the particulars off Joe and post back.

[Steve Wood]

In the old days, spraying aluminum paint on shims and installing while wet was the trick.  Then some starting using spray on copper coat.  I have done both.  Main thing with shims is the block and heads must be flat.

When LC and others started using single shims on IC engines to bump the compression over 9, they used a commercial GE silicone and rolled it on.  With the high combustion pressures of a turbo engine, it really helped eliminate seepage.  Shims will sometimes lift under high boost a slight bit determined by torque and type of head fastener.  then they will sit back down and work again.  A person with good ears can often hear the change in sound when this happens.

This is the weakness of the shim...no elasticity in the seal as compared to compound gaskets.

You probably remember a few vendors claiming they had a magic, private sealer that they would not tell anyone what it was or how they got it....It was/is the GE stuff.  I believe this is what RJR still uses with his shims.

Same deal as the guys that  ground the number off  commercial fuel pumps and claimed they modified them to put out more than factory pumps...Shimmi ng the bypass with a piece of copper wire made these pumps extra special.

[Steve Wood]

I think some guys used the shims with copper coat or hylomar and claimed it worked well.  I asked Billy about Cometics and he said he like to use Hylomar.  It can be hard to find at times but I found some spray cans on ebay.

The secret GE magic silicone that some claimed to have worked directly with GE to develop is claimed to be GE 1200.   I am completely convinced GE worked with a Buick guy to develop a secret turbo buick shim hg sealant...Yep, I completely believe that.  Giant market out there of guys using shims and I know GE jumped all over the opportunity to develop a secret sealer for that business!

I will be interested to know what Joe uses.  Some how, I doubt it is a secret GE product. 

[Scoobum]

There's a pic of the GE sealant and a writeup who worked with the GE engineers to develop it. Did you know CNN is fake news...

[Steve Wood]

LOLOLOLOLOLOL

[earlbrown]

The secret GE magic silicone that some claimed to have worked directly with GE to develop is claimed to be GE 1200.   I am completely convinced GE worked with a Buick guy to develop a secret turbo buick shim hg sealant...Yep, I completely believe that.  Giant market out there of guys using shims and I know GE jumped all over the opportunity to develop a secret sealer for that business!

Now I feel bad for using plain ole inexpensive copper paint that's works perfectly.

....he says sarcastically.



What brand shim gaskets are readily available up in Canadia?

[Scoobum]

Felpros are readily available...an d that's it. You guys are incredible lucky down there for parts and cheap quick shipping.