TWO Head Gaskets for Turbo CR ?

powerband

powerband

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Reportedly there was a turbo kit marketed that used two head gaskets to lower OEM CR to turbo - usable levels along with other proprietary parts.

Interested in any experience lowering CR with thicker head gaskets. Could two gaskets survive a low boost setup?. Playing with CR calculator, the typical composite gasket crush thickness of @ .050 when doubled to @ .100" lowers typical CR @ full point. (.. or two composites with OEM steel shim head gasket between them?)

related info appreciated , and also somewhat opinions . 8)


NA engines would degrade chamber/quench design but with turbo ?.

thanks
 
it has been done, in some circles it is common practice, but it depends on the gasket

if you have an MLS gasket, you could probably stack 10 of them with no problems, but a composite gasket isn't going to hold up to that sort of thing.

the cheap and dirty way out of it is to use a copper head gasket that can be whatever thickness you desire and doesn't deform as much under pressure.

i guess the issue is 'why would you'; the stock engine at 8:1 can already handle 5-7 psi from anecdotal accounts, and if you push it much harder you'll want to go with better slugs anyhow.
 
... the reason for the two gasket option would be to lower CR to a turbo comfortable level using an earlier or previously milled head with smaller comp' chambers . The uncut larger chamber heads are getting hard to find and I already have good - DOxx , C9xx heads (@50cc) and a milled and worked D7xx (48cc). Daily driver will use stock block with ign. , fuel mods ..., . (alternate performance 250 turbo project will use an uncut D7xx head (62cc).)

"Stage I" is small block six bolt-on turbo derived from Buick 'draw-through' V6 of 79-82, Buick pushrod 231cid V6 was similar to Ford inline's powerband.

have fun

. .
 
its a catch-22 kinda thing, well, not really but sorta

if you are running high enough boost to need to lower your CR, you will blow out stacked gaskets, if you don't blow out stacked gaskets you probably aren't running enough boost to need the lower CR.

you can pull timing, jet rich, lower boost, plenty of options to keep from detonating with a conservative setup like that.

the other issue with a big squishy gasket sammich like that is warping your head... also your pushrod lengths change slightly... there is a lot to consider.
 
thats good points about possible head warpage and pushrod length considerations, as mentioned everything's a compromise to some extent ... .

thanks
 
Sorry I can't offer any personal experience for you here powerband, but this seems to be one of those things that everyone will say can't or shouldnt be done but that no one has tried really tried it. It is certainly easy enough to experiment with. Very few engines are as easy to r&r heads as our beloved small sixes and you might be the guy to tell us that this actually works... Or the one who fails miserably and tells us that it didn't. 8) I'd say go for it, but If it were me I would plan on running a single gasket either before or after the double to compare engine behaviour and to see if there is any benefit or not.

I see it this way: by adding 50 thou to the combustion chamber you have effectively lowered the compression ratio by a half a point or so and could theoretically utilize more boost, BUT you have also worsened the quench on an engine that was lacking in that department in the first place. Detonation is likely to be the limiting factor in this scenario and while you may lower the static compression ratio, you will be making it more likely to detonate and you will have to reduce timing or break every ring in the thing. I personally think it would make a great experiment myself. :beer:

I don't know the kits that you are reffering to that offer this advice, but it is likely that they work or they wouldn't be selling them. I would assume if they work they would be for those applications with modern engines having aluminum heads, better cooling, more efficient combustion chambers etc, and electronic controls to help keep detonation at bay.

For the record, I am the little red devil on your shoulder telling you not to listen to the guy with the halo on your other shoulder and suggesting you try it out and let us know. Seriously. :beer:
 
or break every ring in the thing. I personally think it would make a great experiment myself.
... that's why I'm here...

Ten or so years ago put together the '63 with a low miles stock 170 block and built/tricked D&xx head cut .070 (kudos Falcon Six Handbook - headers, 2Bbl etc,). Runs strong with steel shim gasket @ 9.5:1SCR so I can compare performance directly. I have other heads but the 48cc chamber has most extensive upgrade work and current '63 build is turbo learning in progress.

'narrowed down composite Head Gasket CR 'mod' options:

A) Two Corteco gaskets - @ .053 compressed thickness = @ .106"

B) Two Victor @ .045 comp. - @ .090"

or C) An OEM steel shim gasket at @ .020 compressed -BETWEEN two composite. (!)

ALso considering effects on fastener (head bolt) torque'ing with two composite gaskets and compressability and composite to composite surface (not steel) that's reason for steel shim possibility .

have fun

 
StorminNorman found these guys when looking for shim style gasket.
Here's his note to me:
Got 2 of them. First one is the manufacturer, second is a reseller:

http://www.innomach.com/shims.htm

http://www.silver-seal.com/c=gYJl4j9ksD ... hims.ford/

I sent an email to INNOMACH, and he'd be happy to sell directly:

"
Great

If they want to use email, please use the following address:
scottb@innomach.com

Or, just use the phone to get it done quicker

Thanks

Scott Blood
Innovative Machine & Supply
820 St Louis Ave
Valley Park MO 63088
636 825 3335
fax 636 825 3359
Click to expand...
Here's the one they list:
http://www.innomach.com/data/webdata_sh ... ction=form
 
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