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MG TD TF 1500 - Cylinderhead gasket

Hi all,
We need to reduce the CR from 1 to 8,1 to 1 to 7,5 when using a Volumex Supercharger on our 1350 cc XPAG.
Would it be OK to use two standard Headgaskets or is it advisable to make a special made coppergasket with 2,5mm thickness?

Best regards

Anders & Ingvar / Sweden
T Dahlberg

I just installed a 0.094" solid copper head gasket from Cometic for the same reason to drop the compression ratio for my blower.

http://www.summitracing.com/parts/cgt-c4310-043

That is 0.11mm (0.004") thinner than what you asked for.

I priced them from the other major solid copper gasket supplier and it was around $300 USD.

I had difficulties sealing it at first. The copper permatex sealer would clog the nozzle after 2-3 seconds of spraying, then I would have to remove the nozzle, blow it out with the air compressor and start again. I probably didn't put enough sealer on the gasket. After 1 heat cycle, I went back and re-tourqued the head bolts and it was fine.

I also highly recommend getting ARP head bolts from Tom Lange as long as you are doing the job.

Blair
Blair Weiss

I used two headgaskets on a normally aspirated engine as a make-shift solution and it served me well for a few hundres miles. When I fitted the solid gasket from www.headgasket.com I saw that the two gaskets were wet between them, so I don't think it would do for a supercharged engine.
Willem van der Veer

"I also highly recommend getting ARP head bolts from Tom Lange as long as you are doing the job. "
-X2! Money well spent.
David
D. Sander

Should have probably mentioned, that the part number I provided is for the round water passages. I don't know what the banana shaped passage part number is.

Blair
Blair Weiss

and I gave you the wrong part number... it ends in -094,not -043
Blair Weiss

I recently did the same thing to my supercharged engine. I tried the solid copper gasket (0.094") with no success.
I then used a composite copper gasket much like the standard gasket but double the thickness. It has a few thousand miles on it with no problems.

mailto:inquiries@gasketstogo.com

Mort
Mort 50 TD

I see the term cometic on my 409 website and on ebay. What is a cometic gasket?
W. A. Chasser Jr

Cometic is a manufacturer / supplier of gaskets.

http://www.cometic.com/
Kevin McLemore

Anders & Ingvar,
I question why you would want to go that low on compression ratio.
We have run standard XPAGs with up to 6 psi boost on regular gas with no problem. By increasing your XPAG from 1250 to 1350, you will already have reduced your boost, unless you changed your pulley ratio.
JIM
JRN JIM

Hi Jim,

I must check when coming home on Sunday, but I thought that the CR was higher when increasing the volume from 1250 to 1350!

Anders
T Dahlberg

Anders, you are correct in that the compression ratio will increase with an increase in displacement.
A formula from Hal Kramer is:
CR=((2.618+OB)^2)/(2.193(HT-2.522))+1:1. Values are in inches, e.g., overbore as .080 inches.

Simplified is to say that the compression is what you get from pushing the cylinder volume into the combustion chamber. Increasing the cylinder volume will increase the compression if the combustion chamber stays fixed. Bud
Bud Krueger

The compression ratio will increase by raising displacement. You stated your ratio is 8.1:1, and I have no reason to question your calculation. I do not see the need to reduce it.
There are supercharged TF 1500s with 8.3:1 and no issues.
The original TDs were running 72 octane fuel, where we use 87 octane and higher. Beyond 9:1 is when it gets more serious.

The second point I made, which is often overlooked... if you have a blower set up for the original 1250, your 1350 will have virtually the same power, because your positive displacement blower will push only the same amount of air&fuel. So what? Nothing wrong with that. It'll still be peppy. Even if you had a 10,000cc engine- same horsepower, because the supercharger dictates how much air/fuel the engine inhales. The boost pressure will be lower because you are trying to compress a given volume of air/fuel into larger cylinders. If you seek more power, you'll have to compensate with higher blower speed (pulley ratios), aside from new cam, headers, carb, etc.

I get to deal with an supercharged XPAG punched out to 1466cc soon!

HAVE FUN WITH IT!!!


JRN JIM

Jim, with a roots type positive displacement supercharger what you say makes sense but does the same apply to a radial type S/C? I've been reading (a dangerous pasttime) the Februaty, '83 TSO dedicated to superchargers and it seems that the Shorrock type S/C (this may be the type of all modern ones but I don't know) are also positive displacement or at least mostly positive displacement so I guess my question applies only to the radial type which may no longer be used.

Jud
J K Chapin

Positive displacement sort of means "no more, no less" gets shoved in based on rpm and throttle. Lobed, screw, and vane (radial) type blowers are positive displacement. Centrifugals, axials and turbo chargers are not.
JRN JIM

This thread was discussed between 20/07/2014 and 25/07/2014

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