Milling 243's

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Sep 15, 2010 | 02:54 PM

caseypryan

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Milling 243's

My cam will clear a 59cc chamber head just for reference, and I'm wondering if I mill .020 to about a ?62cc? chamber, is that too much compression for a nearly daily driven street car in Las Vegas heat? Also will my compression ratio be about 11:1? and I want to use a stock gasket for my car. It's a stock bottom end, stock block in my 2000 SS

Sep 15, 2010 | 03:09 PM

camz28arro

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With stock bottom end and 0.053 gasket, milling the stock 243's down 0.020 will make it about 61.6cc and give a 10.95:1 compression. The compression should make it more efficient and increase throttle response making it possibly better for a DD.

Sep 15, 2010 | 04:30 PM

caseypryan

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Thank you very much. I thought a stock 243 gasket was .040? do you have any part numbers for the gasket? I would prefer to use an OEM gasket just so I can trust it better..

Sep 15, 2010 | 04:45 PM

caseypryan

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Also I since I am milling it .020 should I use a 7.375 pushrod instead of a 7.400? Thunder racing said I should use the same size and the shorter pushrod may make noise.

Sep 15, 2010 | 04:59 PM

camz28arro

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Quote:

Originally Posted by caseypryan

Thank you very much. I thought a stock 243 gasket was .040? do you have any part numbers for the gasket? I would prefer to use an OEM gasket just so I can trust it better..

The thin cometic gaskets are 0.040 but stock the GM MLS gaskets are about 0.052-0.053, I've had bad luck with the cometics and wound recommend the GM gaskets.

Also since the aftermarket cam usually has a smaller base diameter, the 7.400 rods should be fine. I milled my 243's 24 thousandths and the 7.400 pushrods were still within the tolerances.

Sep 15, 2010 | 05:31 PM

masterz28

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yeah good info above i recently asked Pat G some Q's got some good info from him too. Are you port and polishing your heads?

Sep 15, 2010 | 07:57 PM

caseypryan

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No sir I am not porting/polishing. I'm not looking to spend the extra money. Do you have a part number on the GM MLS gaskets that are .052? I think it's 12498544

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Sep 15, 2010 | 09:00 PM

AW794

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Quote:

Originally Posted by caseypryan

and thank you for the good info camz28arro

You may want to invest in a pushrod length checker. They are typically only 20 bucks from most sponsors.

Sep 15, 2010 | 10:21 PM

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caseypryan

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Can someone give me part numbers on 243 head gaskets? The GM MLS ones. And water pump gaskets (2). Also should I used the 2004+ head bolts or the pre 2004 bolts?

Sep 15, 2010 | 10:41 PM

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beedo

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Quote:

Originally Posted by caseypryan

Can someone give me part numbers on 243 head gaskets? The GM MLS ones. And water pump gaskets (2). Also should I used the 2004+ head bolts or the pre 2004 bolts?

Depends on what year your engine is, if its a pre 2004 it will have short bolts in the first and last middle bolt holes of the head and if its later than 2004 they are all the same lenght.