How much I can deck '59 292 stock heads?

Fuel is 95 or 98 RON-octane.

Mummert's 270 degree camshaft needs 9.5:1 to 10:1 comp. ratio?

Intake manifold will not be problem.


Hyvinkää, FI

If the heads are113s they should be 9 to 1 ratio using steel gaskets which were orininal.The newer composit gaskets are much better and a little thicker so cutting the heads about .020 should do the trick.I myself wouldn't want to go more than .010 just for a good clean up.The .020 should be plenty regardless of the heads providing the've never been cut before.

-Gary Burnette-

Eickman's book gives me original comp. ratio 8.8:1 with steel gaskets and I think, this motor is never opened before.


Hyvinkää, FI

My mistake,the ECZG heads in 1957 were 9.7 c.r. in 1958 They went to 9.1 c.r. and the 113s were 8.8

-Gary Burnette-

Ted quote from older forum....

"Bill, Assuming your 113 heads are 72 cc's, your current combination will be somewhere around 8.53:1. To get to the desired 10.0:1 CR with these heads, you'd need a 13.4cc reduction in the combustion chamber volume. Using the 0.0055" inch of cut for each 1 cc in reduction rule, the 113 heads would need ~0.074" cut off of their decks. This would be a very heavy cut and even if the head surfaces could stand it, this would require some serious intake gasket surface milling to get the intake manifold to allign back up. Decking the block another 0.010" will take away another 2 cc's and subsequently, the heads would only need to be milled 0.063" to get the same 10.0:1CR."


If I take 0.037" off, I get 9.3:1. Is that Right? How about the valve-piston clearance?


Hyvinkää, FI

Has anybody picture or info from that bolt-through-water-jacket-to-support-combustion-chamber-roof-modification?



I think I must cut so much from heads, that I need some old Hot Rod tricks.


Hyvinkää, FI

Rough math says a 0.037” cut on the 113 heads will give about a 6.7cc reduction.  I can’t tell you what this would do to your compression ratio without knowing the specifics on your combination.  Ie. Bore, stroke, deck clearance, head gasket, etc.

 

A a rule, I try to limit the cut on posted Y heads to a maximum of 0.055”.  Of course this limitation is with compression ratios of up to 13.0:1 in mind so if running a compression ratio much lower than this, then another 0.010” of cut would potentially be possible.  As an alternative, cut as much off of the block deck as possible which will also help to maximize piston quench.  This would minimize the amount that must come off of the heads to get to the desired compression ratio.

 

With milled heads in mind, piston to valve clearance with stock sized G or 113 valves and camshafts that have an advertised 0.500” lift or less and ground on 112° lobe centers typically do not require any piston notching or modifications to the pistons themselves.  Check clearances anyhow as variances can step up to bite you.  Going to a larger sized intake valve and/or decreasing the camshaft lobe centerline while maintaining the same valve lift characteristics will create a scenario in which valve to piston clearance will need to be checked with much more scrutiny.  When checking valve to piston clearance, also check the intake valve to edge of bore clearance as this becomes an issue at lifts approaching 0.540” and more.

Lorena, Texas (South of Waco)

DAAMN! I lost my long reply!



But I calculated and I take 0.048 off to get ~9.6:1 ratio.

Valve-piston clearance is not problem with 0.419 valve lift.



Thank you!


Hyvinkää, FI