[StanMan]

I have a 1969 351 (9.480 deck) short block and I was wondering if it is possible to use pistons designed for a late block (9.50 deck). I would thinks so because most gaskets are .041" thick and the difference is only .020". This assumes that the block has never been machined on its deck. Please help.

Stanman

 

[GT1990EFI351]

Most engine rebuild kits need the exact year, even with a split year. Because technically it matters.

 

[Mustang Brad]

I don't think it is fair to assume that the head gasket will take up half the space because, when you do that you are acting like they never run head gaskets on the other engine. I think you should be ok, just ask how much people deck their blocks, and what decking a block .040" brings up your compression, and then always do a P/V check when you assemble.

 

[fast89]

no, you will not be ok!!!! you need .035-.040" quench distance (distance between piston and head). with a gasket compressed thickness of .041" and a piston that is .020 out of the bore, you will most definatly smack a cylinder head. if your running stock rods and spinning it over 5000, you should stay around .040" quench. if your running a good steel rod, you can run .030-.035" but i'd recomend .035-.040 as a good guideline.

 

[StanMan]

Thanks guys.

 

[MAT88GT]

yeah you can do it.....

deck height - rod length - .5*stroke = compression height for 0 deck clearance

use that formula to get a compression height for your specs

 

[Slart]

Most pistons come .020" short of the deck anyway, so you'll be ok.

Be sure to measure it however and make sure you have at least .030" (more if you plan on using heavy pistons, going past 6k, or using aluminum rods). Spin a piston to TDC, put a straight edge on it, and measure the gap between the straight edge and the block. If the gasket you're using is .039, make sure the piston doesn't stick out any more than .009.

- Steve