[newtoponcho]

Gents,
Please give me your thoughts on zero decking my block for this build.
400 block .030 over, L2440 pistons @ .023 in the hole (the ones with the bevel around the top edge). #62 heads cc'd @ 75.
XE262 cam, quadrajet & performer intake, log manifolds & dual exhaust.stock convertor 350 trans,2.78 rear axle.(3800 lbs convertible)
My calculations bring compression ratio to 8.98:1 as is.
Will this engine require zero decking to avoid detonation?
That is my only concern,not squeezing that little extra power out of the compression increase. (just a cruiser).
Thanks in advance for your help.

[303ta]

I'm running zero deck in my 400. .060 over #48 heads and 280AH cam with no issues.

[screamingchief]

If you decide to leave the pistons in the hole,I would strongly recommend using the thin (.027" CT/4.200" bore) cometic headgaskets to get the head to piston clearance a bit closer and hope to get some quench that way.

Otherwise zero decking may be the next option to ponder,to do this you'll need to use a more "standard" thickness/bore headgasket (.040" CT/4.200" bore).

First option (.027"/-.023") is 9.6:1 appx SCR,piston to head clearance is .050".

Second option (.040"/"0" deck) is 9.8:1 appx. SCR,piston to head clearance is .040".

BTW,I come up with 9.36:1 SCR with the pistons .023" down and using a .039" CT/4.200" bore headgasket and 75cc heads and those pistons @ -10.5 cc piston volume.

Dont know how you got 8.98:1 for the SCR?

I'd probably want a bit more cam myself with this sorta SCR,that or a similar duration cam on a wider LSA to delay the IC event some.



HTH
BP.

[newtoponcho]

Thanks for your input,
I came to that number by cc'ing the piston in the cylinder as close as possible to zero deck height (rings installed and lightly greased). I measured 15 cc's. Could this compression ratio be the cause of 2 spun rod bearings that previous owner encountered?

["QUICK-SILVER"]

Originally Posted by newtoponcho

Could this compression ratio be the cause of 2 spun rod bearings that previous owner encountered?

IMO Not likely. Spun bearings are usually caused by an oiling problem: lack of oil, too thin an oil, too hot, over reving, those kind of things.

High compression detonation hammers the top bearing to death. Which could spin if you kept driving with the engine knocking like....like knocking when some people don't know when to quit.