whats the compression ratio
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Junior User
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whats the compression ratio
I am looking to buy the new edelbrock heads for my 400. I have in my possesion the sivrlites from kb. (177 w/ one valve relief) i was wondering what my compression ratio would be. My calculations say 11.5:1 with a 0 deck. Does this piston sit down in the cylinder or out of it and if so what the new outcome goin to be for this.
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From: Canada
Hi,
well,
we will need more infos , like:
first off we will need the advertised compression height of your piston in order to calculate comp. ratio. and if they are dished, or pop-up, we will need the volume in CC. also if they are 30, 40 , or 60 oversize, that will change the comp. ratio. Combustion chamber volume plays a major role there as well. Even your head gasket thickness will make a difference. Do you really have an assembled 0 Deck clearance? sometimes in real life isn't always like we had planned on paper. There is a lot of material to remove off the block to achieve that 0 deck clearance, unless you bought those special piston from TMI.
Give us more info to chew
Werk
well,
we will need more infos , like:
first off we will need the advertised compression height of your piston in order to calculate comp. ratio. and if they are dished, or pop-up, we will need the volume in CC. also if they are 30, 40 , or 60 oversize, that will change the comp. ratio. Combustion chamber volume plays a major role there as well. Even your head gasket thickness will make a difference. Do you really have an assembled 0 Deck clearance? sometimes in real life isn't always like we had planned on paper. There is a lot of material to remove off the block to achieve that 0 deck clearance, unless you bought those special piston from TMI.
Give us more info to chew
Werk
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Junior User
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oh this is mostly just in theory. ok let me see if i can clear this up. they are .060 over thier compression height is the same as the 400. the cc of the edelbrock heads are 60cc and as for head gasket i assume they will be standard which is like .040 after compression. the zero deck clearance is just a perfect world. if its more than the compression ratio will be less. and the pistons are keith blacks i bought them from summit not sure what the valve relief is but i am sure someone will. any other questions that i forgot or need to clear up let me know.
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From: chicago burbs
http://kb-silvolite.com/performance....tails&P_id=140
you know the con rod small ends have to be bushed for these pistons to fit onto 400 rods, right?
they say it's 1.67" compression height and 2cc's relief. i get 12.48:1 with zero deck, 60cc chambers, .050" gasket, 4.1" gasket bore dia, 4.030" bore and 4" stroke. doing the math though, if your block is really at the published 10.297 deck height, your assembly is .047" in the hole leaving the CR at 11.12:1 and your quench clearance at almost .100"!!! even if you use the good gaskets(1013's) at .041" your still at almost .090" quench! i'd get that block measured for deck height, do a little cut on it to square it up, then look into offset bushing the rods to make up the difference. not much more than what has to be done anyway, this is of course all theory until you get concrete measurements on your squared up block.
http://raceabilene.com/kelly/hotrod/compression.html
you know the con rod small ends have to be bushed for these pistons to fit onto 400 rods, right?
they say it's 1.67" compression height and 2cc's relief. i get 12.48:1 with zero deck, 60cc chambers, .050" gasket, 4.1" gasket bore dia, 4.030" bore and 4" stroke. doing the math though, if your block is really at the published 10.297 deck height, your assembly is .047" in the hole leaving the CR at 11.12:1 and your quench clearance at almost .100"!!! even if you use the good gaskets(1013's) at .041" your still at almost .090" quench! i'd get that block measured for deck height, do a little cut on it to square it up, then look into offset bushing the rods to make up the difference. not much more than what has to be done anyway, this is of course all theory until you get concrete measurements on your squared up block.
http://raceabilene.com/kelly/hotrod/compression.html
Last edited by grclark351; Sep 5, 2005 at 05:59 PM.
