help me calculate my compression ratio..
02-22-2011, 11:25 AM
#1
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help me calculate my compression ratio.. ok sooo i am curious what my cr will be..
3.480 crank
5.7 rods
http://www.summitracing.com/parts/TRW-8KL2256F30/ These pistons
55cc heads
stock deck.. Im pretty sure it wont be cut..
impala head gaskets
3.480 crank
5.7 rods
http://www.summitracing.com/parts/TRW-8KL2256F30/ These pistons
55cc heads
stock deck.. Im pretty sure it wont be cut..
impala head gaskets
02-22-2011, 11:37 AM
#2
The description of the pistons says the dome volume is +6.10. If this is put into the calculator on Eagle's site, here's what you get:
Deck Clearance .022"
CR 13.35:1
355.1 CID
Assuming the dome volume is for valve relief, it would actually be -6.10cc. This gives you:
Deck Clearance .022"
CR 11.23:1
355.1 CID
I don't think you want to go with stock deck. It should be milled just to be sure everything's kosher with flatness.
Deck Clearance .022"
CR 13.35:1
355.1 CID
Assuming the dome volume is for valve relief, it would actually be -6.10cc. This gives you:
Deck Clearance .022"
CR 11.23:1
355.1 CID
I don't think you want to go with stock deck. It should be milled just to be sure everything's kosher with flatness.
02-22-2011, 11:46 AM
#4
Well, I put in the stock deck height at 9.025", and .026 head gasket thickness, which is impala if I remember correctly.
If you mill the deck down to 9.00" flat, your piston will be .003" above the deck surface, which is bad.
With the setup you propose, the most you can take off the deck is .020", that leaves you at .002" deck clearance with. -6.10 CC piston is 11.87:1 compression, but a +6.10 as advertised on the link you supplied to the pistons gives you 14.29:1 compression.
In my opinion, you need to deck the block, and either go with a thicker head gasket or dished pistons with negative dome volume. The current setup you propose will be very tricky, and dangerous in my opinion.
If you mill the deck down to 9.00" flat, your piston will be .003" above the deck surface, which is bad.
With the setup you propose, the most you can take off the deck is .020", that leaves you at .002" deck clearance with. -6.10 CC piston is 11.87:1 compression, but a +6.10 as advertised on the link you supplied to the pistons gives you 14.29:1 compression.
In my opinion, you need to deck the block, and either go with a thicker head gasket or dished pistons with negative dome volume. The current setup you propose will be very tricky, and dangerous in my opinion.
02-22-2011, 12:01 PM
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Ok so i called summit.. The +6.10 is the volume of the valve relief.. They are FLAT TOP not dome.. So no worries there.. HKE calculated out the compression to 11.2:1.. So i think it will be good to go..
02-22-2011, 12:32 PM
#7
You will be fine.
Even if you zero deck the block you will be around a perfectly fine 11.8:1.
As the block stands now you will have 11.1-11.2:1.
Qc, you are using 6.1 as a positive number as if it were a dome piston, but it should be inputted as a negative number since it is a flat top with valve reliefs.
Even if you zero deck the block you will be around a perfectly fine 11.8:1.
As the block stands now you will have 11.1-11.2:1.
Qc, you are using 6.1 as a positive number as if it were a dome piston, but it should be inputted as a negative number since it is a flat top with valve reliefs.
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02-22-2011, 01:22 PM
#8
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x2 for this.. i mis wrote.. Thats +6.10 is the actual volume of the relief.. They do not extend up.. They are inverted.. so the physical volume is a positive number but the actual effect is negative..
02-22-2011, 02:41 PM
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If you havent ordered these pistons already I would find a simular piston with the 1/16th ring not the 5/64s, biiig difference is drag between the two.
