Best way to get to 9:1 compression on a 383
12-08-2006, 12:03 PM
#1
Best way to get to 9:1 compression on a 383 Not sure if this is in the correct section- moderators feel free to move it if necissary... Just figured I'd ask in the FI section since it is for FI application.
Anyways, going to be doing a 383. Most likely the TSP's basic components in their short block- Eagle forged 4.0 crank, scat 6.125 H-beam rods, but not sure about pistons. I've done a search and found a few CR calculators on the web, but they need info I don't know: ie gasket size, cc of heads, etc. Rather than ask a bunch of questions about what the stock gasket sizes are, whats the cc of 5.3L, 5.7L, and 6.0L heads, I figured I'd just ask the simple question- What is the best way to get 9:1 CR on a 383? It'd be nice to hear some of you guys opinions that have been there and done it, and how you achieved the CR you wanted with different components.
Anyways, going to be doing a 383. Most likely the TSP's basic components in their short block- Eagle forged 4.0 crank, scat 6.125 H-beam rods, but not sure about pistons. I've done a search and found a few CR calculators on the web, but they need info I don't know: ie gasket size, cc of heads, etc. Rather than ask a bunch of questions about what the stock gasket sizes are, whats the cc of 5.3L, 5.7L, and 6.0L heads, I figured I'd just ask the simple question- What is the best way to get 9:1 CR on a 383? It'd be nice to hear some of you guys opinions that have been there and done it, and how you achieved the CR you wanted with different components.
12-08-2006, 12:19 PM
#2
Chad I would like to add an additional question onto this... Is it better to drop the compression with a bigger dish on the piston or a bigger cc on the head?? For instance, if you were to stay with a 66cc head and go with a -8.6 dish would it be more beneficial than going with -2cc dished pistons and going with a 72cc head?? Or would it be the same end with different means of getting there?? Would there be less chance of detonation with one versus the others or are they going to have the same characteristics simply because they're the same compression??
Sorry to hijack but I've always wondered something similar to your question...
Sorry to hijack but I've always wondered something similar to your question...
12-08-2006, 12:22 PM
#3
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I would try to go with a large head chamber with the smallest head gasket you can use and adjust dish to what you need. My reasoning is that less piston will make it weaker, and a larger head gasket will increase quench which will increase the chances of detonation.
I am sure there are people that have done it with success here and hopefully they chime in.
I am sure there are people that have done it with success here and hopefully they chime in.
12-08-2006, 03:36 PM
#6
Originally Posted by brad8266
I would try to go with a large head chamber with the smallest head gasket you can use and adjust dish to what you need. My reasoning is that less piston will make it weaker, and a larger head gasket will increase quench which will increase the chances of detonation.
I am sure there are people that have done it with success here and hopefully they chime in.
I am sure there are people that have done it with success here and hopefully they chime in.
Originally Posted by SStrokerAce
Yes at a set compression ratio the right small chamber/dish setup usually makes more power.
Bret
Bret
Originally Posted by Old Geezer
Less/no dome, small chambers, and good quench numbers, beats the alternative.
We saw that in use, some 15-20 yrs ago, with the BUICK Stage 2 heads, and the NASCAR Busch engines. Worked VERY well.
Currently running a 274" Stage, on the street, 11:1, carbed, right at 500FWHP.... No led premium.
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We saw that in use, some 15-20 yrs ago, with the BUICK Stage 2 heads, and the NASCAR Busch engines. Worked VERY well.
Currently running a 274" Stage, on the street, 11:1, carbed, right at 500FWHP.... No led premium.
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Originally Posted by the.erinyes
More than likely there will be no benefits although several downsides such as higher piston weight, more stress on rods and crank, higher emissions, less fuel mileage, and lower performance. Quite frankly if there were benefits to be found GM would have used them instead of a flat top piston with a smaller chamber size. In addition, the chamber should be designed to use the dome piston, which would not be the case since the 72cc head also uses flat top pistones.
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12-08-2006, 05:43 PM
#8
No No No....you want bigger cc heads and less dish in the pistons.LSx pistons ringlands are thin enough as it is you dont want to make them even thinner by having a huge dish in a piston.They make a 76cc head if you felt the need to keep as much piston as possible.But most do LQ9 heads and then a reasonable dish in the piston(ie 12-20)
12-08-2006, 05:53 PM
#9
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have used 16cc plus in many engines for years, no problems. it's all in the tune. agree with you on the head though, if you can acheive more cc's from the head, by all means do it.
12-09-2006, 12:23 PM
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Originally Posted by ddnspider
No No No....you want bigger cc heads and less dish in the pistons.LSx pistons ringlands are thin enough as it is you dont want to make them even thinner by having a huge dish in a piston.They make a 76cc head if you felt the need to keep as much piston as possible.But most do LQ9 heads and then a reasonable dish in the piston(ie 12-20)
