heads question
02-14-2009, 02:19 AM
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heads question
if i port the heads on a 4.8 will it help even if i dont have a cam in it yet?
what about milling them for higher CR. is it worth it without a cam?
how much CR is safe on a stock block.
what about milling them for higher CR. is it worth it without a cam?
how much CR is safe on a stock block.
02-14-2009, 02:21 AM
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heads help
if i port the heads on a 4.8 will it help even if i dont have a cam in it yet?
what about milling them for higher CR. is it worth it without a cam?
how much CR is safe on a stock block.
should i swap for 2" intake valves?
thanks
what about milling them for higher CR. is it worth it without a cam?
how much CR is safe on a stock block.
should i swap for 2" intake valves?
thanks
02-14-2009, 02:37 AM
#3
yes, the heads will help even with the stock cam. 1 point of compression is supposedly worth 4% increase in power throughout the entire powerband.
How much CR you can run safely on pump gas depends on your dynamic CR. I believe 8.5:1 is where you start to need 93 octane. Stock DCR is somewhere in the 6 range I believe, so even if you bump up the static CR you're DCR wont be that high with the stock cam. This is how GM can safely sell a vehicle like the trailblazer SS with near 11:1 compression with the full expectation that people will use 87 octane.
How much CR you can run safely on pump gas depends on your dynamic CR. I believe 8.5:1 is where you start to need 93 octane. Stock DCR is somewhere in the 6 range I believe, so even if you bump up the static CR you're DCR wont be that high with the stock cam. This is how GM can safely sell a vehicle like the trailblazer SS with near 11:1 compression with the full expectation that people will use 87 octane.
02-14-2009, 03:48 AM
#6
The max you can mill heads is .040 and not screw up the seal of the intake manifold, supposedly. So, I'd say the most you can mill the 243s to around around 58cc. Stock 4.8 is 9.5:1 w/ 61cc chambers. I don't have the calculations, but I don't think you'll be getting anywhere near 11:1. Personally, I wouldn't push the compression for a teeny bit of power. I'm going 10.6:1 myself and that's it.
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02-14-2009, 09:18 AM
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Yes,
yes,
10-12.5
"swap"?
First have you ported anything be fore? if you dont have the proper tooling and knowalage, you will do more damagethan good, plus the intake valve seat and intake port have a very thin wall seperating them, bust through it, and your done. I would just clean them up a bit, smooth out the exhaust port a bit, other wise leave it alone.
Higher compression will always help, how high you go will dictate what type of fuel you will have to run to avoid detonation.
A stock block can handle 650 hp pretty easy, but with a bit of detonation, it will be died..
You wont be "swamping" intake valves with out major head and seat work...
yes,
10-12.5
"swap"?
First have you ported anything be fore? if you dont have the proper tooling and knowalage, you will do more damagethan good, plus the intake valve seat and intake port have a very thin wall seperating them, bust through it, and your done. I would just clean them up a bit, smooth out the exhaust port a bit, other wise leave it alone.
Higher compression will always help, how high you go will dictate what type of fuel you will have to run to avoid detonation.
A stock block can handle 650 hp pretty easy, but with a bit of detonation, it will be died..
You wont be "swamping" intake valves with out major head and seat work...
