Highest CR on pump gas?
#23
Bigger cam changes the timing of the cycle. if you close too early you leave a bunch on the table. To a point, the pressure is still there it just changed the rpms that it might happen at. As far as lift goes your heads will dictate that, and your springs will try to keep up.
#24
Bigger cam changes the timing of the cycle. if you close too early you leave a bunch on the table. To a point, the pressure is still there it just changed the rpms that it might happen at. As far as lift goes your heads will dictate that, and your springs will try to keep up.
#25
Yes, that's physical limit of the valves. Some heads aren't big enough to need it but if you are looking for every last bit and the springs can handle the valvetrain then get as close as you dare. How long do you need it to last?.
#26
#27
...or go too far and have to flycut the pistons
#29
#32
as very few N/A setups flow better than atmospheric pressures, or atleast to my knowledge they're arent, how could cam selection make a difference (other than valve lift and timing with the piston)?
#33
Google Pat Kelly compression calculator. It'll explain the details. Compression does not happen until the intake valve closes. The longer the duration on the cam, the later the intake valve closes, the lower the dynamic compression for a set combo. There are charts that tell you max safe dynamic compression for octane and temperature. Aluminum buys about a half point of headroom.
Static compression is just the ratio of the combustion chamber size with piston at BDC to chamber size with piston at TDC. Piston design, head chamber, bore, stroke, gasket thickness and bore, and deck clearance set that. Dynamic compression is your true running compression.
Static compression is just the ratio of the combustion chamber size with piston at BDC to chamber size with piston at TDC. Piston design, head chamber, bore, stroke, gasket thickness and bore, and deck clearance set that. Dynamic compression is your true running compression.
#34
#35
Google Pat Kelly compression calculator. It'll explain the details. Compression does not happen until the intake valve closes. The longer the duration on the cam, the later the intake valve closes, the lower the dynamic compression for a set combo. There are charts that tell you max safe dynamic compression for octane and temperature. Aluminum buys about a half point of headroom.
Static compression is just the ratio of the combustion chamber size with piston at BDC to chamber size with piston at TDC. Piston design, head chamber, bore, stroke, gasket thickness and bore, and deck clearance set that. Dynamic compression is your true running compression.
Static compression is just the ratio of the combustion chamber size with piston at BDC to chamber size with piston at TDC. Piston design, head chamber, bore, stroke, gasket thickness and bore, and deck clearance set that. Dynamic compression is your true running compression.
#36
#37
Bumping this up!
Decided to just go with race gas and high compression, instead of risking using pump gas, I'll barely drive it so it'll be fine.
Thanks for your help guys!
Decided to just go with race gas and high compression, instead of risking using pump gas, I'll barely drive it so it'll be fine.
Thanks for your help guys!
#38
Id like to have a little more compression in my stock bottom end motor without changing too much around. Could I just swap to a .026 head gasket and be fine or would I need to make some other changes at the same time? I was going to get the head surface milled down just a touch as well as change the gasket but I dont know what compression just changing gaskets would put me at.
#39
Google Pat Kelly compression calculator. It'll explain the details. Compression does not happen until the intake valve closes. The longer the duration on the cam, the later the intake valve closes, the lower the dynamic compression for a set combo. There are charts that tell you max safe dynamic compression for octane and temperature. Aluminum buys about a half point of headroom.
Static compression is just the ratio of the combustion chamber size with piston at BDC to chamber size with piston at TDC. Piston design, head chamber, bore, stroke, gasket thickness and bore, and deck clearance set that. Dynamic compression is your true running compression.
Static compression is just the ratio of the combustion chamber size with piston at BDC to chamber size with piston at TDC. Piston design, head chamber, bore, stroke, gasket thickness and bore, and deck clearance set that. Dynamic compression is your true running compression.
Those calculations assume the engine is operating at 100% ve with no scavenging going on or anything like it. The whole thing just started so internet experts had another talking point to try to make themselves look smart.
#40
Yes.
Running high compression on a street engine (pump gas) requires that you have proper engine quench (ideally .035" to .040"), optimal dynamic compression (about 9:1 w/the LT1/4)....this is where the camshaft specs come into play....and a spot-on tune.
12.5:1 static compression is very doable when your build has been done correctly!
KW
Running high compression on a street engine (pump gas) requires that you have proper engine quench (ideally .035" to .040"), optimal dynamic compression (about 9:1 w/the LT1/4)....this is where the camshaft specs come into play....and a spot-on tune.
12.5:1 static compression is very doable when your build has been done correctly!
KW
Last edited by KW Baraka; 06-04-2013 at 02:28 PM.