I'm rebuilding my 383 right now. The final components it will use are: victor intake, vortec heads, 750DP holley, MSD ignition, scat 9000 crank, 5.7" rods. The cam is 230@.050, .480" lift. [comp 280H magnum]I'm thinking about changing to a solid lifter cam with a powerband peaking at 6000rpm instead. My question is about the compression. I ran it with the flat top, 4 valve relief pistons for a couple years no prob as a daily driver. This is about 10:1 compression. The vehicle and motor are no longer street legal, so power from 3000+ is all I'm concerned about. I will only drive it to the tract about 25min from my house and back. I can't decide on what compression to go with, 11:1 or 12:1? Also, what kind of compression would flat top, 2 valve relief pistons give me? Av gas/race gas is not a problem to get or use. Any insight is much appreciated.

I get 10.93 for a 64cc chamber, .040" quench and 6cc valve pockets. DCR about 8.68 with the 280 cam. Definiftly in the high octane area. If you want a higher CR, you probably need to change pistons since the deck on the Vortecs is very thin. If the vortecs have 62cc chambers, as some are said to have, the SCR goes to 11.19 and the DCR to 8.88. If the valve pockets are 5.4cc, as Wiscos are, the SCR with 64cc is 11.00, DCR 8.74, with 62cc, SCR 11.27, DCR 8.94. Hope this helps,

I ran a 280/290 @.006 cam with (measured) 7cc flat tops, zero deck and vortecs. My heads measured 62cc and I used 64cc to account for the plug, ring land, head gasket not round, etc. Ran fine with 34* timing at 180* coolant. I also run a sealed cowl hood too. If you go solid, I'm in the process of putting a Ultradyne 276/284f10 in the above combo. I can tell you how it came out. Hopefully it's not windy, rainy, or freezing this weekend.

Also, Pat's DCR calculator has a good compression ratio calculator too.

If you don't already have the intake get a performer RPM or the Air gap.Much better suited to the RPM range.That is unless you are going to be shifting at 6500+.

Originally posted by Scott L:
I ran a 280/290 @.006 cam with (measured) 7cc flat tops, zero deck and vortecs. My heads measured 62cc and I used 64cc to account for the plug, ring land, head gasket not round, etc. Ran fine with 34* timing at 180* coolant. I also run a sealed cowl hood too. If you go solid, I'm in the process of putting a Ultradyne 276/284f10 in the above combo. I can tell you how it came out. Hopefully it's not windy, rainy, or freezing this weekend.
Hey Scott, how did the cam swap turn out? I am seriously considering the exact same cam for the next 383 I am building for 280z using Vortec heads.

Runs better everywhere.
Had to pull 6* of total and 4* vac adv.
28* total, 8* vac now in by 3k with 2k converter in 3600lb w/me n car w/3.08's.
Can't run a 180 stat anymore, 160 only. Not sure if it will take a 180 in the winter. I have a cowl hood so it doesn't get "hot" air, but if it's 100 outside.

I ran some mixed raced gas for about 97 octane and did back to back chasis dyno runs. Tried timing at 28 and 34. Only picked up 5hp.

I'm either cam or head limited. My hp peak is about 5200 w/307 & torque pk at 3200 w/370.
With a deft foot I can sometimes get a no bog run in and get 430 ftlbs at about 2600rpm. The converter doesn't grab till about 2800.

Need at least a 2500 stall due to the lumpy idle.
Put it pulls just fine with my 2k. Staple shifter is real easy to hit neutral in.

For your set up I'd rec a 280/28x solid or bigger.
They say a 106 or 108 is better in a strip car.
With the small vortec port, I think that is hurting the topend. But I get a very noticeable drop in accel at about 6600 rpm. With both cams.
I've got plenty of spring. (now)

My CR is very close to 10.9 with 7cc reliefs.

Originally posted by Scott_68_SS:
Runs better everywhere.
Had to pull 6* of total and 4* vac adv.
28* total, 8* vac now in by 3k with 2k converter in 3600lb w/me n car w/3.08's.
Can't run a 180 stat anymore, 160 only. Not sure if it will take a 180 in the winter. I have a cowl hood so it doesn't get "hot" air, but if it's 100 outside.

I ran some mixed raced gas for about 97 octane and did back to back chasis dyno runs. Tried timing at 28 and 34. Only picked up 5hp.

I'm either cam or head limited. My hp peak is about 5200 w/307 & torque pk at 3200 w/370.
With a deft foot I can sometimes get a no bog run in and get 430 ftlbs at about 2600rpm. The converter doesn't grab till about 2800.

Need at least a 2500 stall due to the lumpy idle.
Put it pulls just fine with my 2k. Staple shifter is real easy to hit neutral in.

For your set up I'd rec a 280/28x solid or bigger.
They say a 106 or 108 is better in a strip car.
With the small vortec port, I think that is hurting the topend. But I get a very noticeable drop in accel at about 6600 rpm. With both cams.
I've got plenty of spring. (now)

My CR is very close to 10.9 with 7cc reliefs. =
Hey Scott,,
Are you still going to do the RaceRite or AFR thing,, that should improve the top end ever so slightly :D

Yes, waiting for spring to go to the strip to see what my setup will run as is.
Been too busy to swap them anyway. Working lots of OT to pay for one of my motors.