Help! would like to buy Dart Pro 1 Big Block Chevy Cylinder Heads. Which intake runner size should I buy? 310, 325 or 345cc??? I have the current parts listed below and will be adding a 1071 blower later this year.

1991 502 mag
Holley 830
Dart intake with a 1" spacer
Crane Performance Cam # 139661 (note cam produced 550 hp in an identical setup with iron ported heads.)
Crane Performance Gold Race Roller Rockers Part # 13750-10
Lunati Hydrolic Race Lifters # 71817G
Stainless Steel Marine Exhaust

Thanks Bill (BAJA 270)null(note cam produced 550 hp in an identical setup with stock iron ported heads.)null[i]

[ 02-05-2002: Message edited by: baja270 ]

Do you want it to run better now or later with the blower? N/A would do better with the 310 or at most 325 and the blower with the 345.

Would I gain anything with the 345cc now???

I have not yet installed the cam but with a natuaraly asperated moter the cam produced 550 hp, and blown (871 blower) with the ported stock heads it was 700hp. Currently I am at 435 hp.

Thanks for the reply

Bill

My opinion, go with the 310 cc runner, and if this is a hydraulic roller camshaft your camshaft is about 15 degrees of duration to big. That cam in a 502 will need to spin to 5900 to be of any use, it will be very lazy from 3500-4500.

Staying natural asp. go with the 310's. Without a doubt.

If you're gonna put a blower on, just go with the 345's because even if you were gonna stay conservative with the boost (in which case the 325's would be a good choice)you, and we all know, down the road you're gonna put more in.

Furthermore, I tend to think a 1071 is too big as is the cam for a 502. That does, however, depend on the amount of boost, rpm and type of fuel available.

In my opinion, roots blowers on a boat should be in the overdrive mode, because of the limited amount of time in the boost range. You end up waisting too much hp just to drive the thing if its too big. Again, that's my opinion.
To give you an idea, an 871, which is my choice for a 502 at 10% overdrive, also my preferred max range, will produce AROUND 9# of boost, at 5% around 8 and a 1:1 which is as low as I would go, will give you around 7.
So, knowing this, if you were gonna stay around 5# you may even consider a 671 at a 1:1 drive.
Just food for thought.

Like I said, it all comes down to how much boost you want, how much you'll be in the boost and most importantly what fuel is available to you.

As far as the cam, I would probably put that in a 572 or larger motor.
A 502 I would stay around the 139741, 234/242 112 .610/.632
I agree with Bruce that your rpm range will be too far up the scale trying to use that cam.

Just my opinion. I hope I could help.
DAVE

Thank you for all of the replys! much appreciated.

Bill