I'm dropping a 355 with AFR180 heads into my Chevelle this weekend. The cam is a Comp XS262S solid. Duration at .050 is 224/230, lift is .477/.488. Recommended lash is .016.

Here's my question...I have heard that a car with good exhaust and a cylinder head that flows well on the exhaust side might work better with a single pattern cam, as opposed to a split pattern like the XS262S. I know I could experiment with 1.6 rockers on the intakes, but would it make sense to experiment with tighter lash on the intakes instead of the bigger rockers? I'm thinking that a lash of .014 or something similar on the intake side will make the intake lobes look "bigger" and more closely approximate the exhaust lobes. Any feedback welcome.

Interesting Q, wonder what both would do. 1.6's AND a .013" lash on the IN side? The modest loss of velocity off the seat ( by using all of the take up ramp, and more), would be somewhat offset by the quicker arm ratio. ???

This should be a good thread!

I put 1.6 on exhaust side 1.5 on intake.This made a scavaging effect and worked well for my 355.

Originally posted by BB485:
I put 1.6 on exhaust side 1.5 on intake.This made a scavaging effect and worked well for my 355. Interesting, most engine make more power with 1.6's on the intakes and 1.5's on the exhaust. Has to do with maintaing port velocity in the exhaust port. The extra lift tends to slow down the spent gases.

Mike,
Tightening up the lash will increase duration. The higher ratio rockers will increase duration, also. It's all pretty easy to try. Give it a shot. If doing this drop the DCR too much, you could pull a bit of cam advance out to increase cylinder pressure. I'm interested in any results you came up with.

Thanks guys. I know the common sense answer is just buy a single pattern cam, but this motor is already together and going in tomorrow, so I'm just gonna do some testing at the track. I figure if the lash has to be set periodically anyway, it won't cost me anything to experiment some. I already have some 1.6 rockers also.

350 cid Small Block Chevy Package
AFR 180cc Street Heads
9 to 1 Compression
1 5/8” Headers
AFR FloPower RPM #5029 and 600 cfm Holley Carb
110E Hydraulic Cam
Intake: .460 lift/218º @ .050, Exhaust: .470 lift/223º @ .050
110 lobe center, 800 RPM idle, 16 lbs. of vacuum

Mike this is the specs that AFR had for there dyno test on the web site. Don't know if you saw it?

Originally posted by 77 cruiser:
350 cid Small Block Chevy Package
AFR 180cc Street Heads
9 to 1 Compression
1 5/8” Headers
AFR FloPower RPM #5029 and 600 cfm Holley Carb
110E Hydraulic Cam
Intake: .460 lift/218º @ .050, Exhaust: .470 lift/223º @ .050
110 lobe center, 800 RPM idle, 16 lbs. of vacuum

Mike this is the specs that AFR had for there dyno test on the web site. Don't know if you saw it? Yes, my combo is very similar...the cam is slightly different, I'm running an old Z28/LT1 factory aluminum intake, and I'm running a 650DP carb. I'd love to duplicate their results, 435lb-ft and 420hp.

The diff. between the cam AFR used & the one you chose is going to be close in lift(factor in lash) & dur. @ .05 (solid vs. hyd.) Biggest diff. will be the seat timing of their cam.

I always thought that old Z intake kicks tail!

Originally posted by 427L88:
I always thought that old Z intake kicks tail! Yes, I have one I bought over the counter from a Chevy dealer about 15 years ago, casting number 14044836. It's very similar to a Performer RPM, but the vacuum fitting on a Performer RPM is right in the darn way to where you have to run a 1-inch spacer under the carb if you have power brakes. The factory manifold is better designed in that respect, plus it's just cool to me being a factory piece, so I'm gonna run it and see what happens.

That cam will work fine.1.6s on the intake valves would be even better, Those heads will like the extra lift.

16 lbs of vacuum at idle? How much does a pound of vacuum weigh?

Originally posted by onovakind67:
16 lbs of vacuum at idle? How much does a pound of vacuum weigh? Ummm, a pound? ;) tongue.gif

OK: 16" of vacuum.

How long is your vacuum???? :cool: