ORVette

I have a rebuilt non-orig. 350 4 bolt with 8-8.5:1 compression and rebuilt 3998993 "Hecho en Mexico" heads with 1.94/1.50 valves and about 75cc chambers(lightly milled). I am running a Holley 1850-600cfm vac.sec. carb with 68 primary jets, Performer manifold, Mallory Unilite electronic ignition(12*init.-36*total all in by 2200), and Sanderson 1 1/2 primary manifolds into 2 1/2 duals. This spring I installed a Summit cam kit with 204/214 dur.@.050 and 420/442 lifts(112LSA). The reason I chose this cam is because it seems to have the exact same specs as the Edelbrock Performer cam and I thought it would be perfect for my TH400 with stock converter and 3:08 rear. It does work pretty well, 18 inches af vacuum @ 600rpm, but it still seems a little soft. This thing definately will not burn the tires, and for a cam that was supposed to build great low end torque, I just don't feel it. I have a '74 Monte Carlo with a SB400 and similar mods with the exception of a Crane 266 Energizer(210@.050-.440" lift), and although I havn't run them side by side, I'd swear my Monte would walk right away from my Corvette. And do it with 1000 extra lbs. My 'Vette idles well, has great vacuum, and gets decent fuel economy, I just expected a little more performance with this setup. Any thoughts?


[Modified by ORVette, 9:21 PM 10/1/2001]

Ganey

Not enough cam for a Vette. Would work good in your 74 Monte if it had a 350.
Get a Comp Cams 260H or XE256 (212 @ .050 intake) for the Vette.

:cool:

Budman68

I'm running that same cam and it works great with fuel injection. Idle normal, very little lope. I'm running high compression, so at 650 rpm you can just about hear every cylinder fire. Just like your stock cam don't expect alot over 4500 rpms. This cam is a torque cam and response well at idle, add 1:6 ratio rockers and you will gain .30 lift alittle more top end.
Good luck

nunus79

Try doing a cranking compression test. I would imagine that your cranking compression numbers are pretty good with your setup but, if your results are like 150 psi, you might want to consider advancing your cam to build some more cylinder pressure.

180 - okay street
200 - good hi-po
220 - good street/strip
240 - strip

tnt76vette

I'm using the Comp 260H 212/212 .044/.044 lift and it does a good job of diggin' me out and really takes over when the 2ndaries kick in, compared to stock...only other mod was a Weiand Dual Plane and chambered pipes, in an otherwise stock L-48 Auto :D

ORVette

Thanks for the replies. I just took a compression test and got within 2psi of 140 on each cylinder. Is there any way to estimate how much pressure I'll pick up by advancing my cam 4deg.? My timing set is indexed for +4,0,-4, so I'm OK there.I considered advancing it when I first installed it, but I thought there might allready be 4-5deg. ground into it, plus, with such short duration and lift I didn't think I'd need it. I can't tell from the spec card if there is any advance ground in, it lacks some of the info normally included on other cards I've seen. Any other input much appreciated.

nunus79

I was running stock 76cc rebuilt smogheads with my current cam straight-up with conventional lifters. I didn't do a cranking compression test with this setup. But I did do one after I advanced the cam 4 degs and installed the Rhoads lifters. I ended up with 155 psi +-5psi. I would think the cranking compression before the mods was less than your setup. So, a 4 degree cam advance alone would not likely net you more than 10-15psi.

I am not familiar w/your cam profile. Is it possible that it is installed a little bit retarded, which could further aggravate the low-end problem? Everybody says to degree the cam in, etc., etc., for this purpose.

If you don't have it already, Vizards book titled something like How to Build a SBC for Max Performance on a Budget is where I am referencing the cranking compression numbers/ranges. Cylinder pressure is what makes the torque! Your cam timing & overlap has alot to do with making cylinder pressure.

ORVette

Here is my cam spec card. I didn't degree it when I installed it, but I put it in straight up according to the marks on the sprockets. I'm also sure that the multi-key crank sprocket was in the proper position for 0 deg. adv/ret and that I alligned its mark with the 0 deg mark on the crank sprocket. I checked my head work sheet and it says they milled .006 off, which would still leave at least 75cc chambers if my math is right. This motor was in the car when I got it and it's kind of a low buck "POWERMASTER" remanufactured job with what I'm sure are low compression pistons to make them safe on their warranties. I should've measured the piston to deck hieght when I replaced the heads, but I didn't. I'm sure it's a combination of low comp. pistons, 75cc chambers, and the thick .041 Fel-Pro head gaskets I used that are adding up to my low cylinder pressure.

If I could just talk my wife out of going to Mexico for vacation this winter, I could solve this whole mess and just buy a better motor. No chance of that though, so I guess I'll have to deal with what I've got. Thanks for all the help.



[Modified by ORVette, 9:50 PM 10/1/2001]