working on a 73 Covette. th400, 3.08 rear. The engine is a 350 4bolt with 9.75-1 compression. No porting or headers. Performer intake & Q-jet. what would be the best 2000-5000 rpm cam for a engine with 9 3/4 compression & the 3.08 gears? Oppinions? thanks

 

I just had my engine rebuilt in my 73 L82 4spd. I went with a Comp Cams XE256H per Comp Cams recommendation. I haven't started the new engine yet .... I would get recommendations from the various cam manufacturers for your setup.

Here's a good article & benchmark of what certain cams and components do for performance.
http://www.compcams.com/Community/Ar...p?ID=521241382

The other advice that I've always heard is that if you are on the fence between two cams - its usually better to go with the smaller cam. Most cam problems occur when people think they need the bigger cam - then the car won't idle and requires lower gears

good luck - I struggled with this for a while myself

 

with stock heads, I say comp cams268H or XE262.

 

Some consideration is not only the power band you want to operate in, but your gears and the stall speed of the converter. If you have a stock auto, the stall is probably around 1600-1800. If you get a can that runs 2200-5500 you are not in the power band when the converter stalls. Basically, if you go too agressive in the quest for power and run an automatic and 3.08 gears you will end up with a something that goes real flat and look when you step on it.

Comp Cams 268 will have a slight lope on a 350, but is a good overall choice. Lay out the specs for the 252, 260, 262, 268 and look at the operating range and the torque for each. Don't forget to look at Crane and do the same thing. The XE series is a more agressive ramp.

When you change the cam, match the valve springs to what the manufactures says you need. Too much or too little pressure kills cam lobes. Good luck on the change.

 

I've run both Comp 268H and Edelbrock Performer cams in various 350's,and I'd pick the Performer for your combination.Shorter duration with everything else basicly stock works well.It will pull to 5000 strong,run to 5500 no problem,work the brakes and idle like a stock 350.
It should.It's only about 10 degrees bigger than stock.

 

I recently installed a 4 bolt 350, flat top piston, 461 double hump heads, XE268h cam engine in my 80. Our set up sounds close afa c/r. IMO be ready to fight the Qjet idle. I will be ordering a 650 speed demon (idle ease circuit) and edl rpm intake next week with hopes of ending the dismantling of a carb just just to change a spring. If you want to keep the qj maybe consider the xe262. I also have 3.08s w/auto and 2200-2400 stall converter. This combo will spin the tires but will not light em up. Hang on once she is rollin.

 

Also look into the "voodoo" line from Lunati. They're designed by Harold Brookshire, a legend in high performance cams. The voodoo is his newest line and he says they are substantially better than any older design. Back to back dyno testing reportedly shows 10-15 hp gains compared to similar older cams.

http://www.jegs.com/cgi-bin/ncommerc...85&prmenbr=361

Either the 256/262 (60101LK) or the 262/268 (60102LK) would be a good choice.

 

I'll have about 9:1 or maybe 9.25:1 CR w 67 cc heads and will be using the Comp 260H cam, same tranny and gears, Holeshot 2000 TQ.
Gary

 

Crane PowerMax 268 has similar specs to XE-262, but wider lobe seperation angle for smoother idle and detonation resistance. Comp also makes a 4x4 version of the XE-262 that has a little more exhaust lift and duration and wider LSA. All three make power from 2000-5000 RPM. The narrow LSA of the XE series requires headers for optimum scavenging. Joe

 

I'm leaning for the Crane powermax 272 ( crane recommended) because though I have the stock 76cc heads, I also have .100 dome pistons that makes a true 9.7 compression. I'm just making sure I don't run into detonation problems. anyone used this cam?

 

I had that cam in my engine before I got it rebuilt. Liked it a lot. It pulled hard to 5000 (I had an unrebuilt L-48) and sounded great.

I went through two XE series cams from Comp that wiped before I went back to Crane for a hyd roller setup. Comp tends to grind on a narrower lobe angle that yields that choppy idle. Comp seems to be getting a lot of magazine coverage these days but there are lots of other good manufactuers out there.

Like I said, I am back with Crane and very happy. My hyd roller is the HR276 which has just about the same duration on the intake but a little longer on the exhaust. Great lift of course. I spec at 214/222 @ .050 and .488/.509 total lift.

Edit for tech info:
Forgot to mention. One of the reasons that people like the Comp cams is that they use an earlierintake closing event to build more dynamic compression (higher dynamic compression ratio) which build low end torque but it does increases the chances for detonation. The later intake closing event on most Crane cams decrease the dynamic compression ratio, losing a little low end but decreasing the chance for detonation. The later ICE also results in that wider lobe sep angle.

For example, I have a 10:1 static compression with aluminum heads. With the Comp XE262 (216@.050 if I remember correctly) I could only run about 32 degrees mechanical advance. With the Crane cam listed above, I can run 34-35 degrees mechanical thanks to the bleeding off of pressure due to the later intake closing event.

 

Anyone having any test results using the Air gap manifold vs. a standard high rise manifold. I'm undecided on getting one, although I've seen impressive gains in the magazines by using one...

 

Ask yourself: At what rpm is most of my driving done? If you change gears that changes everything. W/3:08s you need low end grunt to get you moving. You will cruise at 2,000-2500. Peak tq at 3800 won't help you a whole lot. Think about a 256-262 @.050 cam w/1.6 RRs. That will add about 2o of timing and about .030 lift. That should get you moving and have good throttle response! JMHO

Rick