Crower Cam Problems

[Darwinskeeper]

Just returned from my latest road test and got a discouraging 19mpg at 70mph. After a little thought I'm coming to the conclusion that the Crower 03340 (with 240HDP 114 deg grind) is not producing the economy that I hoped it would. Last Summer's road trip produced 20-22mpg on the highway with a Comp Cams 252H grind (206/206 [email protected]; .425/.425 lift@valves; 110 sep) and I had hoped that the milder Crower (182/190 [email protected]; .386/.287 lift@valves; 114 sep) would produce better low end torque and superior mileage. Sadly I have yet to see the engine break the 20mpg barrier and have seen 17-18mpg on most of my highway runs. I have replaced my Proform HEI with a Performance Distributors' DUI, had the carb rejetted with a wide band 02 sensor and did what I could do to eliminate other potential problems. My only conclusion can be that either the 1.52/1.60 rocker ratios are the source of the problem or that the Crower isn't doing the job I purchased it to do. I'm guessing that the Crower 03340 may have been designed for a fuel injected engine (which the majority of 4.3 V6s have) and may not work well in carbureted applications. I will probably swap to another cam next Spring.

 

[mhamilton]

Sorry that new cam didn't work out for you. Just guessing from the specs, it could be the extra overlap that is dropping the economy on the Cower. The stock cams are 108 or 110 (right ?).

Could also be that it's just moved your power peaks to a different rpm, where the old cam was better at your cruising rpm.

When I was making that spreadsheet of cams, I remember the Cower was very differne than stock and the other major aftermarkets. The Comp took the stock profile and basically added more intake duration, and more lift on both lobes. The cower seemed to move the overlap, and radically change both duration amounts. Not really sure what to make of those changes without a dyno or something.

 

[Darwinskeeper]

Mhamilton,

You're confusing me, I would have assumed that the Crower cam with a lobe separation angle of 114 deg and lower intake and exhaust durations would have had less overlap than the Comp 240H. I have read that a tighter lobe separation hurts vacuum at idle but improves low end torque, so the Crower's separation could be hurting me in my 1200-2500 cruising zone.

It also could be that the short duration for the Crower (182intake/190 exhaust) might have hurt torque in the 1200-2500 rpm range.

In any case, the 252H cam I started out with didn't do that bad for last Summer's road trip, so I'll probably try the next step down with a Comp 240H when I get around to my next cam swap. I've already sent an inquiry to Comp Cams on the subject.

 

[mhamilton]

You're right, I've mixed up LSA and overlap. Lots of overlap is good for high rpm performance, but kills low end and idle. No overlap makes good idle and lots of low end torque. The stock cams were small overlap, and peaked the torque around 2500 rpm, hp around 3800.

But, looking at the GM vs Comp vs Cower, the Comp "looks" just like a GM designed cam. The Cower level 1 lowers the exhaust duration. I don't understand what the thinking is on that. Stock GM exh duration is 194 on even the slowest smog engines.

I'd be interesting to know what comp says. I wrote to them and never got a reply about cam data.