Dennis, cam question
 

Dennis,

I've narrowed my cam choice down to two cams for my 454 Mag MPI (Gen VI):

1. GMPP #24502611: 211/230 [email protected]"; .511/.540 lift; 112deg LSA.

2. Comp Cams 01-414-8-112: 218/224 duration@ .050"; .511/.511 lift; 112deg LSA. (This cam was recommended to me on Comp Cams' hotline.)


On Dyno 2000, these cams produce almost IDENTICAL power curves. The GM cam is about 5 lbs-ft higher from 2000-3500 rpm and peak power is about 6hp higher at 5000rpm. Obviously, these numbers are too close to assume that Dyno 2000 is dead-on accurate. Based on your experience, would you choose one of these cams over the other? Does Comp Cams tend to have faster opening and closing flanks than GM, which might generate more power but not show up in the numbers? Any problem using the stock valvetrain with either cam? Any other advice?

One more note, Dyno2000 shows that the Comp Cam has no overlap (-3.0 deg) and the GM cam has -3.5 deg, so I'm assuming water reversion should not be a concern.

Ric 232
 

I really like the Comp Cams 218/224 but I would order a cam with a 110 LSA. What does the dyno program say when you tighten the LSA?
I would install it with no advance for a more noticable performance gain.

I don't know why Chevy designed a camshaft with 19 degrees more exhaust duration than intake. They must have some reason but nobody else has ever done it!
As far as I am concerned the longer you hold the exhaust valve open the more water you are going to get back into the cylinders at an idle.

I hope I am right about that. But it makes sense to me!

Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

Dennis,

The guy I talked to at Comp Cams stated specifically that I should order w/ a 112 LSA to avoid water reversion. He said this w/o me asking him.

Anyway, when I change the LSA to a 110, the peak torque goes up 5 lbs-ft @ 3500 rpm and 13hp @ 5000, 21hp @ 5500 (higher than I think I want to run). There is almost no difference between the HP graphs with 112 vs 110 until you reach 5000rpm.

Rick, have you considered a 502/502 (ZZ502) camshaft?
.527" / .544" 224* / 234* not sure of LSA

I am going to run this in my 454. Stock valvetrain will work OK, but I am installing Comp Cams springs.
If interested, I can get you a good deal on a new, pull-out cam.

Thats very similar to the Edelbrock Torker 2 flat tappet cam that I use. 224, 232 at .050, lift .527, .553 at 114 and I install it 5 advanced. Works very good in my 468's with no reversion.

These cams are way too small to worry about reversion. ;) I would go with the comp on 112 CL for your application based on the r's you want to turn.

I've got some experience with the GM 454HO cam that you list. I also did the dyno 2000 thang and was impressed with the power I was 'supposed' to pick up (almost 80hp difference at 4600rpm). I installed this cam and Gil manifolds and only picked up 2 mph. Was kinda dissapointed. It pulls waaaaaaaay harder down low, to the point i can blow out my prop fairly easily, but at 4200 rpm, it poops out. It also has a very boring, smooth idle. My friends stock 454 mag idles 'badder'. Might be my heads tho, i'm running the Vortec heads, maybe the rect port work better with this cam.? Any comments on this Dennis? I've been toying with the idea of some Edelbrock marine aluminums now......:p At what speed does the need to go faster go away???:D

At what speed does the need to go faster go away???:D [/B][/QUOTE]

NEVER:D

Good cam for the Vortech heads.
 

Madmax,
I bet that is a good cam for the Vortech heads! No, I wouldn't go with the rectangle port heads. They are just too big for anything but a monster motor. The Edelbrock marine heads are great (hard anodized aluminum and inconnel exhaust valves) but you would have to change the cam again to realize a performance increase.

JDNC1,
I agree that the cam is way to small to worry about reversion. I think Rick is going to be disappointed with the small/if any performance increase. It is very hard to improve engine performance without increasing engine speed.

Formula31
I rebuilt a few 454 engines for a winter project one year and installed the cam you suggested and they worked very well. A really good replacement for the stock camshaft with a good performance increase (also very reasonably priced!).

Dennis Moore

Dennis,

What kind of LSA would recommend for naturally aspirated 540 cubic inch engine with a cam that has something like 234*/240* (about .600" lift) ???

Thanks,
Mark/KAAMA

LSA
 

112 would be the tightest you should go to keep water out of the exhaust at an idle.
Dennis

Kaama, I run an Ultradyne with those exact specs in my 555. It's an EFI engine, so I had it ground at 114. I have 140 hours on it so far. I run Stainless Marine exhaust with captains call. I've seen no signs of reversion and it idles very good at 700 RPM. On the dyno it made 608 HP @ 5300 RPM and 648 ft. lbs @ 4400 RPM. It fell off rapidly above 5300 RPM. I assume it was not nearly enough cam to pull beyond that, which is fine because 5300 was my target peak RPM.

The 500EFI Cam Specs Crane Part Number 169621
230/236 Duration, .598/ .610 Lift on a 114 Lobe Center.

Has any one tried this cam in a 502 mag???

What changes are necessary?? I would assume reprog ecu(possibly bigger injectors ?), dif lifters because of the lift being greater than .56, dif springs

bobl,

What kind of heads are you running and what kind of port work if any? Thanks

By the way Dennis, thanks for your response. I was happy to hear that it was 112*. I have heard that when getting into the larger cubic inch engines that they tend to like wider LSA's---is that a fact or myth? If true why is it that they like the wider LSA's?

Kaama, I'm running Brodix BB2+ heads with a good bowl blend, port match and polish on the chambers. 2.25/1.88 Valve sizes.

Wider lobe separation
 

Kaama

I don't know, I have heard the same thing, I have also heard that automotive Pro Stock Drag Racing engines use 116 LSA and wider. I have heard that wider LSA increases performance at all rpm ranges including top rpm. Closer LSA angles increase performance only in the mid range (they do provide more midrange performance than a wide LSA). Could be that wide LSA is the best for extremely high rpm power.

I think 110 is optimal for a marine engine. Most camshaft designers believe that an automotive engines optimal LSA is 112. Automotive engines with large camshafts that need vacuum for power brakes and a smooth idle need 114 - 116. Not much difference between 110 and 112 but there is a difference between 110 and 114 in midrange performance.

Valve overlap is the reason for water entering the cylinders at an idle. I am a firm believer that a short duration camshaft (because the camshaft has less overlap) can use a closer LSA. Longer duration camshafts (because the camshaft has more overlap) need to use a wider LSA.
Hope this helps someone!
Dennis Moore

DonMan,

What model is your 454? Mag? Carb or EFI? Do you have silent choice or capt call exhaust?

I may wait to see how your cam swap works out. Despite the comments here, I'm very concerned that the 502/502 cam (with 9 degrees of overlap !!) will suck up water. No matter how "small" the cam is, it's the overlap that causes reversion. I simply cannot afford to destroy my engine, or even have to go back and put in a different cam later.