I was planning on running the Crane 343801, but my machinist gave me another option that looks good, its the Comp 33-248-4.
I will give the specs. on both and you guys dish out your experience and opinions, please.

343801- Adv. Dur. 278/290, Dur. @ .050" 222/234, Lift .548/.580
Lobe Sep. 114 degrees, 2200-5200 RPM

33-248-4- Adv. Dur. 274/286, Dur. @ .050" 230/236, lift .562/,565
Lobe sep. 110 degrees, 1800-6000 RPM

Anybody out there use the Comp? Any help would be greatly appreciated.

 

That is the XE274 right?

If so Comp tech support said it would probably preignite/sparkknock in a 9.5:1 390 with stock heads.

Alum they said would be fine.

I like my 801 myself. DD2000 says it is a 1 HP per cube cam with good heads.

 

I would think the Crane would be more prone to preignition than the Comp, because of the tighter lobe separation then the Comp. I'm running a Crane 272 Energizer with 10.5 to 1 comp and it does suffers no preignition. It also has a 110 degree LSA

 

Max, are you going to use this in front of an auto or manual tranny ? And in what size engine ? I have the Crane '801' cam in a 390 with an auto and 3.5 gears, 33 inch tall tires. It is doing fine. The numbers sound strange for the Comp....they claim less seat duration and more .050 duration, but with less lift than the Crane...it doesn't seem possible. The Crane lifter accelleration is already very fast, and the Comp usually has softer (chevy ) lifter rise rates. That and 230 intake @ 050 is kinda big if you have an automatic tranny. But I've seen and had so many problems with Comp that I wouldn't take one if you gave it to me for free. I have had no trouble with Crane, so the choice is easy for me. DF

 

Part of the reason is DF is that Crane measures advertised at .004 and comp uses .006. I don't care for comp either. They make great chevy cams. I wouldn't go too much more aggressive than the 801 either.

 

I'm running it in a .030 over 410 with a 4 speed. Thanks for your input guys.

 

What kinda headwork have you done? You may be killing the engine with the extra duration. YOu may be wasting your time with a dual pattern cam if you have had some major porting done on the exhaust side. If your exhaust ports flow 75% of your intake ports or greater than you don't need a dual pattern. If the heads are stock you are in definite need of one. How much compression are you going to run?

Lower LSAs create more cylinder pressure and give more low - midrange torque at the expense of lower vacuum at idle.

 

Uh, don't you have that bass-ackwards? A LSA thats lower should be an indication that the overlap will be longer , thus increasing the time that the intake and exhaust are open at the same time, this increases the scavenging at higher rpms, but decreases the cylinder's static comp ratio. A higher ( or wider) Lobe separation angle will do just the oposite.

 

A lower LSA will create more overlap but it will pull the intake event further out of the compression stroke therefore raising the cranking pressure. Overlap does not effect cranking pressure as the piston is on its way down during this period. I just went through all this as I thought the same way you did.

 

My heads will be basically stock except mild porting on the exhaust. I am planning on 10.0:1 compression

 

I love the crane 801. You might step up to the bigger crane with 10:1 compression to avoid problems with detonation. It has a duration of like 234/238 and a .554/.563 lift. I'm going off the top of my head here but the numbers will be close. That will kill the torque a little bit though. In a 4X4 I would step the compression down to about 9:1 and get the 801 cam.

 

It's 2 wheel drive, I don't think that I'll have problems with detonation on 91 octane.

 

Ratsmoker,

I want to clarify something you posted above.

You said in one post "Lower LSAs create more cylinder pressure" and in response to baddad's post you said "A lower LSA will create more overlap but it will push the intake event further into the compression stroke therefore lowering the cranking pressure".

Though in one post you called it "cylinder pressure" and in the other you called it "cranking pressure" I have to assume that you meant the same thing.

I have to agree with your first post. A lower LSA creates increased cylinder pressure in spite of the increased overlap. This is because the overlap occurs as the exhaust stroke is ending and the intake stroke is beginning, which makes the piston virtually motionless at the top of its travel. Because the piston is making very little progress in either direction during this phase, the overlap value is not extremely significant in terms of dynamic cylinder pressure. What is significant is the intake valve closing event. With a lower (say 108) LSA the intake event is pulled farther out of the compression stroke (assuming the intake centerline is left at 108 also), increasing cylinder pressure. If we widen the LSA to 110 and leave the centerline at 110 the intake closing event is pushed farther into the compression stroke, reducing dynamic cylinder pressure.

Consider the following two cams with the same duration but different LSA, both ground with no advance or retard.

Int 262/exh 262 LSA 108 CL 108
IVO 23 btdc
IVC 59 abdc
EVO 59 bbdc
EVC 23 atdc
Overlap 46 (23 before and 23 after tdc)

Int 262/exh 262 LSA 112 CL 112
IVO 19 btdc
IVC 63 abdc
EVO 63 bbdc
EVC 19 atdc
Overlap 38 (19 before and 19 after tdc)

Notice that the lower LSA closed the intake valve sooner increasing pressure. Just the opposite for the wider LSA. As for overlap, it's easy to see that 23 degrees on either side of TDC pales in it's overall effect in cylinder pressure compared to the 59 degrees of intake valve into the compressiong stroke.

Now if you start moving your CL around everything can and will change.

If I've missed something here, which is entirely possible as I am relatively new to camshaft basics, let me know. The purpose of this post isn't to accuse, but to clarify, as your posts seem to contradict each other and I agree with only one of them.

-Scouder

 

Wow! I completely messed that post up. You are agreeing with the correct statement anyway. I gotta go fix that! Good catch. That post almost contradicted itself within itself! Cranking pressure should be the right answer for that. A lower LCA raises cranking and low RPM cylinder pressures. At higher RPMs this will sometimes reverse.

 

Ratsmoker,

Cool. I too, used to be an "overlap" guy until I started asking questions and trying to decide on a compression ratio for my engine. Now I'm an "IVC" guy and everything falls into place.

-Scouder