Hey guys, ok I dont know if your gonna be able to help me out or not b/c i dont haveall of the info I prolly should have. Its a rebuilt 402 block, I dont know the comp. ratio but i do know it was done not to long ago. it has a .575 lift in/ex in it now and i got a comp cams xe262h-10 (218/IN 224/Ex @ 0.050) with the lifters.is this cam to small? Should I keep the one thats in it? Its for a street motor, I'll prolly never take it to the track. Thanks in advance.

To be honest,without knowing your compression ratio,its difficult to speculate if you got the right cam or not..it will certainly have a smoother idle than your current cam,as with .575 lift I'm sure it has at least a 232+ duration @ .050

That's a pretty small cam for a big block- even if it is a smallish big block. We really need some more info to give you the real scoop but that cam is probably more suited to a 9:1 or lesser compression motor.

With a 4 speed you certainly can get away with a bigger cam even if it is a 9:1 motor.

But if it's say a 10:1 motor, you will probably end up with detonation problems with that small of a cam.

What's wrong with what's in there? You didn't say.

Troy.

There is nothing wrong with the cam that was in it I was told it was prolly to big for the street, that it was more of a drag cam. If I remember right it has 253 degrees @ .050 duration. Its a newer cam..by that i mean it wasnt run very long. How do I find out the cp ratio? When I got the car ( the motor came with it) The guy told me that it had a valve sticking so I took off the heads and when they/whoever rebuilt the motor never touched the heads so I was going to send them out and get the machine work done and put new valves and everything else in it. I'm trying to learn about all of this as I go so bear with me.

Craig,

Don't worry about being green. We all were at one time. That cam may be a little big but with a 4 speed it may be OK especially if it's a solid grind. Do you know what type of lifters you are running? Did you pull the heads yet? What ratio are your rear end gears?

You will need to find the volume of the combustion chambers on those heads. You can have it checked when you have the heads worked on. You will then have to know the piston volume as well. If they are flat tops, you need to know the volume of the valve reliefs. If they are pop-ups, you need the dome volume. Look for any identifying marks on them like a part# and overbore size. It would also be helpful to know your deck height (how much the piston is in the hole at TDC).

Report back with that info and we should be able to give you more of a definite answer.

Troy.

Craig, Troy is right on.

It will depend on what your compression ratio ends up being as to whether or not the XE262 works good for the street. If its' in the 9.5 range, that small cam is definitely the ticket! I believe that's about what CompCams recommends. It would be much more streetable than the larger cam for sure and the 402 would really be more responsive, peppier, not to mention more gas friendly. :D Frankly, I agree with the 252 degree cam being too large for your 4000 lb. street car.

On the other hand, if the compression ratio is high (10.1 or higher) you may run into detonation problems using the small cam while crusing around (not very enjoyable). graemlins/sad.gif

Good luck and report back.

Charles

troy70SS,

Thanks for all the help so far! As for the lifters I believe they are soild but i'm not really sure. Its they same type as the ones that came with the new cam. As for the rear end, it has 4.10 in it but i think i'm gonna change them to 3.73 or 3.42, depends on how i like the one thats in it. One of the heads are off and are stock as far as i can tell. the pistons are flat top with a little relief for valve clearance. I'll check the deck to tdc of piston clearance this week sometime. I know I havent found out the cr yet but i'm not sure how to yet. Is there some kind of gauge I stick in the spark plug how and turn the engine over? Thanks again guys!!!

Oh, also I'll get the numbers off of the heads and block if that info would be of any help!!

I was going to say that armed with the old cam info, if you did a cranking compression check you could GUESS at the compression ratio. Something like with that big of a cam in it, it better show 160 or less cranking psi. If not then putting the 262 in, ( which is a great mild street chocie) might shoot your dynamic compression too high.

Take some digital pics of the domes and the chambers. Prerferably with a machinists scale for refernce.

Want to be sure you don't stab that new cam in and have a pinging problem.

Whats is the CC of stock BBC heads? I dont have a digital cam so i found some pic that look just like mine, they are here..

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=2738&prmenbr=361

If you enlarge the pic, mine look just like the lower right...Flat top with 2 valve relief. Now all that i have to do is find out what a stock head's CC is. I hope this helps.

Flat tops? Oh heck you can't get into 10:1 with flattops very easily. Your new cam choice ought be fine. Even with the smallest available GM bbc chamber of 97cc, you wont be over 9.5:1 I think ( havent done the numbers - so you need to confirm).

If U have flat tops with valve reliefs in a 402 even the smallest closed chamber head would only net around 9 to 1. Please post the casting number on off the heads. We can give U the chamber size from there. Also post the casting # off the block, Ive never seen flat tops for a 396/402. It seems odd that someone would put that big of a solid cam in a low compression 402????? But if they rebuilt it and didnt do heads who knows. U should hold off on buying parts or putting any $$$$$ in to heads, till U find out what U have.Its not hard to spend alot of money on a motor. Where are U in michigan??? Im in the thumb area. Have somebody locally that's knowledgable on big block look at your setup. Or keep asking questions on this site. The cam U bought sounds like a good street cam for a mild 402. U can email me directly at supersport6667@hotmail.com if I can be of anymore help.