ok i searched and couldn't find what i was lookin for, ive got a 71 4bolt main 350 goin into my car and i just checked the compresion and its perfect. the motor runs perfect. so with the compresion being good im leaving the crank and pistons and rings alone, just gonna put a gasket kit and clean the whole thing but i have a comp cams magnum this one and im plannin on putting it into the motor. so my questions are: should i? what are the chances of effing up the motor? can i just swap it in and not have to fool with anything else? will i need new rockers or springs? do i have to adjust the rockers or springs i have now? will i need thicker head gaskets? maybe more im not thinkin of now. this is my first motor build and id like to keep it in the car thanks in advance

 

you might need new pushrods and new springs would be a good idea the only thing holding you back from just dropping the cam in is the lift you need to get the part number off of the heads and make sure they can support that much lift. chances are they can. but you need to be sure. if they cant and you put the cam in you will cause major breakage inside your engine.

 

by part number do you mean the head casting#? and why would push rods make a difference?
where can i find out if my heads can handle the lift?

 

If you already have a flat tappet cam installed in the engine now, you will not need new pushrods.

Springs, especially if you have the stock crap springs on, would definitely be wise, but not 100% required to make it "work." Again, wise - stock valve springs suck for their intented purpose. Spring upgrade would definitely be beneficial to the valve train.

If they're stock heads, a casting number won't tell you if the lift will be an issue or not. It might be an issue, it might not be. It's really borderline. .480" is the "general" number, but I have seen cases of less. The only way to know for sure is to dummy it up and hand crank the motor slowly, watching all 16 valve springs, and feeling for binding. Unless you have some decent measuring tools.

Your chances of screwing something up, are solely based on how much confidence and ability you have around an engine bay. It's really a pretty straight forward swap. You have to be especially careful not to mess up the cam bearings, but other than that, it's really not that bad. Are you swapping with the engine in the car?

 

no the motors outta the car right now with the top end being disassembled (intake heads etc.) its a stock 71 sbc 350 another thing is with the cam will i run into problems with compression ratio?

 

No.

 

ive heard people say i should run headers with the cam but i dont plan on headers for a while yet is that something else i should be weary of? sorry for all the questions im just tryin to learn as much as i can

 

Headers help the overall performance of the engine. They don't just benefit a cam swap, they just benefit, period. Sure the engine would be a lot better breathing out through headers, but the engine has to breath out of whatever heads you have on there first (stock castings?).

It will be alright until you get headers.

 

ok thank you man youve helped me alot im sure ill have a few more questions later but that sit for now i think. so just to be sure all i really need is new springs? hydraulic lifters came with the cam

 

Upgrading from the stock POS's, yes. New springs are highly adviseable. Get what comp cams recommends. Without looking, I would guess that's probably the 981 set.

Again, be absolutely certain to rotate through a few times, checking for clearance. What you're looking at is the bottom of the retainer hitting the top of the valve guide boss. Or, with the spring off and the valve tightly closed, you can use a micrometer and measure from the bottom of the retainer to the top of the guide boss. Like this:

Take that, subract your "safety" clearance, .050" or so, roughly, and that's your max lift you can run. If it's within spec, you're fine. If not, time to get some machine work done or find a new cam that's within spec.

 

Just go to the COMP website, look up their tech line. Call the number and the guys there can answer any questions you've got. That way you'll know exactly what to expect. Comp is great with their tech help line.