Well my friend is thinking about putting a cam in his engine before we stick it back down into his car. Currently, the bottom-end needed rebuilt and he's getting kind of tight on money, then he seen CMotorsport's deal on cam kits right now and thinks he can swing it. He's staying right around 350 or 355 C.I. with forged pistons and wanting spray. His car is a 6-speed car with no mods currently. When we drop the engine back in, it will have K/n Intake, 1le elbow, and Pacesetter long-tube headers w/ off-road y-pipe into a 3in. cut-out. He was really wanting the Gm-847 cam but since he can get this deal with CMotorsports, The 233/242 .569/.587 115 Lsa is right around that size, right? For now, the only portwork he can afford is what we do on our own. We were thinking just try to port match the intake and heads with a gasket and then smooth out all the casting marks. That's as far as we feel comfortable in doing to his heads, so they will pretty much be stock. And then, would he be able to use his stock rocker arms with this cam? Or would he be running a high risk of collasping the stock rocker arms? Also, would you run the Ex-612's with this cam or not? I know it will be pushing it trying to use these springs, but if he has to upgrade to better ones, there's another $100 that he really don't have at the moment.

 

You will need to change the springs at the least. He also will not feel the full effect of a cam like that with out some kind of head work and a tune. I would suggest ported heads 1.6 rockers new valves new lifters and a set of 30# injectors.

 

Thats alot of lobe sep for the given cam specs. That thing will generate ALOT of compression, watch the pinging if the static compression is over 10 :1.

 

what he said...

that wide of an lsa looks like a FI grind

 

I have the cms 236/245 115 lsa grind cam with stock heads and it runs great. Pretty choppy at idle and not a lot of low end power but top end is crazy.

 

Tune it right and it'll work pretty well, but you will need ported heads to get the most out of it. Some have put down 350+hp at the wheels through a 12 bolt and a 6spd and ran sub 12's (atljar, for example) with the GM 847 and stock heads with 4.33's and LT's.

Jason

 

The 847 and this cam are two different creatures, the 847 has a 112 lobe sep, helping the motor bleed off some compression, the 115 lobe sep will hold more pressure in the cylender.

 

Yeah but compression alone isn't everything in power. If this cam holds compression better than the 847, wouldn't that make it a little better than the 847 towards low end though?

Jason

 

Yes, and it would increase the octane requirements (increasing chance of detonation)

 

Yes, and it would increase the octane requirements (increasing chance of detonation

Man, do you guys ever need cam lessons.

http://www.co.jyu.fi/~rax/lobe.htm

 

a 112 lobe sep will be better low end than a 115 plain and simple.

 

One of the Impala guys was using an Erson something like 221 intake and more on the exhaust on a 116, he was shooting for a good nitrous grind, he said it idled like stock, but in the end performed no better than the 845, even on the bottle, the LSA seemed to be too much of a compromise. Better to use something more like a 112 and pick a tolerable duration, than to pick too much duration and bandaid the bad manners with a wide LSA.