OK I have a 406 10.5/1 sbc. I am using desktop dyno 2003 to help find the perfect grind. According to the symulator to build the best torque curve it wants me to run 260/292 seat to seat duration. I am wondering how a cam with such a big difference in duration will run out.

 

That depends on your cylinder heads. You must have what.. vortecs or something? Something with really bad exhaust flow?
That's strange it specs out a seat to seat duration as a recommendation... Especially a 260 intake seat to seat, that's going to build INSANELY high cylinder pressure. That going to be for use in a truck or something with low RPM usage?
I can't help but disagree with your findings there...

 

I'm less surprised. Yes, the big block chev is a different engine entirely, but consider that GM's performance parts cams for it changed from a 224/224 duration-at-fifty to 211/230 duration, still at fifty, and increased torque from idle on up, and still made the same peak HP at the same RPM.
The cam specs you posted are more extreme, and I'd bet every cam company you call will suggest a bit less of a difference between intake and exhaust. Using COMP's hyd. roller XE street lobes, I'd say a 258/276 or 264/282 would give you a streetable compromise between your old DD program and conventional grinds. For such a small intake lobe, stay under 10:1 with aluminum heads for pump premium gas.

 

Atilla, did you misread? We are talking about an SBC engine eh? Unless you're making a comparison to a BB?
I think with 260 seat duration he'd be looking at about what... 210 @.050"? At the very max? Talking hyd flat tappet here... With a 10.5:1 engine, that'll be a little too much cyl pressure IMHO.

Hey, main question that hasn't been asked yet - what operating RPM are you shooting for here? Or better yet, what cylinder heads? AND, what HP you going for?

 

I played with cams for years taking advice from computer programs, internet "experts", local "experts", etc. Turns out everyone, myself included, was full of bad advice. I gave Cam Motion a call after seeing some impressive numbers layed down with guys running their cams. I told them my entire combo, what my goals were, etc, and they spec'd me out a cam that looked ridiculous on paper but I trusted their judgement and it has payed off, I'll never waste my time trying to find the right cam again, I'll just call them.

I just gave you the best advice you'll ever get when it comes to cams.

...But seriously, you won't regret it.

 

those 2 BBCs, the 454 and the 502, are the only engine I could think of that (1) everyone can look up easily, and (2) has such a large difference in the lobes.

 

Well here's my plan, 500hp/500tq. I am using pro comp 210cc heads, I know there not the greatest but they are affordable. I have trw forged slugs 10.5/1 on a zero deck. My block is fresh though no work at all. So compression isn't locked in yet. Im planning on using a tpi setup. So that in its self will keep my r's down around 5000 maybe 5500. The engine is going in a 92 rs, street drivin.

 

Save yourself some hassle and get a baseline with an off-the-shelf cam. The zz4 cam in the FastBurn 385-horse crate engine from GM gives 385 HP at 5600 rpm, and those heads are 210cc like yours. I have this cam, bought it new from SDPC, never used it, you can have it for $50 plus shipping.