called isky with some cam questions for the 496 i'm building. they recomended a 284/294 adv. 256/262 @ 50 duration. 680/680 lift 110 LC solid roller for the engine if i don't mind playing with valve lash. ( i don't) thats for a 10:1 , rec port , high rise ,aluminium head engine in my 65, 5 speed with 3:90 rear. they think that should peak HP about 62-6500 RPM. what do you guys think.

 

This is one of my DD2000 work ups that is somewhat close to your cam. This motor is now in a buddy's 56 Belair. The 325 AFR heads probably flow a little more and it's a milder roller. So your peak power would be right around 6500 rpm

 

I would say closer to 6500RPM than 6200RPM

 

I have a very similar cam in my 454 (255 AND 262 AT .050) made max power at 6500. Looks like a good cam to me.

 

A lot's going to depend on how well those aluminum heads really flow as well as that intake. While the peak HP rpm shouldn't really change much, I can tell you for sure as engine size gets around/over 500 cubes, airflow gets tough to get. Hp tends to fall off rapidly if you can't get airflow to hang in there well enough. Thus the HP peak could end up much higher with good flowing heads as opposed to poorer ones.

My 262/273 .672/.675 on a 112LSA peaked around 6200-6300 in my 540 with 365cc ports in out of the box Brodix 2xtra's and even with a Team G intake. It dropped almost 140 HP by 7000 rpm!

After serious head porting and a new Edelbrock Super Victor (also ported) it peaked at 7400 rpm (actually still climbing) with a 272/278 .731/.731 on a 110 LSA.

I currently have a 266/272 on a 112 in it, and while I haven't dyno'd it, my "gut" tells me it's peaking around 6600-6700 or so maybe....but with head porting it doesn't fall off at all above 7000+. Seems to be a perfect match so far. Crossing the line at 6500 or so rpm at 140 mph.

There is another 540 here with a similar sized cam with more aggressive lobes using smaller sized CNC'd ports that flow very similar #'s and it peaks around 6200-6300 rpm.

So with the same stroke as the 540's, but without the benefit of the the bigger bores, I'm thinking the 6200-6300 range at best is in the ballpark, and that's still determined by how well the intake tract flows. If the heads really flow the numbers then I'm with you on sneaking into the 6400-6500 range maybe.

What heads intake are you going to use? What 5 speed? That 3.90 is a lot of gear unless it's an O/D.

Either way, it's going to be fun!



JIM

 

ported top prolines, tremec 5 speed OD tranny. for an intake i am using an offy dual quad hirise manifold. seting it up with 2 600CFM edelbrocks.
greg

 

That looks like a pretty serious cam with what appears to be pretty fast ramps. It will definitely run well.

Any flow numbers on the Pro Toplines? Were they hand done or CNC ported? I saw a set of their CNC ones and I swear they had the 'prettiest" CNC job I've ever seen. They were really nicely finished and smooth. The flow numbers on that set of 360cc ones was just under 400 cfm at .800 lift, which is very good.

That intake will be the limiting factor as far as high end Hp is concerned, but the cool factor will be great. I would seriously consider opening up that intake absolutely as much as possible in the runners to allow for more volume.

JIM

 

nope it's a "street" port. translation, no flow bench. i was going to give the intake to the same guy to open up for me. i know it's not the baddest intake out there but i just dig the way they look. I'm trying to do the math on the SCR and DCR. also the "quench" it's all a little beyond me ( Ok a lot beyond me ) but the internet is a very informative place.

 

I called isky again, looking to solidifiy my cam choice. i started talking about all that dynamic compression ratio stuff and ron iskendarien was kinda like"what the hell are you talking about" he asked me to fax over where i was getting that info from. didn't seem to impressed. anyhow, he told me he'd call back after he had read theu that stuff i sent him. LOL guess I'm buying an issky for sure.

 

Lots of discussion out there about dynamic compression ratio. It's a real thing, but lots of folks get way too hung up in it without thinking it all the way through and really using their heads. The cam does allow you to control cylinder filling, but you have to know where the crossover points are.

If you go by the calculators they would lead you to believe that using a big 'ole cam is going to bleed off enough pressure to never detonate. Yes that's true to a point...at lower rpms primarily..but when that engine starts getting some rev's up and the heads start flowing as intended and the cylinders actually start getting full, if the compression is too high, it's gonna eat itself.

They indicate that with one of my old cams in my 540, I could use almost 13.0 compression and be borderline able to use pump gas. I KNOW I could ride around with it that way, but there is no way I could put my foot in it without pulling all the timing out. Just doesn't work that way.

Guys like Ron have been at this stuff a long time. Take his advice....much better than the average guy you get on the tech lines. He knows what he's talking about, not just reading the same catalog you have.

I use Engle for much the same reason.....I can get Mark Engle on the phone and we can BS for a long time about what will do what, what will live etc etc. I have a guy at Comp that I can do the same with....just gotta find the right folks to deal with.

You need to be SURE of your motor's real specs when doing this stuff. Real measured compression ratio is usually much less than advertised stuff. A few CC's really add up here!

Try to get quench as tight as possible...it helps detonation stuff. That means if the pistons are down in the hole .017-.022 or so...as they will be if the block isn't decked..and you have a .042 compressed head gasket..you will have a total quench of .059-.064. That will work, but is not very good quench. Many replacement pistons actually put piston down about .030-.040 even! I have my block decked so pistons are actually .009 "above" the deck at TDC and I use a .037 compressed gasket. That means .028 total quench which is pretty tight. But I've never had a ping on 93 octane even in Houston heat with over 11.00 compression! It works.


Good luck,

JIM
JIM