rworley6641

I am building a BBC 496 for my 1970 restoration. Looking at cams. Want a street cam that will come on at 1800 to 2000 top out at 5800 to 6000. Popular Hot Rodding used a Comp Cams 292 (244 duration at
.50 and .550 lift) for their Street Brawler that made 567 HP at 5700. The advertisement rates that cam at 2500 to 6500 RPM use? Does the addition cubes of the stroker bring on the power range sooner? And what kind of idle quality will I get with. I don't care to spin my two bolt block past 6000, even though the main has ARP bolts and the crank is a forged Lunati with H beam forged rods and forged ProComp pistons.

427Hotrod

You're in the ballpark. What heads, induction, compression, trans, gears, weight etc do you have?

JIM

rworley6641

going with a Keisler RS 500 5 speed trans(first gear is 3 something, OD is .68 or there close), 3:36 rearend ratio, aluminum heads, 320 intake runner; 2.25 or 2.30 intake valves. Haven't bought the heads yet. 496 moves more air than a 454 and most components are rated for 454 use. To fit under a BBC 1970 hood, I am limited to the 1971 LS6 intake :"569" low profile. I am not looking to go to the track or drag race. Looking for superior performance on the street and drive-ability (sp?). Want to go with a hyd cam. Push rods will be .120 thick wall and rockers probably roller tip or steel full roller. Not wanting to rev past 6000 helps hold down the build. Any idea if the extra cubes effects the cam performance rpm area?

TheSkunkWorks

IMHO 6000 RPM is a nice round target for a street 496 that won't break the bank, but is still worthy of a sportscar. I'd suggest you put some modern, healthy flowing oval port heads on it, and epoxy down the LS6 intake runners to match as seen below. If you do select rectangle port heads, I'd stick with small'ish ones so as not to kill port velocity. Either way, go with aluminum if at all possible, and only ones made in the USA. If still an option, specify 4032 forged pistons (lower expansion permits tighter cylinder clearance), and if you don't already have 6.385" rods there are several reasons for which I'd urge you to swap for them. FWIW, I'd probably limit CR to a "conservative" ~10.5:1 with the cam in question in order to leave some margin for inconsistent pump gas, and would consider having it ground with 112* LSA to improve manners a bit.

All else being equal, the 496 will inherently produce it's torque peak at a lower RPM than the 454. Also, apples to apples again, the 496 will have better manners with a given cam than the 454, or tolerate more cam (to a point) than the 454. Change other variables significantly between the two hypothetical builds and you'll be looking at oranges...

Transmission wise, as a rule of thumb I'd shoot for ~10:1'ish total 1st gear multiplication (1st X rear ratio), and wouldn't get too caught up in having the tallest top gear FDR possible with "only" 5 speeds.

In any event, Jim has been around the [big] block a few more times than I have, so I'd certainly value his advice when he gets back to you. My $.02, free of charge.

And, Happy New Year!

TSW

ajrothm

I would go with something like this:
http://www.lunatipower.com/Product.aspx?id=2332&gid=297
•Advertised Duration (Int/Exh): 276/284
•Duration @ .050 (Int/Exh): 233/241
•Gross Valve Lift (Int/Exh): .554/.572
•LSA/ICL: 110/106
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 2200-6400

Or better yet (since yours is a stick) go with this:
http://www.lunatipower.com/Product.aspx?id=2333&gid=297
•Advertised Duration (Int/Exh): 284/292
•Duration @ .050 (Int/Exh): 241/249
•Gross Valve Lift (Int/Exh): .572/.590
•LSA/ICL: 110/106
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 2500-6600


This ^^^ would be an excellent cam in a 496 if you are staying HYD FLAT Tappet.

My only concern is your choice of using the LS6 pancake intake....Thats going to restrict it BIG TIME.... I would still probably run the #60205 cam but...I doubt you'll make it to 6000rpms with that intake on a 496.... It would REALLY be worth changing hoods so you can run an RPM air gap intake......Its probably worth 50-75hp over that LS6 on a 600hp 496. Also, you should stick with Oval ports if you are staying 6000rpms or less....You'll have a lot better low-midrange power...

I would stay away from the Comp 292H, aside from the fact that Comp flat tappets are horrible these days for longetivity, that is a 30 year old design cam..... You can make a lot more power with something modern. I had that 292h in a 1970 LS6 with the pancake intake, LS6 rect port heads, mini dome pistons, 10-1 comp.... It was a total dog... It had no bottom end torque because of the big square port heads and big duration, yet it had no top end power because the intake neutered it...It was a disappointing build.


Jim will definitely get you going the right direction...He is the BB king

roscobbc

Your requirements were similar to my 489 cu in build-up using a 3.08 rear end with M21 4 speed. I chose Race Rite ovals with a relatively mild Howard hyd flat tappet cam (236/241 @ 50 thou' if I remember, although with fairly aggressive opening/closing ramp rates ) - I used L88 type hood with Air Gap inlet and 950 DP carb. This combo will pull from 1200 rpm, with power band starting at 1800 rpm or so. HP is 528 @ 5850 rpm - 565 ft/lb @ 3800 rpm. It will spin up past 6000 rpm if you wish and squeeze-out 15 imperial mpg @ 70/80 mph cruise. I also take in to central London at times without issues (except for aching left leg, lol!) - as one of the other postings alludes to, some of the cams currently on the market have been around for many years and there are better choices out there for discerning buyers.

DRIVESHAFT

If you want to run rectangle port heads, you would be better off keeping them smaller than the 320cc runner size your considering.
Take a look at the Brodix Race Rites. They offer a 294cc runner that would work well for you.

63mako

I would consider a hydraulic roller with the ramp rates, lift, valvetrain weight and your goal of power under 6000 RPM.

rworley6641

Thanks to all who gave opinions. Oval ports sound like a better way to go with a street engine and the cold air induction of an L88 hood is ever more inviting given it rids me of the "569" intake restriction and pulls air from the winshield area. Thanks again to all.

GOSFAST

You can get 525 very nice driveable HP on that stroker with a Comp 11-451-8 cam! Torque comes in around 550# @ 4500, peak HP @ 5600.

We are constantly building these here and always have a few in the works! Most beginning as LS-5's!!

They are all 100% stock appearing and constantly in shows being judged!

They use all the OEM castings, and are based on a 9.5:1 C.R. All are retro-hydraulic and full roller rockers with stock valve covers!

That 244* cam will need some add'l compression! Not recommended on pump and not a real comfortable cruising range.

Thanks, Gary in N.Y.

P.S. Here's a shot of one finished a while back.

trw

GOSFAST KNOWS listen to him.