Ok. First time poster here, but I have been reading some great stuff here for a few weeks. I thought I could get the answers without another dreaded cam question, but can't...Here goes: Building a street 496 with a few limitations-

Factory LS6 low riser intake (hood clearance)
Rect port alum Edel. RPM's
2" headers into a 2 1/2" exhaust sys.
10.2 CR, forged SRP pistons, 4340 crank.
Car is a '71 Vette with 4 spd and 3.36 gears

I talked with Lunati today and the tech guy recommended 402A9LUN (.586/.586, 255/264, 112 LSA). Some on this site have raved about the 288/296F10 or its lil bro, the 276/284 (.585/.600, 243/251, 110 LSA).

I'm looking for great off-idle response, 800 rpm idle with decent vacuum, strong mid range and good top end (6500 rpm max). Basically, the bottom end power of an LS5/LS6 with top end of a LS7. I know the intake and heads are not ideal. Hoping the extra cubes and the right cam can offset them. Fire away!!

I have the 288/296 Ultradyne in my 496 and in my opinion, it's too big for a street car. I'd look for something in the 240-250 @.050 duration range, especially with those rear gears.

What type of cam are you looking for? Do you want a solid FT? If that is the case the Lunati that Gene runs in his 427 (aka: 427L88) would make a nice cam in a 496 IMO. 276/284, 243/251, .580"/.600" not sure on the specs. (help me out here Gene)

Should have killer low / mid range power and good top end. I think it would still be making power at 6500 in a 496, but that is starting to get up there (rpm wise) for a big stroker motor.

Why not the UD/Lunati 288/296 Hydraulic?

Btw, I want to run a solid FT cam. I like the numbers on the 276/284 grind, just not sure how it would run in a 496 with my intake/exhaust set-up. The one Lunati recommended, may be a little stout for what I want. I am assuming a somewhat restricted exhaust (only 2.5" with Super Turbo's) will limit how much overlap I can use, right?

Vette, for sure I wouldn't go any further than the 276/284 lobe, and would agree with Keith, again for a smooth street engine. There's a grind that WASN"T in the UD catalog which is 280/84 I beleive, one step up from the 276/84.

For a mild gear application, I think keeping the .050 durations at 250 or less is a good thought, EVEN in a 496.

FWIW, my eventual 496 will likely use a hyd cam ( I know its a cop out, but its supposed to run/sound like a 325hp 396). I was thinking of using the venerable 280/88, but I THINK I'd like Harold to do a 288/288 single pattern for me, on a 111 LSA. He DID show a 280 single pattern solid once, I beleive it was 248/248, ..600/.600 108 or 110 lsa. PERFECT!

I don't think you have enough exhaust system capacity for a 496 @6500 RPM. The 2 Vettes I had a '73 SBC & a '71 BBC had 2-1/2" exh. The pipes are typically flattened for clearance. I think you need to consider running this motor at lower RPM and cam accordingly.

Ah, thank you Sir, I didnt catch that. Interesting, then the hyd 280/88 would be fine for a 5000 rpm thumper.

Can't run 3" off the heads and reduce to 2.5 after the mufflers , eh? that's really going to cut off your rpms.

Gene,No "real" tailpipes on a 'vette..they're about 6" long..Time for Hooker sidepipes with 2 1/8" primary tubes :D

Aint much familiar with dem hi-dollar cars! ;)

For sure, need to come with 3" from headers then to straight thru 2.5" mufflers.

Or SIDEPIPES! :cool:

Now we're talking. Hooker sidepipes with the internal glass pack removed. Look at all the money you will save on the stereo you will not need. Like the Harley guys all say to justify open pipes "Loud Pipes Save Lives". I think all us car guys should jump on the wagon and make the same decree.

Except stupid old Cali. is starting to "Decibel Meter" cars!!!

Can you believe that!!!

It's a brand new automotive sound regulation, I think??

pdq67

Yeah I saw that on the news. I think you can only get it done if you get a ticket, and once you get a ticket, you can get it measured, and they give you a little thing that 'proves' your car is legal sound wise. That is how I understood it? It doesn't seem like the worst idea, or the best, but I can imagine people tinkering with their exhaust after its been tested.. so whats the point anyway?
I don't get it really. I haven't seen too many muscle cars on the road that are extremely loud at idle/part throttle. then again, i don't think modified cars are as big out here as they are out west. You'd think the real offenders would be the guy in the 1988 corolla with no muffler right?

Matt

Cali and loud pipes. Amazing the direction a thread can take...back to me for a sec. smile.gif

6500 rpm may be a reach. I would say peak power around 5500-5700 rpm, and take it to 6000 rpm or so when shifting. Most of the time I will be in the 2000-4000 rpm range. The car has full length headers, 2" to a 3" collector, but 2.5" mandrel bent exhaust with H pipe. The old pipes were more oval than round, the current pipes are round.

Any ideas where the 276/284 (243/251 @ .050) might peak in a 496? Is that still too much cam for this combo?

sorry, I edited most of my post, I didn't think it would be too helpful.
I basically just said the two other cams I've had in my 460 had 230 and 233 deg @ .050, and were done at 6100 and 5700 (on the dyno, power wise) respectively.

just a thought..

Bigblockvette,
Go to the "SEARCH" form above.Type in "496".Scroll down to "UDHarold....need advice please".Maybe this thread will help. smile.gif

I'd guess at 6200? Goes 6750 in a 440 ci. The 3500-5500 pull would be tremendous! Most would go a bit bigger, lots of folks here using the 288/296 solid in 496s and able lope along at 2000 rpm. There was a thread on that recently. Maybe in that same list.

BB Vette,

I ran a sim for a 496 using the 228 @.050 Hyd Roller that I have and oval ports. The Hp peak was 5000 rpm. Adding the traditional 500 RPM for every 10 deg @ .050 only gets you to 5800 RPM. Add 200 - 300 for heads and I think the 4.25 stroke is still going to peak @ 6000 rpm. Even at that RPM, the motor is putting a lot power to the ground. But in practicality, I would think spinning a 496 (or any long stroke motor for that purpose ) to 6k and beyond defeats the purpose of a stoker motor in the first place. The piston speed becames excessive and in a std block motor, the rod angle comes into play for any longevity issues. I can see higher RPM on a tall deck race motor, but for a street motor, especially in a car like a Vette, I would want my power to come on from 2500 - 6000, that way I could run a very conservative gear. The torque of a 496 should literally throw a Vette down the street.

Hey, thanks for all the feedback. I called Lunati back today and asked for Harold-and lucked out and got him on the first try! Really nice man. Took time to go through my application-even recognized the post-he does read them, even if he didn't reply! smile.gif

For those interested, he suggested 3 cams, the middle one I like best is similar to the 276/284. But, he thought a single pattern would be better with my exhaust and gear (better bottom end). Will do a custom 276/276 (243/243, .586/.586, 112 LSA). I will order it tomorrow...Btw, he had nice things to say about of few of the regulars on this site.

GRN69CHV, I sold a green SS 396 Chevelle to someone in PA a long time ago. Wish I still had that car...

My car is the Frost Green w/ White Vinyl Top, Parchment Bench Seat Interior c/w all the powers and A/C. Originally built in the Cal. Plant. I am just finishing up the frame off reconstruction. Can't wait to log some miles this year. Haven't had a Chevelle for 18 years. There's just something mystical about the way these cars feel, due in large part to the body on frame construction, the vehicle size & wt. and the broad torque of a BBC. It is a great package. Right now I have a 408CI w/3:73's in it, but I really want to do a 496 and run it with some low 3 series gears (3.23's +/-). Have the 496 in there for power and with that long stroke it will tame down the cam so you get the best of both worlds, plenty of power and a very civil idle. We will be real interested in hearing from you once you get yours fired up.

My Chevelle was green with white stripes, and a green vinyl top. Bought it from the original owner 20 years ago. Never should have sold it-I was too young to know any better...This 496 I am building could eventually end up in another Chevelle-with better exhaust, intake, and heads. smile.gif

I am pulling the 433 out of my car next week. Hope to have everything back together by early May. I will definitely post my results.