Re: Stocker Cam Lobe Profile ?
 

Aubrey could you go to a taller tire to kill some rpm through the traps? Some great feedback on this thread

Re: Stocker Cam Lobe Profile ?
 

I'm paying attention here... so,
Cams aren't that expensive. I already have a set of good "civilized" headers.
I'll get two cams. One how I "feel" it should be. The other with 10-12 degrees less duration, and run it in the correspondingly somewhat lower RPM range. I have the 4.88's to use in place of my current 5.13's.
For testing purposes, I'll use my current heads.
I'll make that my goal before the end of this season.

Currently, the engine never sees below 4500 RPM on a run.

Re: Stocker Cam Lobe Profile ?
 

That's a bit too much drop between gears. It needs to stay up above 5000.

I'd expect to use a 5.14 with your combination, I think you'll find the 4.88 won't run well. Consider that most run a 5.00 or 5.14 with a 396 or 427, both of which have 0.250" more stroke.

The secret to going fast is average HP between around 5200 and 7400, and having it recover really well from the shift. You cannot give up average HP to get peak HP, or it will not recover from the shift.

Call Tim, see if he has the lobes to grind you a cam with between 254 and 258 in the intake, and 266 to 268 on the exhaust, between 108 and 110 LSA, 109 LSA, in at 107 is probably a nice compromise. If you can't tighten up your RPM drop, you really need to look at a 107 LSA, in at 105. It may not make great peak numbers, it might not look great on the dyno. But on the dyno, it does not have to recover from the shift, in the car, it does, and if it drops below 5000, it's probably way below peak torque, and won't recover well.

The modern big block lobes will be stable to 8000 RPM, provided you have 250 on the seat, and 525 open, you need a spring rate around 525-550 per inch. You cannot control that big intake valve with anything less. If you're not running at least a 7/16" x 0.125" wall pushrod, it will never work. The pushrod will be a secondary spring, and make everything surge and bounce, even with a gentle lobe.

For a single step header, I'd expect to see something similar to an 1-7/8" to 2", with 16"-17" long steps, for a total of a 32"-34" primary, and a collector about 16"-18" long, merge style, tapering from 3" to 4". If you went for 2 steps, split the 2" section into a 2" and a 2-1/8" section, each about 8" long. That's a real simple merge, you could do more if you wanted.

Re: Stocker Cam Lobe Profile ?
 

On the gear change, of course it doesn't drop to 4500. Transmission has only a 2.83 first gear, so in terms of modern drag racing stick shift... it's almost a close ratio.
I know... not enough first gear for a 3640 pound car.
Also, these engines have a nortoriously long torque curve... never a lot, but very flat. A wider spread in gears would be better. Peak torque is at 4600-4800... still within 5 ft pounds at 5400 RPM. More gear spread would allow the engine to fall back into the real "thick" of the torque.
Simple math, if I lower the RPM range of the engine, I have to go taller gear ratio in order to retain trap speed.

Alan, I don't know WHAT you are using for a spring, but I've studied the hell out of this, and I can't find a single spring that will get near those figures. Also, in these engines, there's no room for a 7/16" pushrod ( the "pinch" in the intake port, adjacent to the pushrod hole, is already paper thin ). Can't be done. I have 3/8" Manton.
Also, header tube length under about 42", with a merge collector... ? Impossible, period. Chassis will not allow it. My headers are about 33"-34" long.16" total collector length.

maybe it's just destined to remain a slug ? ! ! !

Re: Stocker Cam Lobe Profile ?
 

"Currently, the engine never sees below 4500 RPM on a run"


You'd better be making peak torque no higher than 4300 rpm.

200 rpm above peak torque is the basement. If you drop below that it won't recover.

Re: Stocker Cam Lobe Profile ?
 

You might get by with a 3/8" x 0.125" wall. Consider a dual taper, Trend has a dual taper 3/8" - 7/16" pushrod, it's 3/8" on the ends, and 7/16" in the middle. Trend will measure for you to see if they can make something work.

You do not have to run a single spring any more. They opened the spring rule up.

Not sure what you mean about the headers. If your headers are 33-34" long, with a 16" long collector, that's about what I was suggesting, length wise. A merge collector will fit where a plain collector will.

Re: Stocker Cam Lobe Profile ?
 

HEE HEE !!... I could use a pushrod that has the bottom 3 inches 7/16" in diameter, but I'd have to put the pushords in place, then install the heads over them ! !
My pushrods ARE those ridiculous, almost solid wall things.

No more "stock spring arrangement" ?
HHMMM. they really are loosening those rules, aren't they ?

The header tubes can finally merge together, under the frame, at about a 30 degree angle back from straight out the sides, approximately 12" from the outside of the car.
A merge collector piece such as this one that I just used on headers that I built for a customer car.... would actually exit out from under the front fender, extending about 6" outside the car !
Can't be done.

Re: Stocker Cam Lobe Profile ?
 

Aubrey ,You can get Manley to make valves on there Gen2 custom stainless blanks.Also look at how much coil bind clearance you have ,too much may cause spring bounce or surge.We agree with Billy Nees and others ,the headers are probably to big.We see engines that get The National Dragster Tune Up ,Big headers,Big carb,bag of ice on the manifold and take 2 quarts of oil out:).Bill C.

Re: Stocker Cam Lobe Profile ?
 

I know, Bill... the 'ol "bigger is better" thinking.
I suupose I could try and justify it by saying that it alreadhy has the "bigger" carburetion... and that I was just trying to follow suit ?

Anyhow
I just had a lengthy conversation with the Stocker guy at Comp Cams.
One thing I know for sure now... you guys with the BBC's, spinning big RPM, are NOT using a lobe that resembles this intake lobe that is on my cam. He confirmed that it is NOT an RPM stable lobe... especially with inherently heavy valves / high ratio rockers.

So, I have taken heed to everybody's recommendations and advice.
And it looks like I WILL build a new set of headers.

If I can retain even half of what I learn around here, maybe I won't blow up again... and maybe even go faster ? !

thanks guys

Re: Stocker Cam Lobe Profile ?
 

THE stocker guy at Comp Cams = Tim Cole, or Chris Padgitt.

You're in good hands now if that's who you're talking to.

You're going to love what a good stable camshaft and valvetrain does for your engine program. You will now be able to use the cylinder head flow and the carburetors you have.

Let me know if you want to see about getting some REAL good stainless valves for that thing.

When you get the engine right, you should be able to use about a 3.05 first gear and a 5.14 rear gear. Just be ready to get it in second gear real quick.