BBC heads question (Tunnel ram??)

Oddly enough, I just did a cam recommendation for a near stock 396 for a friend of mine for something he is building for another guy. But while on the surface of it, it may seem quite similar to this, the intent is about as far away from what we are discussing here as can be. Mildly ported oval port heads with 2.19s, 2" caslers, a perf. rpm and Q-jet, 10" converter, 4.10's, and M/T drag radials, power brakes (critical info for a cam recommendation). In other words, he is trying to build something FASTER than it looks/sounds, rather than the other way around.
Oh, and yes, there is an element of satire in this post too. Dont say you weren't warned.

 

So....what cam did you recommend? how much rpm do you think the bottom end can take?

 

Isky #396281, in deference to the power brakes. No power brakes, I would have went with the #396292. Both are on a 108 LDA to help build some cylinder pressure, and put area under the curve, and both are pretty much done by 6K. Its going in a early '70s Monte Carlo, I would be expecting it to run 12.70s/80s, based on previous experience with a 427 with similar parts (wieand stealth, 850 dp, and 4.56's) in a heavier car. the 427 went sixties first time out, and eventually went 12.0s with a considerable amount of tuning and a cold air package. And no, it didnt have a tunnel ram...

 

Oh yea, limitations of the two-bolt, small rod bottom end? I have been at 650 hp with reasonable prep, and that looked like the ragged edge. Brinelling on the main cap mating surfaces, funny bearing wear patterns that indicated either the block or crank was twisting longitudinally, and loss of register on a couple of caps(restaked them with a punch and ran it.) no indications of detonation. It DID have what I would consider a poorly machined crank with one short throw, that was probably a factor, but indications were that I was approaching the structural limitations of the two-bolt block. Aluminum rods would probably raise that limit in my experience.

 

That cam is very similar to what I run in street big blocks, and it's not far from what I have in my blown 454.

Interesting about the bottom end. I got to take apart my blower motor last month, it dropped a valve. The engine had 40k miles on it since the last overhaul. It's an LS-7 from 1989, 4 bolt mains, good steel crank, big rods. The bearings looked good, main caps were tight, etc. It's probably making around 650-700 at the crank, just a mild street setup.

 

And usmclx50, I'd be willing to bet that if you pulled those zoomies off and replaced them with a decent set of 2"x 34" primary headers with a 3.5" collector about 16-18" long, that thing would pick a solid 1.5-2 tenths...

 

At the same power level, I think blown/turboed motors are easier on the bottom end than N/A. They would certainly be running less rpm. I do think the crank was a contributing factor. Cam wise, I wouldnt run the 108LDA (more like 112-114 and advance it)in a blown motor, and I would probably want more exhaust duration, otherwise, yes, I would think either cam would work well as the intake profile in a blown street motor.

 

Oh I'm well aware but those look funny if I wanted a supercomp rail id build one... i want a period style car that runs decent and I can drive on the street headers like those scream T-Bucket or Super Comp car so I'll stick to my zoomies and run a lil slower!

 

Actually, I dont recall seeing many zoomies on tunnel ram motors back in the day either. But whatever makes you happy.

 

If it is the 2brl 396 engine it likly does not have the 2.07-1.72 valves. They had the truck valves. I'd stick a q-jet on it and cruise.

 

Really? Mine had the normal size valves. So did the other one I worked on.

 

I thought the LS-7 454 crate motors were long gone by the mid '70's....

Was GM still making those and selling them over the counter??? And what intake manifold came with those???

 

The LS-7 was part number 3965774 and was available for about 20 years. No intake, but it had a flywheel for manual transmission.

 

Ok, thanks!

 

A lot of guys used to buy them for Super Gas in the eighties. IIRC didnt Hot Rod do a "bolt-on" dyno test with Lingenfelter on one back in the eighties?

 

I just seen these and they say 1990 http://buffalo.craigslist.org/pts/2579205185.html

 

Those are a decent deal. I have made over 750hp with a set of similar heads with 2.25 intakes...

 

I agree, The valves on these heads are 2.06/ 1.72....

 

I rebuilt a 396 out of 69 El cmino that had the 2brl and it had truck valves in the heads. That's the only one I ever m***es with so maybe they came out with either. It was a pooch.

 

when i tried to run rec port intake on oval port heads and got on the gas it broke up so bad it sounded like **** and ran like **** the 2 ports dont match and messes up the fuel flow ..i would not do it .

 

If only I had a '69 SS pony car to bolt that LS-7 in..

 

Give that man a cigar!!

 

You can use a rec intake on ovals just fine and make power. Its still done today without port matching on some crate motors from mercruiser. Oval port intakes have a hard time suppling enough air on a race motor, that the larger rec intakes can supply. Even with the port mismatch. It really wasnt untill recently you could get a decent aftermeket race oval intake.

 

Any idea what the 2-bbl intakes are worth? I heard that they where hard to find, but never heard of a price point??

 

a friend runs a 454 all stock except for thumper cam with a tunnel ram & 2 450cfm holleys - it's a real runner

 

I've never had anyone offer to buy mine, and I've had it over 30 years.