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Discussion Starter #1
Hi everyone,

My camaro has a 396 BB with block codes that call out for it to be a 375HP and was stated at time of purchase that it had been rebuilt. However, upon further review i'm not so sure. The exterior parts (intake, carb, headers ext.) looked as though they had been pulled from someones garage. I have replaced the intake, carb and points distributor with edlebrock performer series intake, thunder series 800 carb and hei ignition. On the dyno it only managed a measly 200hp at the rear wheels. I'm looking for advise on what i should do. The options i've looked at so far are getting the edelbrock performer series heads, cam and timing chain set, which would mean the entire top half of the engine is basically new, or getting the hole engine remanufactured. If this engine had been rebuilt, have i over looked something that could liven up this sluggish beast? Are their other options i should look at that are less expensive?

Thanks for any advise or insite.
 

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Don't put to much stock in chassis dyno's.

I have a 468 with hi compression (won't run on pump gas). Not sure how much compression but its high.
The cam is a solid roller, the springs are double with a dampner and roller rockers, the manifold an Edelbrock 454-O Victor. 2 1/4 inch hooker headers.
According to the dyno, I make power to about 6900 rpm. That is a decently wild cam.
This info I take as reliable because you can see the power dropping off on the dyno sheet at 6900.
The motor acts wild and feels wild with how fast it wraps up when you hit the throttle.

Will all this stuff, I measured about 338 on the dyno. :sad:

I was sorely disappointed.

An engine guy I've been working with, who is an experienced hot rodder looked at my sheet and said my tranny wasn't even beginning to hold up to the motor. He said, by feeling it and looking at this sheet, he could see it was pushing through the converter.
My converter is supposed to be a 4k stall but the dyno sheet shows it flashed right up to 5200.

So there are many things that can effect the dyno. Your converter's age and wear and stall point and even your tranny if something is slipping more than it should.

Here is one more little detail. A friend of mine went to the same place and was so unhappy with his results that he went to another place.
His 350 hp 350 was giving him 188 hp on the dyno and so he went to another place and it showed 248.

These dynos are about good for nothing but gauging performance gains from tweaks and bolt ons.
JMO

Don't be sad. Your BBC is probly just fine.


I would optimize what you have, before you go buy expensive bolt ons.

Set your timing, depending on what your cam is. I just timed mine by ear so that I was getting as much advance as I could get without binding the starter.
Do a compression test to see where your engine stands.
Are you running too rich? Are you loading up? Are you leaning out? When you went to the dyno did you do head flow as well?

Check that tranny. Slippage and correct stall?

Take it to the track and run some good fuel with some fresh oil and see what she does on the 1/4.
Your E/T may not reflect what the dyno reflects.
 

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I went back to the photos of your car, and looked at the motor, but with the motor being black and the pic being low res, I couldn't see much.

What do you mean the block codes make it a 375 HP motor (I saw the sticker on the air cleaner :) )? The Special High Performance 396 (375 HP) was a solid lifter cammed, high compression engine. From the way you describe it, if the engine suffix stamp on the pad says it was a SHP motor, it isn't any more (or half the valvetrain has fallen off).

I was trying to see if I could see any identifying marks on the front of your heads, but you're probably going to want to pull the valve covers off and get the casting numbers. Maybe it has peanut port smog heads on it?

Any idea what cam is in it? Was the single plane intake in the pictures on the car when you bought it? How did it run when you bought it? If it is cammed to run in the upper RPM ranges (where a single plane is used), it may not like living down low and feel sluggish. Doesn't explain 200 RWHP though...

Have you checked the timing (initial, mech, and vac)? BB are pretty forgiving on timing, but I'd confirm that it's not really retarded or something.

Overall, you could have a mechanical issue, like a bad cam lobe or two, really restrictive junk heads, bent pushrod(s). Or it could simply be that the parts that have been thrown at it don't work well together.

I have a 402 with cast iron stock oval port open chamber heads, a Crane cam equivalent to the 396/360 HP cam, about 9:1 CR, a Dave's small body HEI, Performer intake, Holley 4175 (spreadbore, 650CFM, vac secondary), and factory exhaust manifolds through a factory replacement dual system. With my TKO and 3.42 rear, she is anything but sluggish.

My point being that even a very mild BB (like mine) will be strong, so it sounds like you have a problem or part mismatch.
 

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BBC? I know that Dart has a 'Top end kit' for BBC/SBC that works great I know of a 396 in a late 70's malibu with this top end kit and a XM278HR from Comp and its a snappy s.o.g......

Ill see if a can find a link.
 

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Discussion Starter #5
Thanks for the info,

During my dyno it peeked at 4200rpm before dropping off. The 350 turbo is probably the original one and is worn out. It also has the original non posi rearend 2:89 gears. Since i have 20's on the back i can't even churp the tires. Replacing the old headers are my next fix as the number 2 cyclinder header pipe has been crushed to about 1/3 of its original diameter and there are a number of other dings and dents in them. The exhaust is also very poorly constructed with pipe sizes getting smaller and bigger along the exhaust path. Was planning on buy the magnaflow american thunder series 2-1/2 kit with the tru(x) crossover.

Thanks again.
 

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Discussion Starter #6
Some more info.

The street rod shop that does some of my work was the one that told me the block number indicated it was supose to be a 375hp engine. It certainly isn't a solid lifter engine and i questioned him about it being a 375hp engine as i though that all the 375hp engines had solid lifters. He said that they also made a 375hp without the solid lifters. I am also still trying to get the engine rebuild spects from the guy i bought the car from. The delay it getting this info has also lead me to believe he may have been lying about the rebuild.

Thanks again everyone.
 

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BBC never shipped with a TH350, all were TH400s. The 375 horse 396 will have HiPerf cast right on the heads just under the valve cover (don't have to worry about decoding it, it will be a rectangular port head). If it says PASS then it has either a Round or an Oval port head (both the 325 horse and the 350 horse used the same oval port head differing in the grind of their hydraulic cam), and to figure out which size heads you have, you will have to post the numbers here or go on line and look them up. Peanut heads are very small round ports with big open chambers which will bleed off a lot of compression.

The early 396 motor was designed for closed combustion chambers and high test gas which is no longer available. So for it to even run today, it has to have been rebuilt; but with what, who knows? If it does, by chance, still have the rectangular port heads get rid of them unless it is a numbers matching engine; because with only 396 cubes it will have to rev to 5000 to make any power at all (heads were designed for racing not street driving).

If all you want is power from a big block go with cubic inches, 396 is smaller than the SBC 400 which routinely puts out 500+ HP when properly modified. A 454 is a good starting place (when a 4.25" crank is added to the mix it gets better). A medium sized big block nowadays is around 540 cubes; with a 705 cid or a 810 cid being the current big boys, depending upon block used (bore spacing). Big blocks do not make the horse power per cube that small blocks do (it is a matter of physics and thermodynamics to complex to explain here), so if you want power maximize the displacement.


Larger Dave
 

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OK: 375 HP 396 had 11.0:1 compression pop up TRW forged pistons, forged steel rods, forged steel crank (which has the same stroke as a 427 engine but different counter weights because the reciprocating mass was less). It had a solid flat tappet cam with a Holley 4 BBL carb, rectangular port heads (they will have a small single small camel hump on the front of the head at the casting parting line if they are HiPerf heads) a different distributor (different advance curve) 2.5" cast iron exhaust manifolds, and came with deep grove V-belt pulleys. The two other 396 offerings were the 325 horse and the 350 horse which both had oval port heads (very desirable on any big block below 500 cubic inches) topped by a Q-jet carb and each had their own hydraulic flat tappet cam grind with the 325 being the milder of the two (go figure).

A 396 has a very small bore for a big block and it can not be over bored to a larger displacement due to it being a thin wall casting (it is so small that the factory had to notch the block to clear the intake valve which is still shrouded by the cylinder wall even though it no longer hits it).

Back when these muscle cars were new, just about every 396 was pulled from all factory installed Camaro s, and replaced with either the more desirable 427, or the even more desirable 454 when it came out in 1970. Because all of the 396 blocks could not be cheaply reworked they were sold to Japan to flood the American car market with Honda, Toyota and Datsun (since renamed Nissan) vehicles. They are getting to be a rarity today, and I’m sure some where on the board is a Camaro owner looking for his number matching motor (he might even want yours more than you do).

Like I said there is no replacement for displacement, since yours is up and running, well and good. Rather than throw money at the 396, save your money for a 454 short block out of a pick-up truck. It bolts right in, comes in the same color and the 396 decal looks just the same on top of the 454 as it does on the 396. Mater of fact my 582 looks just like your 396.


Larger Dave
 

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The VIN won't tell you what engine/transmission combination the car originally had. All it will confirm is if it was a 6 or 8 cylinder car, convertible or coupe. If you can read the block pad under where the alternator sits, you can tell exactly what car the engine originally came out of, its HP rating, and what transmission it came with.
 

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The block pad is known as the partial VIN. And I state "If you can read it ..." because if a motor is decked durring a rebuild that information is lost.

Larger Dave
 

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Hey Dave! I don't recall anyone saying before that a SBC makes more HP per cubic inch than a BBC. HuH???
I lived with my 375 horse 396 for six years before a valve seat fell out of the aluminum heads and wrecked it. That gave me an excuse to build my 427 that I bought in 68, a year before I bought my car.
But one thing I'm sure of, that 396 was strong. Oh, the CR was 11:25.1. You should have heard it with my Mickey Thompson Super Scavengers OPEN at the track. A couple of days ago I fired up my L88 with the new headers open. It brought back the 'feeling'. All huggy. Like a good woman.
 
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