Performance Lacking in a 383 Build.

[garyd1961]

Originally Posted by Ziegelsteinfaust

The intake, and holley won't add the punch your looking for.

My guess is you have 882 or equivalent shooter heads. Your cam is quite a decent going for a nice DD or torque motor.

So he may of gone back to the low 8-1 compression your originally had, and the softens the whole hit of the bigger motor. You will have to take to top end off to see if adding 64cc heads will bump the compression up.

Have you tried setting initial timing to 15*, and total to 36*. Stock D chamber heads need a lot of lead in due to the slow flame propagation.

If that wakes your engine up enough for you. Then I would consider adding a dual plane high rise, and new carb. Or atleast add a 1 inch open spacer for a little more plenum volume.

Why would you run an open spacer on a duel plane intake.
Make sure you have fresh 93 octane gas in it. You should have tons of low end torque with your setup. Probably something simple like a vacuum leak.

[Ziegelsteinfaust]

Originally Posted by garyd1961

Why would you run an open spacer on a duel plane intake.
Make sure you have fresh 93 octane gas in it. You should have tons of low end torque with your setup. Probably something simple like a vacuum leak.

Because it allows the individual cylinder to draw from both sides of the carb.

It evens out afr, and smooths out the carburetor signal.

Plus can reduce the needed size of a carb in many engines.

Provides extra plenum volume some combos really need with out a manifold change. A 1" spacer on a Super Victor manifold is not the same thing on a Performer dual plane manifold. Where the concept really shines by comparison.

Does it work on a dead stock low compression smogger 350. I have tried it, and got no where. This was a last tuning trick on a already well tuned engine.

This is a worse case scenario, but I have done it on a built 350 that I had for a sleeper build I was fascinated in. It had Dart iron eagle heads with about 190cc runners, and 64cc chambers. Followed up with 9.5-1 compression, and pretty wicked circle track mechanical flat tappet cam. I ported a cast iron intake to get as much advantage out of as possible. When I got it running I had the Q-jet on the manifold as normal, and it was pretty wicked. After hours of needle, and other changes.

Well a few weeks later I made a 1.5" spacer out of resin coated wood because of a article I read, and the truck was on the road fully as a back up vehicle. Plus I recovered financially, and emotionally from the project. So I had time to play again. Drivibility went up considerably, and felt power was across the board.

Its hard to say in words, but the cam/carb combo was not ideal. Just when driving the truck when the engine was up to temp it had a bunch of flat spots in part throttle. The spacer smoothed out idle, and removed all but one of the flat spots. That flat spot was at just under 2750rpm under full throttle. Plus I had to lean the carb out again due to more even air flow. So mpg would go up. It got crap mpg anyways so it would be hard to confirm, but memory says it went from 11mpg to 12 mpg. Under the more idealistic conditions, but not really noticeable bombing around town. That engine drank gas.

As for power before it could easily bark the tires hard in second. After it could continue the burn out into 2nd gear.

HotRod, and Carcraft have a bunch of articles on how they work. Plus they hopefully can explain it better then I could.

[garyd1961]

Originally Posted by Ziegelsteinfaust

Because it allows the individual cylinder to draw from both sides of the carb.

It evens out afr, and smooths out the carburetor signal.

Plus can reduce the needed size of a carb in many engines.

Provides extra plenum volume some combos really need with out a manifold change. A 1" spacer on a Super Victor manifold is not the same thing on a Performer dual plane manifold. Where the concept really shines by comparison.

Does it work on a dead stock low compression smogger 350. I have tried it, and got no where. This was a last tuning trick on a already well tuned engine.

This is a worse case scenario, but I have done it on a built 350 that I had for a sleeper build I was fascinated in. It had Dart iron eagle heads with about 190cc runners, and 64cc chambers. Followed up with 9.5-1 compression, and pretty wicked circle track mechanical flat tappet cam. I ported a cast iron intake to get as much advantage out of as possible. When I got it running I had the Q-jet on the manifold as normal, and it was pretty wicked. After hours of needle, and other changes.

Well a few weeks later I made a 1.5" spacer out of resin coated wood because of a article I read, and the truck was on the road fully as a back up vehicle. Plus I recovered financially, and emotionally from the project. So I had time to play again. Drivibility went up considerably, and felt power was across the board.

Its hard to say in words, but the cam/carb combo was not ideal. Just when driving the truck when the engine was up to temp it had a bunch of flat spots in part throttle. The spacer smoothed out idle, and removed all but one of the flat spots. That flat spot was at just under 2750rpm under full throttle. Plus I had to lean the carb out again due to more even air flow. So mpg would go up. It got crap mpg anyways so it would be hard to confirm, but memory says it went from 11mpg to 12 mpg. Under the more idealistic conditions, but not really noticeable bombing around town. That engine drank gas.

As for power before it could easily bark the tires hard in second. After it could continue the burn out into 2nd gear.

HotRod, and Carcraft have a bunch of articles on how they work. Plus they hopefully can explain it better then I could.

The duel plane with a modest came will give you a lot of low end torque. That seems to be what this motor was built for. If you want to convert it to a high revving high hp motor than an open spacer and big cam in the .550 lift range would make it run like a scalded dog. I had a 383 with that setup and it would run but wasn't really good for the street.
I would leave it as is and find what the problem is. Get it running right and it still should have a lot of power.

ETA, Some of you guys are suggesting a bigger cam someone even suggested one in the .600 range. That's fine if you are building something for the dragstrip but for a drivable truck on the street it's way too much. The motor should have way more power than needed with the current setup. Find what's wrong with the motor and fix it before changing the cam and intake. I'll bet once it's running right you won't want to change anything.

[Myself]

Originally Posted by garyd1961

but for a drivable truck on the street it's way too much.

But then again........so is a 10.5:1, aluminum headed, 383..

[Ptjsk]

I can't thank you guys enough for providing your input.

The first thing I'm going to do on Monday is see if I can't find a dyno for it.

Hopefully, that will be able to provide some guidance as to what the motor needs.

Thanks again for all the information.

Pat

[HO455]

Originally Posted by Myself

But then again........so is a 10.5:1, aluminum headed, 383..

Nobody runs a LS3 in their DD truck?

[KQQL IT]

What do the plugs look like?

[garyd1961]

Originally Posted by Myself

But then again........so is a 10.5:1, aluminum headed, 383..

No it's not, a 383 can be a real torque monster and still run smooth. The only thing about the 10.5:1 compression would be the need for premium gas. The aluminum heads just make it easier to run the high compression on pump gas.

[Ptjsk]

Well.....after several months the motor is back out of the Jimmy.

I have 5 broken pistons (at the skirts), and 4 of them have chunks broken off of the top of them.

I really don't know how the hell it even ran.

Keith Black Hypereutectic Pistons. Top oil ring gapped to .026 thousandths.

I think the original engine builder just totally screwed the pooch! Pistons were noisy as hell from day one! Unfortunately, he's since passed.

Pretty much have to start over after throwing thousands down the drain.

I'll find out next week if I have to bore it more or not, and what the plan of attack will be.

Pat

[HO455]

Originally Posted by garyd1961

Why would you run an open spacer on a duel plane intake.
.

I too have successfully used open spacers on dual plane manifolds. In my case it was on a .030 over 400 Pontiac with #62 heads I ported, a Ram IV cam and a set of 3 tube headers. After experimenting with several different combinations of spacers between the stock intake and the Q-jet I found that a 1/2" of stacked gaskets and metal plates that matched the intake holes topped by a 3/4" open spacer made the car quicker in the 1/8 mile. In addition and more important was that it moved the power band up slightly which made it easier to launch the car without spinning the slicks. Consistency wins races. And since it was my daily driver it definitely made the car easier to drive in the rain.
If the firing order of the engine and the physical layout of the intake manifold allowed exactly equal time between intake opening signals as they reached the carburetor then it is unlikely an open spacer would be helpful but since that isn't the case your trying to make the all the compromise work the best.
The picture shows a stock Honda manifold and if you think about it, it's basically half a dual plane manifold with a spacer on it. Just laid out differently.