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Author Topic: What's wrong with my fresh 383  (Read 4162 times)

Offline mach3107

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What's wrong with my fresh 383
« on: December 16, 2008 - 04:07:01 am »
 :dunno:
Ok, I put my freshly rebuilt 383 (casting shows it's a 1964 motor but it's going in a 70 super bee) on the engine dyno and it only made 315hp and 365lbsft. That sounds like stock power. I'm not the most knowledgeable but I'll tell you what I know. It's board 60 over, head rebuilt and worked, cam - intake 240/.3380 and exhaust 246/.3400, HEI ignition. Mopar aluminum intake, timing 38 degrees and I think compression is 9.5 to 1. We dynoed with a 750 holley but also tried a dyno carb and made the same power. I'm running stock exhaust manifolds (ones that came with the motor). If there's any other critical data that is needed, let me know and I'll try and read the build sheet to get it.




Offline Chryco Psycho

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Re: What's wrong with my fresh 383
« Reply #1 on: December 16, 2008 - 04:46:17 am »
first factory ratings were gross power meaning no water pump or any other drag , actually optomistic #s at best to actually make that power means you have more then stock , virtually every car I put on the Dyno reads low , we call the dyno the heartbreaker

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Offline mach3107

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Re: What's wrong with my fresh 383
« Reply #2 on: December 16, 2008 - 05:31:16 am »
I hear what your saying. Builder said header could add up to 100 hp. Any input on that? I was also told that there are much better flowing manifolds from different years?


Offline 6packCuda

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Re: What's wrong with my fresh 383
« Reply #3 on: December 16, 2008 - 08:18:36 am »
Headers will add a little HP. Maybe 15-20. I've never heard of anybody gaining 100 HP with headers though.
Dave

Offline Roppa440

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Re: What's wrong with my fresh 383
« Reply #4 on: December 16, 2008 - 10:05:11 am »
A friend of mine had a stroked 440 that lost 70hp on the dyno when they put the stock manifolds on it. The engine had all sorts of issues though (mismatched parts) so I don't know how much of a factor that was. But it sure didn't like the stock manifolds.
Dave
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Offline Chryco Psycho

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Re: What's wrong with my fresh 383
« Reply #5 on: December 16, 2008 - 11:53:26 am »
with Iron manifplds you need to be very careful with cam design , I did a 440 +6 with iron manifolds ported , ported heads & solid cam in the 576 lift range , it made over 300 RWHP , probably losing approx 35 hp to similar builds with headers

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Offline moper

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Re: What's wrong with my fresh 383
« Reply #6 on: December 21, 2008 - 08:06:37 pm »
what type of dyno? Engine  or chassis?

Offline Chryco Psycho

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Re: What's wrong with my fresh 383
« Reply #7 on: December 21, 2008 - 08:16:08 pm »
Mustang Chassis dyno , basically the lowest reading dyno you can use

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Offline bb71challenger

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Re: What's wrong with my fresh 383
« Reply #8 on: December 21, 2008 - 09:14:22 pm »
Correct me if I am wrong but if the heads came off that 64 engine wouldnt they be of the "nail head" variety? Even with fresh valve job, guides and everything they would still be sickly given the small exhaust valves right? Exhaust manifolds would only add to your problems. When you say its "going into a 70 Bee" that tells me it was on an engine dyno. An engine on a chassis dyno with that amount of power would be less than 200rwhp. Something sounds off. Hope you get it sorted out.
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Offline Chryco Psycho

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Re: What's wrong with my fresh 383
« Reply #9 on: December 21, 2008 - 10:14:01 pm »
If I was using 64 heads I would have the hard seats installed & use the 1.81 valves

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Offline 71chally416

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Re: What's wrong with my fresh 383
« Reply #10 on: December 21, 2008 - 10:32:46 pm »
Yep. The old 383's had small exhaust valves  :grinyes: The first motor I had in HS was a '65 383 and I used to get raped by 340's and 440's and many other cars.  :crying:
Once we had Ronald Reagan, Bob Hope & Johnny Cash. Now we have Obama, No Hope and No Cash!

Offline moper

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Re: What's wrong with my fresh 383
« Reply #11 on: December 22, 2008 - 01:13:06 pm »
All chassis dynos are simple tools. And not as good as an engine dyno at giving comparable numbers. Using the formulas I've always used (and everyone has an opinion on what is "right" or not...) I come out with 378 crankshaft hp, and 438 pound feet tq. The factory rating was 335, and realisitcally the factory floor engines made about 300. On a chassis dyno similar to yours, that's about 268 to the tire. For a true 9.5:1 (which BTW us not easy to get due to piston choices...), a cam with 240@.050 and .507 lift (.338x1.5) is huge. The exh manifolds are the factory log type, you are giving up a bunch of hp an torque. If the intake is a dual plane M1, you're giving up some hp and tq. If it's a single plane, you're giving up more hp and tq than the M1 dual. In any event, if you were to get a true 10.2:1, and run HP manifolds, plus and RPM intake, I'd think it would be much closer to 350 to the tire. Just my thoughts. So what intake and exh manifolds are you running? What piston was used?

Offline mach3107

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Re: What's wrong with my fresh 383
« Reply #12 on: December 22, 2008 - 07:51:38 pm »
Thanks for all the input. Here's some info I have off hand. I'll get the reset. Let me know if there's any other info needed.

It was on the engine dyno
heads- 452 open chamber (I believe)
intake manifold - dual plane mopar

exhaust manifold - ?
pistons - ?


Offline moper

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Re: What's wrong with my fresh 383
« Reply #13 on: December 22, 2008 - 10:18:37 pm »
What did the BSFCs and volumetric efficiency readings look like? It is low for an engine dyno, but as I said, I'll say right off the intake is restrictive. Do the manifolds have a large single tube running from the front exh port to the rear, with the dump between the last and 2nd to last exh ports? With each port dumping into that straight passage? Or do they come up as they come back, and each port has it's own passage as they move rearward? If it's the first type, you're giving up a ton of power there too.

Offline 71chally416

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Re: What's wrong with my fresh 383
« Reply #14 on: December 22, 2008 - 10:39:58 pm »
Any stock exhaust manifold is a loser for HP.
Once we had Ronald Reagan, Bob Hope & Johnny Cash. Now we have Obama, No Hope and No Cash!