383 question

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bb489ss

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Hi all!!

First off, let me just say hello to everyone as I am new to this site. I've been a Chevy man all of my life, but as of last Sunday I now have a 1974 Dodge Dart with a 383 Magnum sitting in my garage!!!!
My question is with the motor, since I really don't know much about the Mopars. I was wondering if some one could give me a ball-park guess on the the power output of this motor and compression ratio. Here is what I was told was done:

1971 Dodge 383 Magnum rebuilt with flat top pistons.
699 oil pan with baffle welded in.
650 Speed Demon carb with vac. secondaries.
452 heads-fully ported with 3 angle valve job.
heads have been milled 0.060 with steel head gaskets.
Holley street Dominator manifold ported to match heads.
Comp XE 268 hydraulic cam. 1.5 rocker arms.
MSD ignition.
Long tube headers-don't know primary size

Not to mention new exhaust 2 1/2", completely new Dana 60 rear with 4.10 gears. 727 trans-all rebuilt. Motor definitely sounds healthy, but haven't really been able to drive it much yet because I need to register it (which I'm doing today). Appreciate any and all input. The car is in great shape and I think I got a good deal on it (around $5000). Thanks in advance!!
 
Welcome to FABO. Post some photos of your car. We like pictures.
 
That sounds like a good combo. Welcome to FABO. You'll never go back to chebbie. That little big block probably is around 375-400 HP I bet.
 
Most importantly welcome to the site. Where you're sitting right know I'd guess 400HP, do you know what the CR is, hopefully at least 9.5 with a zero'd deck. Improvments, your carb is to small especially with an aftermarket intake and headers, mine loved a 750 DP'r. The performer RPM is a better all round manifold but you'll have to get pretty imagineative with the air filter if you don't have a hood scoop. Done properly (bigger carb) with the cam you're running (which I consider mild) and intake and exhaust fine tuning 450HP is easy and 500HP is a good target without going nuts on the compression (imo 10 to 1 best) and an M1 intake and better cam. Oh yea, 383's loved to rev., big bore x short stroke and 6000 with stamped steel rockes is about max., add roller rockers and add 500RPM.
 
I built a twin to that about 10 years ago. The block was blueprinted for zero deck (which on a 383 is critical...) and the heads milled. It was 9.8:1, XE268, Street Dominator, and 3310 750 VS Holley. Small tube headers. It makesabout 420hp on pump swill.
It's a good combination if it was done properly. BTW, that Demon carb is about the same as the typical 4150/3310 Holley 750s. If it were flowed and rated the same way it would be very close to 750cfm. I'm not a fan of Demons but it if it's working for you keep it.
 
Cool. That's more than I wouldda thought. And a 400 would be even more yet. I love how you can just chunk one toegether and it makes respectable power. This is got me thinkin 400 instead of 383 for my next one. lol
 
Thanks for all the info! I was thinking Holley 750 DP too. I never really liked vacuum secondary carbs anyway. The guy I bought it from said compression is 9 to 1, but since I didn't build it I don't know for sure. I read somewhere that the 452 heads are 88 cc chambers and that being milled .060 like they are puts them in the 75-78 cc area. I also thought the cam was a little small too. What size would you all recommend if I change it? I was also wondering because the heads were milled 0.060, if I were to get a Performer RPM, how much would need to be milled off of the manifold so it would fit? I read the Holley street Dominator manifolds are pretty good for BB Mopars, and mine was port matched to the heads, so I'm not sure what to do. Sorry for all the questions, but I want to learn as much about my new baby as I can. I'd be very happy with 450-500HP. My old car was a 68 camaro with a 496 making 690 HP, solid roller, alum heads, etc...ran like a beast, BUT was always needing something, ran hot all the time, and was generally a PIA. I just want to make this motor the best it can be with bolt on stuff an NO major internal mods, except for maybe a camshaft change. Plus, I figure in a Dart, 450 HP is more than enough to make a wicked ride, right??!!
 
The problem with a accurate est. HP guess is actual compression ratio and the head flow numbers. I think everyone so far has provided a great guess though. 400+ if well tuned.
As for a step up in cam size, what is the size of the rear tire? Also, would a new converter be out of the question?
 
Quote: I just want to make this motor the best it can be with bolt on stuff an NO major internal mods, except for maybe a camshaft change. Plus, I figure in a Dart, 450 HP is more than enough to make a wicked ride, right??!!

If it was me and it has been for years since I've always had a soft spot for 383's (so much potential) I would do 2 things before touching the cam. Yes to a 750 DP'r (you're going to be there eventually so might as well start with one) and either Crane or Hughes aluminum roller rockers which would require custom length push rods. The Holley is a good manifold not as good or as high (1" at the back) as the M1 but like all single planes can be doggy off the line, you can counter that a bit with a 1" thick 4 hole spacer. Now the rockers. The stamped steel rockers are crap for ratio accuracy. The last build I used Hughes and before installing them I rigged up the old stamped steel set with a solid lifter and adjustable pushrod. This allowed me to see with dial indicators, the actual push at the valve stem taking the stamped rockers into account and taking the spongeyness out of the hydraulic lifters. The end all be all is that the old 1.5 ratio steel rockers were actually between 1.40-1.42. I then latched onto a pair of brand new mopar steel rockers and they were almost as bad.
So I'd go for the carb first then the rockers and get some before and after times. I was going to do the same but our track shutdown.

While this is all going on you also need to pay attention, as Rob says, to your torque converter and it's sweet spots.
 
Welcome to FABO now from Sc, but Boynton Beach from 1988-2005.

Nice score and i'll second the motion for some pics:D
 
Sounds like a well thought out build,383s,sleeper of the Mopar lineup.
 
Thanks for the info. The converter has a 2400 stall speed. Where can I get the roller rockers you were talking about Demon Seed? And would 1.5 or 1.6 be better? And the pushrods, how can I figure out the length I need and where to get them. Chevy stuff is everywhere. Don't see a lot of Mopar stuff though. Thanks
 
Go to Hughes Engines, they make their own rockers, hold downs and heavy wall rocker shafts, (not cheap) and have a very good written procedure to determine finished push rod length along with correct angle alignment, I'd stick with the 1.5's. They can explain it all. They will also assemble the push rods and send them to you after you use their solid lifter and adjustable pushrod to determine the correct length. Here's my latest installation. On a different subject, a converter with a higher stall 32-3400 RPM maybe in your future.

http://www.hughesengines.com/Index/index.php
 

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Actually,the Hughes rockers are a great bang for the buck.There are cheaper rockers,but tweaking and set up time for another 2 to 3 bills make this a no brainer.Trust me,I went the cheap route once,and paid for it.
 
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