Okay so for some background information my family bought a 1967 Marina Blue Camaro base with what we thought was a 327 in it. We drove it about 200 miles to our house and it seemed fine. We decided to have it built by a trust worthy shop in houston but it turned out to be a truck motor bored over 80 with oversized piston rings on 350 pistons and crank. The shop recommended a 383 and after research we decided to go ahead and let them build it. About 3 months later we got the car back and it looks beautiful. Has a 383 with a mild roller cam, Holley 4 barrel carb, aluminum short block hooked up to a turbo r700 3 speed auto with overdrive (im pretty sure on most of that) with a full magnaflow exhaust. So under the hood it looks seriously menacing but to be honest it cant perform... what so ever. and the timing has had to be adjusted multiple times and everytime it slowly improves. The shop guaranteed a 475 hp engine that they would build, but driving it, it feels more like 200. Im confident my v6 mustang could beat it which baffles me. So what im wondering is, is it just the fact it is a handbuilt brand new engine that needs alot of time to break in and will eventually reach that 475 mustang shredding hp or is this an issue with the build that I should investigate further?

 

It also depends on the gear ratio in the rear. My 33 ford pickup with a hot 350 used to have 410s in the rear and was 12 second truck recently went to a set of 342 since its retired from racing and its absolute dog no power just a lot of noise so I'm going back to the 410s.

Also a 700r should be a 4 speed tranny could be a th350 or 400. Also could be over carbed. I personally don't like Holleys, never had a good one.

 

Im not exactly sure its a holley but oh well and the gear ratio is 3.73 which should do the job I would think

 

Yeah 373s are a good all around gear could be timing, air/fuel mix, carb jetted wrong, not hot enough spark. And also the 475 the shop said it at the flywheel. It's more like 325-350 at the wheels.

 

Which is making me think the timing may be off. A 383 has plenty of low-end grunt, no matter what gears you're running, so it's not that. Check to make sure the correct harmonic dampener was used, some have the timing notch in different clocked positions, although I believe all the 400 style (what you should have) are the same. Also make sure you have the right timing tab, some point to different positions depending on which type of dampener is used. If either one of these is a mis-match, your TDC isn't really where you think it is. Another possibility is if a used/worn dampener was installed, the outer ring could be spun from the inner hub. That will throw your mark off. If it were me, I would get a piston stop and find your true TDC, so you can be sure it's where you think it is, or know that it's not.
One more possibility, but I wouldn't assume that till you do the above, is if the builder did an oops, and got the timing chain set installed off by a tooth.

 

I agree with Camaro69, the timing most likely. And I'd also ditto the timing marks be checked. I just went through this while assembling my BBC engine. Had the heads off and was checking TDC with a stop across the block. I found the harmonic balancer mark was off by about 40-45 degrees! Had I assembled the engine and just assumed it was right, I'd be having all sorts of problems later.
Get it to a shop that can check TDC properly, if you can't do so yourself, and then see if the timing is correct.

 

383 is a great buildable engine. I would suggest timing and may help to get a good engine person to check it.

 

I agree with Camaro69, the timing may be the issue, also check out the carb? maybe running too big?

 

Ok new guy here. You said the block was bored 80 over? Your running that on the street? Small blocks bore 60 over and run on the street tend to run really hot, You end up jeting the carb up more to richen it up to reduce the heat. The heat can effect the way it runs if it is running to lean or causing what they used to call vapor lock. Confirm your timing is correct and make sure you have a 400 balance on the crank if in fact they did the stroker conversion, They may also degreed the cam wrong too. Also what heads are you running. You can do all kinds of lower end mods but if the engine cannot break it will not perform well.

 

A lot of variables to this problem, but the most common are timing issues and a carb that is to big. I agree on the Holley not being all they are cracked up to be, they are very tempermental but are able to be adjusted and updated to fit your needs. But for the novice it can be a real pain to deal with. As for the timing issue, try to keep "fooling" with it. Keep advancing it 5 degrees at a time and driving it after each advance until you get the best performance you can out of it. If it starts to spark knock (sounds like a rattle in the engine when accelerating) then you have gone past it's limits of improvement and you need to retard the timing before serious engine damage starts to develop (that won't happen immediately so don't freak out, damage will only happen if you keep driving it like that for a long period).