Looking at making a few changes to 383

[obredneck]

I've got a 66 coronet with a 383 bored .030, single plane intake manifold, 750 Holley double pumper, 727 w/ a 3600 stall. Not sure what cam or my rear end gearing but running about 3000 rpm at 65-70 so I'm guessing 3.55ish.

Basically my issues are that I've got a flat spot @ low rpm when accelerating from a stop and it bugs the hell out of me.

I'm thinking very hard about swapping in a Performer RPM or Weiand dual plane manifold and am definitely going to change torque converter to something around 2400 range for the stall to help with overall around town driveability.

Also thinking of tossing in 3.23 gears (or stepping down to 3.55 depending on what I find out when I take the 8 3/4 apart this week) to bring down the rpm so that I can cruise the 12-15 highway miles to work more often without getting murdered in my wallet.

I guess my question is, has anyone done a build along these lines? Did power response at the low end pickup? Were there any noticeable issues with loss of power across the power band?

Thanks in advance.

 

[RustyRatRod]

Not trying to be a smartass.....but why not try to diagnose what's there? You may throw parts at it only to still have the same problem. That would suck.

 

[obredneck]

Not thinking you're a smart *** at all. I know that I want to change the torque converter, not really a fan of the rpm range for the shifts. The guy I bought if off of had it set up as a strip car that he could street there. Not exactly the direction I want to take it.

Not thinking it's an issue with the components so much as the combination/intent of the parts. Mainly because once it gets moving, it's a runner and I have 0 problems. Just looking to make some adjustments to get it driving the way I would prefer.

 

[tpodwdog]

when you say " flat spot"... does this mean you step on the gas and it does nothing for a second or two?. if thats the case , sounds like you need a accelerator pump.

if you mean flat spot as in,,,,it dont take off right away, could be mis matched cam to torque converter ?

i have a 3500 Torque converter in my 440 with a Hemi cam and it sure does like to rev high before it wants to go anywhere.....but after that ,,,,like you said , theres -0- problems.

i have had a few recommend a 2800 torque converter to fix that.

 

[Meep-Meep]

Having a look at the accel pump is a good start. Also check float levels.

Now, if you want a nice driver and are concerned about the damage being done to your wallet, the Holley DP is not what you need. Swap that out for a carb that is designed for street use. And you already found out about the converter. What is your vacuum at idle? This will help determine if you have a radical cam and give some direction about tuning. Timing should also be checked or set. 36-38 deg total (without vacuum advance hooked up) all in by 2500. 12 deg Initial is a good starting point.

 

[obredneck]

Dog - Definitely thinking mismatch on the torque converter to cam.........revs high, does nothing and that's where I was going with "flat spot".

Meep - I'll check the vacuum but I have a feeling the cam is not all that radical, at least not from the feel/sound at idle. The DP is on the list of things to change, just not right at the moment.

Appreciate the help folks.

 

[RustyRatRod]

To "ME" the biggest mismatch is the converter to gear. If it was my car, I'd dump a 4.30 in it. I know that's going the opposite direction you want to go, but for the rest of the car, that's the most practical swap since it will match everything up in one fell swoop. The other way would involve an intake swap for better bottom end, a lower stall speed converter (I'm thinkin factory high stall) and maybe even a cam change if what you have now is pretty hot. THAT would net you the end results you're talking about....less RPM, more mileage and probably even more bottom end torque. That would ultimately be a better streetpackage than my more practical swapped out gear, but cost much more on the onset, yet make up for it in the long haul.