Idle shifting issues on new 383 motor/200r4 transmission

ASTEROIDGALAXY

MEMBER
1986 CHEVROLET MONTE CARLO
V8
2WD
AUTOMATIC
2,819 MILES

I have a car that was recently re-done. It has a 383 stroker motor, holly carb, 2400 stall converter w/ lockup, MSD ignition/distributor, and a 200r4 transmission. There is less than 10,000mi on the motor/transmission. I'm wondering if you have some insight on this and could point me in the right direction to fix these symptoms:
1) When the car is started cold, the fuel pressure stay steady at 8 when in park. After the car has warmed up, the fuel pressure jumps from 6.5 to 8 (bounces from 6.5 to 8 every second).
2) Whether or not the car is warm. The RPM stays steady at 1,000 when the car is in park. When the car is in drive (w/ the brake engaged) the RPM stays steady at 500 when the car is cold. It jumps between 500 and 1,000rpm when the car is warm and in drive normally stays around 750 when 75% time. Every 10 seconds it'll jump to 500, the car will stutter like it is about to stall.
3) The car feels like it shifting to early for the speed, would that be a carb adjustment?
4) When shutting off the car, there is a sound that could be described as a cranking/knocking/grinding sound. This is as soon as I turn the key and it stops within 4 seconds. This sound only occurs when shutting the car off when warm. If the car's only been running for ~2min and I shut it off, there isn't a sound.
There isn't any weird sounds or problems when driving (except the feeling that the shifting is occurring about 5-10mph earlier than it should).
1986 Monte Carlo SS

5 Replies

HMAC300

MECHANIC
48,600 POSTS

What you have sounds as if it's running to lean and needs richening up. When it is cold the choke is probabl applied and cuts the air down and richens the engine. When it's warm the choke is open NOT cutting the air down so it leans out. If think if it is richened on the primary side it should be ok. As far as using a 200R4 the question is why? The 700 or 4l60E is a much stronger trans than the 200and if you use the 4l60 e there is a stand alone computer that you can use for it. One thing about a 200 is that the throttle pressure is VERY CRITICAL for that trans so you may need to give it a little more cable adjustment. The sound you hear sounds likeit may be spark knock or detonation. Also could be runon which is pretty much the same thing. BEst thing here to do is put an electric solenoid like they used in the later 70's or early 80's, witht eh key on it is powered up and you adjust the idle that way and have the other carb screw go below that sothe engine stalls. So when you turn the key off the carb goes below the solenoid and stalls the engine so you don't get detonation

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Wednesday, June 22nd, 2011 AT 12:48 AM

ASTEROIDGALAXY

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17 POSTS

When you're talking about a cable adjustment for the 200r4, are you referring to the TV cable going to the carb? Do you know if an adapter is required to properly work with the Holley 750? If the TV cable is misadjusted would that cause the hard shifts I've been recently experiencing? Could you provide me information for properly adjust this cable for the setup? The 700r4 is a much stronger transmission when compared to the 200r4, but would this setup cause me problems with just regular street driving (I don't plan to take use it as a drag car)?

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Wednesday, June 22nd, 2011 AT 1:07 AM

HMAC300

MECHANIC
48,600 POSTS

As you have a 383 in this and not the stock engine you may haveto play with the tv to make it work right. The hard shifting is probably due to someone setting it up that way and can be reversed but I don't know why you would do that. Its better for the trans to shift hard. The 700r4 woldn't give you any problems street driving but make sure you get an electronic shift with the computer so it can be set up i'm sure GM performance would have something for it. Just remember the 700r4 is a lot longer trans than the 200

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Wednesday, June 22nd, 2011 AT 1:11 AM

ASTEROIDGALAXY

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17 POSTS

Would the 200r4 give me any problems in the longer term w/ this setup just for a daily street driver?

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Wednesday, June 22nd, 2011 AT 1:42 AM

HMAC300

MECHANIC
48,600 POSTS

The 200 is a light duty trans but should hold up for street driving, I really don'tknow how you drive and i'm sure you will hammer on it once in a awhile. People have used these because of the overdrive in them.