checked the compression on my #s 69 roadrunner. compression #s warm were 148 to 159.Is this in tolerance? The motor is stock never out of the car.The stock heat riser is still on the car.Oil preessure is fine doesnt smoke runs and drives like it should.The only problem is when you rev the motor up the rpms are slow to come back down . I am getting ready to pull motor to do engine bay and would like to address any problems at that time i do not want to hurt #s motor any help ? thanks

Those numbers are normal. Back then, the engines weren't making the compression that they were rated at. My original 383 had the same numbers you are getting.

when you rev the motor up to say 2 grand it seems it takes a longer than normal for the rpms to settle back down to normal. Or when driving it say you shift to second the rpms stay up between shifts. I have a good return spring the carb plates are going closed . Not that it matters but the carb is a 68 -383 4spd carb that the original owner says was on it since new . . vacume is around 10" with the timing around tdc which i think is somewhat low .

If it's a completely stock 383, 10" is too low. You should be around 12" or a little higher. If the idle doesn't settle after higher rpms, you may have a vacuum leak somewhere or the carb throttle blades are hanging up. Next time you try it, try taping side to side with a very small hammer, on the carb throttle shaft(primary side),just to see if the idle drops back to normal. If it does then you know it's the carb, if it doesn't, then you know it's a vacuum leak or maybe timing. With 10", I'm leaning toward a vacuum leak, or retarded timing. 0* @TDC, with a stick car is normal with the vacuum line off of the distributor.

Vacuum will be low at TDC timing as it should be about 10 degrees Before TDC, advance the timing some and the vacuum will come up to where it should be.....

if its a completely original untouched 4 speed car and carb, you should have a dashpot that looks like the one on my 68, you set that dashpot to touch the lever at 2K if i remember correctly from the FSM and it will drop to idle slower than cars without the dashpot. It should drop about 1 to 2 seconds slower than a normal carb. if you dont have the dashpot then maybe timing or throttle blades open to far???

one more pic

I forgot about the dashpot.
Back in 68 & 69 stick car timing was TDC. Auto's were 2* BTC for 383's.

this is the carb on my 69. Sorry its dark its an n96 car also

With the motor off have someone hold the Pedal to the floor, you should see the dashpot plunger extend out, then you should be able with your finger to depress it in and it should have some resistance once in let go and it should extend out smoothly. They do go bad often

Check the secondary throttle plates and make sure they're not sticking as well.

I could be wrong but from what I remember dashpots were mostly only on auto trans cars. They were used to help catch the idle on auto cars so if you let off the gas real quick in gear it would bring the idle down slow so it would not stall. But I only remember them on auto cars as stick cars did not really need them. But it looks like your carb in the picture has the dashpot on it. Ron

I wasn't doing Mopars back then, but on GM cars the slow closers on the throttle were mostly on stick cars. The reason being that during emissions testing, dropping the throttle closed quickly increased the unburned HC and CO. Stick cars had many more times of throttle-off, throttle-on because of shifting.

R.

That's what I hear also, plus smoother shifting.

69 would have a dashpot and it's a 4speed thing.

Carter 4615S is the stock carb for '69 383 manuals and will have the dashpot. It does slow the return to idle from 2000+RPM. Keeps the vacuum advance raised while dropping throttle while speed shifting, reducing emissions. 4426S for '68 carb and it too will have the dashpot.
http://www.tocmp.com/manuals/Carbs/Carter/Chrysler/1965-1979/pdf/Chrysler121-173.pdf
Scroll down to Form 5526C for '68 AVS parts list
and Form 5534A for '69 parts list. There is a difference in primary rods and secondary jets.

You say this motor has never been out of the car. You MUST check if you have the stock single roller aluminum w/ nylon teeth cam gear as it will cause your low vacuum issue as well as cylinder pressure issues due to retarded cam timing. If it's still in there get rid of it. Check this way: pull the distributor cap and watch the rotor as you grab the fan belt on both sides of crank pulley. Pull the belt so's crank spins in reverse direction of normal rotation. If you spin the crank more than 5 degrees without the distributor rotor moving- you've found your problem.

yes thier is slop the way you describe in the timing chain. Yes it made me nervous . With the timing light it doesnt jump around the way some do . Thanks for all the help guys!

Put in a decent double roller before you pull the engine and redo your tests. It can be done with gasket kit for under $100.