Got a question guys, a little help would be appreciated.

[pinkpanthr]

So my 383 Road Runner sat untouched for 33 years before I bought it. The engine needed a carb, the old Carter was a total loss. I put in a new water pump, oil pump, fuel pump, and MP electronic distributor. Inspected the internals and they seem to be in good shape. (Cylinder walls smooth, etc.) The question is, when I start the engine it run fairly smooth but every few seconds it shakes, and acts as if it has a miss then smooths out again. Is a bit better when you bring the revs up but the problem is still there, just not as noticable. Anything obvious I should look for? Do the valve springs need to be replaced? At least a few of the set compressed for a long time. Thanks in advance.

 

[Garys1969RR]

Sounds like a valve sticking open and then freeing up again. Or possibly carbon particles breaking loose and causing the valve to not seat properly. Then when they clear the valve seat it seals again. But the guide sticking sounds more likely. I have found that if you run the big blocks for awhile, change oil and filter when it turns dark, then run em some more, a lot of the issues seem to disappear. The more you run em, the better they run in my experience. But you MUST keep the oil and filter clean.

 

[terzmo]

I would check the timming....then float levels...could be a fuel flow...I would think a sticky valve would also cause smoke out back

 

[Basket case]

when my cars sit over the winter, they usually act up in the spring. a nice long drive (with a few blasts down the straightaway) clears it up.

 

[Garys1969RR]

when my cars sit over the winter, they usually act up in the spring. a nice long drive (with a few blasts down the straightaway) clears it up.

That's what Im talkin about! Get it on the road and drive it around, let it work out the kinks. Also a new air and fuel filter helps.

 

[67 coronet]

drive it a bit like stated above.did you do anything about the old fuel that was in it?clean out the tank or anything?you could be picking up old fuel deposits.

 

[MarPar]

drive it a bit like stated above.did you do anything about the old fuel that was in it?clean out the tank or anything?you could be picking up old fuel deposits.

x2

 

[cr8crshr]

Sounds like a valve sticking open and then freeing up again. Or possibly carbon particles breaking loose and causing the valve to not seat properly. Then when they clear the valve seat it seals again. But the guide sticking sounds more likely. I have found that if you run the big blocks for awhile, change oil and filter when it turns dark, then run em some more, a lot of the issues seem to disappear. The more you run em, the better they run in my experience. But you MUST keep the oil and filter clean.

I agree here on this. One of the best shade tree fixes is a bottle or two of Marvel's Mystery Oil. It can be run in both the engine and in the fuel tank. What I have found with these BB MOPAR Engines is that you do have to keep running them until they seem on their own to quiet down. I just got my 383 fired up last Wednesday and at first it was really rough and stumbled during the break in. But after about 15 minutes it started to quiet down and smooth out. Check out my post in the Projects section for a link to the initial fire up and you can see and hear what I am talking about. MOPAR really built some great bullet proof engines that to this day after sitting for a long time will work fine after some running and driving. Just a suggestion here...cr8crshr/Tuck

 

[pinkpanthr]

drive it a bit like stated above.did you do anything about the old fuel that was in it?clean out the tank or anything?you could be picking up old fuel deposits.

Fuel system is new front to back.

 

[coloradodave]

At night, open the hood and have someone look at the plug wires while you put some load against the motor while holding down the brake pedal and with the E-brake on. See if there's any arcing from the wires to ground. Also probably a good idea to put in a new set of plugs. Of course you can always check the wires with a multi-meter, looking for about 5K ohms per foot of wire. Good luck.

 

[Cranky]

Did you work on the fuel system any or install new plugs or wires? Getting junk from the tank can mess you up. Did you oil the cylinders and prime the oil system before firing up? If you oiled the cylinders, you could have fouled a plug or two enough to make them misfire. My experiences with sticking valves is you will usually have a good solid pronounced miss and when one sticks open even just a little bet, you'll generally hear the lifters/rockers clack. If any stick closed, you'll bend push rods and can mess up rockers.

 

[pinkpanthr]

Thanks for the feedback guys, a lot of good ideas. Nobody thinks that the valve springs might be an issue?

 

[Cranky]

Thanks for the feedback guys, a lot of good ideas. Nobody thinks that the valve springs might be an issue?

Your springs might be weak but they either work or they are broken. Even weak springs will do the job at low rpm. If they are weak enough, valves that might be prone to sticking will/might stick easier but then you should be able to tell if that's happening by what I mentioned earlier. I'd be looking more closer to the tune (fuel and ignition) than I would be looking at mechanical for your problem....especially if you are not hearing lifter noises.