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Lazy 383???

Joe Palmer

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So a little back ground first: My dad had this engine rebuilt in 2000. The engine builder has built many big and small block chevy's for my dad over the years but I think this is the only Mopar. It is a stock 1970 383 4 speed, .010 overbore, stock crank, rods, stock CR pistons, restoration cam, Holley 600 Vac secondaries stock exhaust. We received the car last month out of dry storage. Car started up fine but would not pull itself into the garage....

So first we changed oil and filter, added new plugs, wires, coil, Mopar electronic ignition upgrade, and voltage regulator.

After that the car would pull itself around the yard much better, but it still revs lazy up to about 3500 (almost feels like its missing with a vibration) 3500-6000 is cleaner. Out on the road it runs like a worn out 318 2 barrel. Wont even squeak the tires without revving it way up (4500 or more)

But, she starts right up, the plugs look real good (brownish white) there is no smoke or any weird noises, The car doesn't overheat at all, total run time on engine since rebuild is about 6 hours maybe 20 miles....

So we had to blow the car apart to get it to paint before Daytona turkey rod run, but I want to have a plan for when the car returns to sort this out. My gut tells me its timing related. I plan to verify TDC and check the valve positions to ensure cam is installed correctly, but after that anybody have any other ideas? Thanks in advance.
 
When you say "dry" storage, does that mean the fuel and antifreeze were drained before storing the car?
 
did you check timing advance when you did ignition replacement if you did and all good then I'd do a compression test and then pull rocker covers and watch rocker movement while running!
lifters collapsed?
 
Is it running on all 8? Wheres the timing? Was the cam degreed? What's the cylinder pressure?
Doug
 
Last edited:
Cam timing is a likely candidate.
Compression test, pull one plug wire at a time and see how it affects it idling.
 
The FIRST issue I see is in your 3rd sentence, 0.010" overbore. They don't make 0.010" oversize pistons for Mopars, Chevys, Fords, etc.. Either it is a worn stock bore, or it gets bored/honed to a minimum of 0.020". If your cylinders was honed (somehow) to 0.010" over, installed std pistons and rings, your going to have a ton of blowby and piston rock. Even with 0.005" oversize file fit rings, the piston still will rock too much affecting the sealing ability of the rings. It needs to be bored and honed to a proper size which is going to probably be 0.030" unless it can be done at 0.020".
 
I would strongly suspect valve timing.. I've seen plenty of timing sets with barely visible markings... Ford & Chevy thats not a big problem, the mark on the gear lines up with the keyway...

So with your guy being a Chevy guy it's easy to accept that... But...

Mopar when the marks are properly aligned the crank keyway is at about 1 clock...

I've seen two engines with the keyways aligned.. They both started & ran but lazy was an understatement...
 
If ignition timing is good & fuel system is OK, I'd suspect cam timing too. It's easy enough to get a tooth off. Told this story before but, had one Cloyes timing set that appeared properly lined up, but I checked valve timing events with the degree wheel & realized I was off a tooth. Tossed that set & got another one.
 
See if I understand this.

20 years ago the motor was rebuilt and driven 20 miles, put in storage and 20 years later, I doesnt seem to run right.

It could be anything from the carb to the mufflers.

Do a cylinder pressure test.
 
Is it running on all 8? Wheres the timing? Was the cam degreed? What's the cylinder pressure?
Doug
Like Doug says, I would guess the cam wasn't degreed in. Your cam could be retarded 6-8deg.
 
What rear gear do you have and what size rear tires?? What is your timing set at? Initial? Timing curve? What port is the distributor advance hose hooked to on the carb.
 
THANKS FOR ALL YOUR INPUT, YOU HAVE GIVEN ME A PLAN OF ATTACK WHEN THE CAR RERURNS FROM PAINT. I WILL UPDATE WHAT WE FIND
 
So we finally dug into this. I pulled the front off the motor and ensured the cam timing was correct, verified engine timing with a piston stop, and changed the plugs again. At this point the car ran excellent in the driveway, but under load it still didn't pull as I would expect. I rechecked the timing and found it way advanced (wife didn't tighten down distributor) reset the timing and borrowed a Holley 650 DP mechanical secondary carb...WOW!! car woke up. I also changed the base gasket which looked dry rotted (i think this may have been most of my issue It was one of those 1/4 inch thick ones) I think this motor would like more carb also. I'm calling it fixed for now! Thanks for your ideas!

IMG_E2428.JPG
 
As you posted, the issue was way advanced timing (aside from a bad carb gasket)? Curious, did you do a vacuum leak check around the carb earlier? What do you have the timing set at now? Thanks
 
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