I cannot get my 383 to smooth out. 2 different ignition modules. 2 different distributors. 3 sets of plugs. 3 sets of wires. New motor mounts made it worse, new tranny mount even more worse! Schumacher torque strap way way worse!
I inspected the converter and the balancer. That are for a forged crankshaft. No balance weights on converter and damper has no teardrop weight mass.
Could I have a cast crank with the wrong damper and converter on it?
Its a 1968 383. Not sure if it was a HP. That mark is missing assuming the engine was decked at one time.
Im at the end of my rope!
Any ideas?
Thank you
I don't think they made cast cranks for the 383?
No cast 383 cranks were made to my knowledge. 400 CI had cast cranks though as did later 440's. You have something out of balance inside that engine I would think.
Thank you.
I'm running thru the things that could cause this. I've had this vibration from day 1 when she came home with me.
Im considering taking it in and having them put a ignition scope on it.
The only thing that's never been changed is the edlebrock 1406. I've rebuilt it 3 times as well. Even messed with the step up springs.
Other ideas? Collapsed lifter? Idles well. Then off idle up to 1300 rpm it shudders like a dead misfire.
Anyway...
Thanks again
I've always struggled with an off idle stumble on those carbs. Have you or could you borrow a holly and rig it up to see if that's your problem?
I've considered just buying a Holley. I've had allot of big spends $$$ with not allot positive result. So I'm shy on spending any real money until I have data or facts to prove the investment.
No. I don't have any friend that have spare carbs to barrow. I thinks the ignition scope and the tail pipe sniffer should point me where I need to go...
a friend of mine once washed his engine when he was in his 20s..it knocked half of the grease out of the balancer causing his engine to be off balance just enough to do the exact thing you are describing sounding like a missfire.. he was pulling his hair out and had several mechanics come up empty before his dad figured it out.. i doubt it could be the same but its worth looking at..
Yes, there were cast crank 383's. 2bbl 383's had them in 71.
Pull vacuum hose on distributor and see if that has any effect.
Also, what's your total timing at 2500 rpm?
I'm at 20 degrees initial with a FBO lock out plate at 14 degrees. All in at 34 degrees. I had this issue before with the other distributor. That one was a MP that made way too much timing. I adjusted it and adjusted close to 14 total. No improvement. So I bought a new reman mom mopar distributor, opened it up and installed the FBO plate. My thinking was that the old MP unit was sloppy and worn.
Time and money spent... No gain.
I've had the balancer off. It's not loaded with grease or grime. I had the tranny out last winter for seals. Could I have bolted the converter up wrong? But I have read that they only bolt up one way.....
So it's either mechanical, ignition, or fuel?
Pulling the vac advance off the distributor makes no change to idle quality. That was noted on both distributors. Dry compression test showed cylinders at 105 to 110 psi. Idle vacuum around 17-19 with a twitchy needle, not a rapid twitch tho.
I'm going to use my mini vac hand pump and apply vac while idling to see if it changes idle quality and that shudder.