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I'm fighting some sort of timing battle here. The car has always had the Holley stumble to it so I started to mess around with the timing and noticed at idle 1000-1100 rpm it was at 33 degrees. I thought well that way too much. Brought down trying 12-18 degrees and the engine would cough through the intake and run terrible. I noticed all in total advance would only go into the 20s. So I set the total advance at 34 degrees and it was a tad better. Still at idle it's at 24 degrees. For some reason I'm only getting a 10 degree mechanical advance. The vacuum advance is not working. If I idle the car down below 1000 rpm it will just slowly stall. It is the typical heads cam intake 355 motor with an ultra double pumper Holley 650. Distributor is all stock. Any advice, ideas welcome. I'm at a loss.
What year?
First off.....there is no such thing as a "Holley stumble"....all carbs will fall on their face if not properly setup......
Secondly....if your distributor is only pulling 10 degrees of advance...it needs to be pulled apart and the advance weight mechanism inspected......
What do you mean the vacuum advance isn't working? You have it unplugged? The cannister is bad?
Also....have you verified true #1 TDC at your balancer?
You must have the timing sorted before adjusting the carb........and I feel you have problems with both.
The vacuum advance doesn't work whether it's plug in or not. With the cap off so I can see I sucked on the vacuum line for the canister and nothing happened. I'm assuming it's bad. I can move it by hand. The mechanical advance is all free and working what seems to be correct. I think you are very right with having trouble with both timing and carburetor tuning. I'll check for TDC when I get back to it.
it's a 1976
Can you post a pic of the top of your engine from firewall to thermostat housing, without air cleaner and chrome/plastic distributor cover? Both you and we often assume things are commonly understood but that may not be the case - a pic helps to get a common understanding of your setup.
The vacuum advance doesn't work whether it's plug in or not. With the cap off so I can see I sucked on the vacuum line for the canister and nothing happened. I'm assuming it's bad. I can move it by hand. The mechanical advance is all free and working what seems to be correct. I think you are very right with having trouble with both timing and carburetor tuning. I'll check for TDC when I get back to it.
it's a 1976
Yes, pics help a lot always....especially one of the advance mechanism with the cap and rotor removed........
76' will have an HEI and all HEI's pull more than 10 degrees.......most HEI's pull 21 degrees except the L-82 350 which pulls 16......
You need to get a new vacuum advance.......adjustable one is preferred.....and adjust it to pull 12 degrees when plugged in. Plug it in to full manifold vacuum......
Here is the distributor. Yes the springs were taken off in the picture. I was going to replace it with the advanced curve key but decided against it for now.
Ok...see the blue circles? The plastic bushings are wore out......
Get a Mr. Gasket 928G kit and see if the bushings work....also use one middle and one light spring.......clean and lube everything with a light grease.....
The vacuum advance doesn't work whether it's plug in or not. With the cap off so I can see I sucked on the vacuum line for the canister and nothing happened. I'm assuming it's bad. I can move it by hand. The mechanical advance is all free and working what seems to be correct. I think you are very right with having trouble with both timing and carburetor tuning. I'll check for TDC when I get back to it.
it's a 1976
I don't believe the human mouth is capable of moving that Vac Adv.
Go to Harbor Freight and get a Mity Vac hand pump for IGN timing, testing vac lines and often brake work.
Where is the rod from the canister that goes into the open hole on the arm?
I don't believe the human mouth is capable of moving that Vac Adv.
Go to Harbor Freight and get a Mity Vac hand pump for IGN timing, testing vac lines and often brake work.
Where is the rod from the canister that goes into the open hole on the arm?
Good eyes! The vacuum advance is not connected to the distributor base plate.
Good eyes! The vacuum advance is not connected to the distributor base plate.
Yeah it is...this is an optical illusion.....the rotor tang is covering the vac advance tang because it is just in the right position......but you can see just a little bit of the lever if you look close.....
So is it basically get the mechanical advance we're the engine is happy and then plug the vacuum advance into the manifold vacuum and then idle the engine back down? I bought an accel adjustable vacuum advance and set it for 12 degrees of advance.
Looks like the mechanical advance doesn't return all the way . Can you move the mechanical advance easily or is it hard to move ? Yes you can run the advance kit but make sure the mechanical moves freely
Looks like the mechanical advance doesn't return all the way . Can you move the mechanical advance easily or is it hard to move ? Yes you can run the advance kit but make sure the mechanical moves freely
Exactly....if it doesn't return all of the way....you can't have a full curve......
The mechanical moves freely. I think it's already advancing because the idle has to be so high. Was I correct on the tuning of the vacuum advance stated above?
The mechanical moves freely. I think it's already advancing because the idle has to be so high. Was I correct on the tuning of the vacuum advance stated above?
Ok. This engine won't run right unless it has a ton of advance. Right now if the throttle is cracked fast it will either cough through the carb or back fire through it. The more advanced the timing gets the less it does it. It's advanced far enough now that the vacuum canister is about to hit the intake. Would a lean engine need a bunch of advance? Is that what Im possibly fighting here? Here is a picture of the headers I've recently taken off of the car. Way lean at the back of the motor on both sides.
I need tuning advice please!
