'69 383 Setup Headache

[lewtot184]

the timed/full manifold vacuum argument goes on forever. take the carb off and look at the location of the timed port. it's right above the throttle blade. tip the throttle blade a few degrees and your into full manifold vacuum (holleys are different). you don't need or want full manifold vacuum at idle jerking the vacuum advance in. the small cam makes plenty of vacuum. put a big cam in and the situation may be different. i use the timed port on both my carter equipped engines; one stock and one with a performance solid cam, and always will.

 

[dieseldazzle]

Regardless of manifold or ported vacuum, when the engine is out of vacuum at 0 on a gauge....such as full throttle or even as you accelerate with part throttle...... the vacuum advance can aint gonna do anything...not sure why everyone gets so confused....

I like manifold vacuum myself.

 

[Addabob]

Ok, I must now say that everything that I thought I knew about vacuum advance is now out the window, and I admit that I don't know jack...

So today, I installed the light springs into the Pertronix to advance the mech advance curve to kick in starting at 1k and all in by 2400-ish. Reset the initial timing to 11* with vac adv disconnected and idle at 500rpm, and 38* total timing at 2500+. I also tried adjusting the carb with the vac gauge, adjusting richer on each bank by 1/4 turn until vac peaked and just started to decrease then backed off 1/2 turn. I decided to try swapping over to the timed vac and see how things worked out, and this is where it started to get wonky.

Plugged in timed vac, and timing was still 11*. Hit throttle and watched vac and timing. At 4000rpm, I had 55* on the gun, which is the 11 static + 26 mechanical + 18 presumably from vac advance. Ported vac was still at 17" at 4000rpm so ok course was all in... I always thought that the vacuum signal would be down close to zero as rpm went up, but that does not seem to be the case. I tried swapping over to manifold vac on carb, and the only change was idle rpm went up to 700.

i have not had a chance yet to drive it to see if it is still bogging... Will try here in a bit and will report back.

vacuum advance theory vs real world is making my head hurt...

thanks all!

Update: so took it for a drive. Overall, drive ability is good, everywhere but from low rpm and hard acceleration. From a stop-to-WOT, motor bogs down and kinda chugs for about 2-4 seconds then finally starts to accelerate. No backfires, no pinging. Hard Acceleration from cruise speed kicks down transmission and does not bog. I had no pinging/detonation. It ran quite well but for the low end acceleration... Maybe my desire to burn some rubber every now and then won't be fulfilled... Funny thing was I could get a decent little squeal with the original 2bbl setup...

 

[mopar 3 B]

Have you checked the fuel supply?

 

[Addabob]

Have you checked the fuel supply?

That is first on the list for tomorrow, need to get a pressure gauge... If I recall the Edelbrock 1806 specs correctly, fuel pressure should be no more than 6psi at idle, and more like 5.5psi. What else should I check around this...? I did install a new filter and lines from the pump to carb. Fuel tank and supply line to pump were replaced a few years ago by the previous owner...

 

[dieseldazzle]

Check fuel supply and also remember that with vacuum advance hooked up and no load on the engine things are gonna look different with your timing light than they will with the vacuum advance hooked up and the car under a load at that rpm.

 

[miller]

Yeah on the vacuum bit. That's why it's unhooked for basic timing. If the carb is set right, once the vacuum is back on, doesn't effect that much.
But, I'm flat old school. Never cared for anything but mechanical advance. Also only set carb mixture using RPMs. Guess I'm set in my ways.

Some might disagree with me, but on your mixture sets (on a 4 holer), have 'em matched up? What I mean is, I'll get my set on each mixture screw, by the RPMs...then re-check each for exact number of turns. If any difference, I split the difference to match each one. Always worked for me.

Was the carb new, or what? The bogging could be off the accelerator pump not set right, or the like...or minor dizzy advance issue.
At least your working things out.

 

[lewtot184]

try tightening the tension on the secondary air valve. also check float levels and maybe put the accelerator pump rod in the top hole.

 

[Addabob]

Yeah on the vacuum bit. That's why it's unhooked for basic timing. If the carb is set right, once the vacuum is back on, doesn't effect that much.
But, I'm flat old school. Never cared for anything but mechanical advance. Also only set carb mixture using RPMs. Guess I'm set in my ways.

Some might disagree with me, but on your mixture sets (on a 4 holer), have 'em matched up? What I mean is, I'll get my set on each mixture screw, by the RPMs...then re-check each for exact number of turns. If any difference, I split the difference to match each one. Always worked for me.

Was the carb new, or what? The bogging could be off the accelerator pump not set right, or the like...or minor dizzy advance issue.
At least your working things out.

This is a new 1806 carb, and I have done nothing beyond setting the choke and 2 idle screws. I need to do some research and read up on the proper settings and how to do it. I will say that this is probably the procedure I am most intimidated by. I am always amazed when I read various things about people who know this stuff like the back of their hands, and the AF mixes and metering rods and jets and... well that is about the point that my head explodes. :-/ But, that is why I got the car, so I could learn more about this stuff and how it works. Things get a lot less intimidating once you tear stuff apart and see what is going on inside. There is just that fear of rendering that operational car into an immovable object due to ignorance ( or worse,stupidity).

Thanks all for your patience, guidance and wisdom. It is appreciated, and I am trying to make sure I do my part in learning and applying your recommendations.

off to the store to get a fuel pressure test gauge.

- - - Updated - - -

try tightening the tension on the secondary air valve. also check float levels and maybe put the accelerator pump rod in the top hole.

Ya, I read a couple of things about changing the accelerator pump rod to top hole, but I figured I would go through the full setup first and learn about all the pieces to insure everything is right. I hope that the rod position will be part of that process.

 

[miller]

Ha! Yeah...we having fun, yet?

Only ONE idle 'speed' screw, on the left side. You mean the two mixture screws, one for each side for the four holers, up front. Don't worry about it. Years (many) ago I learned all that stuff, mostly the hard way. And, I still don't know what the heck I'm doing, just get by.

 

[Addabob]

Ha! Yeah...we having fun, yet?

Only ONE idle 'speed' screw, on the left side. You mean the two mixture screws, one for each side for the four holers, up front. Don't worry about it. Years (many) ago I learned all that stuff, mostly the hard way. And, I still don't know what the heck I'm doing, just get by.

Yes, I was meaning the (2) idle mix screws and not the (1) idle speed screw, or at least that is what I think they are referred as... I was also told that one was adjusting air and one was adjusting fuel, which I don't believe is anywhere near accurate, but I let them go on...

- - - Updated - - -

Quick Update :

I got the pressure gauge and checked out the fuel pressure. It was sitting at about 6.5psi so that looks good. Tried readjusting the idle mix screws again, ended up a little leaner than before by about 1/4 turn. Still had the bogging.

So now I decided to try moving the accelerator pump rod location, and moved it from the original middle hole to the top hole as suggested. I didn't adjust anything other than moving the rod location. Idle was not as good as before, rougher... It helped the low rpm bog, but engine was now not running as smoothly. I pulled back in the driveway and stopped to open the garage door, and motor stalled. Had a heck of a time getting it started again, and even when it started, it was really rough and stalled again. Changed the accelerator pump rod back to middle hole, but still was hard to start and get back in garage stall. So now not sure if I messed up when changing the rod position in that I didn't readjust the idle mix screws or what...everything is back to the original location of when I started today, but motor is hard to start, runs rough and eventually stalls... Not sure where to go from here, but will keep researching and see if I can find more info about the accelerator rod adjustment and what I messed up...

 

[lewtot184]

the position of the accelerator pump push rod has no effect on idle. when the rod is put in the top hole it raises the pump plunger. make sure there isn't any interference with the air cleaner.

 

[Addabob]

the position of the accelerator pump push rod has no effect on idle. when the rod is put in the top hole it raises the pump plunger. make sure there isn't any interference with the air cleaner.

I didn't think it did either, but figured I had missed something given what happened. The air cleaner is an Edelbrock too, so I would be surprised if it were interfering, but I guess I have seen crazier things than that...

 

[lewtot184]

I didn't think it did either, but figured I had missed something given what happened. The air cleaner is an Edelbrock too, so I would be surprised if it were interfering, but I guess I have seen crazier things than that...

you need to try and tighten the air door/valve for the secondaries. the front half of that carb is fairly small and shouldn't be creating a bog. also most of those 361/383 2bb cars had 2.94 or 2.76 rear gears.

 

[66Satellite47]

Sounds like more of an accelerator pump or air door opening too soon or too quick issue rather than distributor assuming you're getting the 35-36* with about 10-12* initial. If you still have the original 12" converter & some tall gears that can magnify the pump shot/air door issue. Bogs are usually temporary lean conditions. Good luck

 

[Xp29h]

I'll add my 2 cents here from another "genius" who really doesn't know squat! However, I've been battling many of the same issues that looks like have been giving you fits too. 2 plus years!

Let me say the bogging off the line I was able to fix, somewhat. My initial timing is at 21 and all in at 38. I'm running msd pro billet dist. And 6al2 box. Originally running a Holley 650 on top a performer dual plane. That intake is a stock replacement. Does help but really didn't do much for me. I changed to single plane Torker ll and Holley 850 with some jetting and cam changes on carb. Now I get off line without stalling but not great. Great top end. I haven't had enough space yet to see full top end yet. Pulls like a son of a gun. But still won't spin the tires.

I have gone completely through the top end of the motor, nothing has made a better difference. I improved a little but not what I wanted or felt where it should be. So....fast forward a couple years of messing with this I'm about three weeks away from a stroked 400 block to a 512.

I hope you have better luck than I did figuring out your 383. I plan on tearing it apart when it comes out and see exactly what's wrong. Previous owner did the build.

 

[Auggie56]

104K ? Timing chain more than likely is shot. Which will cause low performance issues.

 

[dieseldazzle]

Pulled apart a known 46k mile dual roller motor home 440 just last week and timing chain was shot.

 

[Auggie56]

Take your distributor cap off, and out of the way. Leave the rotor on. Put a socket, and a bar on the crankshaft bolt, then turn the engine just a little, then back the other way. What your looking for, is the rotor not turning on the second rotation, much after you start turning the crank. Another way is with a timing light. Set your timing light up, start the engine, then observe the notch on the damper. If it bounces on sat a one grand rev, your timing chain maybe shot. Keep us posted after you try this.

 

[Addabob]

Well, went out to refire the motor and check things out. Pretty hard to start, but finally did. Fast idle was rough. Checked manifold vac and only had about 10-11" (down from 18-19" previously), and then it died about 15 seconds later. The only changes I had made from when it was running decent but bogging was 1/4 turn leaner on both idle mix screws, then back 1/4 turn when it didn't help. Then moved the accelerator pump rod from middle hole to top hole, then back when it didn't help and motor stalled after test drive...

I don't understand all of the places in the carb that can impact vacuum yet, so not sure what the problem could be. Time for more reading...

- - - Updated - - -

Take your distributor cap off, and out of the way. Leave the rotor on. Put a socket, and a bar on the crankshaft bolt, then turn the engine just a little, then back the other way. What your looking for, is the rotor not turning on the second rotation, much after you start turning the crank. Another way is with a timing light. Set your timing light up, start the engine, then observe the notch on the damper. If it bounces on sat a one grand rev, your timing chain maybe shot. Keep us posted after you try this.

Well, method 1 won't be possible as the crankshaft bolt is bigger than my largest socket. I need to get a large set once I figure out how big it is. As for the timing light method, yes, I know I have had some bounce when checking it previously. Didnt realize that it shouldn't do that. I will have to grab the big sockets and do the slop test this week. I guess it may be time to look at what it takes to replace a timing chain... Does this require motor removal? If so, I would be tempted to get someone to rebuild the whole thing given the mileage.