Gain extra benefits by becoming a Supporting Member Click here find out how!
Classic Performance Products Classic Parts
American Auto Wire Classic Industries
Chevs of the 40sDanchuk Catalog
Hellwig Products IncPerformance Rod & CustomEcklers AutoMotive
Nu-Relics Power WindowsRain Gear Wiper Systems
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy



Username Post: Adjustable Dist. vacuum canister        (Topic#354731)
4dr 57 
Valued Contributor
Posts: 4572
4dr 57
Loc: Texas Hill Country
Reg: 11-10-04
01-05-19 12:26 PM - Post#2756643    

hello - recently had a Mechanic tell me my 1980 Chevy Silvarado 350 cu. in. A/T, O-Jet carburator was bad. After disassembly it was easy (measurable) to see that it was warped 7 ways from Sunday from over tightening over the last few (10-15) years, by your truly,of course.

He got the 85-87 Q-jet for a replacement and after a bit it starts and runs perfectly except there is a hesitation off idle.

After reading about off idle problems I decided I should try adjusting the adjustable vacuum canister on the distributor in hopes of fixing the hesitation before doing anything else. But I forgot which way does what!

The plugs are new and the wires are good. He had to replace the ExCel cap and rotor and did so with a stock unit. I believe the timing is initially set at 8* although a friend who put the distributor on his machine years ago said it should be 12*. But then it wouldn't start so I turned it back to 8*. Again this was years ago.

It's warming here for a few days so I thought I would check it out. Any help would be appreciated. Thanks!
Stan

It's all good. mostly




 
Shepherd 
Frequent Contributor
Posts: 1684

Loc: Lake George, NY
Reg: 11-11-15
01-05-19 01:44 PM - Post#2756654    
    In response to 4dr 57

Check this link. http://www.superchevy.com/how-to/engines-drivet rai...



 
IgnitionMan 
Valued Contributor
Posts: 3554

Reg: 04-15-05
01-05-19 05:53 PM - Post#2756663    
    In response to 4dr 57

Just which adjustable can do you have, and, is there a degrees stop plate in use on it as well?

The wrong way to do it is to try to set the degrees using the vacuum rate adjustment through the hose nipple in the advance. The right way to do it is to separate the degrees stop from the vacuum rate adjustment with an inexpensive degrees stop plate for the degrees.

If the degrees are stopped down by adjusting the vacuum rate screw, it never will work correctly.

As far as the hesitation, and the different carbs, if there wasn't a hesitation before the carb change, it is carb/carb gasket to manifold related.

Edit: I just got done reading the attachment listed, mostly inaccurate, and, once again, forces vacuum rate changes when setting the number of degrees used. So very simple to fix, but nobody seems to get it.



 
4dr 57 
Valued Contributor
Posts: 4572
4dr 57
Loc: Texas Hill Country
Reg: 11-10-04
01-06-19 08:03 AM - Post#2756695    
    In response to Shepherd

Thanks Shepherd

From the Super Chevy article:

"Here is a vacuum canister installed on an HEI distributor. The rod from the can is connected to the trigger pickup. As the rod moves, it swings the pickup in the opposite direction and advances the timing. The distance the rod moves in the slot (arrow) determines the amount of timing added."

It seems to me to be saying that turning the hex screw clockwise would 'add' timing b/c the picture shows the rod moved away from the left going towards the right (adding timing) as seen from the right side/passenger side of the engine bay.
Does that sound about right to you? Thanks Again.
Stan



 
4dr 57 
Valued Contributor
Posts: 4572
4dr 57
Loc: Texas Hill Country
Reg: 11-10-04
01-06-19 08:56 AM - Post#2756698    
    In response to IgnitionMan

  • IgnitionMan Said:
Just which adjustable can do you have, and, is there a degrees stop plate in use on it as well?

Reply-
I have no idea if the canister even works, yet.
I don't think it has one of these:
https://www.ebay.com/p/Crane-Timing-Limite r-Plate-...


The wrong way to do it is to try to set the degrees using the vacuum rate adjustment through the hose nipple in the advance. The right way to do it is to separate the degrees stop from the vacuum rate adjustment with an inexpensive degrees stop plate for the degrees.

Reply -
I thought that is what initial timing does. It starts the initial timing by locking the distributor plate.


If the degrees are stopped down by adjusting the vacuum rate screw, it never will work correctly.

Reply-How can this happen if there is an initial timing set in place. But this is true nevertheless.


As far as the hesitation, and the different carbs, if there wasn't a hesitation before the carb change, it is carb/carb gasket to manifold related.

Reply- The newer model carb is just that, and jetted for a 305-350 cu. in. engine instead of a 350 to 454 engine.
Yes it's possible about a vacuum leak even with the new thick gasket I suppose. It would hurt to check - thanks.
The hesitation seems to be at idle when I first take off, not at no-load idle, except when really cold.


Edit: I just got done reading the attachment listed, mostly inaccurate, and, once again, forces vacuum rate changes when setting the number of degrees used. So very simple to fix, but nobody seems to get it.



Reply- If the idle vacuum is to be set in addition to initial timing through engine vacuum, wouldn't 'no vacuum' (engine off) kill any of the canister advance.


I fine it difficultly following your train of thought with the words used, such as, 'stopped down with the vacuum plate.'
However, at the same time the use of a vacuum plate stop makes perfect sense. I would think this would be particularly applicable to a higher rate of initial advance than that of a wheezy ole stock engine like mine...still, it is a positive stop.
Thanks.
Stan




 
IgnitionMan 
Valued Contributor
Posts: 3554

Reg: 04-15-05
01-06-19 08:27 PM - Post#2756745    
    In response to 4dr 57

Well, you probably wouldn't be interested in a complete packet of instructions, tech and pictures on just how to actually fix the problem.

And, I couldn't send them to you for about another week and a half, as I am still in a rehab facility 90 miles from my big computer that has the info on it, learning to walk again. I should be released from here by then, that is what I am told. It has not been fun.

If you are interested in learning how to separate the vacuum adjustment from the degrees, send me an email, and I will add you to the list. I only have my phone with me now, and don't have the info packet on it.

The info is written in plain language, so those that aren't full on techies can easily use and understand it.

gmvacuumadvancemodificati ons@gmail.com



 
4dr 57 
Valued Contributor
Posts: 4572
4dr 57
Loc: Texas Hill Country
Reg: 11-10-04
01-07-19 09:13 PM - Post#2756830    
    In response to IgnitionMan

REhab! Good grief! What happened? This is the 1st I've heard about it.

In the mean while...I drove the truck a few times today...cycled the temps as I stopped and started, and it sat and then driven. Anyway, at the end of the day, the idle lowered and the hesitation went away at off idle.

Then at home, I looked at the carburator for leakage but didn't spray anything to test...really don't know what to use anyway, carb cleaner, WD40? Nothing visible sign of leakage.

I sprayed some silicone spray on the choke bell cranks/linkage. haha my mechanic put some pookey on the Phillips head choke idle speed screw so I couldn't change it anyway, so I'm glad it settled down on its own. Still need to check the initial timing.
Thanks.
Stan



Edited by 4dr 57 on 01-07-19 09:23 PM. Reason for edit: No reason given.

 
IgnitionMan 
Valued Contributor
Posts: 3554

Reg: 04-15-05
01-08-19 12:38 AM - Post#2756847    
    In response to 4dr 57

Yup, rehab to get back to walking again. Somehow, I dehydrated myself, not just light, but, almost died from it, and, I thought I was constipated, and stopped eating, so, severe malnutrition at the same time. I wasn't plugged up, I was the other direction, empty.

We don't have a great hospital here.

They ended up severely over rehydrated me. Not a little bit, but seriously the other direction. And, during all of this, my organs began to shut down, including my pancreas. It makes insulin for the body.

Combination of no food, let alone correct level sugar, and overcload of insulin, looked like I was a serious diabetic. After getting back a bit, they still felt I was diabetic, and kept giving me insulin, even after the pancreas came back to work, and no sugar foods, recipe for coma. I stopped taking the insulin, started to eat a normal diet, and am not a diabetic.

As I was severely dehydrated, then over hydrated, everything below my waist reacted with swelling, legs, feet, everything, not just swelling, serious swelling. I couldn't walk as it took a month to subside, and am now just starting to not get dizzy and try to pass out When I stand up.

I,am getting better, but it hasn't been easy, and I can't get to my big computer to get that done, I am in a facility 90 miles from home and shop, with just my SMART phone. Can't help much without the big computer, nor do shop functions, either.

It hasn't been fun.

If you want the packet to get the adjustable vacuum advance working the way it should, send an email and I will add you to the list when I get back to work.



 
gchemist 
Senior Chevytalk Moderator
Posts: 24618
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
01-08-19 05:25 AM - Post#2756853    
    In response to IgnitionMan

Wow, take care of yourself IgnitionMan. I have your info. I still need to email you about upgrading the distributor on my ZZ4. Right now the truck needs some carb work. Inspection is due by end of this month so I can keep the vanity plates.

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
IgnitionMan 
Valued Contributor
Posts: 3554

Reg: 04-15-05
01-08-19 06:31 AM - Post#2756857    
    In response to gchemist

If anyone has one of the packets with both info 're t and pictures, would you please send it along to those that would like it, that would help them, and me.

Thanks.



 
someotherguy 
Senior Moderator
Posts: 28894
someotherguy
Age: 48
Loc: Texas
Reg: 08-01-03
01-08-19 08:31 AM - Post#2756868    
    In response to IgnitionMan

Holy crap Dave.. hope you get better soon. That's a terrible ordeal at the hospital there.

Richard

06 Silverado ISS / 06 Silverado SS / 06 300C SRT8


 
IgnitionMan 
Valued Contributor
Posts: 3554

Reg: 04-15-05
01-08-19 11:23 AM - Post#2756881    
    In response to someotherguy

That was in Carson City. I then ended up here in Reno. If this had happened where I live, in rural Yerington, well, I don't think I would still be around. Health care has some very serious faults today, and previous efforts to "fix it" really haven't seemed to fix much.



 
4dr 57 
Valued Contributor
Posts: 4572
4dr 57
Loc: Texas Hill Country
Reg: 11-10-04
01-10-19 07:42 AM - Post#2757019    
    In response to IgnitionMan

Hope things are beginning to turn around for you Dave! And I agree that you should take care of yourself too. And that the medical facility your at will help you do so.

the car...err, Truck...
As it is, timing does not seem to be the cause of the hesitation of the carburator.

As for the carburator- as I said above, after cycling it for an afternoon, the idle eventually came down and all was warm and fuzzy. This leads me to question the hot air tube which my mechanic did say was deficient. He wrapped the hot air tube connection with insulation to help retain heat.Possibly around the original, cracked hose- don't know.

I found some 'high temp' silicone tubing that will withstand up to 390 degrees from McMaster-Carr.
Is this tough enough for the job? Thanks.
Stanley



 
IgnitionMan 
Valued Contributor
Posts: 3554

Reg: 04-15-05
01-10-19 03:20 PM - Post#2757057    
    In response to 4dr 57

As I remember it, the hot air tube was run through the pass side exhaust manifold, and stayed a metal tube all the way to the choke stove.

Below the manifold, a rubber hose came from the tube, up to a hose nipple just below the air filter mounting boss, on the carb.

Air path was air filter, down and through the tube, into the choke.

I'd go with the high temp hose, but it has to stay flexible, like regular rubber hose.



 
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

360 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.06 seconds.   Total Queries: 16   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 02:51 AM
Top