Thanks for the reply Reed.

I have a spare carb that also pulled full vacuum and I played with it this morning. When I blew into the timing advance port, air came out a slot above the throttle plate (where it should be I think), so the plate may be slightly open or leaking some way. And I am sure it is the right port. I've perused the 1945 manuals and I feel good about that.

I'll try your recommendation, but maybe I should find out if the throttle plate is closing fully first?

The throttle plate me be incorrectly too far open due to the idle speed screw being turned too far in to mask a vacuum leak and/or timing problem. That is why I recommended you disconnect the brake booster and distributor and then reset the timing and idle sped and idle mixture to factory settings. You will likely be able to close the throttle more/turn out the curb idle screw/lower the idle RPMs, making the hole for the distributor advance port move from below the throttle plate to above the throttle plate.

If the throttle plate were truly fully shut then the engine would die because the carb would not be letting enough air get into the intake. The throttle plate will always be a little bit open at idle.

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Casually looking for a Clifford hyperpak intake for cheap.

Worked on the truck today. What I found...

No matter what I do, I pull around 15-16 in of vacuum even at 500 rpm at the ported vacuum advance. The throttle plate is completely closed at that time, and a small portion of the ported vacuum slot still shows below the plate. Guessing around 10% of the entire slot.

I plugged the brake booster, EGR and ported advance ports and set the timing to +12 at 600 rpm. I turned the mixture screw to get max rpm and and then adjusted the Idle RPM screw to get 600 rpm. I tried to minimize what the Idle RPM screw would do, going back and forth on the adjustments. Maybe this is wrong?

When I reconnect the vacuum advance the RPMs go up about 100 rpm and the timing goes to about +24 in.

The BALLbuster: when I spray brake cleaner into the throttle plate bushings, either side, the motor stumbles and misses. The carb has been rebushed by someone in the past and there is a slight amount of play when I wiggle the throttle plate. Less than a mm, but you can feel the slop. I got this carb off ebay it is labeled Vapex. Did I get a carb that SlantSixDan warns about in his carb posts? Whatever happened to him may I ask?
TIA

When you say the plates are fully shut, how are you judging this? Are the edges of the throttle plate contacting the sides of the carb throat? Are you sure the throttle isn't still being held open by the throttle cable adjusting bolt? Again, if the throttle was truly completely closed then the motor could die.

On the other hand, it could just be you have a lean-burn carb and will never get it to not have vacuum at the distributor vacuum advance sport.

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Casually looking for a Clifford hyperpak intake for cheap.

So a leak at the throttle plate bushing won't matter much? I'll double check, but yes the plate looks like it is touching the carb throat wall.

One way to see how well throttle plate closes is to remove carburetor, and shine a flashlight up from bottom. This will illuminate all the gaps, and spots where plate can be hanging up on any worn spots. Plates should never be fully closed on bore so to allow enough idle air to pass, and also to prevent damage to bore at point of contact in the form of a worn notch which causes excess air flow problems at idle, and mechanically hanging up preventing proper closing to return to correct idle rpm.

Not a good idea using chlorinated brake cleaner where it can be combusted such as testing for vacuum leaks, or cleaning metal before welding. When it burns it produces a deadly nerve gas that will permanently incapacitate with just a small whiff or two. We are talking brain damage, nerve damage, and death if enough of the combustion products are inhaled; this gas in not much different than was used during WWI. Use water, or carburetor cleaner when looking for vacuum leaks.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Wow, never knew how dangerous the fumes are. And I believe it was the chlorinated type. As I watched the liquid boil on intake manifold, I wondered if I was being stupid again.

So doesn't a lean burn carb require a computer? Maybe I got the wrong carb, because there is no computer in this truck.

Went and looked, it was dechlorinated.

UPDATE

Drove my truck 12 times to work and back. 22 miles round trip. Running fairly well...no stumble off idle, ok power I guess. Got 13.5 mpg around town. Cold starts aren't much of a problem after carb adjustments.

Gripes...

The main one is when I hold the brake at a stoplight, the idle gets rough and there is some minor stumbling. I replaced the brake booster check valve. Seemed to help for awhile, but the problem is back or never went away completely. I am going to check the remainder of the plumbing in that area this weekend. When I remove the check valve from the booster, there is vacuum stored in the booster. I can hear it equalize.

The questions are..

A leaking diaphragm in the brake booster could cause this right? Could a vacuum leak at the carb throttle shaft have similar symptoms?

Any help is appreciated.

1. yes....I have had this happen many times on our 69 Chrysler.
2. no, it takes a bigger vacuum leak than that to create it to stumble. Check for a leak on the distributor advance diaphragm or on the hot air door in the snorkel or any other vacuum pull off.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

How big/heavy is your truck. My 3200lb Dart stops great with manual disk brakes. Even my wife has no problem stopping it. She remembers well the high effort required to stop the stock drum brake set up.

I would get rid of the power brakes and find a carb that has no vacuum on the ported vacuum at idle. I have a later model aluminum master cylinder on mine which has worked great for years. I think I took it off a Volare in a junk yard 20 years ago. I made my own adapter by cutting the 4 stud mounting base off the old master cylinder, filing it smooth and drilling it and tapping it for the two studs required on the later master cylinders. The old base bolts to the firewall, and the new MC bolts to the old base.

It is impossible to get it to idle reliably when there is vacuum on the distributor at idle. You must figure that out. As long as the distributor sees vacuum at idle, anything that effects idle speed, such as being pulled into gear, effects vacuum and thus timing. Or, such as applying brakes, will effect the timing, which will effect the idle speed which will effect the vacuum which will effect the timing which will effect the idle speed which will effect the vacuum which will effect timing which will effect the idle speed, which will effect ...................................................etc. It can go into a death spiral and just die when pulled into gear in this way.
Disconnecting vacuum advance seriously effects your economy. These two things will make your truck happy once again.
Sam



Sam

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The truck must be at least 5000 lbs...guessing. I'll be working on it today so I'll look around for the weight.

Thanks for the knowledge. I really want to keep the power brakes.

I am thinking of getting a Holley 1920 Economaster. I bought the truck cheap and I plan on keeping it til death (mine ). I started a parts fund for it from parting out my totalled Jeep so I don't mind throwing a bit of cash at it.

Power brakes are OK if they work right. Is this a pick up or a van? If you can pick up an economaster carb, then do it. I had great experience with one on my former slant powered Duster.

Sam

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Its a pickup.

Does the Economaster support EGR and the air flap in the intake snorkel?

Yes, it does. It is a unique carb and not like all the other standard Holley 1920's.

Take a look at the pictures of mine by clicking on the red link below. You will see that I run all the ports you mentioned. Snorkel air door, EGR port goes to alcohol/water injection, vacuum gauge, ported vacuum for the distributor.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

thanks, one more question about 1920

what about choke, throttle and kickdown...same as 1945?

this is what I want right
http://www.ebay.com/itm/1973-DODGE-PLYM ... 7b&vxp=mtr