i posted a thread a while back about idle trouble with my new 350 crate from year one. i have checked for vacuum leaks but im still having the same problem. has to idle high and will die if i leave the car in D when coming to a stop. it idles high in N to keep it from bogging down all the way when it goes into drive.

I think one of my problems is with my vacuum advance. on my old engine i had a AR 12 on the distributor which i know needs about 16 hg of vacuum. my new engine says it will pull 12 hg of vacuum at 800 rpm. but my vacuum is a little jumpy and stays around 7-9 (maybe still a leak, but i can find it). The vacuum advance might not be the main problem, but i dont think its helping.

should i switch to a vacuum advance like the AC/Delco # D1370a(10* at 10" of vacuum) or the vc1862 (8* at 6-8" of vacuum). Get my total timing to 32* at 3000 rpm. i can only find 91 octane here so i think i need to retard the timing a little.

If i switch should i run the vacuum of the manifold or carb and which port on the carb?

I dont know a lot about vacuum and timing, had a shop do my initial timing but im having those problems and feels like theres no lo end torque. Im going to run by sears today and pick up a dial back timing light and learn this stuff myself so i know whats going on.

Thanks for the help,
Sean

 

First of all, is the vacuum advance connected to ported or manifold vacuum? If the idle speed drops when you disconnect the vacuum line from the advance and plug it, then it's connected to manifold. Which is where it should be. If it's connected to ported vacuum, find a manifold vacuum source and hook it there instead.

The rule of thumb is to use a vacuum advance canister that gives full advance at least 2 inches below your engine's idle vacuum. If you engine has 9 inches, you need a can that's fully advanced at 7 inches. And your vacuum at idle shouldn't be jumpy. It should be steady.

Hook up your new timing light, disconnect the vacuum line to the vacuum advance canister and plug it. Then set the timing to 32-34 degrees at full mechanical advance. According to your specs that would be 3,000 rpm or higher.

Hope this helps.

 

yes right now its not on the manifold...can i tee of the manifold port and share vacuum or do i need it to be pulling off its own port?

ive never timed before- tach doesn work so is there a way to tell what rpm im at with the timing light- not sure exactly how to do this. the timing light will come with instructions and ill figure some stuff out then, but i figured i would ask.


i found that vc1862(seems to be the right one) on another thread on here but i cant seem to find it in any store. is this what its called or is there some equivalent from another supplier?

Thanks,
Sean

 

while at sears getting a Timing Light, or at any local Auto Parts store, also pic up an inexpensive vacuum gauge. I think mine cost $29 or less. You can use the vacuum gauge to measure motor vacuum to determine the best vacuum advance cannister that will be best for your car.
If your tach doesn't work you have a few options - At Sears they sell an Actron Digital Timing Light for $99 that also included a built-in Tach function or they also have an Actron Dwell Tach Volt meter. Assuming your car has an HEI or similar type distributor you don't need the Dwell function but the Tach function would be well worth the $29.99 while you are setting timing and carb adjustments. It's a useful tool to keep in the garage since even if the car's tach worked you can't see it while working under the hood.

BTW, besides for checking motor vacuum, the vacuum gauge is very useful for setting the carb idle fuel mixture and also for diagnosing other issues with the motor in the future.

A Timing Light, a Vacuum Gauge, and a Tach Meter are all essential, and relatively inexpensive, tools to have if you are going to be doing basic "tune-up" type work on your car and all of them should last you a lifetime.

I have the basic Sears branded dial back timing light (but it's made by Actron) and they have it on their site for $49.99.
The Tach meter is $29.99.
The Actron vacuum gauge is also listed on the Sears site at $19.99
Total = $99.97

Additionally, if you can splurge, it would be a good idea to pick up 2 other inexpensive items Sears also carries:
1. Actron IR Temp gauge for $39.99
2. Actron Remote start switch for $12.99