Vacuum Canister to Restore Vacuum
 

454 bored 30 over with a Comp Cams Big Mutha Thumpr. Called them and they said its gonna barley have any vacuum. I was told a vacuum canister can solve this because my power valve and vacuum secondaries are being used at idle because of the low vacuum, causing it to be very rich.

So my question is are there any ways to run a vacuum canister that can boost vacuum to help my carburetor run better? I see people run them for brakes. I have hydra boost so I have no need to route for brakes. Just need to route to create better vacuum to have a better running carburetor. Is this a viable idea?
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Re: Vacuum Canister to Restore Vacuum
 

So change your power valve and put a stiffer spring in the vac pot.
Vac canister won't help your carb run better.
Vac canister only stores vacuum. You need a vac pump to boost it. If you need it.
They cost anywhere from 25 to 250 bucks.
You can adapt one from a newer diesel truck.

Have you maxed your timing curve to get max vacuum.
How much vacuum do you have now?

Re: Vacuum Canister to Restore Vacuum
 

I don't have it tuned quite perfect right now but the gauge says around 5 ish. Right now it has a Holley 750 DP on it with the mixture screws turned 3/4 turn out. It's pretty lean but I drove it and it backfired the other day. I plan on putting a Edelbrock 750 single pumper on. Street use vehicle.
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Re: Vacuum Canister to Restore Vacuum
 

Keep the holley!
It's easier to adjust to run with your cam.
Easier to tune your timing with it in place too.
What's your initial timing?

Re: Vacuum Canister to Restore Vacuum
 

I agree. A canister won't add vacuum. But it will store vacuum and keep it more stable if it bounces around due to the cam.

I think the next step is to maximize your vacuum. Warm up the truck then hook up a vacuum gauge and tune the mixture screws to get max readings at idle. Do the same with base timing. You may need lots of timing. Possibly 16 degrees or more. As RPMs increase, use the idle stop screw to bring it back down, but with that cam, you may need to idle at 1000RPM regardless. Another possibility (and a bit of a hack) is to use the vacuum advance to boost your timing at idle which might boost your vacuum signal a little more. Either way, if you have to run a ton of initial timing, this also means that you need a distributor with a shallow mechanical advance curve to get you to the all-in timing of 34 degrees (+/- a few degrees) with that much initial timing.

Either way, the carb will need some parts changed (as mentioned earlier) for this as well. An Eddy carb would need metering rod and spring changes for sure, so just swapping the carb isn't going to solve it. A mechanical secondary carb may also help slightly. But may present other problems.

A cam like that takes lots of patience with tuning. Might sound good -- but such a low vacuum signal makes for lots of tuning issues.

Re: Vacuum Canister to Restore Vacuum
 

Why not run the Edelbrock? And I'm not quite sure. It hasn't run long enough to really check, last we checked I believe it was around 20.
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Re: Vacuum Canister to Restore Vacuum
 

That Holley can be tuned way better to that cam than a cruddy Edelbrock. That cam will need a ridiculous amount of initial timing.

The vac canister will aid with power brakes... kinda. I have a vac canister with my cam to help with the power brakes. It helps... a little.

Gary