our 340 challenger is only making 7.5in vac at idle and the brakes are not great.I want to keep the power brakes and would prefer not to spend a pile of money on the pump since this motor is only staying in the car for a few months than a 5.7 hemi is going in.Any recommendations for reasonably inexpensive reasonably quiet vac pump options? Maybe a junkyard oem setup or?
I tried a cannister today but was a waste of money,need a pump it seems....

You might need to consider rebuild of the booster. i have power brakes as well. My motor was making 15 inches of vacuum out of the motor/booster combo.

How is rebuilding the booster going to make 7.5 inches of vacuum work?

One idea caddy vacuum pump

Not super cheap though.

hi

yep you need a min of 12 in for power brakes !

what cam in that motor ?

loosen the valve lash some may help a little ??

advancing cam may help some ?

roads lifters maby help some ?

advance inital timing maby easyiest .

thanks sniper for that link,maybe some junkyard scrounging coming up!

I went through this about 15 years ago. Searched high and low for a pump, finally found one that would work for a semi-reasonable price. Hooked it up, pump was bad. Returned it for a second pump, which I had to wait several weeks for. The pump worked but barely, I ripped it all off and swapped to manual 11.75" discs and never looked back.

D.

You need a minimum of 10 inches vac with a manual tranny vehicle, and at least 12 inches with an auto to have safe repeatable braking... I've used the SSBC vacuum pump with good success along with a vac resv canister, the pump is going to make some noise when it's running, just try and mount it on rubber pads/feet to limit the noise/vibration, I hid it in the front fender behind the headlight, and the vac resv canister under the battery tray to keep the engine compartment clean and factory looking


FYI: I had the SSBC pump on a 472 HEMI/auto with a big cam and a dual diaphragm Bendix booster, initially I could only get about 8" of vac, the SSBC/resv canister was good for a steady 14-15" of vac, and steady repeatable braking and good vacuum recovery

Mike

thanks for the tips guys...im rethinking the whole deal today...possibly easier just to switch the car to manual brakes for the summer or better solution is a smaller camshaft which i was hoping to avoid.Having alot of trouble tuning the carb with the low vacuum and of course the car wants to load up and or die when put into gear or idling in gear at a stoplight with auto trans,stock converter and 355s.....
Just trying to decide which is gonna be the least amount of hassle/best results!

BTW this was a mystery motor that came in on an old car deal so had no idea it had such a big cam in it ....

Cheapest quickest way is new cam. You can get one with a good power range and not have to change anything else. That would make tuning, running and stopping a lot better.

Any of those vacuum pumps either aftermarket or salvage should EASILY put 20-22 inches on the booster depending on what the Hobbs limit switch is calibrated to.

I read lots of these vacuum pump threads where somebody leaves the booster connected to the engine and T's in the pump and can't understand why the booster still won't perform.

If you're OK with the way the car performs other than the power brakes, shop around for a vacuum pump with a built in limit switch that cycles it between say 17 and 22 inches +/- , hook it directly to the booster after eliminating the hose to the engine, and you will have go and whoa.

No way you can change a cam for less money and aggravation than a vacuum pump even at SSBC inflated prices.

Kevin

How much initial timing do you run? Big cams usually like as much initial as the starter can take.

Kevin

Some pump options from Amazon.ca. I'm pretty sure the $269 Canadian kit is the same one or very similar to the SSBC pump. I don't know if the OEM replacement has the cutoff switch or not. Easily added.

https://www.amazon.ca/Electric-Boos...;qid=1562195966&s=gateway&sr=8-4

Kevin

Ive got her setup right now with 18 initial and 34 total,blue springs in the carb(edelbrock 1407) and have everything running pretty good except for the loading up at idle in gear which is barely manageable (stick it into neutral at stoplights).......with blue springs rods are down at idle in neutral but in gear they are fluttering. I built this car for my parents so dont want it to be too troublesome for them.Maybe the 5.7 hemi swap will be started asap now that the car itself is nearly finished.
For the 5.7 swap we have a 2014 truck engine ,46rh trans and spectra efi tank,still have to source everything else...

I know this us an older post but I used a pump from PST from Bandit and never looked back. Gave me the power brakes I needed