Mcjoshin

Hey All,

Since putting in the new motor with an aggressive cam, I have very little vacuum and it's obviously affecting both the brakes and the headlights. I just ordered an electric Vacuum pump and was wondering if anyone has put one of these in to your C3 yet? If so, where did you locate it and any tips for installing it?

I may be able to fit it in the engine bay, but was thinking one of the rear storage containers near the battery may be better to conserve space, but I've also heard they're loud so maybe that's not the best idea. Thoughts?

Overall how tough was it? I'm guessing it's a pretty easy install, but not sure as I've never tackled one. Thanks!

Metalhead140

Which pump are you considering? I suspect I'll need one of these for my car too. I was considering the Hella, which is supposedly smaller and quieter, and OEM (so lives longer), but doesn't pull as much vacuum as the aftermarket options.

Mcjoshin

I just went with a simple Summit Racing one. A little cheaper than the others out there and had a lot of good reviews, so hope it works. I would've paid a little more for something compact, but most of them I researched didn't really have dimensions so I just took a chance on the summit one. I looked at the smaller Hella and a lot of people said it died very quickly on them, but I know they offer a more expensive version.

Metalhead140

Ah ok, will have to do some more research, I hadn't read that about the Hella. Got a link to the Summit one? I'll be following along to see how you go.

MIKE80

Here's a thread from when I installed mine.

http://https://www.corvetteforum.com/forums/c3-tech-performance/2653885-ss-brakes-vacuum-pump-install.html

flyeri

A friend has one mounted down low in the area where the vac tank was. He does not have power brakes so activates the pump with a toggle switch thru a relay when he wants to turn the headlights on and off.

fishslayer143

I put one in mine back in 09... My Stroker with my big roller cam has about 5 inches of vacuum at idle, so no brakes at all . ..I had already eliminated the Vapor Canister so that was the ideal location for it, right under the booster .. Got it from SSBC .. It holds a constant 18 inches hg .. Takes about 10-15 seconds to pull down on start up. Its a little noisey with engine off, about like an elect. fuel pump, but I don t hear it after I start engine.. It will cycle as you use brakes to maintain 18 Inches.. Brakes are fantastic.. I connected it to the Reserve tank to power Headlamps too. The only thing running off engine vacuum is my A/C/Htr control

gkull

Off the post, but could you tell me about this motors specs? I have two motors for my Vette with solid rollers. Big cams with big heads and my 434 has a bouncy 11 ish @ 1100 rpm hot idle. maybe you need to just turn up the idle and ignition advance and dial in the A/f ratio or have a pro shop setup the air bleeds with drilled holes in the pri throttle blades.

fishslayer143

No, that won t work..You have 11 in hg, you cam is much less radical. my cam is a Howards Racing Full Roller .578 lift and 256* Duration @ 0.050 ... you don t get vacuum ..Timing is 16* initial and 36 total ,in at 2500rpm.. Its not a timing issue, its overlap. and I don t want to put my car into gear everytime at 1100rpm, it idles at 750-800rpm..There is just no vacuum for brakes from this cam... Its QuickFuel fed , DYNO dialed in..and I don t drill holes in primary blades, QFs have replaceable bleeds to tune with. mine runs like a scalded dog... 525 HP @ 6300 RPM with a built 700R4 and 3.73 gears..

toobroketoretire

Rather than buying an expensive vacuum pump all you need to do is drill and tap the front of the brake booster and install a 1/8" NPT X 90 degree brass elbow and 1/8" NPT X 3/8" brass nipple. Then run a 3/8" hose over to the vacuum tank. With it's huge storage capacity the vacuum tank will keep the brake booster fed with 17-18" Hg of vacuum all the time. After installing my Magnum cam I too ended up with 5" Hg in DRIVE and by connecting my booster to my vacuum tank I solved the problem at no expense as I already had the brass nipple and elbow.

Mcjoshin

Hmmmm... Interesting. I'm gonna have to take a look at this tomorrow. Sounds like a quick and easy fix. Thanks for the info, thats awesome to know! I might PM you about it.

Lobzila

I went with the SSBC pump. Mounted it on a bracket I made behind the center grille. The pump did not generate enough vacum to run the headlights up. I just switched over to the electric headlight set up and solved that issue. My vacum pump is just for my PB booster. Also ran a check valve and T-ed off that line to the engine vacum so at enough RPM when the motor does pull more than 18", it overrides and shuts off the pump. The pump itself was a lot more noiser than I expeceted. I could hear it over my side pipes. This coming from the deaf guy. Good luck and let me know if you want pictures.

gkull

Way back in the day's gone past I had a SR cam and the stockish type brakes worked fine. the lights kind of would open one at a time if you were going fast and then let off the gas.

The answer was how do get more line vacuum because the big front tube is a reserve. The whole problem was all the little tubes under the dash all those controls are vacuum. I closed off one of lines to the dash and I had everything working again

Mcjoshin

This is the one I ordered Metalhead. http://www.summitracing.com/parts/sum-760152

Mcjoshin

Gkull - My cam is running around 500/600 rpm right now at idle. I guess it's possible I need to raise my idle speed a bit. Admittedly, I'm not 100% sure what the idle speed should be at, I have it set basically as low as I can go without the car dying when put into gear. I wonder if raising the idle speed would help? I would hate to lose that lumpy cam sound though I'm getting it dyno tuned next week since I'm at mile high elevation and it's impossible to get it optimal up here without a dyno.

tshort

I too have a vacuum pump and have it mounted next to the gills under the reserve tank. It is loud and a little annoying hearing it run just before you start the car but my car is so loud that once it's started I can't hear it. Eventually I'll go with the hydraboost and get rid of the electric pump. I've got my pump wired running off of a relay.

gkull

You did not say what your ci was or what type of roller cam, but I would guess h-roller because of the low lift. I also had a 800 hp rated 700r4 in my vette for 20 some years with motors idling at 1100 rpm. I just used Vigilanty 9.5 inch multi clutch TC's with 3500 or 3800 stall. I went in and out of gear without a jump or a bang. Air bleeds don't change the idle air fuel ratio. You have to drill throttle blades or restrict the idle cuircut feed. I really can't believe that your motor runs that well if it is less than 427 ci

Mcjoshin

*Just noticed you were talking to fishlayer not me, but still wondering your thoughts on my setup*

It's a 350 block bored out to 355 ci. I believe it's a Comp Cams extreme energy H-roller cam, but I do not know the specific specs on it unfortunately. It was built 15 years ago and unfortunately I just don't remember what was used when we built it :/ It's a pretty hefty cam and on paper the build should be putting out around 500 hp, but haven't had it actually dyno'd yet... that's coming next week. Running a Bowtie Overdrives Level 2 700R4 rated for a steady diet of 500hp (I believe it's a 2600 stall). It's not totally dialed in yet but hoping to get it all tuned right next week on the dyno. Based on that, what do you think the idle speed should be? And I'm guessing that nice lumpy cam sound is lost at that high of an idle speed?

gkull

I know that people love to have bad a$$ sounding rumpety rump motors. But i would rather have go than show. When i ordered my custom lobe cams i would have them ground 4 degrees retarded when compared to say a Comp Cams extreme. My motor sound somewhat mild, but can hit the 7500 rpm rev limiters.

Of course vacuum goes up with rpm. My advice is when you go to the show and shine turn the idle down. I've worked on american V-8 can am cars that idled at 2000 rpm. With the idle up and motor running smooth I always have instant throttle response My house is at nearly 5000 feet.

fishslayer143

You are mistaken.. THATS exactly what Air Bleeds do.. Air Bleeds provide the air in the AIR/fuel idle mix. Quickfuel Bleeds screw in and come in varies sizes to allow for tuning without drilling holes in your carb.. That's old school... QF also has 4 corner adjustable idle circuits that provide a better Idle mix across the plenum, ...and I do not want a 3800 rpm Stall to allow 1100 rpm idle to engage trans. .. I prefer a drivable car w/ A/C to a loose sloppy converter and overheating in traffic. .. And yes it does run well. What HP is yours producing? 525 HP/ 498 FT Lbs Torque from mine.