Vacuum pump needed?

[Erik the Awful]

I wouldn't go so far as to say the cam's garbage, but it's on the extreme end. You're going to need big heads and a lot of rpm to make it worthwhile. Since you're running .520" lift, I'll assume you're running some kind of modified or aftermarket heads, and that your engine combination isn't terrible.

I'd still go with a hydroboost instead of a vacuum pump, but here's what Summit shows. https://www.summitracing.com/search/part-type/vacuum-pumps-street

Keep in mind that if you use an electric assist and you lose electrical power, your brakes may not stop as effectively.

 

[Schurkey]

I wouldn't go so far as to say the cam's garbage, but it's on the extreme end. You're going to need big heads and a lot of rpm to make it worthwhile. Since you're running .520" lift, I'll assume you're running some kind of modified or aftermarket heads, and that your engine combination isn't terrible.

My point is that he hasn't told us dick about the vehicle or the engine in general, but brags up a cam entirely unsuitable to a stock GMT400 engine as the reason for needing a vacuum pump.

Yeah, hydroboost all day long, and twice on weekends.

 

[reservoir dog]

If it's an auto trans your gonna need higher stall converter as well.

 

[RichLo]

Wow, lets not jump on the guy too hard yet. Like Erik said, he may have aftermarket heads because of that .520 lift.

Or maybe he got a good deal on a built engine from somebody. Lets hear the story first.

 

[Wintergreen98]

The motor is a 383 stroker engine has stock heads with aftermarket valve springs and valves I built the motor long ago and the cam I originally bought was recommended to me by a buddy but wasn't what he said it was so I recently swapped the cam since I was already doing a carb swap and had the intake off to get to the lifters. I don't have the kind of money I did when I originally built the motor.

 

[Schurkey]

stock heads

WHICH "stock heads"?

If they're Vortecs, you stand a chance.

If they're TBI swirl-ports, you have a totally mis-matched combo.

If they're older heads...they could be as bad as the swirl-ports, or considerably better than swirl-ports, but not as good as the Vortecs.

 

[Wintergreen98]

WHICH "stock heads"?

If they're Vortecs, you stand a chance.

If they're TBI swirl-ports, you have a totally mis-matched combo.

If they're older heads...they could be as bad as the swirl-ports, or considerably better than swirl-ports, but not as good as the Vortecs.

98 Vortec heads

 

[GoToGuy]

Solid lifters, wow back to high school hotrodding. No envy there. Since your unable to make decent vaccum. Your options are limited choice. No 1 is hydroboost/ factory parts like "legos". No 2 Add on belt driven vaccum pump as in diesel engines require. No.3 Electric driven Vaccum pump / With default to be battety powered in the event of normal power failure. Having alot " GO " - good. Having great and reliable "Braking"- better. Good luck.

 

[Frank Enstein]

https://www.summitracing.com/parts/sum-760152

Use option "B" in the instructions!

Summit Racing SUM-G1464 Summit Racing™ Vacuum Reservoirs | Summit Racing

Free Shipping - Summit Racing™ Vacuum Reservoirs with qualifying orders of $109. Shop Vacuum Reservoirs at Summit Racing.

www.summitracing.com

Set the initial timing as high as possible without fighting the starter on a hot restart.

Hook the vacuum advance to full manifold vacuum AFTER the initial timing is set.

The cam will need a 3000+ torque converter.

Buy the reservoir and tune it well. If it still has a hard brake pedal get the vacuum pump or a hydroboost kit.

 

[Erik the Awful]

I'm sorry, but I'd start by stepping back on the cam. I think it's gonna be a gas guzzling dog. I disagree with Vortec heads being adequate for that cam, especially with the increase in displacement. I'm running unported Vortecs with a Lunati 20080720 roller cam - .507/.515 lift, 211/219° @ .050, 112 LSA, and my engine's out of breath over 4000 rpm. If you're running Vortecs, pick a cam for torque and mid-range. In my mind, I'd be looking for something around a 230° duration and .450-.500 lift, but call and ask a cam pro first.

If you take the heads off and get them ported by a pro, you can probably keep that cam, but you'll be spending almost as much as new heads, and you'll still need a hydroboost or vacuum pump. If you can port them yourself, there's half your solution!