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Topic: Little vacuum with aggressive cam 427

in Forum: C3 Engines

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Little vacuum with aggressive cam 427 (1/6)
10/12/14 8:08pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

Since I replaced the engine and went with a aggressive comp cam for my 427, I don't have as much vacuum as I did before, and everything still will work but only slowly and not simultaneously and I have to get the RPMs up to make this happen.

So I have decided to go with a electric vacuum pump to increase the vacuum.

Not interested in going with the electric head lights yet.

Has anyone done this on a C3 and what type of pump was use and how was it installed (hooked up)

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Re: Little vacuum with aggressive cam 427 (2/6)
10/12/14 8:43pm

rod7515

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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1182

I was thinking I would need to do this with my 72 but I ended up with 14' of vacuum which does very well. Was wondering how much lift and duration are you running now to have that low of vacuum. Also what is your actual vacuum now? Are you sure you dont have a leak somewhere that is making things slower.
Rodney

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Re: Little vacuum with aggressive cam 427 (3/6)
10/12/14 9:44pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

I am at about a 10'" of vacuum and it won't pull enough to make things go smooth.

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Re: Little vacuum with aggressive cam 427 (4/6)
10/12/14 9:50pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

I have done test on all of my relays and actuators and they work fine with a vacuum gauge tester. I also removed my filter to help in getting more vacuum. Check valve is fine, and I replaced the light switch and all the vacuum items under the dash, override switches etc. Also I have all new vacuum lines.

Big cam, no vacuum. I knew that it would happen with this engine, but not to this extreme.

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Re: Little vacuum with aggressive cam 427 (5/6)
10/13/14 1:36pm

Adams' Apple

Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20128

Yea....10" ain't guna cut it.... LOL

Does your car still have the vacuum reservoir? If not, might be worth getting a large one to install somewhere and give that a shot before going to the 'lectric pump. If you go 'lectric, you'll just need to connect the same hoses that are on the intake manifold to the "VAC" fitting of the pump. Not sure aboot the brake booster(if you have power brakes), but the pump should be large enough to handle it also.
I'mma thinking someone here HAS installed an 'lectric vac pump....just can't remember who the heck it was.... Ermm

For some reason, Brian(redwingvette) comes to mind.....

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Joel Adams
C3VR Lifetime Member #56
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(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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Re: Little vacuum with aggressive cam 427 (6/6)
10/13/14 9:47pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

I have the large square type of reservoir and have checked the vacuum on it and it is fine. I just don't get enough vacuum from the engine.

That is why I need some sort of vacuum pump to work the magic of all the vacuum on a 68. I don't have a brake booster so that is helpful nor do I have air.

Just trying to find out what kind of vacuum booster or pump and how to hook it up from someone that has had the same problem.

I would think that there would be several corvette owners who have increased their HP and added a different cam.

Thanks for any help anyone can give me.

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