. everything is slow but works. thought about an electric pump to remedy this small problem.
C3 Minimum Vacuum
Thread Starter
5th Gear
Joined: Dec 2008
Posts: 5
Likes: 0
From: Warrensburg Missouri
C3 Minimum Vacuum
Hey guys (and gals) another new kid from Missouri. Can anyone tell me what the minimum amount of engine vacuum is that a guy can get away with and still be able to operate the headlight doors and brake booster on a C3. I'm getting ready to select a solid roller cam for my stroker project and I need to figure out just how much duration I can run. If anyone has any personal experience as to what works and what wont I'd appreciate any input I can get. 
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Thread Starter
5th Gear
Joined: Dec 2008
Posts: 5
Likes: 0
From: Warrensburg Missouri
Thanks for the input guys, I was aware of the electric pumps but I'm trying to save cash due to tight finances and I'm kind of old school so I'd rather try to keep it "all motor". If the rest of you can get by with eight to nine inches I should be able to run all the duration I want. I talked to a guy on the Comp Cams Tech Line who recommended 236/242 @ .050 on a custom grind with 112* centerline instead of the 110* out of the box to help boost vacuum but it doesn't sound like it's going to be an issue. Once again thanks for the help!
Pro
Joined: Jun 2004
Posts: 700
Likes: 0
From: Lantana TX
This is a good question R-Dub because now I know I have a problem as I only get 7.5 at idle in drive (Not park) and brakes stink and headlights now do not work after a brand new engine.
Duration @ 0.050": 242° / 248°
Last edited by 76 sting; Dec 20, 2008 at 08:21 AM.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Maybe I am confused as I am not as technical as some of you folks here. Shouldn't we mention if we have a small block vs a big block? The durration at 250 will be differnt when comparing a sm to a big block correct?
This is a good question R-Dub because now I know I have a problem as I only get 7.5 at idle in drive (Not park) and brakes stink and headlights now do not work after a brand new engine.
Duration @ 0.050": 242° / 248°
This is a good question R-Dub because now I know I have a problem as I only get 7.5 at idle in drive (Not park) and brakes stink and headlights now do not work after a brand new engine.
Duration @ 0.050": 242° / 248°
Last edited by TheSkunkWorks; Dec 20, 2008 at 11:23 AM.
Pro
Joined: Jun 2004
Posts: 700
Likes: 0
From: Lantana TX
Thanks...I do not want to run a pump (more weight and stuff to go wrong) and I need 10's at the track so am surley not going smaller on the cam, if anything I want to go a little bigger. present CR is 10.3
What concerned me was that folks here have larger cams then I do which is leaving me to believe that something else is wrong with the picture.
Sorry R-Dub did't mean to hijack
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
less vacuum slower the acc. are to operate, they will work with 5" eventually.
how long you want to wait ? .....I would guess 10" min 12" for satisfactory operation of wipers and lights. I choose a milder cam, because of preferring better vacuum.
good luck....69VETT
how long you want to wait ? .....I would guess 10" min 12" for satisfactory operation of wipers and lights. I choose a milder cam, because of preferring better vacuum.
good luck....69VETT
Safety Car
Joined: Oct 2004
Posts: 3,920
Likes: 731
From: Youngstown Ohio
Maybe I am confused as I am not as technical as some of you folks here. Shouldn't we mention if we have a small block vs a big block? The durration at 250 will be differnt when comparing a sm to a big block correct?
This is a good question R-Dub because now I know I have a problem as I only get 7.5 at idle in drive (Not park) and brakes stink and headlights now do not work after a brand new engine.
Duration @ 0.050": 242° / 248°
This is a good question R-Dub because now I know I have a problem as I only get 7.5 at idle in drive (Not park) and brakes stink and headlights now do not work after a brand new engine.
Duration @ 0.050": 242° / 248°
Pro
Joined: Jun 2004
Posts: 700
Likes: 0
From: Lantana TX
I see in your info you have a 383, correct?......my cam is bigger but it is in a 427 small block. The extra cubes tame the cam down, making it less radical though the duration is more. Also your choice of heads and intake comes into play, as better cfm flow makes a more efficient engine. My LSA is 108, but my idle is not as radical as some 244 dur. cams I've heard on 383 motors.
Thread Starter
5th Gear
Joined: Dec 2008
Posts: 5
Likes: 0
From: Warrensburg Missouri
76 Sting, I am not at all offended by the hijack. I jumped in here to try to learn something and I have gotten lots of hard numbers to work with.
I would like to ask TheSkunkWorks to expound a little on his reasoning for suggesting the steel core with iron gear. I assume it would eliminate the need for a bronze distributor drive gear. I'd like to know what the other pros or cons might be. It's been over twenty-five years since I've built a high output engine and things have changed a lot. Back then rollers were only for the big money racer guys.
I would like to ask TheSkunkWorks to expound a little on his reasoning for suggesting the steel core with iron gear. I assume it would eliminate the need for a bronze distributor drive gear. I'd like to know what the other pros or cons might be. It's been over twenty-five years since I've built a high output engine and things have changed a lot. Back then rollers were only for the big money racer guys.