cam + vacuum question
Thread Starter
Pro
Joined: Jun 2002
Posts: 662
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From: chatam nj
cam + vacuum question
81 c3, In running the gm hotcam, vacuum output is lower then what is needEd to run the headlights. besides going electric converaion, what is another fix to make the headlights work (up/down etc).
Racer
Joined: Apr 2016
Posts: 494
Likes: 93
From: Bucks County PA
vacuum canister/reservoir can be mounted anywhere and they are cheap
what are your vacuum readings?
what are your vacuum readings?
Always personal preference, but I've used the comps cams vac canisters in the past with good results. Not exactly rocket science, they are simple and effective in most cases.
http://www.jegs.com/i/Comp+Cams/249/...Fclkhgod8BUGzQ
I've been away from Chevy for a little while, I didn't realize they made the hot cam for the Gen 1 engines. I know of a few who used them in the newer LS1's etc. What are they, about .525 lift or so?? Pretty decent from what I remember, nice "lopey idle . .220/.228 or so? Very cool in a C3..
Last edited by 76C3forme; May 26, 2016 at 03:23 PM.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Close enough the one they designed for the LT4 runs surprsinly strong with some headwork/headers, good manners and doesnt tear stuff up
Trust GM quality to most aftermarket stuff as far as longevity
LS7 roller lifters....what a deal, 100 a set.
Trust GM quality to most aftermarket stuff as far as longevity
LS7 roller lifters....what a deal, 100 a set.
Race Director
Joined: May 2006
Posts: 18,758
Likes: 2,589
Are you saying you dont have enough vacuum at idle?
What is your initial timing set for?
Are you using manifold vacuum to the distributor?
What exactly is the "gm hotcam", do you have a part number?
you are sure you dont have leaking vacuum lines in the headlight system?
What is your initial timing set for?
Are you using manifold vacuum to the distributor?
What exactly is the "gm hotcam", do you have a part number?
you are sure you dont have leaking vacuum lines in the headlight system?
Last edited by MelWff; May 26, 2016 at 03:48 PM.
Racer
Joined: Apr 2016
Posts: 494
Likes: 93
From: Bucks County PA
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Racer
Joined: Apr 2016
Posts: 494
Likes: 93
From: Bucks County PA
Good question. I wasn't aware the Hotcam was available for a gen 1 type of motor. I do see ( like cuisinartvette said) that the people running the LT4 are using them. I'd like to know myself. I'll have to do some searching.
Thread Starter
Pro
Joined: Jun 2002
Posts: 662
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From: chatam nj
yes. recent swap from stock 350 to lt4 and am using the gm hotcam (.525 lift) vacuum at idle is at 9.
the 80's have a vacuum tank. would the vacuum reservoir help make the headlights work?
the 80's have a vacuum tank. would the vacuum reservoir help make the headlights work?
Last edited by silvvette; May 26, 2016 at 04:32 PM.
Thread Starter
Pro
Joined: Jun 2002
Posts: 662
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From: chatam nj
is this the reservoir?
http://www.partsgeek.com/mrmykx9-chevrolet-monte-carlo-vacuum-reservoir.html?utm_source=shoppingcom&ut m_medium=pf&utm_content=hcs&utm_campaign =PartsGeek+ShoppingCom&fp=pp&utm_term=Ch evrolet+Vacuum+Reservoir
http://www.partsgeek.com/mrmykx9-chevrolet-monte-carlo-vacuum-reservoir.html?utm_source=shoppingcom&ut m_medium=pf&utm_content=hcs&utm_campaign =PartsGeek+ShoppingCom&fp=pp&utm_term=Ch evrolet+Vacuum+Reservoir
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
That cam should provide much more vacuum. I was running a cam with a lot more duration and was getting 9 inches at idle. Also my headlights worked fine at 9 inches of vacuum.
Melting Slicks
Joined: Jun 2014
Posts: 2,257
Likes: 501
From: NJ
Above idle the engine vacuum will increase. The vacuum resv. will hold the highest vacuum it sees from the engine thru use of a check valve, so there should be no problem providing the necessary vacuum to power the lights unless you have leaks in the system, Get a vacuum pump tester and try to troubleshoot. 
Thread Starter
Pro
Joined: Jun 2002
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From: chatam nj