Electric Vacuum Pump
Thread Starter
Intermediate
Joined: Oct 2011
Posts: 36
Likes: 1
From: Quitman MS
Electric Vacuum Pump
Guys...input needed: Taking out the L48 in my '79 and installing a 383. I would like to run a Be Cool or DeWitts dual electric fan, an electric vacuum pump and get rid of the charcoal canister system if possible. If I go w/an electric vac pump, is there a high/low vacuum number i need to run? From what I understand, the brake booster, headlights, environmental controls, kickdown for the TH350 all run off vacuum. What should I be concerned with going into this? Btw...new carb will be added as well. Thanks for the inputs...always very helpful.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Guys...input needed: Taking out the L48 in my '79 and installing a 383. I would like to run a Be Cool or DeWitts dual electric fan, an electric vacuum pump and get rid of the charcoal canister system if possible. If I go w/an electric vac pump, is there a high/low vacuum number i need to run? From what I understand, the brake booster, headlights, environmental controls, kickdown for the TH350 all run off vacuum. What should I be concerned with going into this? Btw...new carb will be added as well. Thanks for the inputs...always very helpful.
A 383" will produce just as much vacuum as your L-48 unless it has a killer camshaft in it.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Why are you getting rid of the charcoal canister system? It's a good system. Keeps your gas tank at an even pressure with the ambient environment and prevents gas vapor from entering the air (HC emissions). Zero impact on performance.
toobroke's comment on vacuum vs cam is correct. How crazy of a cam are you doing? I know people running cams in the low 230s on a 108LSA and no need for a vacuum booster.
Are you putting good heads on it? If not, stay away from crazy cams anyways.
toobroke's comment on vacuum vs cam is correct. How crazy of a cam are you doing? I know people running cams in the low 230s on a 108LSA and no need for a vacuum booster.
Are you putting good heads on it? If not, stay away from crazy cams anyways.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I would have to agree. You're not going to need a vacuum pump with any reasonable 383 build with a dual plane intake. Single plane and you can loose considerable vacuum.
My 350 has 219*@.050 with a 108 LSA and still makes 14" of vacuum at 800 RPM at 4000 feet.
Vacuum, or lack there of is directly related to the overlap.
To figure your overlap take your advertised duration on the intake and exhaust add them together.
divide that figure by 4
subtract the LSA (lobe separation angle) from that answer
Multiply it by two. Your answer is the number of degrees of overlap.
IE.
My cam: 270+270=540
540/4=135
135-108=27
27x2=54
54* of overlap.
Hot street driven cars lie in the 50* to 70* range of overlap.
My 350 has 219*@.050 with a 108 LSA and still makes 14" of vacuum at 800 RPM at 4000 feet.
Vacuum, or lack there of is directly related to the overlap.
To figure your overlap take your advertised duration on the intake and exhaust add them together.
divide that figure by 4
subtract the LSA (lobe separation angle) from that answer
Multiply it by two. Your answer is the number of degrees of overlap.
IE.
My cam: 270+270=540
540/4=135
135-108=27
27x2=54
54* of overlap.
Hot street driven cars lie in the 50* to 70* range of overlap.
Last edited by REELAV8R; Nov 7, 2015 at 11:06 AM.
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
Guys...input needed: Taking out the L48 in my '79 and installing a 383. I would like to run a Be Cool or DeWitts dual electric fan, an electric vacuum pump and get rid of the charcoal canister system if possible. If I go w/an electric vac pump, is there a high/low vacuum number i need to run? From what I understand, the brake booster, headlights, environmental controls, kickdown for the TH350 all run off vacuum. What should I be concerned with going into this? Btw...new carb will be added as well. Thanks for the inputs...always very helpful.
Instructor
Joined: Jul 2011
Posts: 181
Likes: 11
From: Boiling Springs
Honestly, like the others have said, unless your running a high cam (from what I heard, over .500 lift) then you are good. I'm running a big cam, a Howard's .515/.525 roller and though about vacuum. But instead of buy a electric vacuum pump I'm modding a hydroboost system. Better brakes, less vacuum loss, and cleaner engine bay. So if you really think a pump is good, think about a hydroboost instead.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Honestly, like the others have said, unless your running a high cam (from what I heard, over .500 lift) then you are good. I'm running a big cam, a Howard's .515/.525 roller and though about vacuum. But instead of buy a electric vacuum pump I'm modding a hydroboost system. Better brakes, less vacuum loss, and cleaner engine bay. So if you really think a pump is good, think about a hydroboost instead.
Increasing lift will make the overlap triangle larger on a given cam if everything else remains the same.
The better flowing heads you get the less duration you will need to fill the cylinders. Not the biggest cc heads, best flowing, with appropriately sized intake runner.
Excessively long duration cams for a street driven car makes for a lousy driving experience.
OP, maybe we should ask, what is the intended use for the engine?
Last edited by REELAV8R; Nov 7, 2015 at 08:33 PM.
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
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Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Not necessarily..It depends on building the proper combination of engine components, matched with transmission and rear gear ratio.. mine is a pleasure to drive in traffic , on the Interstate or in a Qtr Mile grudge match. Did I mention I also have Air Conditioning ?