Having 383 built - questions.....
Thread Starter
Burning Brakes
Joined: Nov 2003
Posts: 990
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From: North Texas
Having 383 built - questions.....
How do I determine how much vacuum an engine will make?
Knowing how much stuff is vacuum controlled on the car, Should I be worried about this?
What drives the amount of vacuum - Cam duration? (I'm planning on a Lunati 230/240 with 487/520 lift.)
Intake manifold.....What will really fit under the hood?
I'd like to run the Performer RPM but I'm afriad it just won't fit. I'm looking for some help in this area. Anyone?
Knowing how much stuff is vacuum controlled on the car, Should I be worried about this?
What drives the amount of vacuum - Cam duration? (I'm planning on a Lunati 230/240 with 487/520 lift.)
Intake manifold.....What will really fit under the hood?
I'd like to run the Performer RPM but I'm afriad it just won't fit. I'm looking for some help in this area. Anyone?
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
What drives the amount of vacuum - Cam duration?
Kind of. It's really the amount of overlap. so a 230/240 cam with wide lob centers like 112-114 has less over lap than the cam 230/240 with 108 lc.
The other factor is type of lifter. Flat hydrolic will produce less vacuum than a roller cam.
I have always been able to run tall single plane manifolds with dropped base air cleaners
Kind of. It's really the amount of overlap. so a 230/240 cam with wide lob centers like 112-114 has less over lap than the cam 230/240 with 108 lc.
The other factor is type of lifter. Flat hydrolic will produce less vacuum than a roller cam.
I have always been able to run tall single plane manifolds with dropped base air cleaners
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Originally Posted by gkull
What drives the amount of vacuum - Cam duration?
Kind of. It's really the amount of overlap. so a 230/240 cam with wide lob centers like 112-114 has less over lap than the cam 230/240 with 108 lc.
The other factor is type of lifter. Flat hydrolic will produce less vacuum than a roller cam.
I have always been able to run tall single plane manifolds with dropped base air cleaners
Kind of. It's really the amount of overlap. so a 230/240 cam with wide lob centers like 112-114 has less over lap than the cam 230/240 with 108 lc.
The other factor is type of lifter. Flat hydrolic will produce less vacuum than a roller cam.
I have always been able to run tall single plane manifolds with dropped base air cleaners
Thread Starter
Burning Brakes
Joined: Nov 2003
Posts: 990
Likes: 0
From: North Texas
MotorHead...
But I see it's a roller cam...any idea how much difference that will make versus Hyd-Flat?
What air cleaner (base) are you running with your Victor Intake?
Gkull...
110 LDA with 106 ........
But I see it's a roller cam...any idea how much difference that will make versus Hyd-Flat?
What air cleaner (base) are you running with your Victor Intake?
Gkull...
110 LDA with 106 ........
Race Director
Joined: Apr 2000
Posts: 17,672
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
The more overlap you have the less vaccum you are going to have. If you have identical duration cams one hydraulic flat tappet and one solid roller the ramps on the roller are more extreme, therefore this allows the cam to have less overlap ( and higher lift ) than the flat tappet cam.
This is the reason why roller cams are great. I can get over .600" lift with the XR280R and have the same overlap as say a CC 280H which has a lift of .480" and if you wanted .600" lift from a flat tappet you would have to get into a solid track only cam in the 270-280 deg @ 0.050" duration with huge overap that would give you very low vaccum.
I think I have it straight here anyone wants to add something that's fine Jjust trying to help out
I am using a K&N setup with a drop base assembly
This is the reason why roller cams are great. I can get over .600" lift with the XR280R and have the same overlap as say a CC 280H which has a lift of .480" and if you wanted .600" lift from a flat tappet you would have to get into a solid track only cam in the 270-280 deg @ 0.050" duration with huge overap that would give you very low vaccum.
I think I have it straight here anyone wants to add something that's fine Jjust trying to help out
I am using a K&N setup with a drop base assembly
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Drifting
Joined: Sep 2001
Posts: 1,427
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From: Boxford Mass
I'm running a hyd roller w/ .520 lift. I was also concerned about vacuum,which was a big consideration for going with a roller. I'm pulling around 20 inches at idle in drive. That was more than my stock 350.
My headlights and wiper door snap open now.
My headlights and wiper door snap open now.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
1970-Bronze. Any Flat H cam in the 230/240 range with 110 lc is not going to produce much vacuum. It will sound more like a race car with a choppy idle. 383's because of their longer stroke are more forgiving.
There are two trains of thought to make power. The cheap and incorrect way taken by most is. Put a hot cam in it! Without enough intake port flow and free flowing exhaust you end up with the race car sound that impresses all the guys at the car hang out. But it's really not a very pleasant car to drive and the gas mileage sucks.
230 intake duration cams are made to spin a 383 ci 6500 rpm and I imagine that it probably wouldn't run the best under 2000 rpm. People use crutches on motors to help them. Like 4.11 rear gears and higher stall converters. But your masking the problem of how 98% of all driving is done.
I wouldn't go above a Crane 278 power max cam in a 383 if I intended to use a F-H cam and drive the car. That will still get you over 400 hp
There are two trains of thought to make power. The cheap and incorrect way taken by most is.
Put a hot cam in it! Without enough intake port flow and free flowing exhaust you end up with the race car sound that impresses all the guys at the car hang out. But it's really not a very pleasant car to drive and the gas mileage sucks.230 intake duration cams are made to spin a 383 ci 6500 rpm and I imagine that it probably wouldn't run the best under 2000 rpm. People use crutches on motors to help them. Like 4.11 rear gears and higher stall converters. But your masking the problem of how 98% of all driving is done.
I wouldn't go above a Crane 278 power max cam in a 383 if I intended to use a F-H cam and drive the car. That will still get you over 400 hp
Thread Starter
Burning Brakes
Joined: Nov 2003
Posts: 990
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From: North Texas
Ok, I call and switched to a Roller Cam. 
The builder really wanted to go with a .525/.540 - 242Âş/252Âş but my heads only support 540 lift so I backed it down. Plus I think the extra vacuum is going to be needed.
Lunati - .478/.480 - 227Âş/234Âş - 112Âş/108Âş
What do you guys think? Did I get to agressive?
I think I'm going with the PERF RPM and I'll just make it work some freekin' way.
The builder really wanted to go with a .525/.540 - 242Âş/252Âş but my heads only support 540 lift so I backed it down. Plus I think the extra vacuum is going to be needed.
Lunati - .478/.480 - 227Âş/234Âş - 112Âş/108Âş
What do you guys think? Did I get to agressive?
I think I'm going with the PERF RPM and I'll just make it work some freekin' way.
