Higher ratio rocker arm?
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Higher ratio rocker arm?
Trying to gain about 3 hg of vacuum in regards to rules.
Would increasing rocker ratio on just intake help increase vacuum?
1.5 to 1.6
Lighter weight oil etc make any difference to vacuum?
Would increasing rocker ratio on just intake help increase vacuum?
1.5 to 1.6
Lighter weight oil etc make any difference to vacuum?
Re: Higher ratio rocker arm?
Opposite, if any change at all.
Lighter oil may help, not 3" though.
What's your current idle ignition advance ?
Lighter oil may help, not 3" though.
What's your current idle ignition advance ?
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
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Re: Higher ratio rocker arm?
How does the motor leak down test?
No reason you can not have 3% if the motor is built right and or fresh.
With heads off the motor if you pour rubbing Alky into the all 16 ports do any of the valves leak within 5 minutes?
What's your compression ratio, are you at the rule limits?
The smaller the chamber the more vacuum you will have .
No reason you can not have 3% if the motor is built right and or fresh.
With heads off the motor if you pour rubbing Alky into the all 16 ports do any of the valves leak within 5 minutes?
What's your compression ratio, are you at the rule limits?
The smaller the chamber the more vacuum you will have .
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Higher ratio rocker arm?
3'' that's probably 20 odd % depending on what the minimum requirement is.
That's a cam change unless he knows of others making the required vac with that cam.
That's a cam change unless he knows of others making the required vac with that cam.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Re: Higher ratio rocker arm?
Things you can do to increase vacuum.
Increase valve lash
Lean idle circuit
Advance timing
Change carb
Increase valve lash
Lean idle circuit
Advance timing
Change carb
Mike Jones
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
Jones Cam Designs
Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
Re: Higher ratio rocker arm?
Dual plane? I just gained 1.5” by going from a 3/8” open spacer and a 3/16” milled down to divided to a full divider and a 1/2” 4 hole spacer.
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Re: Higher ratio rocker arm?
Running a distributor with working vacuum advance on the engine will help the most.88bluestar wrote: ↑Fri Mar 17, 2023 2:50 am Trying to gain about 3 hg of vacuum in regards to rules.
Would increasing rocker ratio on just intake help increase vacuum?
1.5 to 1.6
Lighter weight oil etc make any difference to vacuum?
http://www.rmcompetition.com
Specialty engine building at its finest.
Specialty engine building at its finest.
Re: Higher ratio rocker arm?
Raising idle speed helps vacuum.
Mummert Machine and Development 4 stroke hp
Mummert Y-blocks
Mummert Y-blocks
Re: Higher ratio rocker arm?
If it's a vac rule motor there should be a stipulated rpm reference.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Re: Higher ratio rocker arm?
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Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Studebaker-Packard V8 Limited
Obsolete Engineering
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Re: Higher ratio rocker arm?
14hg @ 900 rpm.
Crower cam saver hydraulic lifters, sbc.
I have a new cam, lifters and valvesprings through JRC-Jones, but not sure ill have time this week to get them changed out, so im looking for temporary way to increase at least the vacuum so its close enough to 14.
Crower cam saver hydraulic lifters, sbc.
I have a new cam, lifters and valvesprings through JRC-Jones, but not sure ill have time this week to get them changed out, so im looking for temporary way to increase at least the vacuum so its close enough to 14.
Re: Higher ratio rocker arm?
CamKing wrote: ↑Fri Mar 17, 2023 11:11 am Things you can do to increase vacuum.
Increase valve lashyes
Lean idle circuitNo, use a vacuum gauge and give it whatever it wants/likes, Mike is correct to a point. Higher overlap cams don't like stoich
Advance timingYes, 32 degrees should be common at 900 rpm idle
Change carb
Heat is energy, energy is horsepower...but you gotta control the heat.
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Re: Higher ratio rocker arm?
Would smaller vacuum port diameter make a difference. Hidden plug inside a 3/16 port with a much smaller hole?
Re: Higher ratio rocker arm?
No. The vacuum gauge deadheads the port so there is no flow. So, a smaller hole does not affect the vacuum gauge measurement. It may slightly dampen pulses, if present.88bluestar wrote: ↑Sat Mar 18, 2023 7:51 pm Would smaller vacuum port diameter make a difference. Hidden plug inside a 3/16 port with a much smaller hole?
Re: Higher ratio rocker arm?
I was in tech with the late model one night. I was watching them tech vacuum on pure stocks. The tech told the driver to raise the rpm a certain amount. The driver put his hand over the top of the 2 barrel like a choke.and worked the throttle with his thumb. I've always wondered if a manual choke work to raise vacuum.