vacuum reading
Thread Starter
Racer
Joined: Oct 2006
Posts: 470
Likes: 2
From: Hunterdon County NJ
vacuum reading
for checking vac I have read to get a source directly at the manifold. Would the reading at the carb. be the same and if not, about how much would it be off. what would be a good vac reading at idle for a 365 hp?
Le Mans Master
Joined: Aug 2009
Posts: 5,474
Likes: 16
From: Houston Texas
St. Jude Donor '10-'12-'13
Melting Slicks
Joined: Jul 2004
Posts: 2,867
Likes: 195
From: Maryland
We dont know which carb you are using. Normally full time vacuum is measured below or at the base plate of the carb. Some you can get full time vacuum off the choke pull off. If the engine is running observe the tach reading. Pull off the hose from the VAC and if the idle decreases you probably are hooked up to full time vacuum. If no change youre probably using a ported source. This assumes you have the appropriate VAC (B28)
Last edited by Donald #31176; Aug 1, 2010 at 09:06 AM.
POSSE ZR-1 Driver
Joined: Feb 2002
Posts: 3,980
Likes: 139
From: Groton CT
Yes, you can check the vacuum at the same point on the carb that the vacuum advance hooks up to if you have a 2818 carb. Use a "T" in the line so your vacuum advance still operates while you are checking idle vacuum.
Thread Starter
Racer
Joined: Oct 2006
Posts: 470
Likes: 2
From: Hunterdon County NJ
I have the 2818
so it should measure 8-10 if I connect gauge at the hose which is on the can (i don't have a T) but would it read the same unhooked to the can?
what power valve would you suppose is in a new 2818? what would be the symptons indicating that the PV is sized incorrectly?
so it should measure 8-10 if I connect gauge at the hose which is on the can (i don't have a T) but would it read the same unhooked to the can?
what power valve would you suppose is in a new 2818? what would be the symptons indicating that the PV is sized incorrectly?
Last edited by geo65; Jul 31, 2010 at 06:14 PM.
Le Mans Master
Joined: Aug 2009
Posts: 5,474
Likes: 16
From: Houston Texas
St. Jude Donor '10-'12-'13
I have the 2818
so it should measure 8-10 if I connect gauge at the hose which is on the can (i don't have a T) but would it read the same unhooked to the can?
what power valve would you suppose is in a new 2818? what would be the symptons indicating that the PV is sized incorrectly?
so it should measure 8-10 if I connect gauge at the hose which is on the can (i don't have a T) but would it read the same unhooked to the can?
what power valve would you suppose is in a new 2818? what would be the symptons indicating that the PV is sized incorrectly?
With my off the shelf 600 double pumper, I had to go from a 6.5 power valve to a 4.5. Ran much better. After that I Drilled 3/32 holes in the butterflies and adjusted the secondaries. Now it's near perfect. I may need to work with the jets a bit.I need to drive it a bit more to know for sure.
If I am not mistaken the 2818 is the factory carb for the 365hp? That shouldn't need any changes.
I guess I should have said, if you have an "off the shelf" Holley change the power valve with that cam. I think the rule of thumb on the power valve is half the manifold vac. So 10hg would be as close to a 5 power valve as possible. In my case it was 4.5 valve.
Last edited by MiguelsC2; Jul 31, 2010 at 06:31 PM.
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