No-Load vs Load Idle Difference
Thread Starter
Melting Slicks
Joined: Sep 2002
Posts: 2,783
Likes: 2
From: Engineers do it better.
Lars, the symptoms are same whether with or without vaccum.
I looked up Holley's website and they recommend that the idle vaccum be checked IN GEAR for automatic cars. How could I miss that
From their site:
To properly size a power valve, take a vaccum reading at idle and if it is above 12" for a standard transmission a 6.5" will be safe to use. For automatic transmissions take a vaccume reading in gear at idle and if the vaccum is below 12" divide that in half for proper size. Example 9" of vaccume in gear at idle will require a 4.5" power valve.
My car idles with 9 inHg.... I need a 4.5" power valve. I will change and post results
I looked up Holley's website and they recommend that the idle vaccum be checked IN GEAR for automatic cars. How could I miss that
From their site:
To properly size a power valve, take a vaccum reading at idle and if it is above 12" for a standard transmission a 6.5" will be safe to use. For automatic transmissions take a vaccume reading in gear at idle and if the vaccum is below 12" divide that in half for proper size. Example 9" of vaccume in gear at idle will require a 4.5" power valve.
My car idles with 9 inHg.... I need a 4.5" power valve. I will change and post results
Burning Brakes
Joined: Feb 2006
Posts: 1,024
Likes: 1
From: AL
if you can do this, you should also be able to make the jet changes. it's best to make one change at a time as you seem to be doing, so if you record the jet sizes you can always go back . . . 0.02
Thread Starter
Melting Slicks
Joined: Sep 2002
Posts: 2,783
Likes: 2
From: Engineers do it better.
I thought about that too, but I want to leave the jetting part for the dyno. This way I can get an ACCURATE setting, instead of going by 'feel'. I am no computor 
Another question for PV selection:
Do I need "standard" or "high" flow PV.
What about the dual stage PV? Are they better?
Another question for PV selection:
Do I need "standard" or "high" flow PV.
What about the dual stage PV? Are they better?
Melting Slicks
Joined: Sep 2003
Posts: 3,050
Likes: 2
From: Orange Ct
Apparently these are automatic cars, is anyone using a stall speed converter? 1200 RPM`s when warm is way too much. It must also be hard on U-joins too. With a proper converter the idle from neutral to any gear should not drop over 50-100 rpms with a solid lifter cam and idle at 8-850. Similarly with a hydraulic but at 700.
The real problem is too much cam and too low a stall speed on the converter.
Race Director
Joined: Oct 2000
Posts: 15,124
Likes: 79
From: central FL, near the beach.
i have the 270H in my 61. Yes! this cam would leap off the line with a higher stall, 2500-2800 should do it.
choppy idle at 800 in N, stick.(i can see u guys having a problem with Auto, this would require richening the IFR i suspect, see pg 122 HOLLEY CARBS HP BOOKS) a good final exam!
i put the 270H in, in 94
but i do remember it didn't like to idle at first.(someday i may increase the IFR .002")
i combined ported and manifold vac. with a .062" restriction in manifold.
that fixed it, except if the idle would drop it would lose vac and stall(rarely happens)
i use a 13" PV. the holley PV guys retired and the new guys don't know squat. http://community.webtv.net/MATTGRU/pv
choppy idle at 800 in N, stick.(i can see u guys having a problem with Auto, this would require richening the IFR i suspect, see pg 122 HOLLEY CARBS HP BOOKS) a good final exam!
i put the 270H in, in 94
but i do remember it didn't like to idle at first.(someday i may increase the IFR .002")
i combined ported and manifold vac. with a .062" restriction in manifold.
that fixed it, except if the idle would drop it would lose vac and stall(rarely happens)
i use a 13" PV. the holley PV guys retired and the new guys don't know squat. http://community.webtv.net/MATTGRU/pv
Last edited by Matt Gruber; Sep 20, 2007 at 08:08 AM.
Thread Starter
Melting Slicks
Joined: Sep 2002
Posts: 2,783
Likes: 2
From: Engineers do it better.
Race Director
Joined: Oct 2000
Posts: 15,124
Likes: 79
From: central FL, near the beach.
clean the jet block, tiny dirt could cause lean!
i had that hapen once on my 72. made it stall.
should idle at 900 in N, and 550-650 in D.
my 72 has xe262 218/224 idles 550 in D 8-900 in N
Don't be afraid to buy a book on yor carb.
Thread Starter
Melting Slicks
Joined: Sep 2002
Posts: 2,783
Likes: 2
From: Engineers do it better.
I just purchased "Holley Super Tuning Guide". It's in the mail
I still need opinions on:
Do I need "standard" or "high" flow PV.
What about the dual stage PV? Are they better?
I still need opinions on:
Do I need "standard" or "high" flow PV.
What about the dual stage PV? Are they better?
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Race Director
Joined: Oct 2000
Posts: 15,124
Likes: 79
From: central FL, near the beach.
there are 2 schools of thought on pv's.
regardless,
u need to get the size of the pvrc to be sure a 2 stage isn't too small. perhaps it can be drilled? not sure.
as i describe on my pages, holley doesn't make a 13",and the 10.5 i tried sucked. so in my school u just stretch the spring.
regardless,
u need to get the size of the pvrc to be sure a 2 stage isn't too small. perhaps it can be drilled? not sure.
as i describe on my pages, holley doesn't make a 13",and the 10.5 i tried sucked. so in my school u just stretch the spring.
Race Director
Joined: Oct 2000
Posts: 15,124
Likes: 79
From: central FL, near the beach.
here is an example from my notes:
my 4165 pvrc .052"
main jet .059
main jet = cruise
main & pvrc = heavy foot
125-212 2 stage, opens 1st stage at 12" giving .040" 2nd stage give full flow, whatever pvrc is.
this 125-212 would be interesting to try
my 4165 pvrc .052"
main jet .059
main jet = cruise
main & pvrc = heavy foot
125-212 2 stage, opens 1st stage at 12" giving .040" 2nd stage give full flow, whatever pvrc is.
this 125-212 would be interesting to try
Race Director
Joined: Oct 2000
Posts: 15,124
Likes: 79
From: central FL, near the beach.
i drove 10 mi today and took note of when my 13" pv opened. only about 10-15 seconds total! lots of stop and go.
so really i could
1. raise pv to 14- 14.5"
2. lean out main jet for better mpg.
.
checked my IFR in my spare carb: .o28"
that's tiny! may go to .030 on my 61 that's 14.8% richer from .002" !
so really i could
1. raise pv to 14- 14.5"
2. lean out main jet for better mpg.
.
checked my IFR in my spare carb: .o28"
that's tiny! may go to .030 on my 61 that's 14.8% richer from .002" !
Last edited by Matt Gruber; Sep 21, 2007 at 01:00 PM.
