Holley 650 double pumper question - Team Camaro Tech
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post #1 of 14 (permalink) Old May 3rd, 11, 01:11 PM Thread Starter
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Tim
 
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Holley 650 double pumper question

Guys, I have a Holley 650 double pumper with the mechanical secondaries. I have it running on a 355 small block chevy with maybe only 6-7 lbs of vacuum out of the intake. I am having trouble with it idling below 1400 rpm. I was told that I could adjust the "secondary idle screw" from the base of the carb.......and open up the secondaries a little. Has anyone heard of this.....do you think that it would help in my application? Thanks!

'67 SS 6spd
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post #2 of 14 (permalink) Old May 3rd, 11, 01:31 PM
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Re: Holley 650 double pumper question

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Originally Posted by tvinton View Post
Guys, I have a Holley 650 double pumper with the mechanical secondaries. I have it running on a 355 small block chevy with maybe only 6-7 lbs of vacuum out of the intake. I am having trouble with it idling below 1400 rpm. I was told that I could adjust the "secondary idle screw" from the base of the carb.......and open up the secondaries a little. Has anyone heard of this.....do you think that it would help in my application? Thanks!
I would think you need to make sure the secondary set screw is not holding the rear plates open.
The second thing I am thinking about is the size of the PV with 6-7 in hg. For that kind of vacumn signal, the PV need to be a lower number like 45 or 35 and I have seen some 25.

What could be happening is the PV (power valves) are trying to open when idling and dump fuel, unless you have some high float levels and gas is running in thru the venturi.

Don
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Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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post #3 of 14 (permalink) Old May 3rd, 11, 01:35 PM Thread Starter
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Re: Holley 650 double pumper question

Secondary set screw is not holding rear plates open......as I do not see any fuel dripping down into secondaries. PV has already been changed to a 45 as sugguested by Holley. I seem to remember already correcting the float level.

'67 SS 6spd
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post #4 of 14 (permalink) Old May 3rd, 11, 05:32 PM
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Re: Holley 650 double pumper question

Does the engine still run if you completely close the primaries with the idle adjustment? If so, you must have a vacuum leak somewhere. High idle not created by too much fuel; its created by too much air.

1969 Camaro - Intense Blue Pearlcoat/white (Baldwin-Motion paint scheme), stock 6.2 liter L92 with VVT, LS3 intake, Doug's Headers; Tremec TKO, 3.73 12-bolt posi.
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post #5 of 14 (permalink) Old May 3rd, 11, 07:39 PM
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Re: Holley 650 double pumper question

Along with looking for a vacuum leak, check your timing before tearing into the carb too much. You can also have low vacuum if your primary idle mixture adjustment is way off and if your valves have too much preload on them you will get lower idle vacuum.

As for opening the secondary throttle blades, some guys do it but I don't see it as properly tuning the carb unless it's a 4 corner idle by design meaning it has secondary idle mixture screws.

...Dennis

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post #6 of 14 (permalink) Old May 3rd, 11, 08:46 PM Thread Starter
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Re: Holley 650 double pumper question

Engine dies when primaries are closed too much. There are no vacuum leaks. Timing and preload are fine.

'67 SS 6spd
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post #7 of 14 (permalink) Old May 3rd, 11, 09:27 PM
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Re: Holley 650 double pumper question

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Originally Posted by tvinton View Post
Engine dies when primaries are closed too much. There are no vacuum leaks. Timing and preload are fine.
What is "fine", what is your timing set at? What is the preload on your lifters? If everything is as you say then your engine is in poor mechanical condition (rings most likely) or your cam and heads are grosely mis-matched.

...Dennis

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post #8 of 14 (permalink) Old May 3rd, 11, 10:31 PM
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Re: Holley 650 double pumper question

every body seems to be on top of this one--really need to know cam, comp ect--did it run fine before or with other carb--if it really has only that much vacuam at idle and everything looks good--you would have to get the smallest power valve # 25 or put a plug in it
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post #9 of 14 (permalink) Old May 4th, 11, 11:07 AM Thread Starter
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Re: Holley 650 double pumper question

Thanks guys. This engine only has 70 miles on it now, it was built from an Edelbrock kit. Timing looks to be 22 degrees at 1400 RPM (can't get it to idle lower) Below are the topend specs, including cam:

The 2098 top end kit includes:
Performer RPM hydraulic cam/
lifters #7102.
two performer RPM heads
# 60899.
timing cover and seal # 6997
cylinder head gasket set # 7361
RPM air gap intake manifold # 7501
intake manifold bolt kit # 8504
cylinder head bolt kit # 8550.

The #7102 performer RPM hydraulic flat tappit cam
is a little radical for a 350 even if it were a 4 speed,
if its an auto car you would have a real mess on your hands without a high stall converter. Here are the specs on the cam.
Int. Dur. .050 = 234
ex. dur. .050= 244
adv. int. dur.= 308
adv. ex. dur.= 318
lift int.= .488
lift ex.= .510
LSA 112

'67 SS 6spd
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post #10 of 14 (permalink) Old May 4th, 11, 12:11 PM
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Re: Holley 650 double pumper question

I ran this 7102 cam in a zz3 crate motor but roller version, I did have to have a 2k stall convertor. Behind a manual trans it worked well .

Don
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post #11 of 14 (permalink) Old May 4th, 11, 06:16 PM Thread Starter
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Re: Holley 650 double pumper question

Thanks Don, what was your idle RPM?

'67 SS 6spd
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post #12 of 14 (permalink) Old May 5th, 11, 09:14 AM
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Re: Holley 650 double pumper question

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Originally Posted by tvinton View Post
Thanks Don, what was your idle RPM?
750/800 in gear with 700r4

Don
TC # 349
Zdld17:69 Z/RS,306, NOR141111, 9N554XXX, 12A, X3G, 59/59,723, AFR 195,CCC282/290HR, TKO 600, BU1122B1E Owner since Dec 1968

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post #13 of 14 (permalink) Old May 5th, 11, 11:49 AM
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Re: Holley 650 double pumper question

Quote:
Originally Posted by tvinton View Post
Thanks guys. This engine only has 70 miles on it now, it was built from an Edelbrock kit. Timing looks to be 22 degrees at 1400 RPM (can't get it to idle lower)
22 degs @ 1400 could be way lower at 800 rpm. Most distributors start the curve at 900-1000 rpm. I would increase the advance by 2-4 degs at 1400 and then try to lower the idle as far as it goes and is someone steady. Being "on the curve" it could jump around. Then check the timing again, if my hunch is right it will idle at a lower rpm and the timing will be less too. If you still need to get the idle down a bit more do the same again.

If that works for you hook up your vacuum gauge and adjust the mixture screws for most vacuum, then back out about 1/8th turn. Reset the idle again and adjust your initial if you think it needs it.

...Dennis

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post #14 of 14 (permalink) Old May 5th, 11, 05:02 PM Thread Starter
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Re: Holley 650 double pumper question

Thanks Dennis........will give it a shot!

'67 SS 6spd
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