07-04-2017, 11:04 AM | #1 |
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Holley carb question
I recently installed a Holley 3310 750cfm carb on the 300hp 350 ci motor in my 71c10. its jetted 72 in the primaries and 74 in the secondaries. I am experiencing stalling at low rpms, ex. slowing down for a turn or coming to a stop. I recently resealed the manifold due to oil leak. I have a rough idle so I will checking for a vacuum leak at the manifold. Any suggestions on a starting point.
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07-04-2017, 11:15 AM | #2 |
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Re: Holley carb question
Check your timing also.
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07-04-2017, 11:38 AM | #3 |
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Re: Holley carb question
Dizzy is set at 12 BTDC on initial timing. I was pulling 12 in of vacuum @ 850 - 900 rpm. anything less than that and it would stall.
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07-04-2017, 11:41 AM | #4 |
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Re: Holley carb question
At what rpm did you set that 12 degrees initial timing?
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07-04-2017, 11:42 AM | #5 |
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Re: Holley carb question
1000 rpm
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07-04-2017, 11:56 AM | #6 |
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Re: Holley carb question
So that means your 12 degrees could be actually closer to 4 to 6 degrees.
At that rpm you're well into the mechanical timing in the distributor. It usually starts kicking in at about 850. You need to get your idle down to at least 750 rpm to get an accurate reading. Bump your timing up 8 degrees and then slow the idle down on the carb. Fine tune from there adding more timing and slowing down the idle until you have it idling around 750 rpm. Curious what intake you have? |
07-04-2017, 11:58 AM | #7 |
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Re: Holley carb question
ok. need to check for vacuum leaks first to solve problem of surging
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07-04-2017, 12:00 PM | #8 |
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Re: Holley carb question
Will motor increase rpm if I spray brake cleaner around edges of manifold while running looking for vacuum leak.
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07-04-2017, 12:11 PM | #9 | |
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Re: Holley carb question
Quote:
Your surging might not be from anything other than no initial timing and your primary throttle cranked open in order to idle and idling on the power circuit. |
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07-04-2017, 12:25 PM | #10 |
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Re: Holley carb question
would improper throttle linkage adjustment be a contributing factor to the stalling?
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07-04-2017, 12:50 PM | #11 |
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Re: Holley carb question
Maybe!
What would you call improper? |
07-04-2017, 01:09 PM | #12 |
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Re: Holley carb question
allowing the venturis to complete close blocking airflow
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07-04-2017, 01:16 PM | #13 | ||
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Re: Holley carb question
Pretty big carb for a lower performance 350. The 3310 comes with a really heavy vac secondary spring (black one) right out of the box. You will need to switch to a purple or yellow spring. You will also want to step down your primary jets as well. Can't remember off the top of my head what they come with as far as pump squirters go. But you'll need to probably change that as well. How do your spark plugs look? Black and wet?
A 3310 isn't even working until over 3,000 RPM's in most applications. Gary
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07-04-2017, 01:19 PM | #14 |
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Re: Holley carb question
Primary jets are 72's. I cant remember what spring is in the vac. secondary. haven't checked the plugs yet
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07-04-2017, 01:22 PM | #15 | ||
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Re: Holley carb question
Try 68's up front. The metering plate in the rear is fixed to flow, I believe, like 72 jets.
Gary
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07-04-2017, 01:25 PM | #16 |
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Re: Holley carb question
ok
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07-04-2017, 01:42 PM | #17 |
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Re: Holley carb question
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07-04-2017, 03:06 PM | #18 |
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Re: Holley carb question
just checked metering screws. I can screw them all the way in without motor stalling. I did discover vacuum leaks at base of carb and manifold. Back to square one.
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07-04-2017, 03:31 PM | #19 | |
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Re: Holley carb question
Quote:
What's your motor set up like? What intake? What cam? What headers? |
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07-04-2017, 03:34 PM | #20 |
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Re: Holley carb question
Edelbrock RPM, 1 5/8 long tube headers, GM .450 int. / .460 cam, 222 dur. on both intake and exhaust @ .050. Iron heads
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07-04-2017, 03:54 PM | #21 |
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Re: Holley carb question
Your basic 290 hp crate.
No compression, poor heads, too much cam. But tuneable. Fix your vac leaks and then put some timing in it and adjust your carb. Here's a link on timing. http://www.badasscars.com/index.cfm/...d=76/prd76.htm Did the intake come with the motor or did you put it on? |
07-04-2017, 04:01 PM | #22 |
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Re: Holley carb question
Sounds to me like a vacuum leak that has forced you to open the idle speed screw far enough that the primary blades have uncovered the transfer slots, which means your carb is actually in between states, operating on the transition circuit, which you can tell because the mixture screws don't function.
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07-07-2017, 06:08 PM | #23 | |
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Re: Holley carb question
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07-07-2017, 07:52 PM | #24 | |
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07-08-2017, 09:32 AM | #25 |
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Re: Holley carb question
Found the problem. It wasn't the intake or the carb base vacuum leak. The Holley carb has a crack in the base. I installed my old Edelbrock and truck runs like normal.
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