360, vacuum secondaries help
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Senior User
Joined: Dec 2004
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From: Iowa
360, vacuum secondaries help
workin on my 67, 360 mildly built, 670 street avenger.. been having some issues with motor running lean, been digging into the carb lookin around did figure out my secondaries are not opening at all, has the black spring (thickest) could that cause the secondaries to not open at all? i did do the paperclip test not free revving in driveway haha
Lead Driver
Joined: Aug 2003
Posts: 7,592
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From: **** hole San Jose ca.
What do you mean runing lean from the secondaries if not opening. It must be over advanced timing, Or the primaries jets our to small. what size our they? If under #57 then maybe.#62-67 should run ok. If the secondaries diaphragm is leaking for some reason they won't open. What's your timig set at..? Is this a new carb or one from ebay or one that someones messed with before you got it..??
orich
orich
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From: Iowa
well i know the secondaries not opening isnt the lean issue, just dickin around with the carb i figured out that they wernt opening and was just kinda curious if the black secondary spring would cause them not to open being to thick. lean condition- i went up 6 jet sizes and no effect, ran the same so i know its something else, power valve is ok 6.5, not sure about timing made a mark on balancer after build and kept it there what are u guys running for timing mines a 360 mild build (.030 over, shaved heads, mild comp cam, edelbrock performer intake, hedman headers etc...)
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
well i know the secondaries not opening isnt the lean issue, just dickin around with the carb i figured out that they wernt opening and was just kinda curious if the black secondary spring would cause them not to open being to thick. lean condition- i went up 6 jet sizes and no effect, ran the same so i know its something else, power valve is ok 6.5, not sure about timing made a mark on balancer after build and kept it there what are u guys running for timing mines a 360 mild build (.030 over, shaved heads, mild comp cam, edelbrock performer intake, hedman headers etc...)
Postmaster
Joined: Jan 2009
Posts: 4,584
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From: Chesapeake, Va.
It's hard to believe, but he could just have a small base gasket or the butterflies could be just slightly larger than the manifold bores. Suggest you take the carb off and start over after measuring and checking everything.
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Actually this is what vacuum secondaries is all about. They only open if the engine needs the extra air under load. If you expect them to open when you rev the engine in neutral you are badly misinformed.
Oh and yes the black spring will delay the opening, but again if the engine isn't revving high enough to need the secondaries to open, they will NOT open.
A 360 only needs a 625 CFM carb at 6000 RPM. At 4000, 416 CFM, so you have way to much carb to start with. Too much carb is the biggest mistake hot rodders make.
Oh and yes the black spring will delay the opening, but again if the engine isn't revving high enough to need the secondaries to open, they will NOT open.
A 360 only needs a 625 CFM carb at 6000 RPM. At 4000, 416 CFM, so you have way to much carb to start with. Too much carb is the biggest mistake hot rodders make.
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From: Iowa
yeah idk whats goin on, im thinkin its timing or ignition cuz it all started when i replaced the distributor and module.. everything in carb seems to be fine just waiting on a few gaskets to put back together. tested secondaries with a zip tie tied to the diaphragm rod, every gear wide open throttle did not open even alittle bit and the secondary butterflies still look brand new (brass coloring) i know the secondaries not opening is not causing the lean condition im just trying to cure both problems at once.. but if the carb was to big wouldnt it run to rich?
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Postmaster
Joined: Jan 2009
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From: Chesapeake, Va.
Try to locate a good or original carb for that engine and see how it runs. If it seems to cure the problem you will need to start working on the carb, but if the problem continues, AHA!!!, it's another problem. a Golden Rule in repairing and hot rodding is; NEVER MAKE MORE THAN 1 MODIFICATION AT A TIME and NEVER TRY TO CURE 2 PROBLEMS WITH 1 REPAIR.
Hotshot
Joined: Jul 2005
Posts: 13,834
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From: Middle Tn.
We have a carb shop near here that rebuilds holleys for $200 bucks and every carb they rebuild goes on a test mule/dyno engine to ensure proper set up and operation. That makes it worth it to me. When you get the carb back, fine tune the idle jets for your engine and your good to go.
Senior User
Joined: Aug 2010
Posts: 113
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From: Moreno Valley
workin on my 67, 360 mildly built, 670 street avenger.. been having some issues with motor running lean, been digging into the carb lookin around did figure out my secondaries are not opening at all, has the black spring (thickest) could that cause the secondaries to not open at all? i did do the paperclip test not free revving in driveway haha
Feel lucky of your engine opens them under a load untill 3800rpms
670 is a large carb for a stock compression 360
the secondaries only open under a load with enough vacumn
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