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Discussion Starter · #1 ·
I bought a 67 camaro and it has dual vacum secondary holleys on a high rise intake. I know my way around holleys, but am still new at it, and have no idea where to start with it.

Right now the thing runs terribly, and constantly backfires through the carbs. It will idle fine when warmed up, but has a pretty bad hesitation and still backfires through the carb if you nail it...I'm thinking I need larger accel pumps?

I know how to set the butterfly's on the primary butterflies, but don't know how I should set them on the secondary side.

Do both carbs need to be tuned the same, or does one have the be tuned different than the other.

How will I know how big of an accel pump I need to get?

It has an adj. fuel pressure regulator on there now and its set to ~9psi
 

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i assume were talking about the holley 600s list 1850 . if so first get it to idle and get a baseline vacuum reading . now you can get the correct powervalves. i ALWAYS use 2.5 powervalves on tunnel rams ,no matter the vacuum ..now i dont no your compression and cam specs so this is just an asumption , but is your compression high 11.0 or more? if not you really need to run a high initial timing 20 or so . now on the secondaries ,i recommend closing them down as much as possible ,and tune just the primaries. Start with stock jets and work the direction you think it should go (up or down) .Your discharge nozzles most likely aren't the problem. MAKE SURE THE FLOATS ARE SET !!!!.....LOWER THE FUEL PRESSURE TO 7LBS MAX ..

LET ME KNOW HOW IT GOES.

JASON
 

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Discussion Starter · #4 ·
ok I got some info here.

the carbs are

mechanical secondary
single accel pump
450cfm 4160

I took the bonnet off and the tops of the carbs were all sooty and black, and the carb was wet right underneath the accel pump(only one in each carb)

as far as the motor goes, the previous owner said it was 11:1 compression with camelback heads(not sure if the compression number is accurate though). The cam is pretty lopey, and its got the tunnel ram weiand intake on there.
 

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total different story now!! THOSE CARBS ARE THE WORST THING HOLLEY EVER MADE !!!
when you stab the throttle the secondaries open and they don't get any extra fuel SO YOU GET A LEAN BOG!
try larger discharge nozzles and larger jets ..

good luck
 

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Discussion Starter · #6 ·
total different story now!! THOSE CARBS ARE THE WORST THING HOLLEY EVER MADE !!!
when you stab the throttle the secondaries open and they don't get any extra fuel SO YOU GET A LEAN BOG!
try larger discharge nozzles and larger jets ..

good luck
so I'm assuming thats why I get the lean backfire and a huge atom bomb of smoke off the carb when I rev it.

so now I'm also guessing I need to run large jets in the rear of the thing to make up for the lack of squirters. Which would mean the thing would be running rich all the time.

so what is my best option I have here about fixing this problem...its got the 31 squirters in there now and I won't know the jet sizes until tommorow.
 

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well if its a 4160 it won't have rear jets ,but plates , you can either drill the jet holes bigger ir swap to metering blocks..
As for the shooters go up in size maybe 45-50 ,or drill them until they work good. ANOTHER OPTION IS 50CC PUMPS. but i remember having some interference last time i used them (cant remember the problem though).
IS your timing set with high initial ?20 or so?
 

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66 El Camino 57 Chevy pickup 2004 Tahoe
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see my post in your other thread. Please don't post the same question in both forums.

While you're here see Jason's post at 4:21. You'll find it familiar when you read mine over in Engines.
 

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i had a similar set up with 4160 vacuum secondaries,hi-rise,355 10.5-1 & trick flow 205/160 alum.heads. just a 1500 stall,488 gears & this thing ran like a raped ape.i can get you the jet size & even sell these if interested,let me know.
 

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Discussion Starter · #10 ·
i had a similar set up with 4160 vacuum secondaries,hi-rise,355 10.5-1 & trick flow 205/160 alum.heads. just a 1500 stall,488 gears & this thing ran like a raped ape.i can get you the jet size & even sell these if interested,let me know.
that would be great if you could let me know the jet sizes so I could get a ballpark of where I should be at.

I was looking at the carbs and the guy put spacers underneath them, so I'm assuming those aren't helping and I'm going to rip them off.

Tommorow I am going to measure the vacuum, go buy larger squirters, appropriate power valves, and a jet kit.

what should I set my timing at inital and advanced? When should the timing come into full advance?
 

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dark,

64 huffer doesn't have the same carbs you have, the jet size in his carbs is not likely applicable to yours.
 

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a friend of mine ran a very similar setup. 68 firebird, 10" converter with 3.73 gears. engine was a 400" with AFR 195 heads, weiand tunnel ram and 450 holleys. we rebuilt the carbs to stock spec with the exception of i think 33's (31 stock)on the squirters. power valve was an 8.5". engine had a 294S comp cam. the jets were stock listed#122-582. run as much initial timing as possible and really work on the idle adjustment. set up both carbs as exactly as possible. ran the linkage non progressive. this car ran clean and crisp. the midrange was awesome. after it was warmed up just hit the key and it fired right off. best of luck mike
 

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Discussion Starter · #13 ·
I've been screwing around with it all day and the problem seems to be just getting worse.

I havent been able to get it running well enough to get the vacuum reading, but I did take out the 8.5 power valves and install 6.5 power valves, its also got 58 jets in it right now.

The carbs were all messed up, I took them off, adjusted the butterflys to the idle transfer slot properly, backed out all the idle mixture screws 1.5 turns, lowered the fuel psi from 8-9 to 6-7, upped the squirters from 31 to 40's, adjusted the float level properly, and its running worse than ever now.

Before the thing was a pain in the ass to warmup, and when warm it had a terrible hesitation and ran very badly. Now when I try to start it, the thing just shoots flames a foot in the air out of the carbs.

I'm at a loss here and don't know what to do next.
 
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