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Old 10-17-2013, 08:24 PM   #1
Greasemonkey327
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Carb? Timing? fuel?

So I just got a 72 c20, 454 th350. When I stomp on gas it bog down then recovers and revs good and has a ton of power. I can ease into it and usually be fine. Occassionally get a little studder. but when ever its wide open it bogs. What am I looking at? it has a holly 3310-4. Good carb? worth rebuilding or should I replace?

thanks for the help guys
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Old 10-17-2013, 08:43 PM   #2
geezer#99
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Re: Carb? Timing? fuel?

Rule of thumb!
Timing first, carb second!
What's your timing set at?
Where's your vac advance hooked to?
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Old 10-17-2013, 08:48 PM   #3
Greasemonkey327
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Re: Carb? Timing? fuel?

side of carb, im going to check timing tomorrow, also fuel was low and sucked up alot of crap. I replaced fuel filter at carb, is there one before? Its a clear filter so its definitely got fuel now. Also going to do plugs and wires. Thinking of getting cut to fit ones? taylor or msd etc... good or stay with stock? and what plugs are recommended? thanks
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Old 10-17-2013, 08:53 PM   #4
geezer#99
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Re: Carb? Timing? fuel?

'Side of carb' means what? Ported or manifold?
What's timing at?
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Old 10-17-2013, 09:00 PM   #5
GuyO
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Re: Carb? Timing? fuel?

Sounds like it is loading up so I would 1) advance timing, if that doesn't work 2) dizzy springs then if not already adjusted 3) turn the idle jets in until rough idle, then back out 1/2 to 3/4 of a turn. Its possible that off idle it is too rich.
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Old 10-17-2013, 09:12 PM   #6
Lee H
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Re: Carb? Timing? fuel?

Quote:
Originally Posted by geezer#99 View Post
Rule of thumb!
Timing first, carb second!
What's your timing set at?
Where's your vac advance hooked to?
90% of all carb problems turn out to be ignition problems. Get the ignition system dialed in, full tune-up, make sure both the mechanical & vacuum advance are working properly and coming in at the right RPMs. Then turn to the carb. Check things and come back with some readings. Lots of very smart folks here ready to help out.
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Old 10-17-2013, 09:17 PM   #7
zeldman
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Re: Carb? Timing? fuel?

Power valve?
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Old 10-17-2013, 09:23 PM   #8
hugger6933
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Re: Carb? Timing? fuel?

My first thoughts before I got through reading your post was the power valve. Didn't you say in another post that is had popped once or twice? Or was that another I am thinking of? A lot of post start to run together when you read a lot of them and try to answer a lot of them. check the power valve they are super sensitive to backfire. If that is not it then by all means do as the others are saying but that needs done anyway to have a good running truck get it in tune so it will be happier, then you will be too. Jim
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Old 10-17-2013, 11:11 PM   #9
rcazwillis
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Re: Carb? Timing? fuel?

Recently spent a lot of time chasing a bog on acceleration on a road race car. Ended up being the accelerator pump cam was the smallest available. Changed it to the middle size cam and problem went away. Holley recommends increasing the squirter size 3 up before changing cams. The stock one will be some where around 28-32. Get one 3 numbers higher. See if that solves the problem. Next solution will be accelerator pump cam.
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Old 10-18-2013, 02:23 PM   #10
Greasemonkey327
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Re: Carb? Timing? fuel?

No backfiring. Ever. Had that problem before. Can't seem to find my timing light. Guess I'll have to buy a new one. Gonna try and do tune up this weekend. Thanks for the help guys
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Old 10-18-2013, 03:15 PM   #11
GASoline71
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Re: Carb? Timing? fuel?

The Holley power valve blow out problem was fixed in the early 90's. So if the carb was built after 1994, then it has PV blowout protection already built into the base plate. I've had a couple wicked backfires at the track, and the powervalves are just fine in my 3310.

What spring is in the secondary housing? If the cam is snotty, it won't build the vacuum needed to open the stock stiff spring. So you might need to chande to a lighter one.

Gary
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I would never rebuild a 305.
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I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
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Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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