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Can't figure it out...

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Old 01-11-2018, 06:35 PM   #1
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Default Can't figure it out...

OK troubleshooters...here's the challenge:
I'm trying to complete my "restoration" of a 1970 Nova, but the engine just won't cooperate.
I've had all the machine work done and the short block assembled by my favorite machine shop. I completed the engine assembly, as I've done many times before.

The problem is, the engine won't run without fuel-fouling the plugs in about 5 minutes! The carb is a 650cfm Holley with vac. secondaries and the only thing I've done to it is jetted it down (#64pri & #69sec) for altitude (5500 - 6000ft.)

Engine spes are:
.030 over 350 motor
Edelbrock dual Plane Intake
Holley 650cfm Vac 2ndarys #64 pri, #69 sec.
Accel 52000 series distributor w/Accel coil

Comp-cam & kit - Hyd flat tappet
Dur. 218 int./224exh, Lift 0.462 int./0.469 exh.
installed straight-up
Timing @ 12 degrees initial
Sealed Power pistons w/valve reliefs, approx.. 9.35:1 CR
Stock heads (487) w/ 1.94int & 1.5 ex.
AC R45TS plugs gapped at .035
Any ideas?
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Old 01-11-2018, 09:16 PM   #2
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What do yo know about the carb? Used it before?
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Old 01-11-2018, 09:53 PM   #3
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Try a different brand plug...
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Old 01-11-2018, 10:34 PM   #4
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First check your float levels and make sure your power valve is seated correctly and not blown.https://forums.holley.com/entry.php?...r-Valve-Tuning
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Old 01-11-2018, 11:08 PM   #5
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Carburetor was new out-of-the-box. I just changed the jets.
Did check float level. Pulled the bowl plug and got just enough to run out to put a damp streak down the bowl.
I'll try some other plugs...
Never have messed with the power valves in the Holleys. But I'll give it a try.

Thanks...
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Old 01-12-2018, 12:06 AM   #6
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Did it ever backfire thru the carb since you've had it?
I don't know if they make Holleys different than they did in the past but they used to blow out the power valve with a thru the carb backfire. Many people would pop them on first start because they didn't have the timing close enough on first start up.
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Old 01-12-2018, 07:41 AM   #7
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I've had holleys out the box that were not right, trash got left in the metering block some how. When it's running you don't see fuel dribbling through the ventures do you? You don't have your idle set too high where the throttle blades are open to far where you are on the main circuit and not the idle circuit? Had a carb that that's the only way it would run. Could never ever find out what was wrong with it, picked up a craigslist $150 750DP and it fired right up, idles great.

Last edited by biketopia; 01-12-2018 at 07:46 AM.
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Old 01-12-2018, 09:34 AM   #8
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I had the same carb on my mild 396 Suburban when I bought it. PO hadn't 100% finished the truck so tuning had not been done yet. Long story short - it ran like absolute S. You had to eeeeeaaasseee into the throttle. Give it even a quick quarter throttel stab and it would almost stall. If you held it in a gear and slowly let the revs build up you could then romp on it but it would initially stumble then take off. Also always smelled like gas, plugs confirmed richness. I re-searched a lot of stuff about Holley's then did what I always do......went and bought an edelbrock carb along with their internally regulated manual fuel pump. Fired right up, adjusted the idle. DONE.

I haven't tuned it (lazy, bought the kit though) and it's a bit lean which makes sense since it's a big motor with decent heads, intake a very mild cam. But I also know that it's super easy to do so because I have a couple of times in the past.They are just so much easier to work on in my opinion. I''m not looking to be a carb tuning expert and I just feel like you practically have to be if you've got a Holley that isn't right.

Also bought an FItech that I'll probably install 6 years from now. But for now that little carb is doing just fine. Edelbrocks may not be the highest HP carbs but this is the third one I've taken out of the box and had it run well. One went in a 69 Camaro with a healthy cam etc and we never even bothered to tune it. It was just **** right out of the box. Guess what that carb was replacing......??? A shitty running holley 750 double pumper with a single plane intake. Bought the carb, Perf RPM manifold and same fuel pump. Absolutely ****, the owner was thrilled. Car runs much better and is so much more responsive.
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Old 01-12-2018, 09:38 AM   #9
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Is Elbert named because it's near Mt Elbert?

I lived in Colorado when I was a kid. Went back there this summer to see some family. Mt Elbert was one of the more famous mountains out there, I was in Leadville!!!
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Old 01-12-2018, 10:15 AM   #10
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AnotherWs6...
No, this Elbert is the opposite direction, just Northeast of Colorado Springs.
Kinda rural, which is just the way I like it...

Thanks all for the info. I'm going to start with a new power valve. If that doesn't do anything, it's different carb time.
Sort of a shame to spend $370 for something that doesn't work. But, it will probably turn out to be something I did.
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Old 01-12-2018, 10:28 AM   #11
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Sounds a lot like the floats sticking. Pull the bowls off and carefully inspect, sometimes they can get burred up a bit or some flashing catches and they hang up. Power valve seated/gasket possible too. Possible needle/seat damage

Some carbs are gack, cant say why.
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Old 01-12-2018, 01:38 PM   #12
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cam:
Yeah, I have checked for floats hanging-up. They are free of any obstruction(s).
I'm going to change out the power valve in order to rule that out.

Thanks...
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Old 01-12-2018, 01:41 PM   #13
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Check for vacuum leaks. I use quick start and spray around hoses/base etc while running to see if idle changes. Coil might be weak or ign misfire. Accelerator pump isssues maybe? Linkage tweaked? Spark plugs too cold? Tons of things to check. Hope some of this helps ya
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Old 01-14-2018, 06:00 PM   #14
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.35 gap is not enough with that set up. Try .45 gap.

Tim
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