oldfogey47

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:Any ideas?

chevymec

iTrader: (19)

What do yo know about the carb? Used it before?

mytmouz

iTrader: (2)

Try a different brand plug...

LLLosingit

iTrader: (4)

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

oldfogey47

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...

LLLosingit

iTrader: (4)

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.

biketopia

iTrader: (5)

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.

AnotherWs6

iTrader: (17)

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.

AnotherWs6

iTrader: (17)

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!!!

oldfogey47

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.

cam

iTrader: (9)

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.

oldfogey47

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...

cam

iTrader: (9)

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

timharber

.35 gap is not enough with that set up. Try .45 gap.

Tim

oldfogey47

Well, at this point, LLLosingit gets the gold star!

I rechecked the float levels and they were fine.
I then installed a new Power Valve, buttoned it up and it fired up and ran fairly well, considering I still had the black plugs in it and I know the idle mixture is off.

So, now I can put some new plugs in and hook up the vacuum gauge and see if the idle mixture adjusting will cooperate.

Thanks all...

LLLosingit

iTrader: (4)

I don't think I ever earned a gold star in school... I wasn't a good student lol

RS1979

oldfogey47

Thanks to everyone...

I've installed new plugs, gapped at .045. Added some fresh gas and it started and ran pretty good.
It still wanted to eventually stall out. I noticed the choke didn't want to open very far, so I blocked it full open with a piece of soft rubber in the linkage.

Then I started it and it ran like a champ! I could get a nice 700rpm idle and could adjust the mixture which smoothed it out. It ran at idle until I finally shut it off. YAY!!!

I think the electric choke is not working correctly. I talked to painless performance and they told me which block connector on the firewall side to use, but I'll have to check it to see if there's any juice.

Thanks again...

RS1979

AnotherWs6

iTrader: (17)

Good news. Glad you got it figured out. Carb problems are so aggravating. That's why I just buy new ones, lol.