Holley Issues Continue......

[Doppleganger]

I swapped a lightly used 600 (that was on a 350) in place of the under achieving 390 the truck came with. Had an issue where the rear float was dry and the idle was way high.

Got both floats set perfectly - set the idle screws.....everything topped at about 18-19 inches of vacuum. Gauge said it was all in the normal range. The screws were way out to begin with....had to turn them in about 3-4 complete turns just to start. Once those were set the idle wasn't screaming high anymore....but is also as low as it can go (idle screw).

So I take it around the block......anything over 20-25mph and it just shuts off - thats basically ANY pedal action. I toss it into neutral and restart.....keep going but 20-25 is it. Like its just at idle. ANY acceleration and it doesn't backfire or stumble - it just shuts off. When sitting in park, I can rev it and it sounds and acts fine.

No one around here knows anything about carbs anymore - probably waiting on an app for their phone. Screwballs at a nearby 'speed shop' said to bring it by and they'd try. Oooooh....actually try? Wonder what that would actually cost? I'm done with it.

 

[78C10BigTen]

Ask @Honky Kong jr , hes pretty good with holley crap

 

[bucket]

Does it just pop, sputter and die? If you romp on it from a start, does it die sooner than 20 mph?

Sounds like a lack of fuel supply.

 

[Doppleganger]

If I romp it the thing literally just shuts off - no backfire or sputter like with the 390 - just a quiet 'I'm outta here'. Its like I turned the key off.

If I ease into it....it shuts off. Thing starts on a dime now and runs nice...in park....at idle. Thats where the fun ends.

At least with the 390 I could ease into it and gradually get it up to speed. If I romped that, it would backfire and die on the spot. When I first swapped the 600 in, I could romp it (in park) and it sounded great - but stunk - was running pig rich to beat the band and had an idle (I have no tach) that I would guess was in the 1500-2000rpm range. The front float was way high and the back float was empty - lol.

 

[Matt69olds]

Do you get a squirt of fuel from the accelerator pump when the throttle moves? The slightest movement of the throttle should result in fuel from the pump squirter. You may need to adjust the pump lever.

Next, lightly sets the idle mixture screws, then turn them out 3 turns each. Start the engine, warm it up completely, then turn one idle screw out a 1/8 turn, then the other. If the engine speeds up, go back to the first screw and back it out another 1/8, keep going back and forth until the idle speed stop increasing. Reset the idle speed, go for a drive. Hopefully it runs decent.

This is assuming the ignition timing is set right

 

[C10MixMaster]

I swapped a lightly used 600 (that was on a 350) in place of the under achieving 390 the truck came with. Had an issue where the rear float was dry and the idle was way high.

Got both floats set perfectly - set the idle screws.....everything topped at about 18-19 inches of vacuum. Gauge said it was all in the normal range. The screws were way out to begin with....had to turn them in about 3-4 complete turns just to start. Once those were set the idle wasn't screaming high anymore....but is also as low as it can go (idle screw).

So I take it around the block......anything over 20-25mph and it just shuts off - thats basically ANY pedal action. I toss it into neutral and restart.....keep going but 20-25 is it. Like its just at idle. ANY acceleration and it doesn't backfire or stumble - it just shuts off. When sitting in park, I can rev it and it sounds and acts fine.

No one around here knows anything about carbs anymore - probably waiting on an app for their phone. Screwballs at a nearby 'speed shop' said to bring it by and they'd try. Oooooh....actually try? Wonder what that would actually cost? I'm done with it.

sounds like your secondary metering block has issues. did it sit for awhile before installing on the new engine? might just be gummed up. i would pull it do a quick check to make sure all fuel and air bleed passages are clear and the power valve could also be blown. turning in the idle mixture screws would have compensated for the power valve leaking.

 

[Doppleganger]

Do you get a squirt of fuel from the accelerator pump when the throttle moves? The slightest movement of the throttle should result in fuel from the pump squirter. You may need to adjust the pump lever.

Next, lightly sets the idle mixture screws, then turn them out 3 turns each. Start the engine, warm it up completely, then turn one idle screw out a 1/8 turn, then the other. If the engine speeds up, go back to the first screw and back it out another 1/8, keep going back and forth until the idle speed stop increasing. Reset the idle speed, go for a drive. Hopefully it runs decent.

This is assuming the ignition timing is set right

Timing is right on - the rest......probably not so much. Will do and report back - thanks a bunch!

sounds like your secondary metering block has issues. did it sit for awhile before installing on the new engine? might just be gummed up. i would pull it do a quick check to make sure all fuel and air bleed passages are clear and the power valve could also be blown. turning in the idle mixture screws would have compensated for the power valve leaking.

Have thought about this possibility - carb is less about a year old - fella I bought it from got it from Jegs in December '17 - pulled it last March to go FI. It was a 350 in an 86 Scottsdale.....kind of thought it'd be a plug n' play but no dice. It was pretty spotless when I got it but doesn't mean something isn't gummed or crudded up inside. Going to try what Matt69Olds says then pull the carb and dissect it if thats doesn't do it.

With no laziness intended....this is one of those things I'd love to take to a shop and pick it up when it runs good. lol I have 2 cars here that need finished and unloaded in the next 6 weeks and not alot of time to keep messing with this thing.

Should have left the 390 on it....was at least usable.

 

[Nonstop]

I might be odd man out on this, but have you checked ignition? You say it was having issues and backfiring before this. I am wondering if it is something in the distributor or coil or even a module. Just food for thought.

 

[4WDKC]

Saw this on another forum and just want to make sure, were there any spacers between the carb and intake when you did the swap? The spacer was removed and the guy didnt pay attention to the fact that he installed a squarebore carb on a spreadbore intake.

 

[Doppleganger]

Yep - there was a spacer from the last swap - its still on there. The large front vac line is capped and the small vac line (from the vac adv) is under the front where it goes now too btw. That aberration of a fuel line is how it was....only reason I stayed with a Holley. Previous owner was a total hack.

If I could just get this thing to be usable, I'd start collecting the TBI parts. Otherwise, its going on the block shortly as I need a truck.

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[bucket]

I still think it sounds like a fuel delivery issue, especially since both carbs have the same issues. I dunno, this stuff can be real difficult over the internet.

 

[Doppleganger]

I've got 2 new Carter pumps on the shelf.....was thinking about swapping one out just for shts n giggles. Also going to play with that accelerator pump some too. I dunno.

I could remove all of it and put the new Q-Jet on but thought I could get one Holley to work and get by and peddle the 'new' QJ to help fund the TBI.

 

[Nonstop]

Before you throw more parts onto it, try a couple of tests. Check your fuel level through the sight plug. Also disconnect the fuel line and place it into a container. I forget the exact numbers, but check that it is putting out enough volume and pressure.

 

[Doppleganger]

Before you throw more parts onto it, try a couple of tests. Check your fuel level through the sight plug. Also disconnect the fuel line and place it into a container. I forget the exact numbers, but check that it is putting out enough volume and pressure.

You talking the site plugs on the side when you set the float levels? There's plenty there. The previous owner (his son actually) butchered the fuel line - was a nice pre-bent piece that went from the pump to the carb. I was thinking of removing it and finding a barbed fitting to go into the side of the pump then run a new fuel hose to the carb from that.

If I had a pressure gauge I'd check what its flowing.

The 390 ran fine. Only issue was you had to ease into it at stoplights and such....if you romped it, it would backfire, stall and then you'd restart it again and go easy. But once I got going I could get it up to 55-60 no problem. Ran even better after it was run awhile.

I'll check the accelerator pump in a bit.

 

[Nonstop]

You talking the site plugs on the side when you set the float levels? There's plenty there. The previous owner (his son actually) butchered the fuel line - was a nice pre-bent piece that went from the pump to the carb. I was thinking of removing it and finding a barbed fitting to go into the side of the pump then run a new fuel hose to the carb from that.

If I had a pressure gauge I'd check what its flowing.

The 390 ran fine. Only issue was you had to ease into it at stoplights and such....if you romped it, it would backfire, stall and then you'd restart it again and go easy. But once I got going I could get it up to 55-60 no problem. Ran even better after it was run awhile.

I'll check the accelerator pump in a bit.

You do need to know pressure, but just as important is volume. That is why you do the volume test and put it in a container and measure volume.

As for sight plugs - yes, that is what I am talking about. Is the fuel level to the bottom of the plug? Does it pour out when you remove the plug? Floats might be set too high.

If that stuff checks out, check ignition. How good of a spark are you getting? Color? Signs of spark jumping? Timing advance working? Check the free stuff first.