Ok I have a holley 750DP and I can't get it to lean out at idle. I changed the power valve with a 6.5 and still it is rich. It is not flooding that I can see with the cleaner off and the bowl levels are set right. I took the carb off and the idle slots were way to far open for it to idle at about 1000. I can't get to idle lower than that with out it dieing on me. I closed the slots to spec but the car wont idle like that. If I turn one of the idle mixture screw in fast it will die but if I do them alittle at a time one by one i can get them all the way in and it will still run but it will burn my eyes. Fuel pressure is 4 psi.

My set up is:

385 ci sbc
holley 750 edlebrock rpm
XE284 comp cam
186 heads ported

 

Read the holly tuning sticky at the top of the forum... That cam isn't really that big and shouldn't be causing problems, something's up.

 

Jets too rich?

A 6.5" power valve shouldnt be opening at that idle, unless the engine is just barely running.


try changing the jets, and check for vacuum leaks.

 

Jets don't affect idle.

Check for clogged air bleeds. Don't forget that even though only the primaries may be adjustable, there are idle circuits on all 4 barrels.

 

I think I might know part of the problem.....and its not good. My buddy said he saw some white smoke from my exhaust yesterday when he was following me. I have what looks like gas in my coolant but the oil looks fine so I hope its just a intake gasket. The motor is new so I hope I don't have a head gasket problem in the first 150 miles. But the smoke is diffently white he said. That is probably causeing the rich *** smell. He said it wasn't much smoke just alittle

 

I see your in Alaska, was this a cool morning you did this? Most cars have that white fog in the mornings. Was the cloud transparent or definately a solid white?

When I cracked a cylinder head in the middle of winter I pretty much whited out the entire intersection I was in hehe! Only did it in gear for some reason.... in park or neutral it'd rev like normal.

 

If it's running really rich you might see white looking smoke. Try unhooking a vacuum line on the intake and see if it improves. That Holley have plastic floats? Those are the greatest after they get old. And be sure and check the back side of the carb for problems too.

 

Yeah its like 45-55 here right now and that might have something to do with it. I am going to re-torque the heads and intake gasket just in case it might help.

The smoke is pretty transparent I would say.

 

i'd say not enough initial timing. That cam wants 22 degrees initial, 34-36 total. advance the timing at idle and you can close those slots. Don't drive it like that until you limit the mechanical advance.

 

Its at about 16 right now so I will run it foward some and limit the advance or just lock it out with zip ties and set it to 34 and see if my starter can start it that way. It should be able to it is a summit mini rated to like 12 to 1 or so.

I tightened down the intake and the white smoke seems to be gone. The screws are about at 3/4 turn out now and it is idling a lot better but it still seems a bit rich. If I take a smaller vac line off like the vac advance while it is running it doesn't seem to make a lot of difference but if I pull the brake booster off it will cut out and die. The vac gauge kind of bounces between 10 and 11 so it is hard to tune per engine vac. Could this be because of not enough timing? Could that also contribute to sub standard gas mileage?

 

I had similar problems. I fixed mine by adding a pcv valve, more initial timing, and reconnected the vacuum advance to manifold vacuum. My spark plugs stay clean and no more eyes burning.

 

without reading anything but the title im going to say blown power valve

 

The power valve has been changed and it didn't help. I am going to adjust the valves again tomorrow as well play with the timing some more. It doesn't seem rich now but I haven't checked the plugs after a little tinkering but the idle is not consistent. It is pretty rough and runs rough until about 1800 rpms or so then it smooths out. All ost like it has a mis evry 5 seconds or so, the rpms fall for a second then come back up. The idle is never smooth though. I think the timing may help and if the valves ar mis adjusted that may have something to do with it as well. The vaccum at idle jumps around more than I would like but I can't find a vaccum leak.

 

timing and valve adjustment fix those first then figure out the carb

 

Ok, so fixed the rich condition/ burn my eyes condition by opening the primaries blades so the transfer slots are just barely visible. Fixed the random idle and fluctuating vacuum my adjusting valves and fixing a massive exhaust leak.

Idles way better now but I need to make another post in the elec board because now all of a sudden I am blowing the guage fuse over and over again and I can't find the short.

Thanks for everyones help. I will follow the stick from here to get it all dialed in.

 

i starreds bloqn rhaR GAUGE FUSE TOO BUT A PNBIGEER FUSE IN AND NO MORE PROBLEMS

 

Well this was a major short it was blowing bigger fuses. A wire was pinched between the motor and trans.

I got it idling OK, not great. But now it breaks up real bad off idle all the way through the rpm rpm range. I think the jets might be too small. I have 66 in the primaries and 72 in the secondaries. I haven;t tried to drive it per the directions of the the sticky because there is obviously a problem. It was just breaking up off idle but I adjusted the squirter and I thought I had fixed it but apparently not. It has a new power valve in it. Does it sound like it is too lean? I can't really give it any timing and it is worse with the vacuum can connected. I don't know much about carbs but it sounds like it is too lean what do you guys think?

 

66/72 seems small... Think I'm running 74/82 jets in mine. Accelerator pump arms, make sure they're adjusted right. You should be able to get fuel out the squirter soon as you touch the throttle. Make sure when you're at full throttle, you still have a little travel left in the pump arm so you don't bottom out the diaphram. What do your plugs look like? Better yet, just change them and take a read off the new plugs after driving the car around.

 

yeah I think I will change the plugs tomorrow and probably just go up to the 68 primary jets and see if it gets better and what the plugs look like then. Ithink I must be way lean though because it breaks up real bad. It will rev but the rpms are all over the place any where off idle and it sounds terrible. I had 68 jets in the primaries beforeand didn't have any surging like the sticky describes so I went down a jet size to try and get the surging but now it is running terrible. Could it be a combination of the fact that the carb was set up terrible before and with the valves being misadjusted and now that the carb is set up better the jets are way too small? I mean even a 68 or 70 seems small for my combo. Am I off base completely?

 

I'd put the stock sized jets back in the carb and go from there, guessing they'd be 72/76.

 

If it isn't surging at cruise, your main jets aren't too lean. Off-idle stumble, assuming your accelerator pump is squirting properly, is from having too low a number power valve. 6.5 is stock and works for most mild set-ups, but you may benefit from a 7.5 or higher.

But, since you said it's breaking up at all RPMs, it might be too lean in the primary jets. 71/80 are stock for a 4779-6 & up.

 

Yeah I am going to have to change the power valve then. I went to 72 jets in the front (all I have right now) and its not any better. I did attempt to drive it though and the results were not good. It stumble real bad off idle but if I hold the throttle in that spot it will smooth out and drive (this is regardless of throttle amount applied). Once driving it doesn't surge or anything but if I add a lot of throttle it will bog and then just cut and pop making all kinds of nasty sounds and not going anywhere.

My question is this I guess, if the power valve is the problem would it only cause the problem when accelerating hard? I was wondering because I notice that the vacuum goes up if I increase the throttle which wouldn't even open the power valve if it was bigger, right? The accelerator pumps squirt right as the throttle moves at all.

What can I do to try and isolate the problem. I started out trying to fix a rich idle and it appears I did but it never had this problem before so here is what I adjusted:

The secondary blades opened to the trans slot is just beginning show and the primaries are making a nice square now .

I adjusted the squirter so it squirts right as throttle is applied.

Tuned the idle mixture screws until best vacuum was achieved.

Adjusted the valves and vacuum is pretty stable now (within a half or so) vacuum is about 12.5 in park. about 900 rpms or so


Does the power valve still explain my issues since it is the same size as the old one?

Thanks everyone for you time by the way

 

**************DISREGARD MY PREVIOUS STATEMENT**************


I forgot to mention I took my cap off while looking for the short and one of the pins going from to the dist to the cap backed off. It was the power wire. Pushed it back in and it revs fine now.

Now I can follow the sticky to jet it down to where it need to be once I go down and buy a few more jets.

Thanks for all the help, its kind of embarrassing but I left the last post so other that search can learn from my oversight.


90% OFF ALL CARB PROBLEMS ARE IN THE IGNITION!!!!!!

 

nice i hate searching unanswered threads... thought this was the carb from hell