Holley fans,

I admit it, I like Holley 8007's, like tuning them, am running one on my truck, adn what happened yesterday I woulda said COULDN"T happen, because there is no hand messing with the carb....but!

My Holley has the changes to make into a 4150. Now on an offy manifold feeding my new head (9.2CR, oversize valves) and has been feeding gas to a fine running engine. Got it settled down (per previous posts) with a 6.5 PV, 51 jets, 31 shooter. and purple spring. On a 727 in gear draws 15 inches vacuum, at no load idle, 18 - 19 inches steady.

I run til hot Friday and checked idle speed and vacuum before putting in a new seat and carpet. Put 'em in Saturday and climbed in to cruise to see what a new seat felt like. As soon as I turned on the engine I had black smoke out rear, eyes stinging and gas smell and idle rough as a cob. Vacuum wobbling from 13 to 15 at no load. Remember, perfect idle and run day before, sit overnight in garage, then this.

This is from the Holley that was running perfect before and was extremely sensitive to any tweak of the idle mix screw. I found I could turn both idle mix screws ALL THE WAY IN and the engine would still cough along and idle at 1,000. I sprayed brake clean at all seams and gaskets and found NO leaks. I made sure the choke plate was open. Fuel line is screened at inlet and has new fliter and line. Fuel pressure gage says 3 psi, but that is where it always runs. 2dary throttle plate opening was set to spec using the screw under the base of carb, and there was no backfiring, besides which I put in a PV blowout preventer kit.

Obviouly the mix is way too rich and fuel is getting in somewhere even with adjustment screws closed.! But I don't want to just pull parts randomly and miss an interrelated problem set.

What in the heck could have happened from one day to the next in an untouched carb? I think valve lash is set correctly because I set em last week hot, but could tight valves ever cause such a problem? Anyone ever hear of such a strange thing happening to a Holley? Maybe float level change...but how, sitting overnight in a garage?

Obviously I am gonna have to pull er and check it out, but if anyone has any ideas.....

THANKS
rock
'64d100

the fuel presure is a little low I run 7psi but it is on a double pumper. Try removing the neddle and seat and look for trash there may have to look through a maginfying glass. a small piece of trash there will cause that problem. TRhanks Ron Parker









It Aint Over Until I Win

Trash on the needle/seat can be fixed sometimes by reving it and covering the carb with a rag.

Did you back fire it? Maybe the PV?

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

maybe the power valve went bad. Happened to me before. OR needle/seat assy is good suggestion. Removing the side bowl level plug would help (watch for gas spilling!) maybe the float sunk... also happened to me. fuel pressure seems fine to me for a street car. Maybe (have you ran the truck without air filter?) some debris got into the idle air bleeds (the larger holes on top of the boosters) a shot of carb cleaner or compressed air may fix it (NOT with your engine running!)

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Is it an old carb or new carb? (if you had to add the PV backfire protector then you must've gotten a pre-92 carb that needed it?)
When you installed the carb you followed the factory proceedure and pulled the float sight screws and jiggled the vehicle to see if the gas level is up to the bottom of the screw hole (even after rebuilding it and setting the float per the manual).

Next question's are:

Have you tryed more PV and less shooter (31's are pretty big, red/orange or pink pump cam? and a 6.5 PV leaves a big window during the need for power/gas, unless during acceleration the vacc. needle takes a massive dip toward 4-5...).

Another question, is your manifold mated to a stock exhaust manifold/ dutra duals with an intact heat riser. Occasionally when run hard, during heat soak if not using a 'thicker' gasket, the carb bowls can cook and the gas will take the first exit (in this case the main and secondary venturies), pretty much puking most of the gas into the intake)...

Last question, was there a temp change between tuning and the morning run? Choke setting, cold engine, and massive pump shot can cause a big morning black cloud if you tuned the fire up on a warmer afternoon, warm engine tuning, etc...

???

-D.Idiot

I'd say something is stuck in the needle valve....

Simple attempt at a fix is to pinch of the fuel flow and let run until the engine starts to die, then unpinch the fuel line..... If something was stuck in the needle valve this usually flushes it out.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I vote for a bad power valve. I have had them croak/rupture and leak for no good reason too many times, especially the ones that come in the rebuild kits. I have found that buying the Holley brand you get a little better quality.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I'd say, if this were a casino:

75% on the power valve
25% on loose jets (maybe you didn't screw them tight enough and the rattle unscrewed them till they popped out)

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

80% Fload over (needle/trash)
15% Power valve
5% loose jets

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

It's too bad that in the automotive industry they don't equip our cars with fuel water separators. When I was a marine mechanic that was a must!

If we had a good unit available that would eliminate the crud making the needle and seat percentage a lower number........

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I had something similar once that turned out to be charcoal from the charcoal cannister. I started using a clear plastic fuel filter between the carb and cannister after getting a replacement cannister from the junk yard.

I could start the car but it wouldn't stay running unless it was revving up. As the revs came down it would spew black smoke!

I opened the hood and started the car with a screwdriver across the relay, then tweaked the throttle to keep it running. I had the air cleaner off so I could see what was going on and when it was running the booster was pissing gas. Could have been the PV or the needle/ seat/ float- either way the fuel pump was running the fuel metering show instead of the carb.

I took the carb (which was recently rebuilt by me ) home and rebuilt the needle and seat again with a holley trick kit. I went back to where my car was parked, stuck the carb back on, and drove for two more weeks before I even changed the fouled plugs (which actually cleaned up on the highway a little anyway)

Cost less than a tank of gas and has been trouble free ever since. Had me freaking out for a minute though. Good luck

rdr

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madam im adam

I ended up putting on of those small VW/small engine clear filters on the carb vent line so the charcoal can't come in the carb. That is certainly no fun when you get a burp from the cannister.

I still would like a nice small fuel water separator before the carb. Anybody know of any automotive style units with a spin on filter

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Exwifes Isuzu truck used to get that charcoal in the needle! Luckily it was a Hitachi carb with EZ access to it. Didn't have to tear the whole thing down.

Carquest used to sell a spin on filter the size of a PH8 filter. I used one on a Ford van for years that had holes in the top of the tank and rain water would get in. It had a petcock on the bottom I would drain every oil change. I mounted it back by the tank.

_________________
'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick