off idle bog.. stumped

[DJs74]

yea it was 15in steady on the vacuum. i tired to day and capped the pcv port and didnt change anything. as far as i know the motor internally is stock. ive tried with this new pertronix dizzy at 8 9 10 and 11 deg of timing and didnt change anything either. i looked for a vac leak but could not find one. should i try more timing than 11? ive also played with the idle screws. starting at about 3/4 and working my way out and still nada.

My original suggested vacuum range of 15 - 20+ was based on unknown internals like camshaft, etc. For a stock engine with a 4 bbl intake added - I agree the vacuum should be right around 18 - 22 inches (easily).
Is there any way you can borrow or might have access to another carburetor to try? Basically process of elimination... I wish you were closer, I have 3 extra here you could try.
If you cannot adjust the bogging out with carburetor changes and timing changes - I really suspect an internal vacuum leak with the intake. These intakes (especially BBFs) are very picky about the torque sequence and values. If the intake is not toruqed down properly, you can potentially have a vacuum leak between cylinders and not necessarily a vacuum leak to the outside world -thus, the carburetor spray is of no value because the intake is actually sealed off externally.
The air / fuel mixture screws should be somewhere between 1.5 - 2.5 turns out as a starting point & general rule of thumb. Once you unscrew them to a certain point, there is no longer any change because the screw is not restricting the port at all.
If possible, try to use a vacuum gauge while adjusting the screws - your are looking for max vacuum at idle. Also, try to keep the screw adjustments equal between both sides and try 1/4 turn at a time adjustments.


DJs74

 

[77bronk]

yea i tried to adjust them at idle. and stayed around 15-15.5 after adjustment. just tried the black cam with a 35 squiter nada. then the black cam with a 31 squiter... nada. im done all i can. think its time to call in a professional which i hate to do.

 

[carmi]

Had a similar problem with bogging from idle, almost to the point of killing the engine, that was caused from worn spark plugs that were gapped at .068. Evidently even with an MSD box that is too much (lol). Unlike yours, mine was hard starting sometimes (not consistent). It would also buck occasionally while driving. Felt pretty silly after I located the problem but I spent weeks rebuilding the carb, putting in a new fuel pump, adjusting jetting, and the accelerator pump before I finally figured it out. As others have stated I would definately spray brake clean or carb cleaner to search for potential vacuum leaks but I would not rule out the ignition. Would be quick to check the plugs. I was fortunate to have another carb to put on and try out and the same problem existed with both so I was able to rule that out as the culprit.

 

[77bronk]

think i might start looking for a new carb..

what do yall run? or advise i should get? holley or edlebrock or something else? which size and model?

 

[Lmfp]

i have a street avenger 670 on my 351w. I like it though i don't go rock crawling with it. hasn't stalled on me in the stuff i do play in (mud riding and playing in some sand pits). i believe they have a 470 also.

 

[77bronk]

was it a bolt on and go with the stock jets in the box? or was tinkering involved? i have the edelbrock performer intake aswell.

 

[ugly74]

Is there any play at all between the accelerator pump arm, and the adjustment screw?

 

[77bronk]

negative.. adjusted per spec. then i even tired little loose way loose and little tight and way tight. nada. this sucker is going in the trash and a new one is getting ordered. im done fooling with it. i want to go drive this dang thing further than down my block!!!

 

[DJs74]

think i might start looking for a new carb..

what do yall run? or advise i should get? holley or edlebrock or something else? which size and model?

Carburetor suggestions:
If your motor is basically stock, try to stay with lower CFM's in the 450 - 600 range (600 being a max)
I swear by Holley but I'm sure others will give you their preferred brands. My suggestions would be a 470 CFM truck avenger / 450 CFM 4160 / 570 street avenger.
If you have an automatic, make sure you specify "kickdown" linkage

Good luck,

DJs74

 

[Lmfp]

I actually had to put bigger jets on my 670. It was running lean out of the box for me. I think i might have when up 2 jet sizes on my primaries and about the same on my secondaries but its been a lil bit since i did that so i don't remember exactly. Runs really strong. heck i let it sit for a couple months pumped the gas once and fired almost immediately.

 

[Lmfp]

I looked up my orders and i ended up with the 70 main jet and i think a 72 secondary. I also have a mild cam with aluminum heads and eddy performer rpm intake makes it a lil more thirsty i guess.

 

[77bronk]

Welp after multiple calls to holley. Two of my ford buddies trying to solve the problem. And new ignition system . Fuel system and rebuilt carb twice. I said screw it and bought a new edelbrock carb. Bolted it on hooked the fuel and linkage up and fired right up and runs great no more bog . Idle great and has great throttle response. And I didn't touch any adjustment on the carb just bolt on greatness! I can finally drive my bronco further than around the block. Anyone want a junk holley lol

 

[broncnaz]

Glad your running better. Of course now your one of the bolt on and it runs better people. I can guarantee that carb could be a lot better than it is currently. But as like so many others they bolt on stuff and if it works they are happy little do they know its still far from ideal. Hope you dont plan to go offroad edelbrocks are pretty finicky on hills. As for the Holley Send it my way

 

[77bronk]

im sure ill tinker with it a bit and see what i can get out of it.. but im just so happy now its finally running right.. i dont plan on doing much off roading, maybe a mud pit or 2. nothing too extreme, shes going to be more of a weekend cruiser.