Stock engine still running rough

[YellowBronc]

I thought I was on the right track today in engine repair. Seems I was wrong. I may need some help in trying to diagnose the main problem.

The rundown of equipment:
1975 Bronco but to get the correct spark plugs, we had to use what was called for in a 1974. (possibly replaced engine??)
It's a 302 WITH points. two barrel carb.

This is what's been accomplished so far:

1) Replaced plugs/plug wires/dist cap/rotor/points/ and condensor. A small change but not much. Truck still hard to start and stalls when coming to a stop or going from park to drive.

2) Replaced carburetor with a new unit. Still no tremendous change. After reading about timing chains I thought I would look there. Vacuum gauge reads 12" at idle. With engine not running I can move the crank 12-13 degrees before the rotor in the distributor will turn. (checking the slack in the chain)

3) Changed the timing chain and gears. (Very loose chain. See picture) Vacuum at idle is 14" now. It does run better but still very rough. timing is set at 8 degrees BTDC. It still wants to stall when going into drive. Idle mixture screws on carb are set correctly to get the highest vacuum possible.

It really has no power from a dead start and slow to climb small hills on the highway once it's going. Appears also to have alot of blowby as the PCV can't keep up. It feels to me like a small miss somewhere. Oh, I almost forgot, total advance (vacuum and mechanical) goes to around 32 degrees

I just want to get this running better for the time being until I can get to a different engine that needs pulled out and picked up. Any other thoughts I might try.

My next thoughts are with the ignition???? Coil maybe? Distributor? Or am I beating a dead horse?

 

[67ster]

From the look of the insides , it looks like it's tonque is hanging out . Run a compression test , that should give you a better idea of what's up , sounds like the rings are worn if the PCV won't handle the blow by . A burned valve or flat cam could be causing the roughness . Is your vacuum gage steady or does it jump ?

 

[YellowBronc]

From the look of the insides , it looks like it's tonque is hanging out . Run a compression test , that should give you a better idea of what's up , sounds like the rings are worn if the PCV won't handle the blow by . A burned valve or flat cam could be causing the roughness . Is your vacuum gage steady or does it jump ?

Fairly steady. Doesn't bounce more than 1/2" either side of 14".

 

[76 explorer]

you absolutely sure you dont have any vacuume leaks? i just went through the same thing and it ended up being a freakin gasket leak....



although the motor does look like it has seens better days :-[

 

[Skuzzlebutt]

Two things:
#1, Excessive blow-by indicates worn rings &/or cylinders.

#2 Low power after everything adjustable is adjusted properly indicates worn rings &/or cylinders.

 

[70_Steve]

Do a compression test. The dry vs wet test will give an indication of the condition of the rings (PCV not keeping up). The difference between cylinders may indicate a burned valve (a small miss somewhere).

FWIW, your pic and description of your engine is exactly like my old 302, except mine had a big miss (two burned valves). I yanked it and put in a 351!

 

[wildbill]

;D ;D ;D The look's of the inside of your motor just go find a good 351W and go for it. Dont put any more money in that motor it dose no good to wip a dead horse good luck. Bill %)

 

[YellowBronc]

;D ;D ;D Dont put any more money in that motor it dose no good to wip a dead horse good luck. Bill %)

That's what I was thinking at this point. I'll do some compression checks and if they turn out bad I'll put the whip away and let it die with dignity.

 

[Rustytruck]

With it running and warmed up squirt a little water with a spray bottle on each exhaust port and see if you have a cold cylinder. its possible to have a bad component or low compresion on a cylinder. swap or change components and see if the problem moves with the swap. With such low vacuum I would run the initial timing up to 12 to 15 degrees as long as it doesnt knock. If you have a dual vacum distributer un plug the rear port closest to the cap and plug the vacuum hose. this will give you greater responce. Not knowing what emmission equipment you have if any its hard to point you in a poper direction. It looks like you have a worn out dog there but who knows. a compression test dry and then wet with oil will tell you alot more. How bad were your old plugs a picture of the ends of those will tell the story.

 

[Vasque]

Vacuum

From the look of the insides , it looks like it's tonque is hanging out . Run a compression test , that should give you a better idea of what's up , sounds like the rings are worn if the PCV won't handle the blow by . A burned valve or flat cam could be causing the roughness . Is your vacuum gage steady or does it jump ?

Can you tell me where the vacuum is that you are describing, and where it is located?

 

[mtkawboy]

Spray some Wd40 around the carb and intake gaskets. You will hear it pick up RPM when you find it. If it has an EGR valve try poping it open and letting it shut, sometimes they get carbon stuck underneath. You need to do a compression or leak down test on it too in order to determine exactly whats going on..

 

[Madgyver]

A compression test will tell you what's up and/or get you closer to solving the problems Do it dry and take reading and then do it wet by squiting some oil into the cylinders. I was having the same problem with my stock 302. I changed carbs, Went through plugs and wires and then later I found out my timing chain jumped, It was a stock replacement. It had less than 30K miles on it, so I never suspected it to be the problem.