WiredForStereo

Last fall, I decided to replace the head on my 85 pickup. Everything worked fantastically except bad valve guides caused some smoking. I also at the same time replaced the starter, clutch slave cylinder and put in a 5 speed tranny.

When I got the whole thing back together, there is a new problem. From about one third throttle to about two thirds throttle, the engine is worthless. Sometimes it coughs and lurches. I took it to a shop and paid $60 for the guy to tell me it was some oil residue in the rotor cap. He offered to replace the entire distributor for $400, to which I declined. Replaced the cap and rotor (or "rotor bug" as the guy called it) for $9 but the problem remained.

Replaced stock carb with Weber. No change. If anything, it's now more pronounced.

A friend car nut thought the timing was off due perhaps to a slipped tooth on the timing chain, so now I have replaced the entire front of the engine and nothing has changed.

The problem was not there before and now it won't go away. I have replaced literally everything on the engine except the short block, the distributor, the valve cover, the intake manifold and the air conditioning compressor.

One thing I did discover is that when I unhook the distributor advance vacuum hose, it doesn't make much of a difference. Idle mixture may be off.

Please help.

theBurlyone

maybe the valves aren't adjusted correctly?

WiredForStereo

Done several times since installing the new head.

85RunnerSR5

Check all of your vaccum lines. It sounds like there is no vaccum supply to your distributor, therefore the timing won't be able to advance under load. Engine RPM should change when you pull the hose off.

csharp100

Sounds like the vacuum advance on the distributor is not keeping up. Maybe it is time for a new one.

WiredForStereo

Not doubting your solutions, but the problem has been the same with two carburetors and three different vacuum hose routing solutions. I don't know why it would have changed when I put it back together. I will reinvestigate the vacuum hose and see about the distributor as well.

DAN08

I definately think you are on to something with the vacuum advance. Do you have vacuum getting to the distributor? If so possibly the advance unit itself is to blame. When in doubt re check all this little obvious things again (Fuel, spark, timing, vacuum) before going after the complicated fixes. I am always amazed at my own ability to miss the simple little fix. Good luck!

Etype R

Sounds like a vacuum leak to me, they can be easy to over look when you put everything back together.

jackwolf

"The problem that won't go away. (Hesitation, lack of power.)"

Sorry... I thought you were referring to the economy.

slisdexia

I agree with the vacuum advance. I just wonder why it seems to not be a problem at higher throttle openings

WiredForStereo

Even then, there's a definite lack of power compared to before. It's like 0 to 30% throttle is normal, 30-60 is gone, and 60-100 is like 75% horsepower of what it was before. I have to be running in the secondary to maintain highway speed which I never had to do with the old carb (when everything was working correctly) and I shouldn't have to with the Weber either.

Just to be thorough, could there be a problem with too much compression with the new head which was machined? It does currently have a tank full of premium just in case.

85RunnerSR5

I still think your vaccum advance isn't working. Check your hoses for splits, tears, looseness, and restrictions. Here's a trick I learned in college: get a can of starting fluid and lightly spray around your vaccum hoses (don't get to crazy with the spraying). If engine RPM's stay the same, then there are probably no vaccum leaks. If RPM's increase, you've got a leak.

Hope this helps.

Plumbrbob

I have had distrubutor problems that acted like that I am not a pro at rebuilding them so I got a new one and stabbed it in WHOA it was like night and day.

csharp100

From my understanding there have been problems in the past with the vacuum advance on the yota's distributors. A new Cardone reman distributor at autozone is about $98.00 with a $70 dollar core.

85 chevota

One thing you might check out is the fuel delivery, if you've got a restriction ie: collapsing fuel line, plugged filter, or even bad gas cap with the tank vent hose plugged it could give the problems your describing

camo31_10.50

okay...i gots another problem you guys might be able to help me with..

i have SORT OF the same problems this guy is having...although mine lurches and sputters when the pedal is on the floor..i have about 0%-80% then from 80%-100% i have NOTHING..its almost like it starts to die..the tach jumps around like crazy i have NO power..

we're checked vacuum hoses..didnt see anything out of the ordinary..but i'll try the starting fluid trick..

do you guys think this could be the dist.

like i said from 0%-80% seems fine..never any problems..but that last little bit makes it spit and sputter..im gonna change my fuel filter and see if it helps..if not i'll check vacuum..thanks for the help guys..

PM me if you want to that way we dont overrun this guys thread..lol

sorry about the thread jack WiredForStereo

DAN08

Forgive my ignorance, I am not to familiar with the older yota's and you have two listed in your profile. Is it Carburated or Injected? It almost sounds like an accelerator pump issue. Sounds like a lack of fuel problem to me. Check your fuel pressure.

22REw/HP

my thought is your timing is a "half tooth off' call me during business and i'll explain. 800-450.3177..............22re.com. Its a very easy and common trouble that your having and most of my novice rebuilders call w/ the same problem!!!!!!

22REw/HP

p.s. The cam timing is set by the pin in the cam not the dimple on the cam gear. the cam pin goes to 12:00 that makes the marks (dimple)on the gear @ the 11:30-45 position.

CRafferty

lol, very helpful.