Hello all,

I've been gifted a 1976 d100 with a 225 and three on the tree. Ahh another project....

I've gotten it running albeit very roughly. It has the Holley carb and a bunch of ignition parts were replaced by a previous owner. I rebuilt the carb with a walker kit and installed new spark plugs.

I'm looking for wisdom on diagnosing what's the issue. It is a remanufactured carb and from reading posts here it seems remanufactured carbs are always suspect. My hunch though, is there's an ignition is as it stumbles terribly at idle and wont idle below 1700rpm. It clears up and runs smoother at 2000rpm but is low on power even at higher rpms. With a timing light on it, it idles best with the distributer at maximum retard. Seems counterintuitive to me.

Also has anyone changed a throw out bearing on this trans? How easy? Is the trans pretty light? Its screaming and definitely needs to be replaced

Thanks !

Jeff

Just a WAG, but sounds like the timing chain may have jumped.

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Ahh yes! That would make sense to the symptoms. Is it possible to confirm that without taking the timing cover off? Turning the engine to TDC and checking the distributor rotor would help but couldnt also the distributor rotor be off a few teeth?

Personally, I'd check all the easier stuff before you start worrying about cam timing. If you haven't checked the valve lash yet, checking and adjusting it to 0.010" intake and 0.020" exhaust (when hot) is generally a good first step when tuning up. Valve lash being too loose or too tight can cause all manner of problems.

Poor idle could also be a vacuum leak. You might want to check around with a can of starting fluid with the engine running. The throttle shaft bores on the carb could be worn out. Could also be a clog in the idle circuit if you didn't get the carb body cleaned out well enough during the rebuild. There's a really good post from SlantSixDan explaining to me how to flush crap out of this exact carb while running, which I can dig up if you want.

Low power at higher RPMs could be a different issue. I don't have any great suggestions, but I'll note that aftermarket caps and rotors are unfortunately a really mixed bag these days, so being new doesn't necessarily mean they're any good.

How much ignition retard are you seeing with the distributor adjusted all the way back? I'd verify the TDC mark on the balancer is correct with a piston stop tool, so you know your ignition timing is what you think it is. The outer ring can slip if the rubber is deteriorated enough. If the mark is off, you can make a new TDC mark until you get around to replacing the balancer.

If you really need to check the cam timing, you should be able to do it without pulling the timing cover. Once you've verified true TDC on the balancer (or made a new mark), you can check cam timing by removing the belt, bolting up a cam timing wheel, pulling the valve cover, and checking the #1 intake centerline with a dial gauge. It's a pain in the ass to rig up, but since all you care about is timing you don't need to worry about the exact lift numbers and don't need to pull the rocker shaft.

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Thanks for the suggestions.

I've checked for vacuum leaks and there don't seem to be any. I came from the motorcycle world so I was very cautious to clean out the idle circuits in the carb...I used an ultrasonic cleaner.

Using the timing light and having the vacuum advanced plugged...it maxed out at about 25 degrees btdc which is where it idled the best. And obviously this is assuming the timing indicator on the crank is correct.

I've been holding out on checking the valves as my back has been hurting but that also seems to be a possibility as it really feels like either one or more cylinders are missing or not firing at idle. If my back is up for it Ill do the valves tomorrow.

Vote # 2 on checking / adjusting the valve clearances. (lash)
That is always the first thing I do when tuning-up a solid lifter engine.
DD

Good call on the valve lash!

Since the truck wouldnt idle I had to set cold lash and man were they bad. Probably 3 cylinders had no lash on either or both valves. Yikes! I did a compression test afterwards and all cylinders were in a 115 to 135 range. I know that no lash is bad for the lifters and cams so perhaps theres some damage there? The rocker cover was really stuck on there which makes me wonder if the lash hadnt been checked for a long time. Also no lash can burn exhaust valves right?

I checked the crank timing mark to TDC on cylinder 1 and that was spot on. The rotor on the distributor had quite a bit of back and forth play. Perhaps 10 degrees, Is this normal?

Feels good to be narrowing down the issues. Now just to let my back recoup and get it running....literally its sometime easier for me to climb into the engine bay to work on the little 225 in the big d100!!

D

Could they have put the spark plug wires in the wrong places on the distributor cap? Advanced the timing so to speak by 1 cylinder off, then having to compensate with full distributor rotation. You also mention that it runs poorly with no power at higher rpms? Would this not be indicative of cylinder wall taper? With engine cold and checking compression at slow rpm, the rings can accommodate, but at high rpms the rings can't compensate fast enough, causing low compression at high rpms.

Hey, you said you this truck was gifted to you, I wouldn't call the issue "woes" now.
How many miles showing? Know anything about past maintenance on it? Is this running issue, the reason the past owner gave it up? Did they do anything to try and fix the issue? If so I'd be retracing their steps. (Thought of that due to above comment about"plug wires 1 position off" above)

And remember/ these days "new" parts does not mean "good" parts!!!

Yeah by gifting it was more like unloading it on me as he had to get rid of it. He had it for a few years and never did anything with it as the prior owner to him was a "mechanic that knew nothing" according to him. Its too bad it sat for so long outside as it was in super good shape and now has some surface rust.

So after looking more into the sloppy distributor rotor...it was sloppier than I remembered and would not return. Pulling it out revealed a big chunk of the gear missing. So now I've got a gear on order.

Im hoping that with the valves adjusted and a new distributor gear that it'll solve the main issues and just leave some carb tuning.

I have a 78 with a three on the tree as well. Bearing was easy peasy, but if you are going that far go ahead and change the clutch and pressure plate as well. Drop the driveshaft pull trans out and down. Fairly easy to do but even easier with two people. Just remember this. The bell housing won’t come off first if you need to take it out. Drop the clutch and flywheel first if you need to to. Don’t ask how I found out out

Make sure to read on this forum how to properly install the dizzy gear. I'm sorry I don't have the link to point to, but someone may chime in on it.

Brian

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