The Stovebolt Site Forums The Shop Area Engine Shop Engine Shudders?

My engine has picked a shudder whenever you apply throttle. Truck is 1/2 ton 49 with a stock 216. I've put about 700 miles on it since completing restoration and plugs, points, wires are new and carb is rebuilt. Plugs, points and timing are all ok. There is dirt in the fuel line that I am no doubt getting out of the tank. I've replaced the fuel filter several times but still picking up dirt in the filter. The truck runs almost ok but is definitely down on power. It does not smooth out as you increase throttle.

I'm thinking I've gotten dirt in the carb. Any other ideas? Thanks.

i'd still recheck the timing. also check & see if the advance mechanism is working properly ( both mechanical & vacum ). are the plug wires in the right order?
robert

hrockwell,

If it's and engine shudder..a miss, on acceleration, it is probably ignition related. The obvious conclusion would be a plug or plug wire. If the truck idles with a miss you bring in the valvetrain equation. The drill would be to do the simple igintion stuff first. LOOK at the plugs. Check the wire and cap. Someone on this site mentioned parking in a dark garage so you could see a leaking wire better...arc zappo!

The complete diagnosis would of course be a compression check, valve train inspection and timing check..with a light.

You first want to see if you can tell what system it is in, ignition or mechanical. Then see if you can pinpoint a specific cylinder.

The dirty fuel filter won't really be a factor, that's usually a run or no run situation. If you go to the tailpipe and listen while the truck is at an idle you can usually hear a miss.

When you accelerate, the ignition has to overcome increased cylinder pressures, this is why you will pick up a miss then. SOOOO, the first thing on the list is to see if the truck misses all the time, or just when you goose it.


Stuart

Have you checked the plugs since it started doing this. If the fuel mixture is rich with todays gasoline you can carbon up a plug in short time. Have you checked the point gap? Sometimes the rubbing block can wear down & cause the points not to break on some cylinders. Do you have a in line fuel filter before it gets to the fuel pump? Some dirt & water may have gotten into the carb.

These carbs are so simple that I would take it apart & clean it out. I have a 49 1/2 ton with original tank too. I have 2 of those glass filters in the fuel line. One right at the tank and one right at the carb. The one under the tank got gunked up weekly for about 2 months. Now I clean it about once a month. I still get a little bit at the carb filter which tells me some gets in the carb. I took the top off the carb & sure enough, there was some gunk in the bowl but it was running fine. So, if I have 2 filters and still getting gunk all the way to the carb then maybe you should at least take the air horn off & peek inside to see if the carb bowl is dirty. My2¢ Good Luck

If all cylinders are firing smoothly, then you have a problem with the clutch. A worn and dirty clutch will make a shuddering feeling as you accelerate, and will continue to do so at any throttle input if in really poor condition. It will seem that the power is really down also.

If you aren't really careful when you put a clutch in you can contaminate it with grease from the pilot bushing, from your hands, etc. You need to make sure to use plenty of brake cleaner/laquer thinner/etc. to make sure the surfaces are clean. If there is any bluing on the pressure plate or the flywheel, they HAVE TO BE RESURFACED otherwise the clutch will slip.

A long shot but worth looking at. I had a similar problem and after trying everything I found a crack in the flare of my vaccum line between the carb and the distributor. Put in a new line and it was cured.