The Stovebolt Site Forums The Shop Area Engine Shop Poor performance

I have a 235 6 with rodchester 1bbl engine is freshly rebuilt new plugs ,wires ,points condenser, cap, etc. Valves adjusted with engine at operating temp at 6 and 16. Timing is set correctly, compression 150 or close on all cyls vacuum steady at 18.

It idles perfect problem is it will not run at speed > 1400 or so RPM. It sputters and backfires when you push it. It will get RPMs up if I pump the throttle otherwise just sputters. Just put a rebuild kit in carb and float adjusted to specs..

Any ideas??

Timing? Advance not working?

Fuel pump not putting out enough volume?

Perhaps! How much movement is there supposed to be with the vacuum advance? The fuel pump is new.

Sounds like a problem w/the carbs accelerator circuit. 1st check is to make sure the short linkage that connects the plunger to the throttle lever is connected. Thats a very small clip that holds it on and they can pop off after a fresh rebuild (BTDT)

Naw accelerater circit is attached and I can observe it spraying fuel.

I can't remember if the Model B has a power valve or not. If it does, that could be the problem. But if you carefully followed all the rebuild instructions, the carb is probably not the problem.

Yes has power valve but I think Everything was put back correctly.

Had a similar problem years ago. Turned out the new points I installed had very weak spring tension. The engine would idle perfectly but as soon as I accelerated points would " float " causing performance like you describe.

Definitely the vacuum advance not functioning part is ordered.

Thanks for your help.

Replaced the vacuum advance and it was a little better but still wont run at RPM. Sent the carb in and we will see what happens when it get back.

Are you sure you don't have a couple of plug wires crossed? (CW 1,5,3,6,2,4). Hope this helps. HAPPY HOLIDAYS!

Points and condenser?

I think that you need to make sure that the points you installed have both of the straps/springs installed. As mentioned before with only one spring the points bounce and it won't run other than at idle.

Great job guys, another problem solved!

I used to have a sputtering issue with my 292 and it ended up being a vacuum leak in the carb...would idle fine, but when you'd hammer on it, it would sputter and sometimes die.

Put the new carburetor on it still runs poorly at RPM misses badly. Any other ideas would be welcome ???

Have you checked your compression? Also sometimes if the timing is set wrong it can cause issues like that. Also check you intake ports for vacuum leaks...while the engine is idling cold spray some carb cleaner in the intake ports( DON'T spray it on the exhaust ports) and if the engine stalls...vacuum leak. Hope you figure out the problem soon.

Some points sets come with a removable strap/spring. If this is left of the points will float when the RPM's are increased.

Compression 150 or close in all 6 . Vacuum 18 with no fluctuation guess I will re check all the timing stuff. Points look OK.

Are you sure the vacuum stays at 18(which is a little low)at higher RPM's? You may have a plugged exhaust system. Those mice can be tricky.
I would also be sure the dwell stays steady with RPM's, I'm still not ruling that out.

I remember an incident from many years ago, where I took a dune buggy with a turbo charged Corvair engine to the sand drags. Got smoked by a mildly rodded VW. My buggy ran great setting at the line but when I showered down on the accelerator peddle it developed a bad miss and had no power. Got back to the pits and pulled out my dwell meter and found the points had somehow closed up. Readjusted them using the dwell meter and it ran great the rest of the day. Just a thought!

as the points close up, for every degree of dwell increase, the crankshaft timing is retarded two degrees.
Jerry

Turns out that it was a weak spring on the points. It runs absolutely perfect now. Damage done? Lost the patina on the carb! Sure fun finding the problem though.

Thanks for your all's help.

Will try and post pic later on when it looks a little better.

Almost a month.

Just over a month!

Oh! Forgot to post answer to problem. The point tension was not stiff enough replaced points again and it ran great.