I have a 250 inline 6 that is acting a little funny. The first two cylinders are not firing completly. Numbers 1 and 2 are almost fouling out compared to the last four. The plugs are gapped at .035. It has a fresh head job. The wires are good, as are the points.
How does it sound at idle? What condition is the cap, rotor and wires? Have you triple checked the firing order? Does it smoke black at idle? Have you confirmed the choke is opening completely? Just trying to get the full picture here. To check out the spark plug wires, swap the good running 5 and 6 cylinder wires, for the poor running 1 and 2 cylinders and see if the condition follows the wires. Really look at the cap closely too. If it's over 2 years old, or has some mileage on it, just change it out, they're cheap. If you change cap, change rotor too. -Chris
It sounds normal at idle. The cap, rotor, and wires are all good and fairly new. They were checked with an ohm meter the other day and seemed fine. Firing order is right, it just started acting up recently. Dosen't smoke at idle. Will blow a little if you stomp it while sitting still, but has always done this. It blows less once the motor has warmed up. It has a manual choke and it is working correctly. What I recently noticed is while driving, once it gets to a steady RPM it will start to make a fast duhduhduhduhduhduh(hope thats understandable). Once it starts this noise, you can let off of the gas or give it more gas and it will quit until it reaches a steady RPM again.
Are you running an electric or mechanical fuel pump? What's the fuel pressure like? When was the last time you were inside the carb? I almost wonder if the needle and seat are not sealing correctly and you're getting a bit of over flow washing down the throat. It's a little weird that it's only happening to 2 cylinders and they're they front cylinders at that. Usually it's the rear 2 that will run a bit richer just because the forward motion of you accelerating pushes fuel to the rear a bit more. I'd still swap around the spark plug wires. I had a TR6 that showed great on the ohms meter, but when I got it up to temp and was driving, it would miss out. All I changed was the wires and it was fixed. Really fooled me too... -Chris
It has a new mechanical fuel pump which has good pressure. It has been a little bit since I rebuilt the carb. I changed the plugs the other day thinking it might help, but alas it didn't. Changed them out and let it run for a few minutes and ended up with the same thing. That's when I started checking out the rest of the stuff. I'll go get some wires and post once I change them. Thanks
While you're at the auto parts store, grab a compression tester too. They're typically not that expensive. Post up what the cylinder readings are. I've seen poorly adjusted valves do some funky stuff... What are your valves adjusted to when cold?
If its a 250 with an integeral intake manifold they are notorious for cracking heads. Look for water in those 2 cylinders or really clean plugs with no carbon. Both the 1 barrel car motors & 2 barrel truck motors do it. If the head is bad you would be better off finding a non integeral intake head and an intake and going back with those parts
...and if it doesn't have an integral intake manifold, the gasket could be leaking on the front intake port that feeds cylinders #1 and 2.
It does not have the integrated head. My brother has a compression tester. I'll try to test it tomorrow.
I tweaked on the valves a little and it helped. It runs alot smoother but the valves still need a little tweaking. I rechecked the compression and got the following results. I'll do a little more tweaking on the valves once I get a little more free time. Before--------------After 1-90----------------114 2-98----------------122 3-110---------------120 4-112---------------122 5-117---------------116 6-115---------------112 I also figured out the carb needs to be rebuilt. I think the plunger is sticking.
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