Engine stumble while accelerating

All that junk built up on the reluctor wheel certainly contributed. The paint overspray probably doesn't help much either. If the wheel was that bad, what do those points look like?

I think the second thing I would do is get that distributor all cleaned up, REALLY cleaned up. Before you too crazy on cleaning theough make sure the shaft isn't all wobbly in it bushings. If it is relatively free of play, commence the cleaning. Then buy new points. When you go to drop it in you can not line up where the rotor was pointing. The gear is helical (curved teeth) so the rotor will turn as the dist engages the drive gear. You have to turn it one way or the other and once seated determine if you have it on the right tooth or not. Remove and turn until it is back where you want it.

If the dist shaft is loose in its bushings it needs to be rebuilt or replaced. If replacing, ditch the points. I have an almost new Buick HEI with a performance curve for sale, if you are interested PM me.

Judging from the amount of junk you cleaned out I suspect you have found the problem.

 

I'm really not sure why the picture looks so pink. There really is no overspray on the inside of the distributor. But anyway...The distributor is in really good shape, physically, and the points and condensor were new one year ago. Some of the powder built up in the points but came off easily with a dry towel.

I tried to put that distributor back in the hole about 20 times. I just couldn't get it lined up back where it was. It really doesn't matter now, I'm going to set the timing where it is. I might inquire about the HEI, I have to go through the bills first.

 

Doesn't really matter where the dist lines up. You do need to find TDC and hook wire #1 to where the rotor points though. Otherwise you might have a bugger of a time starting it to set the timing. Pull the plug from #1 cyl and slowly crank until compression blows your finger off the hole and the balancer mark is more or less at 0.

The rotor will turn what seems like a quarter revolution when it slides in. I just try to get it so the vacuum advance can points towards the right headlight. That makes it easy to grab when setting the timing, watch that fan though!

 

I got the car started and drove it around the block to warm it up. I got the timing set for now. It was pouring down rain so I couldn't get it perfect but it's okay for now. When I drove it around the block it didn't cut out so maybe cleaning up the dist. fixed it among other things.

Something else I found...the two idle mix screws were turned so far counter clock wise they were about to fall out. I couldn't get the idle set while I was adjusting timing but then I adjusted those screws it and it worked (again, it was raining pretty hard so it's not perfect).

I'll give it a test run on the way to work in the morning and report back. Wish me luck.

 

Tuesday - Set initial timing to +15 but my timing mark for 30* has warn off the balancer so I'm not sure what my total is. It stops advancing somewhere around 2500rpm though. - Still stumbles onthe freeway

Wednesday - Dropped initial timing to +12, readjusted idle speed, checked dwell which was running about 42-45*. Went to parts store and picked up new coil. Strangely the dwell dropped to 32* but I see it spike to 45 here and there.

Today (Thursday) - If I accelerate, I here popping out of the exhaust - not so much a backfire I guess. When going on the freeway it still stumbles at higher rpms like it was doing. The problem is still there. When I say stumble, I mean it happens every 15-20 seconds while driving at 65-70mph.

The parts store has points distributors for $31. Is this my next step? Also, I should mention I here a tapping sound on the driver side of the motor. It almost sounds like an exhaust leak or lifter. I started hearing it about a month ago and haven't experienced any problems.
MARK

 

Did you get that new coil in? You said the ohm tests were in spec but those readings can change when the coil gets up to operating temp. Did you install a new coil wire with the sparkplug wires? If your dwell meter works correctly and your dwell is changing as you check it looks like a problem in the distributor. If you can buy a rebuilt point dist for $31 that's a heck of a deal and if that doen't work I'll buy it off you. The tapping probably is an exhaust leak.

Dave B

 

Yes sir I did get the coil installed last night. I also installed a new coil wire with the plug wires. I won't hold you to buying the dist. after I get it but I will offer if it doesn't work.

 

sharky ...one the dwell should not spike two the dwell should be 30 if im not wrong .......i think id do what d.berry said go with a new dist ////31 dollars isa cheap fix try that and put the timing back too factory specs and see what it does////luck pete

 

why not buy a rebuilt hei from autozone for 125.00 and drop it in then no problem with setting points.and you will eliminate the distributor problem.no core charge also.my 2 cents.Ray
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575M MARANELLO

 

I need a little more than 2 cents. I can afford $31 but not $125. Especially since I just paid $24 for the coil and $41 for the wires/plugs.

 

oops sorry didnt know you spent money on plugs and wires.see if they will take them back,yah never know,tell em they dont fit. i also have 73 century that had points in it,dropped hei in it and works perfect.see yah Ray
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SICK FROM AVANDIA

 

sound like youve got a bad dist. i thought that mine had no play in it but i just couldnt get rid of this miss that my engine had all the time. it was more noticeable at speed cause i was working the motor a lot more. but after i put in my new dist it solved this miss and slight back fires that i would get sometimes. so go ahead and buy a new dist or go to your local salvage yard and by a used hei unit, even if its out of a 305 or 350 you can still use it but you have to put you old dist gear on it.

 

You can use a distributor out of a Buick 350, with a gear change. (350--14 teeth, 455--13 teeth) You can not use a distributor out of a "305 or 350" if it is a Chevy

 

Points Rule!

Don't knee jerk replace the distributor. Points are cheaper than hei modules and are probably not your problem anyway.

You really need to get a handle on your total spark advance. Too much advance at cruise will cause an intermittant surging just like you describe. First test - disconnect and plug the vacuum advance and take the car for a spin, see if it still surges.

Second test - if the car stops surging when you do the first test: Get a piece of masking tape and draw two lines 1.75" inches (one and three quarters) apart. Cut the tape at the lines and put it on the balancer with one end lining up at the timing mark. You now have a 30 degree mark. Disconnect and plug the vacuum advance, run up the engine and see how far past the tape the spark advances. You shouldn't have more than about 34 degrees total mechanical timing.

If you have more than 34 degrees of mechanical timing, check the advance stop bushing in the distributor. It's under the advance mechanism - look above the points. There's a pin and slot that limits the amount of mechanical advance. GM used plastic bushings to stop the mechanical travel. If you have all advance in by 2500 rpm like you say, and if there's not limit on the mechanical advance, and you have a stock vacuum advance diaphram you might have as much as 50 or more degrees advance under cruise.

Put a new bushing in there if needed. Otherwise, I think you're on the right track.

 

I wanted to continue giving the points distributor a try so I ordered one last night. It will be in after I get off work today. I like cheap parts!

At one time I had made the 1.75" mark on the balancer but I can't find it. I'll inspect the new distributor, drop it in then get some real numbers after I remark the balancer.
Thanks

 

Alright I picked up my points dist. on my way home from work. I'll get it installed tonight probably. I went ahead and unplugged the vac advance and plugged it. The car ran about 10 times worse. The stumbling was horrible and very embarrassing. I pulled over as soon as I could and plugged it back in. Then it took about 3 trys to get it started again. The smell was nasty too after it got running.

Pretty interesting indeed.

 

New distributor installed. This time it only took one try. I lined it up the first time. I marked the balancer and set the initial timing to 12* and the total came in at 2600 rpm but was only about 24*. I bumped the initial to the edge of the timing tab and the total was 28* at 2800 rpm. I guess maybe I need lighter springs.

I turned the points screw clockwise because it wasn't even reading on the dwell meter (it was pegged past 45*). I got it down to about 35-38* but I'll keep messing with it later. What does the points do anyway (there's your stupid question of the day)?

I took a test drive and didn't feel the miss yet. I'll try it on the freeway on Monday.
MARK

 

Are you sure you are reaading that dwell meter right? Correct dwell is 27-30 degrees. Can't believe it was even running at over 45.