Strange 68 200 Running sound

[dudeigota66]

I have a 68 200 that refuses to idle calmly. When i first got it, it had the holley replacement carb for the autolite but it jerked alot at idle and would shut off if i didnt give it enough gas. I have since replaced it with an autolite i had lying around and it definately calmed the jerking down but it still has a sound that makes me think it misses. It runs great for ten seconds or so then it goes poof and then idles again then goes poof a few more times. When i take off it sometimes shuts off but not commonly. I have checked it with a vacuum gauge and got a jerky reading between 21 and 19, messed with the timing and am still having these issues. What could be the problem? Spark plugs? Wires? Cap?

 

[bubba22349]

The Valves! How is the compression reading cylinder to cylinder?

 

[dudeigota66]

Would the valves cause the poof sound? I haven't checked the compression but i will as soon as i get a compression tester. What coould be wrong with the valves? Could this lead to a rebuild?

 

[Invectivus]

The car runs fine otherwise while cruising and under basic acceleration? Also, you say it shuts down from a stop sometimes, but if you put your foot into it at speed, what does it do?

Not being an expert, I'd still lean toward your autolite being gummed up, and the holly (and maybe the Autolite to a lesser extent) having a mis-adjusted float? When I get on my car from a stop, my accelerator pump kinda dribbles rather than spraying in fuel, and it dies unless I baby it. it also had an unsteady idle when i leaned out the idle screw too much, you might try backing that out a bit, see if it smooths.

 

[bubba22349]

Would the valves cause the poof sound?

Yes it could.

What coould be wrong with the valves?

If the engine sat unused for a time a valve or valves can be gummed up or dry with some rust or galled. Other things like seats not sealing, carbon build up on back of valve & steams or the valve guides are not getting enough oil. Have you had the valve cover off to check the condition of the engine inside?

Could this lead to a rebuild?

That would be hard to know with out seeing and listening to it run. So Maybe but it might only need a good clean up on the top end and make sure the valves move freely or remove head and do a valve job.

 

[dudeigota66]

Is there something I can use to clean out the valves? Something specific for these kinds of engines?

 

[bubba22349]

Nothing specific for the engine. You can try some water to decarbon the cylinder head, engine running and warmed up good slowly dribble a little water at a time down carb throat has to be running faster than an idle to keep it running. Use to do about one or two 12oz. Bottles. Have you pulled the valve cover yet? You can see a sticking valve when its running, clean the sludge out and make sure the rockers etc. are oiling some neglected engine have clogged oil passages to the top end.

 

[JackFish]

http://www.classictruckshop.com/clubs/e ... ac/uum.htm
http://www.secondchancegarage.com/public/186.cfm
http://www.international-auto.com/fiat- ... gauges.cfm

Here's some tips on reading a vacuum guage.
Maybe it's a timing issue. I'm not a points guy so someone else would have to tell you how to check that.

 

[dudeigota66]

I got some Marvel Mystery Oil and dumped a few ounces in the gas tank and on the oil. Im hoping that helps. And no i havent done any compression checks or removed the valve cover. All my stuff is at home and im in Riverside so i cant do anything on it. Im hoping the mystery oil will help. Could the carb cause something like this as well?

I installed pertronix on it when i did the engine swap. Would i tune differently for ei?

 

[bubba22349]

Could the carb cause something like this as well?

I don't think that's likely with an intermittent problem (bouncing vacuum gauge). Do you have a tach to set the carb to best idle? Than you can be sure the carb's right

 

[dudeigota66]

I don't, not with me. But as soon as i go home i will make sure everything is good.

 

[bubba22349]

Take it easy on the trip back

 

[wsa111]

Get rid of the pertronix especially if its a pertronix 11.

Hook a timing light up & see if the spark is spastic, jumping around.

If so put points back in & see what happens.

The pertronix 1 is a good unit, but the 11 is junk. Bill

 

[64 200 ranchero]

i hate petronics, mine fell apart all the time, the tape that holds the magnets togeter would melt and the magnets would fall out

 

[dudeigota66]

It is the pertronix one. And i will definately check the spark when i get back.

So far ive driven around 5000miles with the pertronix and it hasnt given me any major problems.

 

[Frankenstang]

As wsa111 and 64 200 ranchero mentioned, pertronix has been known to give some folks issues...specifically the magnets coming loose or moving around...this would throw your timing to who knows where. It sure sounds like a timing issue. Has the distributor been pulled and restabbed at some point...may have been stabbed incorrectly.

Otherwise I like Bill's idea of throwing points back in and see if that corrects the issue. I'm not familiar with the pertronix, but the issue I've heard of at least a couple times up here is exactly what 64 200 ranchero mentioned...tape that holds magnets in place comes loose....others have never had trouble with them. Switching back to points temporarily would eliminate that possibility. Good luck

 

[dudeigota66]

I have done a tune on the engine after 3000 miles of running it. I changed every filter, every plug, oil, poured in some marvel mystery oil and now im getting ready to change the transmission modulator and probably flush the tranny. Im also gonna clean up the block and tranny to make sure there are no more leaks. So far after 20 miles after the tune up and 160 miles after running the marvel oil the poof is minimal if any. I took out the plugs and found them to be a perfect brown color so things appear to be healthy. The only issue was the buildup that had accumulated in plugs three and four, it was a significant amount that looked like brown chalk, made me extremely glad i did the tune up. It runs much better than it did before and so far no more stalls or pauses.

Now to tackle the transmission and clean everything up for the headers and exhaust.

Then maybe a suspension swap and a t5, some disk brakes too. Oh and a power booster. Then the interior and a nice sound system to cruise.8)

Still gonna fine tune the ignition with a tach and im thinking about the DS2 but im not sure if the change is worth the trouble. Any opinions or experiences on this would be great.

Thanks Alot for the help guys

 

[bubba22349]

If you have the stock LOD distrib. than a DSII is worth the trouble to install.

 

[bmbm40]

Get a DSII as soon as you can.

 

[dudeigota66]

Is DS2 really that much better than Pertronix? Cause there is a local yard that has one from a 79 Fairmont Futura. The whole system is in tact too; with the box and cables but the Pertronix is working so i havent really given it that much thought. Im thinking ill go and get it. Would it a drop in swap?