spark not advancing

[jmjohnson]

I have an old (64') GM 120 4 cyl that idles ok but will backfire at full power. I have replaced/installed wires, cap, plugs, rotor, electronic conversion, filter, rebuilt carb. I checked the timing @ 500 rpms but I don't know what scale the lines are. I have a zero and six lines on the advance side, but no other numbers, just an A. Is each line a degree? Or two,three? It seems to run better when it is a little ways off the chart on the advance side. The book says it should be set at 6 btdc. Plus, The spark does not advance at higher RPMs, I even cleaned up the weights, the springs look ok. The rotor will spring when twisted one way. I don't have a timing light with advance. Any ideas why spark is not advancing.

 

[Haut Medoc]

Re: spark not advancing

Welcome to iboats 2* per line...<br />Do not run it advanced that way or you will cause detonation & burn holes in your pistons....<br />It may sound like it is running better, but it isn't....<br />If you don't have a timing light with advance, get one & verify .....<br />Is this problem new or did it occur after the conversion.....<br />If it is not advancing then the problem is the dist. or the upgrade....<br />Did it run OK on points?

 

[jmjohnson]

Re: spark not advancing

I still had the backfire problem with the points that why I tried the electronic conversion. I plan on setting it at 6 btdc like the book says but I still don't know if each line is one or two degrees. I'm assuming that the timing should advance as the rpms go up and you should see that without the advance timing light, right? If the distributer is bad would I have to replace the whole thing? The distributor shaft does have some up and down play if you pull on the rotor.

 

[Haut Medoc]

Re: spark not advancing

Backfire through the carb is never a good symptom.....<br />I would do a vacuum test & a compression test for starters to check the condition of the valve train....<br />Yes, you should see advance without an advance timing light, but to just eyeball the curve is impossible....<br />Distributers are rebuildable, but it would be easier to get a new one if you have no experience working on them...<br />Did you lube the weights & springs at all? <br />Not with WD 40, but a true lubricant?<br />They may be sticky even if they don't feel stuck...<br />2 degrees per notch is correct, BTW....JK

 

[KaGee]

Re: spark not advancing

When I was refurbing my engine, I took the distributor out and removed the plate. The weights were all corroded and only moved when forced with a screwdriver.<br /><br />After disassembly and a detailed cleaning with an anti corrosive cleaner, I let the components sit in a oil bath. I reassembled and used an anti corrosive lubricant. Inspection a year later and everthing was as I left it... clean and working pretty! Advance works as it should.

 

[jmjohnson]

Re: spark not advancing

I lubed up the weights and reassembled and retimed it. Advance is now working and no more backfire. Thanks for the help