Ignition Troubles

[Daniel Griggs]

This is my first post, so please bear with me. I seem to be up a gainst the wall with some ignition problems. Here is the presenting problem: the engine will not rev past about 4000 rpm, the timing just can not be set right, if the timing is advanced, it will rev a bit higher but detonation then becomes a problem, it the timing is retarded the engine just will not rev past 4k but the detonation stops. Bear in mind, this engine is just a tired 240 with an E88 head. Not a high compression/highly stressed monster.

I have checked the following: checked for leak down of the vac advance diaphragm, checked for any obstruction or binding of the moving parts in the distributer- none found.

I have reached the end of my own mechanical abilities. Any further input would be great. Should I just grow a set and buy a cool new billet distributer?

[Bambikiller240]

Set the timeing to the factory spec, then try adjusting your carbs.

When I rebuilt my engine last year I had similar problems. It turned out to be that the carbs were out of adjustment and could not supply the rebuilt engine's needs. A quick tune of the SU's and the problem went away.

[Daniel Griggs]

Thanks for the info bambikiller. As it turns out I have the dreaded low rent DGV carbs. Why somebody would put these on a 72 is beyond me. They came with the car. These carbs have been professionaly rebuilt, the tank has been cleaned and reconditioned, new seamless fuel line installed, as well as two new filters. (one at the tank and one before the new fuel pump) For what it is worth, the valves have also been adjusted per factory specs in the Haynes book. This all ran great all the way PAST redline about a month ago. Are there any other diagnosis tricks I could try for fuel delivery vs. ignition problem(s).

[Daniel]

Are the chokes turning all the way off?

[Daniel Griggs]

The chokes on the Webber DGVs are working just fine. Silky smooth action

[beandip]

How are the filters? could be starving for air or fuel. I think I would look at the air filters first. Try a run without any and see if this helps , One shot wont hurt anything unless you are running on a dirt road.

[Daniel Griggs]

I did a good 'ole flashllight inspection of both filters. (clear plastic) No trash was found.

[SledZ]

I have had that problem and it was because my points were slowly closing. I must not have gotten them tight enough when I replaced them.

[Daniel Griggs]

There are no points in the dist. I have a preteronix electronic ignition module. Is it possible that there could be a mechanical failure in the 32 year old distributer that would prevent it from advancing the timing enough through the rev cycle? (idle to redline)

[Bambikiller240]

Yes, it certainly is possible. You would need to disassemble the distributor to confirm. The vac advance plate is actually two plates with ball bearings sandwiche in between. Need to remobe advance diaphram and pull the advance plate to see if the balls are gone, or it is bound up by dried out grease.