pre-ignition problems

[jeremy]

Any one have any experience with this? I have a 69 ,2000 which i pulled all the stock smog stuff off and bought a recurve kit for the distributor and timed it so its like a 67.5 pre-smog motor. anyway, It pings like crazy even with good gas. I had to really retard the timing to make it run right. But now its not as responsive. Any suggestions?

Thanks!! Jeremy

[S Allen]

The farther your timing is advanced, the more likely your engine is to ping. The higher your compression ratio is, the more likely your engine is to ping. Have you done a compression check? How did the car run with the old smog dizzy?

For a recurved dizzy, you get only 15 degrees mechanical advance so you want to set the timing to 16 degrees. Assuming the dizzy is installed correctly, set the "notched" scale in the center and adjust timing using the inverted bolt towards the engine. You can then fine adjust the timing using the scale for adjustments in case of bad gas (pinging) or altitude. (Advanced or Retarded) This is handy even if you are out on the road with no timing equipment as getting it back to the previous adjustment is fairly easy.

Did you pull the dizzy when you recurved it? You could be off a tooth and never be able to get it right. If that is the case pull the dizzy, turn the shaft one tooth width, turn the OIL PUMP SHAFT too and drop it back in. One tooth off can drive you crazy. Good luck.

Steve

[TR]

Hey Jeremy, Long time no see, hope all is well!

Assuming all of your timing is functioning correctly, it is imperative to change your carb needles in the SU's! Most people miss this step and run their motors lean. Ztherapy will have what you need.

Timing-Make sure the advance is working properly, both mechanical and vacuum. The mechanical should slide very smoothly with one finger and return without a hitch. The vacuum should also move smoothly when you suck on the tube.

Check the timing with one of the $100 lites that allow you to read the amount of advance at every RPM. Use the set screw on the carb linkage so the RPM are very steady when reading the timing. Try every 500 or 1000 RPM up to 4000.

The 15 degrees should climb smoothly to about 3800 and then level off at your max advance. Anything above 35 degrees is damaging to a motor of this vintage. I think 28 to 30 is the max desired for a roadster, but double check with whoever you got the recurve kit from.

The smog vacuum advances pull a lot more than the non smog ones. The smog 1600 gets 8 degrees, the smog 2000 gets a whopping 10 degrees. The non smog cars only got 5 degrees of vacuum advance. This means that to stay under the detonation point, you may have to set your idle closer to 12 degrees.

A cheapo or nicer electronic setup makes a huge difference and makes it really easy to set the timing. Check out the WYCROC guys for a good conversion. Get rid of those points!

See ya, TR

[SLOroadster]

My 69 (looks like a 68) 2000 didn't ping much when I pulled the smog stuff off. I have the B cam and SUs. I did get the nonsmog needles for the carbs however. A previous owner recurved the distributor before I got it. I think mine was set at 18 degrees static and would only ping a little under really hard acceleration. My block is bored .040 over, but my head is flawless. If your cam supports are shimmed than your head has been milled. If this is the case definetly do a compression check. Mine was showing 185 on three and 180 on one (I think the valves on the soft one were not quite ajusted correctly)
Will

[Guest]

Thanks for all the input!!
I'll check it out.

[Jeremy]

Oops, The guest above is me. I forgot to put my name. anyway, thanks for all the info. I never did change my jets in the SU's. I think that might be it.

Jeremy

[SLOroadster]

Jeremy,
Is your idle lean? If so try a set of "RA" needles and cut them down to .093" at the shank and .092" through the first 3/16" of the needle. You could also try a set of N25 needles, you probably won't need to shave those down. I think I was running about 18 degrees static advance. Because the "b" cam was designed for the solexs, you won't find any settings for it with SUs in the shop manual. I played with my timing and carbs for a long time before I got them to run well. I also had issues with my throttle seals leaking, causing the carbs to run a little rich. Also be sure to run premium gas. Double check to make sure your head hasn't been milled. The easy way to tell is if the cam towers have spacers under them. The bigger the spacer the less advance you can run due to a higher compression ratio.
Will

[Jeremy]

What are RA or N25 needles? I just ordered a set of pre-smog type needles for the Su's. Hope that works.

Thanks, Jeremy

[SLOroadster]

RA and N25 are different profile needles, I think the N25s are the nonsmog ones.

[Lorna c]

I know this is old but I think I need some other changes because of my switch to non smog ..needles I saw was important . I have some but don't have a clue on what's what .. should I start a new thread for this or jump into this one ??