Spark plug gaps...

[RyanH]

Hi. A few threads on this but all with slightly different sizes.

I have a 2.2 1970 911T with stock Webers and original engine configuration. Plugs are from PP and are as per recommendation. Right now I can't recall what they were? What should the gap size be?

Going through all the usual suspects for back firing, carb popping/spitting etc.

I recently seen a thread on the forum where the 55 idle jets were replaced with 65, any feedback on this?

Thanks guys...

[Rich Gas]

as far as gaps with stock config .028-.035. They usually come pregapped at .028. I have an 84 stock everything with new wires,coil,cap, rotor and the previous owners mech was running .044. If you have better ignition bits you can run wider for various reasons. Not an expert on this topic.

[tirwin]

I don't think there is a one-size-fits-all answer. It depends on your ignition system, plugs, plug wires, gas octane, rich/lean, etc.

A general rule of thumb is to start at recommended .028" and increase in .005" increments until problems appear and then reduce back down.

[kach22i]

Originally Posted by tirwin

I don't think there is a one-size-fits-all answer. It depends on your ignition system, plugs, plug wires, gas octane, rich/lean, etc.

A general rule of thumb is to start at recommended .028" and increase in .005" increments until problems appear and then reduce back down.

Good answer.

[Peter Zimmermann]

Webers on a 1970 T? That means that we're discussing a Euro/RoW model, correct? OK, here's what I learned over many years in the trenches, if you have a Bosch CD ignition and NGK BP7ES plugs, gap them to .032". If you have Bosch W225 T30/W5DC/WR5DCs, gap them at .030". DO NOT use Platinum plugs for your application. Also, there are miss-prints in a number of tech manuals regarding plug gaps, so be careful with your info.

Do not go to 65 idle fuel jets - stay with the 55s. That said, carb popping/backfires are usually caused by; (1) miss-adjustment, or (2) dirt/debris stuck in an idle jet. To check that, clean the area around all six idle jet carriers - use a good aerosol parts cleaner and a new/clean, small, parts brush. Then, one at a time, remove each jet carrier. Do this with clean hands/maybe latex gloves, and have a place on a nearby tool tray or workbench that is as clean as you can get it.

Examine the tip of the jet for dirt. If it looks clean, pull it loose from its carrier and hold it up to a light source and be sure that you can see through it. If it's clean put it back together and re-install it. Repeat with the other five jets.

BTW; before doing any of the above, be sure your ignition point dwell angle and ignition timing are set to factory specs!

Next step, adjustment. Let us know what you find. BTW; NEVER use a cloth rag to wipe carb jets! The chance of getting a piece of fuzz lodged in the jet are great; always use a puff of compressed air to do clean-up work. If you find a stubborn piece of dirt, very carefully use a small OD wire to dislodge the crud. Take great care to not scratch the jet orifice!

[RyanH]

Great advice....

I just pulled all the plugs and they are healthy looking, checked for 0.028 and all ok so I might increase to recommended Pete.

I'll cancel the idea of increasing the idles!

Going through dwell and timing again then will have another go at carbs...

Time and patience?

[RyanH]

Pete, what is a Euro/RoW model?? I don't have the history but I know it came from the States to me here in Australia. What would I be looking for to confirm model? Cheers...

[cdagnolo]

Ryan, I believe he's referring to Europe / Rest Of World. This pretty much means a non US spec car iirc.