Spark plug gap confusion, 502MPI
 

The engine plate says the MR43T plug gap is .035 but tune up info for this 1997 502MPI mag says .040 so what is right??????
The new plugs came gapped at .040. I know there are updates and new releases on information with all kinds of equipment after mfg so I wonder if there is an update where this set up is supposed to go to .040?? Anyone have current info or knowledge of why the engine plate and the tune up info say different numbers?

Also, if I change to .040 then I will have to adjust timing for the different gap I guess. What is the procedure for setting timing on this engine?
TIA

no timing change, gap to .035 and go have fun

or .040.nobody will know that they are gapped at .040 except you.

whats 5 thou among friends, unless were talking bearings, lifter bores ect...........lol

DO I NEED TO SET THE GAP WHEN INSTALLING A NEW SET OF PLUGS?
A: Maybe. A spark plug part number might fit hundreds of different engines from many different manufacturers. Although the NGK factory will set the gap to a preselected setting, this may not be the right gap for your particular engine. The incorrect plug gap for your engine can contribute to a high rate of misfires, loss of power, plug fouling, poor fuel economy and accelerated plug wear. It is always best to check the gap against the manufacturer's specifications. If adjusting the gap on fine wire or precious metal plugs such as platinum or iridium, be very careful not to apply any pressure or prying force to the fine wire center electrode or insulator as they can be damaged. The gap should be adjusted by only moving the ground electrode.

Another consideration that should be taken into account is the extent of any modifications that you may have made to the engine. As an example, when you raise compression or add forced induction (a turbo system, nitrous or supercharger kit) you must reduce the gap (about .004" for every 50 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology) you can open the gap from .002-.005".

If you have any questions, please contact the NGK Spark Plugs Tech Staff:
Tech Support - Click here

The manufacturer of your vehicle, the company that produced the aftermarket products you've used and/or your service technician are all additional sources of gapping information if you've modified your vehicle.

.035 just buys you more time before misfire. LOL.

I set up all normal Chevy V8's with regular Delco plugs at .035" because that is what works for me.

ac delco plugs MUST be gaped at .0375 or they will misfire,lol.

What ? Me no comprendo. Or are you joking around too ?

haha.

Just make sure there is a gap. They don't fire well when you drop a plug and the gap closes.