Is anyone using these plugs in a n/a engine? The speed shop i got my heads from suggested them but they seem too cold.
gw350 stock bottom, 190cc al. heads, holley 600, msd ignition, comp xe274

How far should the plugs stick into the heads? I ran them into the heads and they stick a little less than a 1/4 inch into the chamber.

thanks for any info.

 

I won't put anything but Delco plugs in my car. Too many years trying to diag some idiot's car only to find out a shop put in the wrong spark plug.

You can do it any way you prefer but at a minimum you should measure how deep the spark plug came into the old cyl heads by using a straight edge across the head and a very good Ruler and compare the same measurement with the new heads . If the plugs dont come in further than they did on the old heads you're safe

 

hooga, do you have a cross reference to a delco plug? I can't compare that heat range off the top of my head unless it's a delco P/N.

FWIW, I went from an LG4, to my new hot 350, 10:1 iron heads (416's), and went 3 heat ranges colder, with a non extended tip.

 

Thanks for the replys. I'll measure the depth when i get them off today.

There is no cross reference for an ac plug. I looked thru autolites website and couldn't find one for that particular plug. I guess i will just have to pull one after running them for a while and see if they are fouling.

 

The Autolite 3933 plug is from their racing series of plugs. Has a copper core and a cut back electrode. Is a gasket seat, 3/4" reach (the threaded portion), and 5/8" hex.

When inserted into the chamber the end of the threads should be flush with the chamber surface.

For some data points I use the standard Autolite 3924 plug. This is in an aluminum head. the stock plug for the Corvette's with aluminum heads is the 3926. What is a hotter plug then the 3924.

RBob.