NGK vs. AC Delco spark plugs

[70 Forest Green Zee]

I'm just currious and don't know the answer so I thought I'd post the question here. I've always used AC Delco plugs in my 70 Z28 with the stock LT1 engine. I've heard so much good about NGK plugs that I decided to try a set. My question is this....the electrode on the NGK is substantually longer than the AC Delco plug....will this cause any problems? The pictures below are an AC Delco R43, and an NGK XR5 V Power both of which are the correct plug for my application. Your knowledge is greatly appriciated!

[John Brown]

The XR5 looks more like a R43S than a R43. On a Z28 the tip of the plug might touch the piston, if you still have domed pistons. You might want to see if you can cross reference the R43 plug and see if it crosses to something other than the extended tip XR5. Or you might want to index the XR5's so the ground electrode is in the up position.

[Salvatore]

I run R44S in my 69 Z and have no problems. You will know if they hit. The electrode will be closed. Is there an NGK chart I can use to cross reference AC Delco plugs to? Thanks, Sam

[Mr. Chevy]

I think you will be fine. What I would do if you really want to be sure is put one in, disconnect the main coil wire so the car won't start and crank the engine over once. Pull the NGK plug out and check the electrode. If it does hit it shouldn't damage the piston like it would if you fired it up and ran it at a much greater rpm at idle..

I did this with my car just for my own peace of mind when I switched to the NGKs. They are great plugs and you will notice a world of difference..

Rich

[Mr70]

Sam,does THIS help?

[JimL78]

I always ran AC 43N sparkplugs in my L78. I couldn't find them when I went to get my car last year so I put the equivalent Autolights in it. Thought that was sacrilegious putting Ford plugs in a Chevrolet. Over the winter I found some NGK plugs that look identical to the 43N. They are B7ES. The heat range seven doesn't have the projected tip like the fives do. Maybe you could use the seven heat range in the shorter plug and it will match up to the old ACs.
Jim

[YENKO DEUCE REGISTRY]

My XR5's don't hit the pistons, and they work great!!

[@wot]

The pics you posted show two different types of plugs, one is a projected nose, the other is not. If you don't want a projected nose, and can't find a NGK "normal" cross reference, go to a racing plug if you can find the right heat range. I use a cold NGK racing plug in my L78, and they work fine. They are a .460 reach.

[70 Forest Green Zee]

Update to this whole story...I put in the NGK XR5's and they run great...after Marlin's post I wasn't too worried because he has the same engine in his Deuce as I have in my 70 Z28. Bottom line, so far from how the car runs with the NGK's, I like um!

[njsteve]

Those NGKs are great. I switched out the hemi and the 455HO to NGKs from Autolites and it was a noticeable difference.

Listen for yourself:

455HO with Autolites:




455HO with NGKs: