I have these heads and I need to confirm some plug info:

Heads P/N 10088113
ZZ4 350 HO Cylinder Head
This aluminum cylinder head assembly for small-block Chevrolet V8s is ideal for street rods, fresh-water power boats, and high-performance applications. GM Performance Parts' aluminum cylinder head assembly combines the benefits of light weight, advanced design, and an affordable price. This complete head assembly includes valves, chrome silicon heavy-duty valve springs, retainers, 3/8" screw-in rocker studs-everything an enthusiast wants in a high-performance cylinder head package! GM Performance Parts aluminum cylinder head assemblies are based on brand new Corvette light alloy castings (P/N 10088113). The Corvette cylinder head's advanced design features include D-shaped exhaust ports that enhance the flow of burned gases, high-velocity intake runners that provide crisp throttle response, and centrally located spark plugs that improve combustion efficiency. Valve seat inserts for 1.94" diameter intake valves and 1.50" exhausts are installed in the 58cc combustion chambers. Raised rocker cover rails with machined sealing surfaces virtually eliminate rocker cover gasket oil leaks. This high-performance cylinder head assembly is used exclusively on High Output 5.7-liter small-block V8 engines. Unlike production Corvette cylinder heads, it is outfitted with special heavy-duty valve springs (see part number 12551483 for technical specifications). A pair of aluminum cylinder heads offers a weight savings of approximately 50 pounds over comparable cast iron cylinder heads. (A bare aluminum casting, less valves and springs, weighs 19 pounds, versus 44 pounds for a bare cast iron head). This reduction in total engine weight of 25 pounds each can improve handling, acceleration, and fuel economy.

I figured I would give the AC delco rapid fires a try. I removed autolites AP106. My concern comes from the parts gal behind the counter having some trouble working the cross reference computer thingy. Are these equivilant plugs? Also, from the limited searching I have done since last night it seem the #3's are for vortec style heads.

I would appreciate any feedback on these(compatability wise) beforeI try to install them.

Thanks!
Jason

also, I plan on using .35for a gap unless otherwise reccomended.

I always use Rapid Fire #8's (AC MR43LTS) gapped at .045.

The other option is Rapid Fire #5's (AC FR5LS) also at .045.

Thanks ZZ!

Does anyone know how to figure out the heat range ratings for the rapid fires? I am a little concerned about my compression as it is and I dont want to got too hot on the plugs!

Thanks again

#3 interchanges to:

104 Autolite
W16Y Champion
41-974 AC

If you can find a heat range chart for Autolite or Champion you might be able to get an idea.

my only experience with rapid fires is that they fire too rapidly- put them in a car of mine and even followed the application guide, and got nothing but detonation out of it. same with a friend's car.

well thats not what I wanted to hear, but I went with the #8 because thats what GM called for with the head.

ACDelco says they dont use "heat ranges" with their rapid fire plugs (customer service). But the ap106 is pretty hot according to the chart I saw. Thanks for the input and Ill throw in my .02 when it stops raining here.

Jason

Well, I've had nothing but good results in every engine I've tried them in.
graemlins/thumbsup.gif

Are the stock Vortec truck plugs the rapid fire type?

I used the Rapidfire #3 plugs in my old supercharged 93 Z28 Indy 500 Pace Car and it ran awesome with those plugs. I have Rapidfire's in my 91 SS454 pickup right now and the truck flew through emissions easily and runs great. If you have problems with pinging, it's not the plugs, it's something else with the engine.

just changing out not too very old regular AC plugs to the rapid fires in my old 94 Lumina with the DOHC 3.4 just made it rattle like crazy and lose about half the fuel economy. i used the plugs that were recommended for it, and took them out about 200 miles later and put the old plugs back in- then it ran great again. same with my Nova. same with a friend's 3.1 powered Beretta. hell, i'll use parts store cheapo Autolites or Champions that foul up and misfire right out of the box before i'll use rapidfires again.
the lesson i learned is that just because they have a tv advertising campaign and funky ribs on the electrode, doesn't mean they are better- or even any good.