89formula#1

Hey guys, I switched my car over form TBI to carburation with an HEI ignition system. I have always put plugs in it that are for an 89 firebird with a 350 motor. Now at work yesterday I got thinking and thougth to myself that in 89 all 350's were FI and had electronic ignition so i looked up plugs for a 73 camaro cause they are carbed and have HEI and the plugs were different then the one for the 89. The white insulator around the resister u can't see if u look at the plug from the side, as with the one for the 89 it sticks out the top. Now my question is to you: What is the difference here? Also I am going to put these plugs in my car and see wut happens. I'm not sure what to gap them at though so please let me know. thanks

RB83L69

That difference has nothing to do with TBI vs. carb. It's extended nose vs std nose. The "S" at the end of the A/C spark plug number means extended nose.

"HEI" stands for "High Energy Ignition". It's just GM's trademark for their electronic ignition. So, all cars with "HEI" have electronic ignition. 73 cars didn't have HEI. They had points. HEI came out in late 74, and was on all GM cars starting in 75, and up until they started using the coil pack systems. Although, for all I know, they may refer to those with their trademark of "HEI" as well, for whatever difference that makes.

The extended nose type will probably work better in your application; it usually does in street cars with modern gasoline.

Gap them the same as you always did. .035" - .040" should be fine.

None of this is going to make much difference regardless; hardly the sort of thing to devote more than about 2 or 3 consecutive neuron firings to.

F-BIRD'88

You have World S/R heads. You should be using a 5/8" hex .460" reach tapered seat plug. (commonly called peanut plugs)

U should be using a AC R42T or a AC R42TS (projected tip)
or a Champion RV10YC (projected tip) or a RV8C(non projected tip)
These are the right plugs for your street high performance application. gap them at .035"

A new set of plugs will always help.

nathan2003

hey there, like you I have also made the switch from TBI to carb and as we all know on out tbi, we had a .035 gap, now heres where i disagree with everyone else here. since i have a carb now and hei distributor i need to gap my plugs at .045.... i'm very certain that that is the correct information... so gap at .045 and i agree with fbird88 get some acdelco, R42TS plugs..





nathan vetter

Damon

Nathan's right. Any car equipped with an HEI ignition can take a plug with a .045" gap (assuming you're not running nitrous or boost). My favorite plug to use with most cast iron heads (including the S/R Torquers) is an Autolite #24. Slightly projected nose, designed for a .045" gap and it's a semi-shorty style plug that will clear most headers easily.

89formula#1

I'm runnin autolite 26's rigth now, its the plugit calls for stock and the plug they call for for a 76 camaro with a 350 witch is HEI. I don't like ACdelco's, i've had a bad experiance with them.