i have been thinking about changing the plugs in my car for a couple of weeks now, but i dont know what ones are the best. these are the plugs that i have looked at

split fire platnum
ac delce rapidfire
bosch platnum +4
accel plugs

which of these plugs is going to make the best difference in my car and why? i have an 85 iroc with a 350, but i dont know were the enging came out of. it might be from an older truck.

I like the Bosch +4 because they expose the spark to the fuel better. They sure cost a lot! I put them in my S-10 (with '94 3.4 SFI Camaro engine). It was eating a set of plugs every 18000 miles. I haven't had them in long enough to see how they are holding up. With 4 electrodes they have to last longer.

------------------
'69 RS/SS396 pro street
427/4spd/9"

For one racing season, I tried different types of spark plugs every couple of weeks trying to find that magic combination that would make my car fly. I tried NGK, Bosch Platinum, Champion, Rapid Fires, and found that none of them made any improvement over the cheapo AC Delco's for my application. I did find that playing with the spark gap did make quite a bit of difference in performance. Anyways, I still use the cheap AC Delco's and have good luck with them.

I'am with Bravewink on this one, good ol' AC's have been my favorite.

------------------
My '68 Camaro (http://hometown.aol.com/Dougs68Camaro/index.html)
Doug G.
68 Camaro
406 ci.

My favorites have always been the ac rapidfires because I've always fouled the other ones quick,but I also have my eye on the new platinum 4's.

I have a 68 with a 350 and a few mods that include a Comp cam, headers, HEI and a 600 cfm Holley and I tried the AC rapid fire with negative results. The car backfired thru the carburetor at about 5000 rpm's. The solution for my case was a set of Bosch Platinums (originals) at $1.99ea. at my local Pep Boys. I have used them for years in all of my other three cars with good results. If you have an MSD box, like a "6A", then you are going to have a little less duration out of them but normally I use them for around two years or more depending the car and it's application or use. This is only a sugestion, good luck...

I gotta agree with bravewink and Doug G. I've tried them all, I'm currently running the Accel in my Blazer, as my last trial test, but everything else is running AC again. I don't know that I believe the U-groove and Split-fires are really all that effective, and this is why. Electricity takes the path of least resistance when it arcs. And in the case of the U-grooves and Split-fires, you will not get it sparking across both poles simultaneously, the electricity will flow through the one which is closest to the end electrode, and will keep doing so until it has worn down, then switch. I guess you could get a little longer life with them, but then why not use platinum for that. Just my opinion, but regular AC spark plugs are cheap (I got friends at a parts store that will sell them to me for $0.99) and I can't justify spending $5.49 a piece for Splitfires. I'll just change the AC's five times over the next ten years.

------------------
Bing
1956 Chev 150 2dr sedan 302ci
1965 Chev Malibu 2dr hdtp 496ci
1967 Chev Camaro 327ci

what gaps are you guys with HEI running on your plugs?

john

I too have tried many different spark plugs. Don't waste your money on the gimmick plugs. Out of all the ones I've tried, I like the AC delco rapid fires.

------------------
1971 Corvette
383ci, 10:1, DFI, AFR190 heads, CompCams XE282 H-roller, 3000 stall, 3.70 gears

If you want to experiment, try back cutting the ground electrode on a cheap set of plugs. We cut a set for our 302 and it picked up HP on the dyno, we also run a Super Comp Camaro and the Champion race plugs are already done in this manner when we get them. But remember all engines dont like this I've heard some people complain of detonation.

Do any of you guys have information on AC plugs as far as heat ranges for the different plug numbers? I had the info at one time, but I guess my dog ate it.

------------------
David
68 SS Camaro
72 Chevelle
73 Nova Hatchback

BTDT, IMHO it's all a bunch of marketing cowpies. I have a mill that eats plugs. To date, the best are still the old AC fr3LS, followed closely by, are you ready, Autolites.

Its all marketing. Just like Fram filters are the best, right? WRONG. AC, Wix etc are much better.

Think if you buy the products that advertise THE LEAST you'll end up using the better brands.

------------------
Gene C.
67 Chevelle SS 427/L88 (http://www.chevelles.com/showroom/chaas00.jpg)

Someone said playing with the gaps made a difference. Has anyone found that gaps other than what is reccommended work better?

If you have an MSD unit, use the cheap plugs. It gets real expensive replacing Split-Fires every 3 months. I use AC FR4LS.

SO far, the best results I got from gapping the plugs were .040 for an HEI, and .050 for Mallory breakerless. These are the only two ignition systems I've played with so I can't account for any others. I just started at .030 and went up by .005 until I got to .060 while I was at the track and tested each gap.

I have had the best luck with the NGK race plugs. My MSD doesn't seem to eat them up. I have gone over a year without even changing them and they were fine. I normally change the race motor plugs every three months and put them in my street cars. The ACDelco plugs have also worked fine in a pinch, but I have never run them long term.

------------------
------------------
Mark

1992 Firebird 355/Six Speed (Soon to be LT1)
1991 RS 350 / 700-R4
1987 Toyota Pickup 383 / 500 + HP 10.963 @ 119.95 Slicks / 11.997 @ 114.23 Radials
"Speed KILLS, so drive a FORD and live forever!"
http://personal.lig.bellsouth.net/~racer383/

I found that most plugs work the same, but if you set your plug so that the gap is facing up in the engine. The plugs fire much better. Before you put the plugs in mark the resister so that the gap is facing up.
It works great

goat jj, never heard of the gap facing up, do you mean up towards the chamber? We always index ours so the ground electrode is between 9 and 3 o'clock preferably 12. Anything else and the piston has a tendency to shut the gaps. Wes

Exactly!

Have run small-blocks for more years (decades?) than I want to remember; gave up on AC's about 30 years ago. Tried lots of others, finally settled on Champion J14YC's for all-around use (J12YC's for the strip). Some Autolites work as well, but I haven't used them in so long, I can't remember the numbers. Mostly stock ignitions - have no experience with CD setups. My (stock) 10.5:1 2x4/270 '57 Vette and my (stock) 11:1 '69 Z28 are both very happy with J14YC's for normal usage. The 2x4 270's all run a little rich, and the Champions don't foul in it - AC's do.

------------------
JohnZ
'69 Z28 Fathom Green

This might sound stupid, but always liked Autolites. Seemed as though they were just a schosh warmer then AC's in the same heat range and just felt better. Weird,eh can't explain it. pdq67