Technical > Matt Shaff's Engine Shop
Spark Plug indexing
George:
I am considering trying spark plug indexing . I have read several online articles and not sure it's worth the hassle. What's your opinion?
I have a 13.4 : 1 SBC ,355 CID, Dart 230 cast iron heads, Hilborn stack injection, alky, MSD 12LT mag. I have no interference problems with spark plug to piston. Running NGK 8,gapped at .018.
Thanks . George
Frontenginedragsters:
George:
If you have no interference problems now, I doubt that indexing would provide any improvement.
In the old days when we ran stock 461 castings on a small block, we had to index.
It was typical to angle mill those heads .125" to .150".
This brought the spark plug right to the deck. I found that if you indexed 180* from the normal - meaning you
pointed the ground strap up, the combustion chamber could "see" the spark plug.
I believe your Dart heads have the spark plug slightly higher than the old Chevy castings and you dont have to cut them so much.
By the number posted in your personal box, your little small block hauls ass!
Tell us more about your combo. Whats it run in the quarter mile?
Matt
masracingtd1167:
Here is something we found . I am not 100 percent shure this worked but I would like to share it with you guy's . I run injected alcohol with a tunnel ram manifold . When I started spraying it with Nitrous we would sometimes burn the side electrode off of a plug ! The funny part was that it would be different plugs every time . I always index my plugs but between 3 and 6 o clock was good enough or so we thought . Even with a safe tune up It would burn a plug but never the same cylender . Finally we tried indexing the plugs very carefully so the open part of the gap was facing toward the intake valve . From then on we never burned another side electrode . I guess the cool air and fuel would keep the electrode from burning . I would be interested to see what you guy's think about this.
George:
--- Quote from: Frontenginedragsters on March 18, 2013, 06:27:56 PM ---George:
If you have no interference problems now, I doubt that indexing would provide any improvement.
In the old days when we ran stock 461 castings on a small block, we had to index.
It was typical to angle mill those heads .125" to .150".
This brought the spark plug right to the deck. I found that if you indexed 180* from the normal - meaning you
pointed the ground strap up, the combustion chamber could "see" the spark plug.
I believe your Dart heads have the spark plug slightly higher than the old Chevy castings and you dont have to cut them so much.
By the number posted in your personal box, your little small block hauls ass!
Tell us more about your combo. Whats it run in the quarter mile?
Matt
--- End quote ---
Matt, It's been on the dyno making 640 hp. It's got Hilborn 327B 2 7/16", Waterman 400, 16As nozzles, usually start with an 80 bypass. Heads have been ported, no welding or putty. Scat std. weight crank and Callies rods. Ross pistons 13.4:1. It's been very reliable. It has only been on the 1/4 at Bowling Green Ky. That was the HHRR 2010. We were just figuring thing out and with the help of Scott Parks we got it to run 8.32 @ 155 mph. At that time we were running a Hoosier 12x29 tire. We soon changed to the Goodyear 2585 and went from 1.12-1.15 60' to 1.06-1.10 . We also bought a Race Air and got better with tuning.( Notice I didn't say good) Also improved the engine heads, compression and cam last year ( was 607hp). I would guess we could get it into the low 8s now?
The reason I am considering spark plug indexing is we tend to run best when it's rich and we are getting what I think is too much fuel in the oil, even with a vacuum pump. I'm thinking if I index toward the exhaust valve it might help. Don't know but I'm looking for others to share their tune ups?
Thank for your input. George.
masracingtd1167:
George it may not be too rich . How hot are you getting it? and how much dose the temp increase durring a run?
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