SN17

I have a small block Chevy 91 RS bored/stroked to 383. 9.7:1 Comp, Stock heads and medium aggressive cam. I spray 150 NOS Power Shot system. I noticed my idle getting rough so I pulled my plugs today to inspect and found # 5 and #6 ground straps burned halfway off. Also #8 has a heavy build up of white stuff on the strap and electrode. I'm thinking I have a lean condition and/or detonation.
Any thoughts?
Thanks
Dave

Injuneer

Wrong plug choice.... too hot, and probably not the right ground strap configuration. And possibly accelerated by running lean.

What plugs were you running?

SN17

Join Date: Aug 2008
Posts: 2
SN17 has a reputation level 5-49

I was using AC Delco R45TS plugs. I am begining to think they may be two hot. I talked to NGK Tech and they recomended NGK 7773s as two heat ranges below the stock plugs and I changed them tonight. I also think my timing was to far advanced. My light says I was at 38. I went to 36 this afternoon and she ran much better and was much stronger. I use 93 pump gas. I also had a lean condition when I did spray. That may have also contributed. I leaned out because the single pump I have wasnt able to feed the carb and the nitrous system combined. I added a dedicated fuel pump and seperate fuel cell to the nitrous system last week.
Dave

tomcowle

Too much timing and not enough fuel. For the style of engine and low hp of nitrous I think your original plugs are fine.

Hopefully your pistons survived it.

Injuneer

I don't know how the R45TS compares to the R45LTSP that came stock in my 94, but mine were probably the worst possible selection for nitrous because of the projected nose and the resulting long, skinny ground strap. The strap turns into a cherry red glow plug, no matter how well the heat range of the plug is matched to the engine's requirements. Joe Pettitt's "How To Install Nitrous Oxide" book shows a picture of the stock LT1 plug and cites it as the plug not to use. By comparison, the NGK plugs without the projected nose have a short, heavy strap that will resist burning up. I installed my first kit in 95, and it didn't take long to burn the ground straps off.

AutoRoc

The tune is probably fine when the pump(s) was keeping up, just too much timing. 36-38 degrees on motor may be fine...and then while spraying you need to pull 6 more degrees out. Try 30 degrees total. I bet it won't burn any more straps off and it should actually run faster. This works because while ingesting the nitrous, the combustion process is happening faster and more violently. Less ignition lead is needed for max HP. Goodluck!

tomcowle

The "P" I'm pretty sure means projected tip, the r45ts (without the P) as stated will work fine at the hp levels he is spraying.

I use ngk plugs, they are the easiest for me to read. On the 738" Buck engine I help tune plug reading is really critical especially with all 3 system going. This past weekend at the ADRL race at Norwalk we needed to learn on all three stages every pass.

Injuneer

Actually, in 1994 the "P" meant platinum (they currently use "800" to represent platinum). In the AC/Delco nomencalture, "S" represents an "extended" or "projected" tip. Just to complete the breakdown, the "T" means tapered seat, and the "L" = long reach.

He's using a resistor plug, 14mm thread, heat range 5, tapered seat, and projected tip. Not the best choice.

SpeedZ28

Actually, If you have the money, Zex makes a spark plug specifically designed for running with nitrous. Its a copper core plug, with tripple fire. You can go to zex.com, go to product info, go to spark plugs, go to v8 engines, and look at the second plug down. They are made with a colder heat range and they have a table that displays the heat and spark comparison, this is what is says basically;
Spark Transfer Ability-1/M-OHM-Cm
Copper:596
Iridium:189
Platinum: 95
Heat Transfer Ability-J/M-Sec.-Deg.
Copper: 401
Iridium: 147
Platinum: 72

Which basically explains that platinum plugs are not the best choice for running nos. If you do not wish to spend the money on these plugs, at least get Iridium.

Good Luck.

jakesz28

Heat range , projected tip and too much timing.

tomcowle

You know, I found it hard to believe that the R45TS and the R45LTSP plugs could be that bad of a plug for small nitrous usage so this weekend the local chassis dyno had a "dyno day" and I went testing. I dug thru my old plug bin and found the r45ltsp's that were originally in my lt1 engine then I bought a pair of r45ts's.

First pull was with the 100hp set-up, I put the r45tsp in #1 and the r45ts in #2 and guess what, no burnt straps. Car picked up 68hp. afr was a little rich

Second pull, I added 1.5 degrees of timing over the 1st pull and ran it, no burnt straps. Car picked up 81hp. afr was really sweet.

Third pull, I added 1.5 more degrees of timing over the second pull and guess what, I started to nip the r45tsp plug but the r45ts still looked okay.

Forth pull, changed to the 150hp pills rolled the timing back 3 full degrees from my last run. I adjusted the fp a little put 2 "new" plugs in and gave it a whirl. The car didn't burn any straps off or show any signs of it.

If I was smarter I would haved filmed it or at least took pictures of this test

AutoRoc

Good info Tom!

Can you tell us Where you started at with timing? Alum. head? Octane?

SN17's iron heads and maybe low octane might be part of his problem also or not?

tomcowle

37 degrees on motor on the hose pulled 3 degrees timing initially, 93 pump gas on the motor, 114 in the nitrous cell. LT1 aluminum heads.

AutoRoc

Very cool tests...

So you pulled 3 degrees to start...pulled 1.5 on the second...pulled NONE on the 3rd pull at a 100 shot level...


Then pulled only 3 degrees on a 150 jet and hurt no parts, etc.. cool

On the third pull with No timing taken out(37)..Did it make more power than pulling 3 degrees, anddid it make more power than pulling 1.5 degrees?

What RWHP did it gain on a 150 by pulling 3 degrees.?


Thanks again! I love reading this stuff because I run VERY conservative tunes. I pull 11 degrees for a 200 hit, run a -9 plug, and Q16 fuel in an 11.5:1 engine...hehe. Plugs barely get hot after 3 hot laps. I'm always weary of leaning on it.

jakesz28

Tom just a thought for you but he said he had 38* timing. I have seen timing lights compared on the same motor without any changes very up to 4-6* I personal do not like the craftsmen timing light with the adjustable dial for this reason it was the worse one that day so could he have had a little more timing then he tought?