jethro

I've posted this once before, but I still need help... bad. I installed a 150hp shot nitrous (NOS kit 5151) on my 1987 5.7L cast iron head, stock internal engine. It had Rapidfire #1 plugs gapped at .045... ran great. But that plug will not work with the nitrous... the thin grounding strap heats up, breaks/burns with nitrous. Several manuals call for a R44T or R44CFS (copper core) plug, or even a R45T as a replacement, but the car won't idle with those, it runs cold, rich, and misfires, especially with the 44's, though a little better with the hotter plugs R45T's. Eshaust pipe looks rich, too.
A member suggested NGK UR4's... but the car still won't idle right, but a little better than the AC Delco R45T's... I'm at wit's end in what to run... NOS doesn't seem to know either. Do you think this could be a poor ignition system that doesnt allow enough spark at low rpm (idle), for these plugs, whereas it runs great with the Rapidfires...

HELP!

Bobalos

This does smell of a bad ignition system. I would do the complete tuneup & see where that takes you (timing, cap, rotor, plugs, wires, COIL). IMO, there is no reason why your car should not be able to run on plugs other than rapid fires. figure this out & I think that you will solve your problem. also there is no need for a big super big dollar ignition system. this is a stock motor with a little shot, a good working ignition system on a good tune up, should be fine.

thats my2c

BW

Omar

Are you running any type of ignition box?


Also, the rapidfires are platinum. You shouldnt use platinum with nitrous.

jethro

thanks for your replies!!

I have new wires, new cap, new rotor, a 12 year old Accel Blaster, that's about it... I didn't know that about the platinum, and the NOS ppl didn't either! LOL. I fired the nitrous once, went to pits and took out plugs.... burned/detonated the grounding strap off 4 of the 8 plugs! Car still ran great like that! Ha.

But these new plugs.. the NGK U R 4's are not platinum, and I would love to run them, but even though they are the recommended plug, the car just can't seem to fire them...

I think I will install an MSD ignition system...

any suggestions on type... or other ideas?

Snowracer

hey I hate to ask a stupid question ,but,.....does it still run well on a new set of rapidfire plug's.....It might be worth checking just in case, you know( "one pass ,burnt electodes...etc") Just a thought

F-BIRD'88

You have an ignition problem that has nothing to do with the spark plugs.
For Nitrous use select a plug that is 2-3 heat ranges cooler
than what you would use stock.
These slightly cooler than stock plugs will not foul under normal use either.
That is, if: an R45 is stock , use a R42T gapped @ .035"
Platinum plugs tend to run hotter, that's how they last so long.
This is not the best for nitrous use.
Also if you are melting plugs at that power level:
you may/ do have a LEAN MIXTURE either the Nitrous/fuel ratio
is too lean or the motor air/fuel ratio is too lean.
Your fuel pump and or filter/lines may be restrictive, starving the
motor for fuel at high speed.
You may also have over- advanced ignition timing
and or are using poor low octane fuel.
NOTE: It is not unusual to foul the plugs the first time you use nitrous on a motor. The increased combustion will loosen any
combustion chamber deposits (carbon), and then they stick to the plugs. The only remedy is to install new plugs.
The plugs will then stay clean, once the motor is "cleaned out" from the initial NOS blast.
Ignition timing should be 32 to 36 deg total @ full advance for N/A use
and may need to be 2 to 6 degs less while on the nitrous.
Hope this helps.

Bobalos

I agree with F-bird88, the car not running on other plugs is not the fault of the plugs but a clue that there is a problem with the ignition system. fix the ignition system, ensure that it works fine on ANY plug you put into it & then get back to the NOS & have a good time.

If it were me I would first start with a new coil, a 12 year old coil could very simply be beat to death. it does not take but a few weeks of a slight miss to significantly reduce the output of a coil (IIRC, the real number is close to 35% loss with a "slight miss" over 5 or 7 weeks).

BW

jethro

I just ordered a crane ignition... check out the article in Chevy Performance magazin... much better in output than an MSD, and comes with the coil as a package... all this for 189 dollars... I'll post a follow up as soon as I get it installed... hope this is the problem, but regardless... it was time to replace this stuff.

Thanks again all

B4Ctom1

do not run any fancy tipped plugs with nitrous. no little split this's or 4 thats's. those things have such small electrodes that they stay glowing red hot during the nitrous cycle duration and work like glow plugs to prematurely fire the charge, beware. we spent about 7 hours after work (1am) trying about $500 in sparkplugs in a very unscientific test of sparkplugs on a very consistent 300 rwhp car. we tried everything from $30 ea silverstones to 99 cent champions. and the winner was a set of non-resistor (they dont even screw with the radio) autolites. the total from best to worst was about 5hp and 5ft# rear wheel.

jethro

Pretty funny about plugs, huh? And I know ur right about the nitrous advice, in fact I have done a lot of reading on the right selection of plugs... I'm sure the ones witht the thick, short grounding strap will work once I get this ignition installed... should have it on in a few days (Tuesday).

Anthony Biery

Check fuel press.

11ellswray

iTrader: (1)

was it ever taken care of?

project89

iTrader: (1)

lmao necro thread

Ronny

iTrader: (1)

Gosh this was just getting me excited ! LOL