GlockLT4

Ok, so .. 11.55:1 compression in my 383 ... on 93octane gas (seems to be working fine). I am getting a miss, it's not the wires, the opti is new, i have a 70k+volt crane fireball coil.

NOW ... my spark plugs are of course NGK TR55's. They are gapped at .050".

What gap should I be running? I was told this could be the cause for my vibration and misses. I have been recommend to run anywhere between .045 and .030" . What should I run??

J Z06

383-LPE FR5LS Plugs @.035. Stock gap.

11:1 CR

GlockLT4

Thanks JD!

J Z06

Anytime! From one PLAGUED dood to another :lol: Well, I am not..the car is hehe ;)


[Modified by JD 90 383, 5:22 PM 3/16/2002]

GlockLT4

hehe.. i'm trying to get out of the "plagued" club though ... :jester Eventually I'll be out of it.

J Z06

I've told myself that a few times! I hope you have better luck than I do.

60 miles on the new tranny(according to your sig) Come onnnnn! I did that last night :D




[Modified by JD 90 383, 6:19 PM 3/16/2002]

Nathan Plemons

MSD recommends a gap of .040 - .050 on 10.5-13:1 compression. Obviously that's with one of their ignition boxes, so you'll probably want to back it down a little bit if you don't have one.

In this case the MSD might actually solve your misfire, but I would verify it first before you spend the money on it.

GlockLT4

So the MSD just makes it spark multiple times, right? If it does, then that gives a much better chance for a spark to ignite the mixture, and that would hopefully fix it.


[Modified by Glock'94, 5:37 PM 3/16/2002]

Nathan Plemons

In theory the MSD increases the voltage on the input side of the coil which increases the voltage on the output side as well. Below 3000 rpms it throws multiple sparks such to help ignite the mixture better. Above 3000 rpms it does not have time to do multiple sparks, but rather one large more powerful spark. That's the theory anyway.

They are supposed to be good for nitrous, high compression, or boosted applications where a spark can normally be "blown out." Low compression engines like my old cutlass wanted a gap of .060.

In general it's best to run as big a gap as you can get away with and it still fire. The MSD is supposed to help you increase that gap. At least that's how I understand it.

h rocks

I've run a .052" gap forever with my MSD. Nothing but "good vibrations". ;)

GlockLT4

Thanks Nathan .. i'll look into the MSD then. I'll see what other kind of documentation I can find about it. Would $75 for a used MSD be a good price?

Nathan Plemons

Sounds alright if it still works.

GlockLT4

New ones are like $125??

8388

I run the MSD 6 AL, forget the stereo while the engine is on ! Curtis, make sure that none of your plug wires get too close to any other sensors or electrical wires that send a signal's to the ECM, especially if using a spark amplifyer like the MSD.

I gap my plugs at .40, but I run a supercharger. for a normally aspirated engine with a good quality spark amplifyer .50 or .60 would be ok.

I actually did alot of tuning with carburated engines, and did see power gains by increasing the jets and widening the gaps on the spark plugs at the same time, of course with an MSD hooked up, but remember when doing this type of tuning, playing with the timing is also required.