Anybody ever have this problem? Night i put the gen 2 vmp 800hp kit on my 08 shelby, it pulled strong as hell. Next day i went out to some roll races and when I went WOT it started misfiring and pulled a code for Cylinder 8 misfire 10 minutes later. Pulled out cylinder 8 spark plug and the gap was at .57 when i gapped it at .27 the night before. No problem, i regapped it to .27 and it ran perfect for another 2 days. Went to another roll racing event, same thing happened, except this time it was cylinder 7 and cylinder 3. Same thing, gap opened up to .57. So i pulled them all out and put a brand new set in it and i have yet to really beat on it but I didn't want to until i found out what the deal is. Anybody ever have this issue?
Spark plug gaps opening when VMP kit installed
- Thread starter ajnasrah20083
- Start date
Unless the ground strap is deteriorated, I can't picture how that would happen.
not sure on plug specs but they are the ones that vmp sent me with the kit. it has a 2.4 pulley. it's obviously something to do with cylinder pressure, what would likely raise that that high to make it to that? I think it's detonating.
Whose tune? You may need to provide them with a datalog and see if they need to dial back the timing. A G2 with a 2.4" pulley on a 5.4 is making way more boost than you should be running on pump gas.
One reason the gap would increase would be due to the shortening of the center electrode. Is the end of the center electrode rounded like it may have melted? Have you done anything to the ignition system?
Not true.
That's what I run and boost is in the 17.5psi. range at near sea level.
Plenty safe for 93 octane.
#7 cylinder usually is the one that leans out first. I would guess you are lean and getting a lot of heat on that cylinder. The strap may be getting hot enough to get soft and loose its gap setting. Definitely back off the racing until you get some data logging. Everything in that cylinder could be getting the same heat damage.
Post pictures and we can tell you for sure .
this is exactly what happened. the electrode was relatively shorter than all the other ones and that's honestly why the gap got smaller, not because the actual strap is moving. ignition system is stock. car takes a minute to start on because the fuel pumps aren't Pumping enough pressure to where it starts right up. I have to prime the fuel system 3 times so that it turns right on without having to crank it for 6-7 seconds. that's the only thing I can think of but I don't see why that'd affect the ignition system. other than that everything is stock electrically/fuel wise
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Send me a datalog. But first send me your car info and all details to [email protected]
If we recently supplied you with plugs, they're Brisk Racing and they're pre-gapped.
If you're having a misfire, stay out of the throttle. The 2.40 is a lot of boost. If you're not running HIGH quality fuel, you should be. ONLY BP, Chevron, Shell or Sunoco
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im working on the data log as we speak. it's giving me a lot of trouble. that's all I run. it's not misfiring as of now since the new plugs
It is doable with good fuel, but plenty safe it isn't.
Shoot me the email please
You know engine builders must be rubbing their hands together when they read threads like this. I keep reading really stupid posts about how you can make 700 h.p. on pump fuel etc. There are so many factors that will melt down a motor and people persist. People read and believe people here that don't even make 600h.p. let alone 700. If you don't know call VMP, Lund Racing etc. and they will tell you free of charge before you race a 1000hp Corvette and blow the motor.
Showing 17.5 psi. boost, not that far off from 18.. Good for me.
Higher numbers could contribute to stock exhaust which I don't have. I know I lost .5 lbs. boost just adding longtubes (no other changes)
Can't complain.
Car's been running great, 5+ years and over 67K miles.
Did pulley/tune before first oil change, over 700HP for the last 3 years.
Does that mean the motor will last forever Nope, does it mean I'm playing with fire, Doubt it.
I good and well know it can blow if something goes wrong, (bad gas) that's the chance WE ALL take when we start modding these cars.
You've seen people blowing STOCK motors also on here.
the vmp 800hp kit has been ongoing for years now and this isn't my first kit on these cars. you risk blowing your car up whenever you do anything to the car. race gas or e85 isn't an option for me because e85 stations are nonexcistant around here and the whole idea of octane booster out of a can from autozone was never my cup of tea as you fry a lot of shit when you run that stuff too much. I feel like people have trouble out of pump gas if the car sees a lot of track time and a lot of racing where as my car would see the track once a month and only 3 pulls that one day, and roll racing every now and then. this week was probably the most I'll ever drive the car as I've missed the "raw"
power these cars output.
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I am not familiar withe 800 H.P. kit, what were your your e.t. and mph at the track? And this was on pump gas?
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