Hi, I just finished on the dyno and have a big issue. Here are the specs of my build;
-383
-mildly ported heads ,stock valve size
-224/236 -114 cam with 1.6 roller rockers and behieve springs
-58mm bbk throttle body
-forged bottom end, je extreme duty blower pistons 31cc 9:1 comp
-bbk shorties with hooker catback exhaust
-dual fuel pump setup with 60lb injectors
-vortech s-trim 7'' crank & 3.33'' pulleys
-msd 6a with msd coil
-methonal injection

The problem is it falls flat on its face at 4200 rpm's, just like it hits rev limiter. Acts like it is blowing the spark out.
It runs great right until 4300rpm.
Had autolight 103 plugs gapped at .035, but changed them on the dyno to ngk 6tr's at .035 did not help.
It has good plug wires.
By-passed msd, did not help.
Tryed different maf sensor and it did not help.
The afr is right on, the tune is good and fuel pressure is great.
Tried more timing and that also did not help
It made 385rwhp at 4200rpm at 4lbs boost.

I am guessing it has original oppti and cap and rotor 108,000 miles. =Is this the problem???
Bad coil???
I do not want to just toss more money at it if I don't have to.

Any other ideas, please help!!!!

Thanks,
Dallas

 

You might want to close that gap to around .032-.030

 

id say your going in the right direction with the opti or possibly coil

 

I don't think your blowing out the spark. I made 560ish @ 6000rpm at 10psi with stock ignition. But that doesn't mean somethings not wrong with your coil, bad wires, etc...............Joe

 

The plug wires are fairly new and seen to be good. I did not see any arcing underload on the dyno. I am going to try the stock coil and a new coil wire tonight. It seems to be ignition related, every pull the graph was erratic and differant from the prior pull. On the street in first three gears it runs great and pulls hard right untill 4200 and then it just cuts out.

 

Is it possible to have valve float at that low of an RPM?I had bad luck with behivees at 5700 but i hear that they are good springs. Good luck let us know what happens.

 

What is your inlet tubing like? It's not the weak orange dryer hose like the ATI set up is it? I remember seeing cases like this, even NA, where the inlet tubing would collapse under higher RPM and the car would act just like you describe.

 

I made a custom steel 3.5'' inlet tube with a huge k&n filter, and also a steel discharge tube with the MAF sensor on the pressure side.

When the car was NA it had no problem reving to 6400rpm, but I will not rule that out.

It cuts out so bad after 4200 rpm WOT it will not build boost past 5 lbs.

 

I would look into the springs. What pressures do you have? I don't think you can get over 330# on the seat. I know when I was looking for a set they were to light. Good luck though and keep posted.

 

What is good valve spring pressure for his car? Are those beehive springs enough for boost?

 

Air is an insulator, the more you cram into a cylinder the harder it is for the spark to jump the gap, I'd shoot for .030 if I were you. Opti and coil tends to give problems all around the power band, not a specific RPM in my experience. Valve springs could be it too, I'm not familiar with those.

-Pete-

 

Are you shooting straight methanol? or methanol & water? And is it adjustable? If there's water, I'm wondering if you are just bogging it with the injection. If it's adjustable, you can make t come in a little later, or try a smaller nozzle, or less pressure.

 

50/50 mix, but we unhooked it to see if that was the problem and it still did it.

 

What is the boost doing?

 

It reaches 4-5 psi and just stays there and power just falls off.

I am going to reset my valve lash this afternoon and close up the sparkplug gap to .030

I am also going to try the stock coil to eleminate that.