Marble_Sharp

iTrader: (5)

Any ideas?

Car seems to run strong up to 6,500 rpms. Then, there is a noticeable miss above that.

One of the plug wires seemed a little loose, so I ordered new wires. Not sure why it would only miss above 6,500 rpms with that though.

The miss does not show up on the logs. But again, it is very noticeable at the track.

1lejohn

iTrader: (9)

Are you hittting the limiter? Fuel pressure dropping?

SweetS10V8

iTrader: (4)

Could be Valve float.... what cam and springs do you have?

Marble_Sharp

iTrader: (5)

Rev limiter is set at 7,200 rpm.

Don't think it is losing fuel pressure. I will go out and give it a try and see though.

Marble_Sharp

iTrader: (5)

Springs were tested and set for cam by a shop that only works on heads. Brand new heads and valve train from MAST Motorsports.

I have morel limited travel lifters and T & D adjustable rockers. Rocker preload set to specs given by T & D.

Top 3 suspects right now -

1 - Losing spark. Ordered new wires. The current wires are sloppy.

2 - Fuel. Need to check injuector duty cycle, fuel pressure.

3 - Valve float.

Will be too cool if simply changing the plug wires fixes it. But my record would indicate it won't be that easy!

1lejohn

iTrader: (9)

Are you running a stock tuned PCM?

Marble_Sharp

iTrader: (5)

yes.

I ran same pcm prior to rebuild. I did not have any issues running up to 7,200 rpm's.

Marble_Sharp

iTrader: (5)

I should have mentioned the car ran fine up to 7,200 rpm prior to rebuild of engine.

New heads, valve train, lifters as well.

SweetS10V8

iTrader: (4)

Im still thinking valve float, how much do your valves weigh? T&D rockers are super heavy and casue vavle float with a valvetrain that isnt a good combination. Throw on your stock rockers, if you can, and see if it clears it up.

Marble_Sharp

iTrader: (5)

Thank You for the information.

Won't be able to try the stock rockers, they won't work with the limited travel morels. Already tried that before spending the money on the T & D's.

Marble_Sharp

iTrader: (5)

Ok - went did a couple of pulls to check fuel. Didn't lose fuel pressure, held in the mid 50's.

I did notice though that the wideband shows it getting very rich when it starts missing. It drops from 12.8 down to 10.8 - 11.2 range.

Marble_Sharp

iTrader: (5)

Spring pressures are as follows -

seated = 193 lbs
open = 460 lbs

1lejohn

iTrader: (9)

What about battery voltage is it dropping? At higher rpms there is a big load on the elec system. Bad coil or coils , elec connections and grounds

Marble_Sharp

iTrader: (5)

Strike 1 - new plug wires didn't fix it...