High VE values on a NA 347

[JimMueller]

I replaced the sensor this morning and it now says my WOT is ~10% rich across the board. Cruise regions are still pretty close, but all PE regions appear to be 5-10% rich.

Something else I finally 'caught on tape' was that my engine RPM's basically refuse to move much higher than 6800RPM's with the limiter set to 7200 everywhere. I'll post the log tomor.. er, later today

It felt funny to be at WOT, feeling the car stop pulling, and watching the tach basically sit in place at 6800 RPM without any rev limiter bouncing, etc. My recent dyno's all end before 6800 but no obvious problems there. Any ideas of what I can log to help isolate why it's choking around 6800?

[JimMueller]

Here's the log... given that excess PID's have been removed and I can't tell truly what was going on, I have some questions.

1 - Beginning at frame 31350, why do the RPM's stop climbing and effectively just bounce around between 6800-6900 RPM?

2 - In the same region, why does the MAP bounce around so much?

[JimMueller]

I spoke with Texas Speed (TSP) and Raymac Racing. The former built the assembled heads and the latter sold me my LS1 rev-kit and also has contracts for Nascar engines and the Craftsmen truck series engines.

TSP said the cam is out of it's RPM range by 6800. They said they setup the spring height to 1.81-1.82 when assembled. They suggested I could try reducing the installed height to 1.79 and that should take care of any valve float. They didn't feel it was necessary to shim to within .050 of coil bind for this cam. If adjusting the installed height didn't fix the issue, they said to look in the tune.

Raymac said I'm experiencing valve float. They also said the cam is out of RPM and when it gets that far out of it's range it will cause float. They thought I might be able to get another 100RPM by switching from 3/8" pushrods back to 5/16" pushrods (as well as some HP), but the best bet is to get a better valvespring than my current Platinum Duals sold by TSP. The have a drop-in kit which would get me another ~30-40lbs open pressure. They also said that Ferrea recently released a valve spring kit good to .670 lift, but Ferrea wants about $1000 for the kit. Um, no...

Raymac also mentioned that they always shim to within .050 of coil bind on street motors, and within .030 of bind on race motors.

So I guess I'll try swapping back to 5/16" pushrods just to see if there's any more power. If not, I'll keep the 3/8". I'm not sure if getting that extra 400RPM is worth the hassle of buying new valvesprings and installing them.

[EC_Tune]

Yeah, you can actually see in the AFR where the valves float at frame 31420. BTW: It looks like you have the engine very rich in PE. Time to trim down those VE values...

[JimMueller]

That's the difference between the old and new wideband sensors... I'm working on it

[BTLD_LS1]

Just thought I would add this, it is my tune in my 347, specs in the sig. I recently had the intake port matched to the heads and TB ported to 85mm and the tune is way off now, but as you can see my VE tables are quite high. I also have it tuned rich to be on the safe side once I decide to juice it, but just so you have something to compare too...

Just wanted to add the car quit making power @ 6900 which was obviously a function of intake restriction as it now pulls to 7500 no problem now, hence why I need to redue the tune.