With my new injectors installed, I finally tried to see if I can get up where I used to go with my engine. I used to be able to get up to around 5400RPM (that's where red line is) before I did an overhaul to the engine. Now it won't go above about 5000.

During the overhaul, I put in a new crane cam, hydraulic lifters, and crane dual valve springs. Valve spring height and spring pressure were all checked and verified. Also changed to 10.4:1 pistons from 9.1:1, and put in a new (stock) crank. The cam is pretty close to the old one, but I don't remember exactly what it is. Oil pressure is fine (> 50 PSI). Exhaust system is the same as before. Heads were ported/polished, and I put in bigger diameter SS valves.

So, I think maybe it is related to tuning in the '747 because I should still be able to go up to redline.

What should I be looking for to determine if it is the ECM limiting me? Mixture seems OK, it is still running rich at 5000. What should my spark table do up there?

Any help will be much appreciated.

 

Just as a check, look at the valve stem tips. If the wear pattern looks like an * instead of a -. Your valves are floating. You might not hear it. Assuming you don't have rotaters still.

What cam are you running?

 

Scott,

I don't happen to have my engine apart right now to check for * or - on the valves but I appreciate the information. That is really good to know. I've had to rebuild this engine twice already (cam failed on first rebuild) and I don't want to do it again.

At Grumpy's suggestion, I leaned up my VE2 table at higher RPMs and was able to get up to about 5100. It's still pegging my WB O2 gauge though, so I guess it's still too rich. I'll keep trying.

I expect to probably start getting valve float above 5500 RPM or so on this engine so if I can even get to redline I'll be happy (I don't run it that high anyway, but just want to get it right).

I will have to find my cam card to see what the cam is. It's not a real aggressive one, and I had them grind the lobe separation angle to be more EFI friendly, that's what I remember.

 

If you're leaning out your vol eff tables too much then you would be better off changing the injector constant.

 

Nope, just leaning them out up at the high RPMs. Just did a run and was able to run up to 5500RPM, so I guess this is the right way to fix it. I'm still a little rich in PE mode at some RPMs (a little lean at others), but am working with the open loop AFR vs. RPM to get it right.

 

Running too rich up high will definatly kill power. I had the same issue right when I went to the 28psi of pressure . Engine wouldn't rev up past 5000, same as you.

 

I agree , rich at high rpms is the biggest killer, spark timing or lean conditions didn't hurt my ability to rev, only richness did.