I guess I don't understand a vacuum advance that doesn't purely run on vacuum. At cruise is where you want it

Agreed. The Mallory system never made sense to me. Great distributor though.

Are you speaking of the big nut on the bottom? The big nut on the bottom affects the mixture across the entire band since you're changing the position of the jet with respect to the needle. It is not just an idle mixture adjustment even though the FSM does call it the "idle adjusting nut." You will see definite changes across the spectrum as you vary the mixture nut position.

Testing shows this, using Steve's data:

Yes, I am speaking about the big nut on the bottom. I agree that it affects everything. However, its effect diminishes as the vacuum piston lifts (large throttle openings) due to the taper rate of the needle and the difference in area of the annulus.

The part thottle mixture can be adjusted with the spring and/or the needle taper without any effect to the idle. Full lift mixture will depend on the needle size.

I gave the 30wt oil a try in the dash pots. I did not notice any difference compared to the 20wt. The 20wt was a significant improvement from the AFT with regards to a lean spot on tip in but that seems to be near the best weight of oil for my setup so I'm going to go back to the 20wt.

I think that's all the tinkering I'm going to do for now. I'm spending two days on the Houston MSR track next weekend (driversedge event) so I want to put some miles on the current setup to make sure everything is lined out. I don't want surprises on the track.

Steve,

did you try anymore ignition advance?

I bumped it up a couple of degrees and did a few runs. I reproducibly got very light detonation near the top of 3rd gear. Nothing in 1st or 2nd just 3rd. The AFR was in the high 12's when it pinged so I'm pretty sure it's not fuel related. I did not get any pinging with throttle roll (at least none that I could hear). Backed it down a couple of degrees and all is good again, no more detonation.

I will run a few gallons of 110 octane leaded mixed with a full tank of 93 octane at the track. That's what I did last time and the car pulled like a freight train. Can't wait!:classic:

Please consider the Drivers Edge event in May at MSR Cresson. I think you will enjoy the track and I would look forward to seeing another Z there.

Jim K.

110 octane cures all:cool:

You just might always have detonation issues with that later e-88 head. With a WIDE open chamber design, it might not like timing. I feel fortunate that my early e-88(semi-closed) head has faired so well with timing advanced.

Have fun tearing it up(the track)!

Please consider the Drivers Edge event in May at MSR Cresson. I think you will enjoy the track and I would look forward to seeing another Z there.

Jim K.

I'd love to make it up to Cresson some time this year but there are still a few spots open at the Houston track for next weekend. Come on down if you've got the time.

110 octane cures all:cool:

You just might always have detonation issues with that later e-88 head. With a WIDE open chamber design, it might not like timing. I feel fortunate that my early e-88(semi-closed) head has faired so well with timing advanced.

Have fun tearing it up(the track)!

I'm in the market for a big valve head and cam to play with. I'd like to try my hand at some minor porting and polishing. If you know where I can find a solid one for a good price let me know!

Look around, they are out there. Unfortunetly, your late e-88 head isn't one of the better heads ------without major work. I think that is amplified by the fact of that big flowing rebello bottom end.

Hybridz has a great thread on just Z heads.

I did my own polish and port and unshrouding which would help your e-88 greatly

Exactly what I want to start playing with. Tinker, tinker, tinker. It's a disease.