Tough Tuning Question

[240260280z]

it's Steves 260z... I visited with him and we had a blast tuning it.

The PO left us scratching our heads/ cursing many times....for example the locking nuts on the rocker (lash) adjuster pivots must have been 100 ft-lbs... some were so tight it took two of us on a wrench to loosen.

The vacuum advance canister had a leak so there was no vacuum advance; only mechanical. This makes the 32 degrees observed [AT IDLE] even more difficult to accept.

[SteveJ]

I don't recall spraying the starting fluid around the rear carburetor. I did the spraying around the front carb before Philip did the valve adjustment. I'll take some contact cleaner to the timing light, too. 

[siteunseen]

I had to put my 17mm crows foot on an impact wrench, compressor at 130 psi, then use a propane torch on each and every one.  I don't think the valves had been adjusted since new, 1977.

[SteveJ]

Did you do before & after measurements, Cliff? I'd be curious about how far out of adjustment yours got to be.

[siteunseen]

It's like taking before pictures, I don't think about it until it's too late. 

[SteveJ]

So, here's the update. I replaced the plug wires last night and ran the engine today. I found the rear carburetor wasn't pulling as much air, so I increased the air flow to match the front. I did a test that Philip showed me that he called the "equally $h!++y test" and found the rear carburetor was pulling its own.

[SteveJ]

My previous post was a little premature. I played with the timing some tonight and went to re-tune the carburetors after dropping the timing down. The rear carburetor was weak again. Following Mr. Warner & Mr. Pilgrim's suggestion, I attack the rear carburetor with starting fluid and heard the RPMs increase when I sprayed around the insulator between the manifold and carburetor. All four nuts were loose. I tightened the nuts and finished adjusting the carburetors. The rear behaved much better.

[siteunseen]

Good feeling, isn't it!  I'm having a blast tinkering with mine.

 

I've got Memphis on my mind.

[240260280z]

Great detective work!  Resolving the bugs one at a time.

[madkaw]

So I wonder in these instances of carb balance issue if it would benefit to isolate them better by removing balance tube and plugging the intakes ?

[240260280z]

I think that is a great idea.  Passini hates balance tubes and states they do more to adversely affect performance (on webers). 

[madkaw]

It has sparked debate on the triples about the balance tube and tuning with it attached. I set my triples without the balance tune first, then I balance with it installed . I would think in most cases with SU's it would not be necessary , but in a weird deal like this it might be required.