260z to 240z flat top to round top su conversion

[Stanley]

I read a science fiction story when I was a kid, maybe it was by Asimov. Anyway it was a future world when robots did everything. Somehow, the robots started getting cranky and sick. A smart robot mechanic noticed the robots had a lot of unnecessary parts. So he removed those unecessary part and suddenly the robots were much happier and did their work better.

[Guest tmsaws]

That's pretty much what I'm doing with this car, a lot of unnecessary parts. Unfortunately I've made the mistake of getting rid of too many things before so thats why I'm here. The car is actually a 4-speed, I'm pretty sure it's original, but beats me.

[Bruce Palmer]

Any of those holes can be chased with standard pipe taps so you can use standard plugs...... Don't tell anyone.....

Edited October 16, 2012 by Bruce Palmer

[5thhorsemann]

Any of those holes can be chased with standard pipe taps so you can use standard plugs...... Don't tell anyone.....

I was going to suggest that very thing, you can sometimes get away with running the plug through the MIP die backwards. You will loose the taper on the plug threads, but a good sealent like locktite thread sealer will do the trick on a low pressure or vac circuit. I wouldn't use this fix on a fuel system though.

[Stanley]

Right, no AT - should have worn my glasses. The AT vac line if you had it would be Tee'd off the master vac connection.

BTW make sure there's no vac or exaust leaks. My air galley tubes that go into the exaust manifold were rusted out and made fumes til I had them cut off inside and welded shut.

[Guest tmsaws]

Guys, i'm having issue tuning the carbs. I hooked up the antibackfire(green), plugged misc. holes(red), and connected the pcv(blue). The carbs won't run well without running rich or run at all. The mixture adjusting nut has to run really rich, dont know what to do. Help guys?

[Guest tmsaws]

*also running high rpm the car backfires through the carbs, especially the front.

[Captain Obvious]

I suspect you've got a vacuum leak somewhere and you are running way lean. Are you sure you didn't miss a vacuum port somewhere?

[5thhorsemann]

How does it run with the air filter installed? If the tuning is too far out the air filter(s) make a difference.

[LeonV]

Sounds like either a vacuum leak (likely), or timing is way out (possible).

[EuroDat]

Here is my two cents worth, for all its worth;). If you need a manual for the carbs try downloading the fsm on http://www.xenons30.com/reference.html

You might be frustrated now, but you made the right move. The round tops are the better units. Flat tops are commonly known as emmision carbs and therefore less performance.

Goodluck with it.

Chas

[Guest tmsaws]

okay so I'm getting a vacuum leak somewhere. I know theres a slight leak in the throttle butterfly but would that really cause this much of a problem? idling at 5-7 turns of the mixture nut. Ill post a video when I work on it again tomorrow. also, I noticed the linkage bar/balance screw that shuts the car off smoothly is too short, is that a common problem? I'll try to take a pic tomorrow as well.