I've got a 73 240Z with the original Hitachi flat tops, and very low miles. I'm going to remove the smog control stuff, since I don't need it in Massachusetts anymore. The car has sat for a long time, and hasn't run in a year or so. I took apart the carbs and found a stuck float needle. I haven't started the car yet, I'm waiting until I have cleaned all of the fuel lines and the fuel filters are all replaced, but I'm sure that was the problem.

A friend who has worked on older Z's before suggests I get the car running properly with the smog stuff on, then remove it and adjust. It is my understanding that these carbs work much better without the smog stuff, so why not get the carbs running and tuned with the stuff gone already? What parts of the smog equipment (i.e. shared vaccuum lines, etc.) directly affect carb function? Any advice and/or tips would be appreciated.

just replace them with early round tops and save yourself the trouble.

I hear a lot of differing views on this board about whether to keep the Hitachis or trash them for older SU's. The car only has about 26,000 miles on it, and other than desmogging, I want to keep it original.

I'd want to get it running as is, first, and not to complicate the equation too much. If you give in to the temptation to pull the smog stuff off of the car and then can't get the car started, you won't have a baseline to work from.

Flush the fuel and go through the fuel system, get the car running and tuned halfway reasonably, and then pull off all of the anti-pollution stuff. Less potential trouble that way, and people will be able to help you more easily if you get jammed up somewhere.

If you ever decide to go back to the round tops, just store the flat tops somewhere. That way, in the event that you ever decide to sell the car, you can say that it's low mileage, and has the 'better' carbs, but can easily be put back to original condition.

Get a set of SUs complete.Remove Hitachis(manifold & all).Store the Hitachis and use the SUs.

I have a SU manifold minus everything except the x-over tube.

The flattops were a poor attempt to meet emissions requirements until the Fuel Injection system was ready for market. If you want a museum piece, keep the flattops on the car. If you want to drive it and enjoy it, swap them out for a fresh set of round-tops and put the flatties away where they will stay in #1 condition.

Go with the roundtops if you are desmogging the car.

If you want to do it right, go to www.ZTherapy.com and look at their roller-bearing shaft rebuilt roundtops. Pricey, but a permanent solution to the carb problem.

BTW, you'll also need wide spacers for the round-tops if you swap, and longer manifold studs.

I'll gladly pay shipping for any 73 Flat Tops anybody wants to discard my way, maybe even pay a couple of bucks too... Literally 'a couple'... Shipping costs more...

PM Me for Address and shipping information.

Best answer-clean and box up the complete Flattop assy(heatshield, manifolds, Balance tube and carbs) and get a complete assy of three screws from ZTherapy(Bruce has a twisted sense of humor-run with it!) bolt 'em on, tune them as directed, and find what you have no clue was missing in your car! I had a '73 with flat tops that I thought was well tuned until I swapped to three screws...night and day difference, never would have thought if I hadn't been persuaded. Best thing to do to a '73 with the original drivetrain.

Here is most of what it looks like!

I just swapped good running flat tops off my 'new to me' '73 for my Z therapy carbs that were on my old '73 and it was a great improvement. With all the hoses and junk on the flat tops I'd be afraid I'd mess up the way they ran trying to remove any of it. I can't even bring myself to put the flat tops on my old Z and it is just going to be sold when I'm done swapping parts off of it.

Ditto with the general consensus.

Swap out the "flat-tops" with a good set of Round Tops.

Save the Flat tops AND any other of the smog items you remove (air pump, vacuum solenoids etc.) and put them in zip-loc baggies or just in boxes until that day years from now when you sell the car or give it to your kids.

While that thought may be untenable at this point in time, when you're looking to move into a nursing home they'll be an added plus to the next owner. He may not put them on, but they're an original piece of the car.

Or he may bless you for it when the Republic of Californicate's concept of imposing non-existent and ludicrous smog standards on 40+ year old cars rolls around to your state and he's required to put on the original smog equipment .... whether it was functional or not .... or pay a fine.

Don't laugh. They're looking to "decrease pollution" by the 1% of all cars represented by older cars that are still around, while ignoring that those 35+ year old cars are better maintained and less driven than the average 5 and 10 year old cars.

Wait till you have to find a 35 year old air pump that you can install on your pristine 72 Z just to placate some DEQ weenie.

2¢

E

With all you guys taking off functional 73 Carbs, and my standing offer to pay for shipping to relieve you of them...I'm offended nobody has taken me up on it.

I paypal right away so you can ship quickly!

P.M. me if you're not interested in those old boat anchors.

Seriously guys, I'll take them off your hands!