Zedyone_kenobi

Blue, the car can rev to 7000 rpm without any issues stationary, and revs pretty freely... This phenomena only happens under load and only on part throttle. With the throttle opened 30% in 2nd gear I get to darn near 5000 rpm before it happens, in 3rd gear with the throttle opened 30% I get to about 4500, in 4th gear with the throttle opened 30% I get to 4000 rpm. THe harder the car has to work against a mechanical load, the sooner the AFR hits 16+:1 and starts popping and the car stops accelerating. But if I am currently popping and stuttering, if I floor it, I go strait to 12.8:1 and all is right with the world.

yessir. I have three sets of brand new rotors and caps! haha I still need to perform the carburator cleaner spray check. But I am saving that until after my vacuum round. I am getting desperate. How desperate you ask? I have already called Rebello and Datsun Spirit about an entire rebuild, from oil pan to valve cover. I can leave nothing to chance. That 2.7 purist motor Rebello has is looking VERY tempting right about now! Then again, I would really love to tear it down myself and rebuild it with my own two hands.

I wish you were right my friend. I just tried the ultimate overkill ignition test tonight. I left my old dizzy on and installed the newly reset carbs from Ztherapy. Started right up and idled great as always. Drove well below 4000 rpm as always, but again, I was leaning out and popping at part throttle as the rpm reached north of 4000 rpm. So I got out of the car and hooked up the vacuum advance. Drove the car again, with exactly the same results as before. My dizzy is free inside to move, I tested the VA diaphragm and it help vacuum just fine. So Now I was ready for the swap. I installed a brand new pertronix into my D611-54 dizzy, put on a new cap/rotor, and installed it sans VA hooked up. Drove it again, and whala. Same thing. NO change at all. My first dizzy was timed to 17 deg BTDC with and without VA .. .leaned out at part throttle Second dizzy was timed 11 deg BTDC w/o VA ... leaned out at part throttle I am ready to write off the ignition has anything to do with this. I have tried Three pertronix, Three distributors, 2 coils, and anywhere from 7 deg BTDC to 17 deg BTDC, with and without a VA. It was getting late so I did not want to annoy the neighbors, but all the VACUUM gage stuff is next. I will try to see the following: I will see if the VA nipple is pulling adequate vacuum while driving to operate the VA I will see what my manifold vacuum is doing when this leaning is going on vs WOT I will get back you guys on that. Then I will perform the leakdown test on all 6 cylinders

Well you can have a vacuum leak from the intake to head, the PCV tube on the balance tube, and the power brake booster line on back of the manifold. One sure fire way of checking the float level is to hook up a clear tube on the bottom of the fuel bowl. Unplug the coil, and crank the motor over. Then go look to where the level is in the clear hose. You should be a certain level (22mm) if I recall (check the FSM) from the joint between the cap and the fuel bowl. Adjustments of the float is done by slightly bending the tang that contacts the float needle. If you live in a cold weather area, the lines help heat up the carbs faster. I live in houston, and like yourself I removed my coolant manifold lines.

Yes I checked valve lash. Nothing is crazy out of whack or lose. Hard to say for sure, as it was not hot and it was not cold. More warm. But the feeler gages felt within the realm of acceptability. I have a dizzy in there with a working vacuum advance. It is just plugged up. When I get her running tonight hopefully (I installed the carbs last night) I will be able to play with timing again with AND without vacuum advance. On top of that I have another OEM distributor that has not been recurved with a NEW pertronix, new cap, and new rotor, and new wires, I may swap that in, set it 5 BTDC and give that a try. I will flush out the ignition part of this thoroughly by the end of this weekend. Although, keep in mind, I already swapped dizzies with somebody else and this problem still existed. So this is one last ditch effort to run this to ground on the ignition side. While I know no two engines are the same, but many other people have run without a vacuum advance and high static initial timing without any issues. So part of me thinks this is something more clever. A leak down test will give another data point, as will the vacuum readings

UpDATE: Had a talk with Dizeasedz and he suggested I do a leak down test. I have acquired a leakdown tester today and will try to get that hooked up tonight to see what I find. PS-It was great talking with you Guy. Thanks for all the VERY helpful advice on the engine build. I will be in touch soon to discuss that further.

I will be interested to see how this one compares to the one I am running. Thanks for that. I had forgotten about that post from a while back. I will see if I can get a picture of the weights stamped inside as soon as I can.

I have a 71 240Z an this is not the OEM distributor to my knowledge. My car came with a D615-52 which is currently on the car (but recurved from www.advanceddistributors.com). I have no idea what this came from. It was an ebay find that was just too inexpensive to pass up. I have ordered a new pertronix to put in it and new taylor wires to keep for another build I have in mind. Which year, make model came with a D611-54. Any idea?

I have an infrared heat gun that I use to measure, well anything from the temperature of my grill, to the air coming out of my vents. My question is with your heat shield under those triples is there enough room to touch the pipes. I mean I guess there is since you did it, but VERY cool Nice use of science. I agree with steve, time to buy another diagnostic tool!

Thanks Adam, I am not even running my vacuum advance at this point. I am relying totally on mechanical advance. Well I got my carbs back last night, and I plan to put them to the test. After I get the car back together and I do all my other trouble shooting, if it still does this I am going back to timing. I picked up a newly rebuilt D611-54 single point distributor. I ordered a new pertronix, more new wires (I wanted red ones anyway), new cap, new rotor, new vacuum advance and will try timing from scratch again. I know that distributor is not OEM for my car, but it should work well enough.

could have been an impurity in the metal that caused a local weak spot and then it lead to fracture. But I can forward this pic to some of my NASA failure engineers.

more importantly, VTO should buy these and make a replica in 15" sizes we can buy at an affordable price. I LOVE these rims, but the cost is just too high for my car.

Thanks Blue. I have acquired a very nice OEM distributor and will be swapping mine out with it. I have taken it on good faith that it was curved correctly and maybe it is. I am going to build up a whole new distributor with a new pertronix system and see where we go. I am currently STILL waiting on getting my carbs back. THey have been shipped apparently. I did run a jumper from my battery straight to my coil before and the problem still persisted as I thought the stock tach was doing something crazy. I am getting 13.2 volts to the coil if I remember correctly. for all intensive purposes this still looks like a smart vacuum leak, but I will be darned if I know where it may be. I still have to try to get a full suite of readings from my vacuum gage after I get the carbs back. Then hopefully somebody can do the same and we can compare. I will take a look at the links you posted Blue.

Thanks Andy, but I have a 71 240Z. I cannot imagine why it would be any different though

Datsun is only being released in three other markets not including Japan or United states. So it is really a non starter. They will not release a BRZ competitor in the united states. Personally I have been a dedicated Subaru guy for the past 11 years. So it would be a BRZ or nothing for me.

Well congrats man! I am always happy to hear a problem resolved. I am still trying to fix my issue, but I have jumped my resistor and still have my weird issue. Best of luck man!

Best of Luck buddy! And I do love that 912, such a great car. Like so many before me, if I ever sell the Datsun, I will be getting either a GTV or a 911

I have been considering getting my engine rebuilt just to freshen her up, and I have been considering only going with Rebello. But if Datsun Spirit does good builds, I can consider them as well. Any body hear of how their engines stack up? Again,I am looking for a mild rebuild, not a road racing scorching road terror

Keep in mind folks that the front body work you are running makes a huge difference in what size tire you can run. Lazeum's car looks awesome with that air dam on it, but I could never get away with a 225/50 on my stock valance with my car sitting on tokikos springs and struts. I rubbed with 205/60's, so I had to run 195/60's. (15x7 0 offset rim) I may be able to get away with 205/55's, but it will be crazy close.

Isn't this the same car that was at a Mecum auction a while ago and the bidding got up to 45k and it did not meet the owners reserve!

Thanks very much sir. I certainly appreciate it Steve, I will be in touch. The next time you hear from me though may be to help me take off my hood! HAHA When I get the carbs back, I will report back in. I will look into another completely stock dizzy as well. I have time on my hands just sitting around waiting for carbs!

Steve we can try if you have a spare set of carbs, I will get an extra set of insulators

The reason I am hesitant Steve is two reasons 1 when I pulled the carbs off my intake the first time the gaskets on the insulators came off in pieces, if that happened to your car you would be in a tight place since yours is a daily driver 2 I really do not think its the carbs any more. I realize I need to try another pair for completeness. But I think the results will be the same Blue we swapped dizzies and coils Steve's dizzy had another pertronics as well Carbs will be here next week hopefully the troubleshooting can continue I am going to focus in great detail for vacuum leaks in strange places

Well I fully expect the problem to exist, since technically nothing has changed. My plan of attack starts off in data collection and then moves to vast sweeping changes. First I am going to run the car with 0 changes from how ZTHERAPY gives them back. Report back Second Hook up vacuum gage inside car and see what vacuum is doing while the lean out phenomena occurs. Report back Third Spray carb cleaner all over intake while running to try to spot leaks or cracks. Report back If all of that does nothing And a set of seemingly good carbs do not fix it I am going to go crazy I am going to pull the head and send it to Rebello for the works E31 setup. I am going to install a new oil pump new timing chain, new tensioner , new balancer, new crank gears , etc. I will get it running with my SUs, them slap on some webers or Mikunis Yes I am serious, yes I am ready to spend money. Mark my words, I will fix this

Nope did not want to bug anybody, but I really do not think its the carbs My carbs are on their way back. Ztherapy said they were set too lean but everything else is fine. I will gladly pay shipping if anybody wants to loan me some GOOD carbs