Seanw987

I used the 240 harness car side and the 280 tach harness tach side and ran a seperate wire for the signal running from the tach feed on the MSD unit. Tach didnt work so I simply put in a 8920 and that did the trick. Just followed the directions and wired it between the msd signal and the tach as directed. No fancy wiring at all in regard to the tach conversion. I did add a relay for the adapter but thats a no brainer. I followed the walkthrough and that was my experience. Never got around to the passenger floor board resister check because I had results. Vehicle wiring harness is from a 72. My info may be more suited for the sub group of msd6al users. I will check how my MSD is wired and inform here. attached is the reference diagram i used. found it online, possibly here, and it worked for me.

Thanks for the tach conversion write-up. It worked like a charm and went quickly once I managed to pull the 240z tach out from behind... pita. The use of an MSD 8920 tach adapter was needed to get things working in my case. 1971 240z MSD 6AL and bluetooth 123tune distributor. I now have my tach functional.

im on 3rd tachometer replacement. This one "seems" to act fine.

Thanks Guys. The brake booster is new as are all the lines. The Ballast resistor was replaced with a NOS part. The new pertronix(under suspicion now) doesnt require the ballast so I feel it should be removed however I think the last time I saw my car it was still wired in the circuit. I will Follow-up. Thanks Again.

Update. Still no success. Mechanical all gone through(again). I'm back where i started suggesting that this is something "In" in the car ie. a wire, a bad crusty connection or an electronic component failing under heavier load. Still full of hope that this issue can be resolved.

Also. The engine was Top dead centered with all components in alignment........ not much good news so far here........

yeah all smog is pulled. I will let the guys in the shop know about the gap solution.

I poked my head in the shop yesterday. A stock cam has been tried with no noticable difference. It just sounded wimpier than when it had the perf. cam . no improvement to rev range. Vaccum readings were taken, im not sure what they are but they seemed normal, it was noted that when the balance tube vaccuum lines were removed, the idle went up, not down.....

Yes, I must admit. These guys at the shop are really being put to the test. I gave them a mystery build motor made with parts from every type of Z. They werent expecting this to be such a complicated swap but they are keeping thier cool (they still let me in the shop) under these extenuating circumstances. The time they are spending on the car has been more than I've been charged for and they refuse to give up. I hope to have the car back daily but I know I wont get it back until its Right. Thanks Again Guys

Thanks guys. I'll pass this info On. The shop pc crashed this week.

the pulley has one mark. and looking head on at the engine, this marker is towards the left side, about 10 or 11 O'clock position...

Also , Mechanic told me today he is going to tdc the engine again by hand with the #1 cyl and compression method. this has already been done once but the crank mark was way low, near oil pump last time he checked it. Maybe this is a clue? Revving only to 4500 not 5400 rpm. rebuilding carb did not fix issue. I think cam/crank timing is off.

heres the pulley and the marker. this is not the marker i bought but a marker that the mechanic had as extra or one that came off my old motor. im not sure. I know its not the new one i bought as i painted that one blue.

I will take a close up of my pulley and the timing mark . I will have to go down to the shop to take it but I will go today. No, I havent actually driven the car with new motor yet. So It may be sluggish or less than what it should be. As far as "Timing Dropping Off". I guess I meant that the mechanic noticed a problem (i wasnt there) with the timing not being correct when he revved it up to 4K. He advanced timing and it performed "better" but not perfect. The carbs were rebuilt and micro polished by a group named paltech.. yahoo search them if interested in more info. They have a site. The front carb may already be rebuilt and installed by today so there may be some more updates when i return from the shop. The entire fuel system was nasty when I first got the car. So the first thing i did was to restore/replace all fuel lines and have tank dipped and treated. its as good as new. There was varnish gas when i first got the car. now its just clean as new from tank/s to carbs and all hoses/lines in between.

Some Progress Made. I went to see the Z this past friday and I got some good news and some bad news. The good news is that the car is revving to 5400 RPM now. The bad news, minor as it is, Is that either the pulley or the timing Mark(on the outside of the block next to pulley) are not correct. I did buy a new marker from a seller on Ebay for the new motor. Maybe its not for my engine? The mechanic noticed the timing drop off when the engine was revved to 4K. He adjusted the timing and Voila! 5400 rpm. He then noticed the front carb running rich no matter where he set the needle.... Paltech Restored Carbs. So now he is rebuilding the front carb and get it working right. On the old engine they were able to get it to rev to 6K with carb adjustments. I'm hoping this is the cure although now I feel the title of this thread is wrong and I posted my first message in the wrong forum.... Sorry. All the help and suggestions here have been incredible and I thank all of you. I will most certainly let you know the Final outcome and steps taken to resolve. This has been a real mystery. The only thing that is still lingering in my mind is that the old owner of the car said the old motor was doing this same thing when he parked it 18 years ago. I put Different carbs on the old motor since day one when i got the car. Thats the first thing I did was the fuel system and replacing the carbs. There may be some coincidence involved in this mystery. These rebuilt carbs are the same carbs on the new motor now. Paltech - SU Carbs Round Top ,4-Screw- 425$ micro polished and rebuilt, ready to install with minor tuning and a rich no matter what needle.

so your suggesting a cam swap?

Yes, thats from al's ebay ad. The cam looked to be in great shape(machined) and the springs are double coil springs. Of course "looked fine" means with the eyes not a feeler gauge.... I dont that its the issue although with completely disassembling the motor, there is not way to be certain that everything is within spec. dont forget the old motor did this too and only after tweaking the carbs a lot to give more fuel did it rev up to mid 5K's but still was not right 100%.

The Cam is a performance grind on old stock.not just stock re-ground to stock - Not sure if thats even possible.

True that I didnt know about The reputation of Datsun-Parts LLC. I had purchased a few smaller items from him on ebay prior to the motor purchase. My dad offered me alot of the same advise posted here with a few extras. He told me to take off the air cleaner and light a cigarette. Hold the cigarette so that the smoke is drawn into the carb. Watch the way the smoke is drawn in. If it glides in seamlessly then its good. If if staggers or pulses in, then the chain /cam timing is off and the valves timing is screwed. Also recommended that the tach be removed from the circuit and jumpered in this case to eliminate it as a suspect. Also said removing other fuses to other circuits and noting any changes in performance is worth a try. Squirting gas into the carbs and seeing if it would rev out more. bypassing electrical by jumpering from battery directly to coil, i think this was already tried. Recommended I install a clear inline gas filter so I can watch level changes at 4K- see if it runs low... all sound advice. The original owner of the car said that the old 2.4 motor was doing the same thing when he parked it last. But it was revving up to 5800-6000 range before i brought in the "Nice New Motor" I only came here as a last resort for information. I know mike and art have put alot of time and effort into making my car right. I think I threw them a wicked blind curveball. One last word of wisdom my father bestowed on me tonight was this, "When you find out what it is, It's going to be something simple that was staring you in the face the entire time." Thanks Dad. Thanks Mike and Thanks Art and Thanks to all that posted here so far. This will have a positive end. Keeping you posted... Sean

Brand new MSA 6-1 header and new MSA exhaust. Fuel Tank was treated and lines are clean, new filters,pump,sending unit, and All of this was bypassed at the carbs, with elec. fuel pump and separate gas tank(5 gal). same issue. Im thinking Electrical. Maybe something in the secondary ignition circuit. Original owner mentioned that the car had the same issue 18 years ago when it was driven last but he didnt seem to mind or care to address it. Now the new 2.8L motor is doing the same thing. distributor has been replaced.

Thanks, I will try that tomorrow and see what happens

I need to mention that these symptoms were also identically present when the car had the original 2.4L engine with stock components ie cam.

This is a new engine and when I took it into the Z shop here in Los Angeles, they checked the timing on the cam, adjusted valves, pulled oil pan and checked/torqued everything they could. The cam is a performance grind and the car idles great and runs great up to 4K when it hits what i think feels like a rev limiter, thats the best way to describe it. Banjo filters will have to be checked, since i'm not the one working on the car, I am not sure if they have been checked, but i assume that when the carbs were swapped for a known working pair.... it had different filters but same result. Timing light indicates advance is working and engines firing on all 6. The mechanics working on the car frequent this forum and i am hoping they will help to elaborate on the issue in this thread. They have had this car since Thanksgiving and i'm sure they would love to see it out of the garage and on the road up to Angeles Crest. Thanks for the suggestions. Please keep them coming.

HI, This is my first post here. I have a 1972 240Z. It's story from my attaining it is chronicled here --> Linkhttp://www.cardomain.com/ride/2977492 The car has been at the mechanics, a Specialty Z Shop, since around Thanksgiving. The car has had a new engine installed and just about everything else one could think of mechanically, has been replaced. The car won't rev past 4K. Carbs have been swapped, fuel system bypassed(for testing) coil, distributor,points/pertronix, all have been changed out, even the tach. Wires to and from the coil and distro have been checked/replaced. My Q: Has anyone experienced this problem before? Follow -up Q: What was done to correct it? Or to sum it up, WTF is going on?!?!? $7,000 later and still no properly running Z wants to know. Any and All Help appreciated. Sean:bulb: