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Fresh Motor; Running, but not well.


Mpower280z

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I rebuilt a F54 Block and N42 Head for my 78 280z. I just had it running for the first time in about three years the other day. It was not running well though. It ran good enough to drive, but didnt seem very peppy as though the timing was off or it was running on a select few cylinders... But still able to go down the road.

I tried to make it run the way it should, so I re-set the valve timing. I put everything back together and still no luck. It now seemed as though the head gasket was at fault with the way the motor turned more freely. I replaced the head gasket and torqued to proper specs... Still no progress.

So now I decide to take the valve timing apart again and do one more check over everything. I installed a new Cam sproket, timing chain, spark plugs, plug wires, AFM, and distributer. I now have exactly fourty-two links between bot timing marks. The Cam sproket is set at the number one position and reaches its timing mark with the crank pulley at 5 degrees. Everything now seems correct. I have good compression, good spark, gas, and air... I think. I put everything back together and it runs. Its very hard to keep an idle and everytime I blip the throttle, it wants to shut off. I checked for vaccum leaks, there is thirty-five psi in the fuel system, and I am just getting so confused.

I had it driving down the road a few days ago and ever since I tried fixing the hesitation problem, it hardly keeps an Idle.

The next paragraph below is what I wrote on Zcar.com and some responces I recieved last night after working on it. Sorry theres a lot of reading on this, but I need all the help I can get. Thanks!

280z Valve Timing

Author: MPower280

Date: Jan 29, 11:17pm

I attempted to set the valve timing after a head gasket replacement and ran into a bit of a problem. The car ran before, It lacked compression from a shot head gasket so upon replacement I seemed to have gotten a little confused about the Valve timing.

I set the number 1 piston to TDC and the timing mark at 0 degrees. I then set the cam/sprocket at its timing mark on the number 2 position. After installing the timing chain and rotating the motor around the cycle, the camshaft sprokets notch winds up about 3mm past the timing mark toward the engines rotation. The crankshaft is back at 0 degrees on compression stroke when this occurs. I tried moving the sproket and cam one tooth anticlockwise and found that the notch sits further away from the timng mark, but on the other side. I did use a wedge in the timing chain when I removed the sproket so that annoying chain tensioner wouldnt move, but anything could have happened. The chain does seem to have too much slack on the distributer side.... I cant remember if thats normal though. Looking down into the timing cover, the tensioner looks ok. I also think it might be important to know that I rotated the engine through the cycle by hand and did not see the timing chain slip over a tooth.

I did try firing the motor with the cam past its mark and did get it to run.... kind of... I think I can, I think I can, I think I can.... Nope, I cant. Adjusting the distributer helped, but it still ran very rough.

What do the numbers 1, 2, 3 on the cam sproket indicate? Advance/Retard, but where do I want mine to be?

Tomorrow I will be removing the timing cover and so forth to get a better idea of what might be going wrong in there. Until I do that, any advise would be much appreciated. Thanks.

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Re: 280z Valve Timing

Author: coyote

Date: Jan 29, 11:58pm

i am not sure what you might have done wrong (if anything) but dont forget that once the chain is set at the proper marks on tdc , it will change marks once rotated. the pulleys are different sizes so they will not line up at each roatation like they started. if you were to turn one rotation the marks would be off ie if you were to back it up that same one rotation they would line right back up.

if it runs better with the dist advace maxed out you might have it off one tooth on initial set up

factory nissan mechanic since 72

co-owner of z car shop in phx , az

Spankysautobody.com

72 Z-won best engine comp. twice @ MSA 99 and 03

73,77,86 Z

(2) 74 Z won Best of Show @ MSA 04

90 cpe,93 vert , 94cpe..took 1st place modified class @MSA 2006

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Re: 280z Valve Timing

Author: Primer&Rust

Date: Jan 30, 12:15am

I would get the engine back at top dead center, take the cam sprocket off and put the cam dowel point upward to the top bolt on the camshafts front plate. The # 1 cam lobes should a be point somewhat upward. Than put the cam sprocket on in the #1 position and give it a try assuming this is a stock camshaft

Sweet 280z

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Re: 280z Valve Timing

Author: MPower280

Date: Jan 31, 12:52am

Ok... I completely disassembled the front of the motor and checked everything out. I brought the lower end to TDC aand set the cam sproket at its timing mark (number 1 position). The tension on the chain now seems normal and the tensioner itself is corrected. I replaced the timing chain and cam sproket. I also made sure there were exactly fourty-two links between both timing marks. I fed the oil pump and shaft into its position with the holes lined up correctly, but it seems as if you were to line up the holes and then push it though the timing cover, the shaft will rotate when it meets the gear on the crankshaft. So anyway, I get it all back together and rotate the motor around the cycle by hand. Now when the camshaft timing mark meets the sproket timing mark on the compression stroke, the cankshaft pulley reads five degrees... if that matters. Then I reassemble the rest and attempt to fire it. I get the same deal... Only this time I can get the motor to idle somewhat well, but when you blip the throttle it wants to shut off and its a challenge with a quick hand for ignition timing to keep it running. So now I decide to try replacing the AFM and that didnt make a difference either.

I checked for vaccum leaks, fuel pressure is at 35psi, I have great spark, electricle seems to be in order, I installed new injectors (not rebuilt), tried changing distributers, plug wires, replaced spark plugs... However, there is no cold start valve; going for that cleaner intake manifold look. Ran fine without it before!

I dont know what else to do... My friend said that maybe I should try tweaking the AFM... Just thought I'd check with your opinions first.

Before I forget, I'd like to mention that the guage is not reading engine temp, but even then the motor ran before.

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Re: 280z Valve Timing

Author: MPower280

Date: Jan 31, 12:54am

And one more thing: The rpm needle seems to be "jumping" at idle, but steadys itself out when rpm picks up... Dont know if that matters either.

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huh. :ermm:

besides the new motor and body work done to the back end, what else have you done? Did you restore the entire car? Reason I ask is because maybe the gas Tank could be dirty inside and clogging the fuel filter and restricting fuel flow???? I'm just trying to think of the simple things first :) The fuel pressure in the 280Z's is suppose to maintain 36.3 PSI Factory.

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Be sure to check your injector connectors and make sure they are all getting a good connection and that they are all firing. You said that you replaced them, so you may want to go back and double check to make sure you got all those connections tite. With experience on my l28, it was running a little rough, and we found out that the number 5 injector was not firing. It turned out that it wasn't getting a good connection and the clip was not holding it on tite enough, so after some "fiddling" with the connection, we got it to fire and now it runs smooth as ever and runs on all six, so it's just something you may want to check.

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76Datsun280z, Its funny you mention your number 5 injector not firing. I had just discovered that my number 5 wasnt firing as well! Funny how things work with these cars. Anyway, I fixed the wiring error and still have the same problem. I even put a noid light on all 6 injector wires and got a little light to shine. Do you know how bright the noid light is supposed to be? I only watched a dim light blink for the pulse. At least there is a pulse!

DatsunZsRule, The car has quite a number of modifications and upgrades to the excisting structure. I planned on installing a 500+hp 383 Stroker V8 into the car, but that plan was scrapped when I couldnt find the time to weld in the roll bars and improve the unibody's structure to the extent a motor like that requires. However, I did do some other things to stiffen the structure. Being that the floor of these cars acts as a foundation, I installed custom floors with 16 gauge steel and modified them not only for more strength, but to better fit the more modern sport seats in. (that is a recent modification that has not yet been photographed). I also welded in the frame rails under the cockpit using 16 gauge steel and coated the underbody in fiberglass to help seal out moisture and salt... if I were to drive in the winter. A layer of asphalt undercoating was applied because it covers the ugly look of fiberglass and is a lot tougher that your typical undercoating found at the near by Autozone or Napa. The rest of the structer is in very good shape and required no modification or repairs.

As you might notice in the picture I have posted viewing the front brakes and suspension, I have taken all the suspension pieces and beed blasted the corrosion off. I have a guy in Kenosha, Wi who works at a plating company so I just drop off a box full of parts and pay him under the table to run it through the process. After plating I then decide what part I want painted and what parts to leave gold or silver. The plating is a good idea because with or without paint, it will never rust... for another thirty years at least. Other than that, I added a set of MSA's Sway bars (strongly advised for safety. stock, these cars have way too much body roll) that measure one inch in the front and 7/8's in the rear. All bushings are polyurethane and or new. I installed a set of KYB performance struts that offer next to zero body roll along hard conering. The brakes are all stock, but have been cleaned and plated to look nicer. Oh and minus the Brembo rotors. The car is lowered about three to four inches all around to close the ugly gap between the top of the tire and the apex of the factory wheel flares. Then I decided to buy the Motorsport strut bars for both front and rear.

The engine is an F54 Block with a square port N42 head. I had the proper machine work done and purchased turbo head bolts. The camshaft is currently at factory lift until I see how it reacts to the turbine which will be installed in the near future. The head was hand ported and polished by myself and a friend who was teaching me how to do it... Very simple! I am trying to go for the "clean look" on the intake manifold, so I have a single fuel rail and no cold start valve. I have yet to find it safe to eliminate the AAR. I have a 60mm throttle body, but havent figured out how to install in properly yet. The block is painted black, the head is alluminum, the intake manifold is left blasted and cleared for a deeper alluminum color, and the valve cover is gold infront and faded into a copper color to the rear. Looks nice on a black car! I also installed MSA's headers and wrapped them with that insulation to subtract heat also purchased through Motorsport. The transmission is a five speed out of a 280zx turbo. Its not rebuilt, but It seems tight and smooth. The drive shaft is alluminum and the rear end is an R200.

Keeping that F54 cool is a custom made Griffin alluminum radiator with a 2300cfm electric fan controlled by the coolants temp.

The body of the car I mostly left alone. Its a great looking car with or without the bumpers. I think the body lines of that car were ahead of its time and needed very little work to get it looking right in my eyes. As you see, I "shaved" the rear end smooth, added MSA's front spoiler and lost the front bumper to go with the lines of the rear. I like the front spoiler because if your looking directly at the front of the car, you can see the fronts of the tires. Just makes it look more aggressive. I also need to order the carbonfiber front bumper MSA offers.

The interoir has become quite fancy. I installed a nice set of leather sport seats that hold you in better and will work with any 4-point harness. The carpet is all new and had to be custom fit to the modifications I made to the floors. My friend did a very nice job installing a CD player connected to four Infinity speaker located behind and to the side of both driver and passenger allowing excellent sound quality. I bought that rally steering wheel and hub from motorsport, but that will only be tempoarty until I find the right Momo. hmmm... It took me five month to pick the right tire size, how long do you think it will take me to select the right steering wheel?

And as you might have noticed, the wheels are 16x7 konig troubles. hmm... thats kinda funny; It took five months to select a tire size and I cant even remember what size they are. I had to add custom made spacers to all four corners to bring the inner wheel further away from the spring. No worries, the wheels arent sticking out like those lowrider pick up trucks! Infact they are perfect with the wheel flare.

I have put hundreds of hours and thousands of dollars into this car and Im sure you can now see why I am a little depressed and upset that with all that work and money, it still wont run! I appreciate the advise about the possible fuel blockage. but my filter is clear and the gas tank is brand new. I have 35psi running off the return line and can adjust it to whatever I want it at. If I cant figure this out by tomorrow, I will be trailering the car to a garage first thing friday morning. I'd really like to avoid that though in all ways possible.

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WOW long reply HAHA LOL Awesome job on your Z though man.

Well first off let me say congrats on all your hard work. Sounds like you'll have a real fire cracker there once you get the kinks worked out :)

You have done a lot of modifications to it from what I've read. Me being more familiar with the original factory set up on the 280Z's, I probably won't be as much help to you. Sorry.

Hopefully someone will chime in with some thoughts & opinions that will help you and you won't have to take it in to some shop :)

Good luck and let us know how it turns out.

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And one more thing: The rpm needle seems to be "jumping" at idle, but steadys itself out when rpm picks up... Dont know if that matters either.

Check the AFM connections!

Are they gold/coppery like they're supposed to be, or are they limey and green?

I had the exact some problem for about half an hour in my garage one summer day: The idle would jump up and down, as though the tach. were on a trampoline, and "smooth out" as I gave it gas.

I realized that I'd forgotten to plug the AFM back in. I rectified that mistake and bingo, problem solved.

'Best of luck to you!

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I dropped it off at the garage last night. Today, we figured out that the coolant temp. switch was bad so it was replaced. It fired right up and held a smoothe idle, but as soon as I drove it down the road it began to buck and hesitate. It would not smooth out even in higher rpms. Finally, I pulled over to check the timing and while adjusting it the car simply shut off and wouldnt start again. I swear, this thing has a mind of its own. It will run for a bit then shut off just as quick as it started and say "I dont wanna!" haha. I even think I heard the car laughing at me while trying to diagnose the problem(s) myself! haha.

The guys I dropped it off with are considered the number 2 shop in the Chicago land area so they should be able to figure it out. I took them about three minuts to find an error in the temp switch... Sad to say that was a problem I spent three days trying to find! Ill be meeting up with one of the guys from there tomorrow to further our attempts at getting her going so Ill be sure to post an update tomorrow night. Thanks!

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We don't have the 280 in the UK but on the basis of my knowledge of FI I would suggest that perhaps your ECU is on the blink or the throttle switch is not working. First line of attack is to clean all the electrical connectors, WD 40 etc, especially as the car has obviously stood for a while.

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try this one, Did you check the distributor shaft alinment? If you put the dizzy shaft in wrong it doesn't matter if the timing chain is right your timing will always be off. I have an F54 N42 combo, but Im running SU's (less crap to go wrong)I had that problem when I rebuilt mine It was off by one tooth and it ran like crap, but it did run so it could be different from your problem. Also I would never use the bosh jettronic FI, It was cool for 1975 but so was the commador 64. I'm just say'n... know what I'm say'n.

Good luck and let us know what the #2 nissan guy in all the land has to say

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Ok, there were a number of things wrong with the car. After finally correcting a few wire misplacments, The engine fired right back up, but still showed evidence of the same problems of hesitation and that timing feeling. After establishing a way to get more fuel to the engine (tricking AFM) and timing the ignition with precision, the engine began to fuction more along the lines as its supposed to. There was still a problem. He later found that the gasket between the throttle body and the intake manifold was the wrong gasket. To a person who is not experienced enough, the gasket could easily be mistaken for the correct one being that there similarities are strikingly alike. So after that, she fired right up and drove well. Now that I was actually able to put a good load on the engine, I found that the clutch slips at mid to high rpms. That was a new clutch! Now the transmission needs to come back out. Its ok though, I am much happier that its finally running the way its supposed to.

I want to thank all of you for your advise and support through this. You have been very helpful and Im sure your kindness will not go overlooked. I will be sure to post some pictures of the progress made so far.

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