my current project

[clutchdust]

just want to post a pic of my current project car. this is only my second foray into the Z car world. a brief history is in order:

the car belonged to my honey's dad. she also had a Z (her first car) that she ended up having to sell a couple years ago for reliability, and monetary, reasons. she was very, very sad to let her Z go but after working on it for her, it was for the best. the car was cancerous and had subframe damage, the $hi+ to worth ratio was way upside down.

for her birthday last year, i got with her dad and got her this car which had been sitting for 12+ years (he had been keeping it for sentimental reasons, and to pass on to either of his kids who wanted it. she did.)

after that long, i had to pull the fuel tank and have it steamed to clean it, bought a new battery, disassembled and cleaned the gunk out of the carbs and fuelpump. i ran new fuel lines, drained the oil, changed the filter and replaced the radiator and water. all this and when it came time to start it, i got nothing. after some poking and proding, there was no other conclusion than the rings siezed (at least that was the best, worst case scenario). so off comes the head, and no, i didn't drop the cam chain. sure enough, #6 cylinder was rusted to the wall. apparently the unfortunate victim of a head gasket failure more than a decade in the past. luckily, here in nevada, we're pretty dry so almost all of the rust was strictly from the coolant leak. after soaking the piston with PB blaster for 3-4 hours, a few whaps with a 16oz hammer on a wood drift and she freed right up. i hit it lightly with a cylinder hone and very minimal pitting was left. so, back together everything went. another half day of fighting and tinkering and she actually ran! i set the timing and balance the carbs and let the car run for a good 1/2 hour. now it was time to take it out and run her through the gears, well, after the 15 year old tires were replaced. fresh tires and around the block we go, sort of.

to shorten an already long story, the carbs were running super rich. i got them toned down a bit so that the car can run and actually drove it 15 miles from a friends shop where i was keeping it to my house in time for her birthday surprize last july.

the car still has fuel issues and i'm looking for solutions but she's pretty straight.

so no more waiting, here you go:

i can tell you one thing for sure, after the battle i've had with this one and her previous Z, the L24 in mine will probably never run again. it will go the way of the dodo and a small v6 will find it's way in the engine bay. hey, that rhymes!

[Arne]

Welcome! Good looking car, looks like a good starting point.

Rebuilding the L24 will be simpler than swapping in a V6 of some sort. And swapping in a running L28 will be simpler yet. Food for thought.

[clutchdust]

while that may be, i've always been a chevy guy and putting my hands on chevy v-6 parts are going to be far easier and cheaper than the old nissan parts ever will be. not to mention the better weight and balance of a compact v-6. but all is not lost, there will be an L24 looking for a good home.

[kenz240z]

Hi Gary, that is a sweet looking Z car! What year is it? The '73's have an electric fuel pump mounted back by the fuel tank. There is a fuel filter in the tank that can cause fuel delivery problems, especially in a car that has sat for a long time. The filter can get clogged with sediment from the tank.

I had this problem with my Z, it would start & run fine, but on the highway it would develop a fuel starvation problem, top speed was around 55/60 mph. It got worse to the point where the engine would die after driving for a few minutes. Took awhile, but I finally tracked it down to the clogged filter in the electric pump.

[clutchdust]

this one is a '72. i thought it might be fuel starvation problem as the car seemed to idle and free rev fine. then, when driving, it would stumble once in 3rd or 4th gear. 1st and 2nd would be fine but generally by the time i hit 3rd, it was done. i did notice that i could shift into neutral and just idle and after a few seconds it would respond again. i attributed this to weak fuel pump so i installed an aftermarket electric 5# unit with no decernable improvement. i know it's not the fuel line since i had the tank flushed and ran a 5/16" rubber fuel line (temporarily) to bypass the plugged steel line. i've also installed a pertronix kit but haven't gotten everything tuned back up to see how it runs now.

ken, funny to see you and your location. these cars are actually from longmont. my g/f family moved from there back around '92.

[ChrisA]

Never mind, should have read Kens post more clearly.

[kenz240z]

Oops, Chris thanks for catching my error. The filter is in the pump...

I've been living in Longmont since 2000, before that I lived in Lincoln, NE (Havelock, specifically...).

The engine in the 240Z is a pretty simple beast. Here are some suggestions to get it running in top form. Hopefully the engine is in pretty good shape and the rust in the cylinders hasn't hurt the compression too much.

1. Adjust the valves. Refer to a factory service manual or other shop manual for details.

2. Set the timing - I'm running round top SU's and an intake off a '71 on my Z. All the emission control devices have been removed. I set mine at 15 degrees BTDC.

3. Adjust the carbs. Check the float level, make sure the choke cracks open the throttles & pulls the fuel nozzles down, and balance the carbs. Refer to the FSM or shop manual for details, there are more steps to this if all of the emissions devices are still on the engine.

Here are some helpful websites:

http://www.jetlink.net/~okayfine/sutech.html

http://members.core.com/~ckotting/tuning.html

http://www.picturetrail.com/gallery/view?p=999&gid=1803105&uid=786489

http://www.teglerizer.com/sucarbs/techtip6.htm

I've wondered about a Buick V6 swap into a Z car. No distributor like a small block Chevy, so no issues with it hitting the firewall, or having to relocate the hood latch.

[clutchdust]

ken, i'm half way there. i adjusted the valves per the haynes manual. i checked timing today but i'm a little fuzzy on the setting. all my SBC stuff had a graduated pointer that gave me individual degrees, like 12* before and 6* after TDC. the nissan doesn't appear to be that explicit. looks like a couple notches in the crank pulley and a pointer and your just either on a notch or in between them?

there's no smog equipment on the car and the carbs were disassembled, soaked in solvent for a month and cleaned with a toothbrush before reassembly. with the aid of a friend who has alot more experience with the simple design of the SU (round tops), i got it running but fine tuning has been elusive.

this car is my g/f car so i want to pull as much out of it as i can without getting really stupid. i've pretty much decided to go with the 390cfm holley 4 barrel on a common manifold and a header. this should perk up the stock motor fairly nicely and be a good foundation should i decide to bump compression and/or change the cam in the future.

right now, getting the car to perform reliably is first and then getting not to suck gas so bad is second. i cannot believe how much gas i've gone through just trying to tune this damn thing! is this normal? i must have used 4 gallons in 20 minutes and the car never moved out of the driveway...

[kenz240z]

Hi Gary,

Sounds like the engine is running a bit rich. Have you pulled the plugs to check their condition?

The timing marks and pointer are set up opposite of a SBC. The marks are on the pulley instead of on the tab mounted to the timing chain cover. There should be 5 notches on the 240Z crank pulley. Facing the engine, the notch on the left is TDC. It is also a deeper notch than the other 4. Each of the remaining notches marks 5 degrees of advance. The 72 factory service engine manual shows the timing at 5 degrees BTDC @ 750 rpm for a manual, 0 degrees @ 600 for the automatic. I have my engine set at 15 degrees BTDC, you might start at 10 considering you've got the emissions stuff removed.

The automatic equipped cars came with a dual point distributor. One set of points for normal application, the second set of points is advanced 10 degrees and is switched in at temperatures below 30 degrees F. It's part of the emissions control system. I have an automatic in my Z and the PO swapped the distributor out for a single point unit.

Have you checked to insure the needle & fuel nozzle aren't binding up in either carb? The needle & nozzle need to be realigned anytime the carb body is disassembled. The way to check is to remove the air cleaner and remove the dipstick in the top of the carb. Then use a finger to raise the suction piston. Make sure it raises up smoothly. Then remove your finger and let it drop. It should make a "clunk" sound as the piston hits the body. Also verify that it does indeed drop all the way. Any binding will only cause problems.

Check that the fuel nozzle moves freely in the carb body. You should be able to pull it down by hand about 1/4". Pulling the choke lever back should do the same thing. Tighten the idle mixture adjusting nut for each carb until it is up against the carb body. Then turn it out 2 and 1/2 turns. This should get it in the ball park. The FSM says to adjust these for the best idle. Both need to be set at the same number of turns.

Wipe the carb dipstick dry and put it back in the carb. Then take it back out and see how much oil is in it. The oil should come up to, but not over, the top line on the dipstick. The oil in the carb keeps the suction piston from rising too quickly when you accelerate. The carb then provides a richer mixture, kind of like the power circuit in a down draft carb. The FSM says to use SAE 10W-30. I bought a little bottle of carb oil from MSA and use that.

All of the previous adjustments can be dead on and the car will still run poorly if the carbs are out of balance. If you have a rough idle and the car is sluggish from a stop I'd suspect that the carbs are out of balance. The balance screw is on the linkage between the two carbs, and is right next to the rear carb.

First, make sure that both carbs are flowing at idle. Back out the balance adjusting screw to make sure the carbs are operating independently, there should be a little slack in the linkage now. Adjust the idle speed screws on each carb about 1/8 turn at a time to set the idle and make sure both carbs are working. I'll adjust one carb until the idle speed increases, then back the idle screw off just a touch, then over to the other carb and do the same thing. I'll go back & forth between the two carbs until I get it right. If the balance screw is adjusted too far in, the engine will be running only off the rear carb at idle. Too far out and the front carb will open sooner.

Next, tighten the balance screw a little at a time until the engine speed just starts to increase. This should be causing the rear carb to open up. Back the balance screw out until the idle speed just backs down. Then tighten the fast idle screw at the top of the manifold to get the engine up to 1500 rpm. This is where a Unisyn or other device comes in handy. I don't have a Unisyn, I have a little tool set that has a pair of round tubes and wire pointers. You take the dipsticks out of the carbs and put the tubes in, then the pointers go in the tubes. Makes it real easy to see how high the piston in each carb rises, and this can all be done with the air cleaner still on. Or, you can use a piece of rubber tube & your ear to compare flow between the two carbs. Put one end of the tube just inside the carb opening, and the other near your ear (not in it!) and listen to the difference in sound. Or, use your eyes and watch the piston in each carb, make sure that they are both open the same amount. No matter what method you use, adjust the balance screw so that both carbs are open the same amount at 1500 rpm. Then back off the fast idle screw until there is a small gap between the screw and the lever.

Following these steps should get the engine running good. Of course, the distributor cap, rotor, wires, plugs, coil, etc... should all be in good condition, and hopefully the engine has good compression.

[clutchdust]

ken, thanks for the write-up. the admin should probably put that as a sticky for people just getting a car running.

i have replaced the coil and installed a pertronix in place of the points unit. the plugs are new delco rapid fires and it does appear to be running rich. i have done just about everything you suggested except i was advised to use ATF in the pistons. maybe that's my problem??? that would explain why it appears to flood out under load going through the gears, but run fine when free-revving. i will change that this week. i have one of those cheezy carb balancers but it seems to work o.k.

the problem doesn't seem to be getting the car to idle or rev o.k., untill i drive the damn thing. then it just wants to go haywire on me.

i'll take a scotchbright pad to the pulley and shine up those marks a bit to see where i am. why do you advance so much over factory specs?

[kenz240z]

Hi Gary, I've heard of Z owners using ATF in the carbs, not sure if changing it will yield a real big difference or not. But, anything is worth a try. Also, most folks swear by the NGK plugs. The '72 FSM specifies NGK BP-6ES plugs. Here again, maybe it won't yield much difference, but then it just might! Don't give up, you'll find the culprit sooner or later. Check the float level in each carb again, just to make sure it's not too low, that will cause a rich mixture.

I'm probably running the timing a bit too advanced on my Z, but it accelerates well, even uphill without any pinging. Victor Laury has a great post explaining engine timing:

(http://www.classiczcars.com/forums/showthread.php?t=18411&highlight=timing)

According to the FSM I have for the '72, only the USA and Canada got cars with the emissions control devices, the rest of the world got 240Z's without all of that! These cars apparently also got distributors with different advance characteristics. The FSM specifies the timing at 17 degrees BTDC for these non-emission engines.

I have a theory that Nissan was shooting for 29 degrees total advance for the engine. The timing spec for the USA/Canada engine with manual transmission is 5 degrees BTDC, with distributor model D612-53. If I interpret the 12 to mean the distributor initial advance, that yields 24 degrees crank advance, plus the 5 gives 29 degrees total. For the USA/Canada engine with automatic transmission, the timing spec is 0 degrees, with distributor model D614-52. So, if my theory holds, the dizzy has 14 degrees initial advance, yielding 28 degrees crank advance. For the non-emission engine, the specs are 17 degrees BTDC, with distributor model D606-52. I'm guessing this dizzy has 6 degrees initial advance, yielding 12 degrees crank advance. Add the 17 degrees and you get 29 degrees total advance.

I've got a dizzy model number D611, so I'm guessing I have 22 degrees crank advance, plus the timing at 15 BTDC gives me 37degrees total, which is on the high side. But, like I said, the engine runs like a top, starts easily, and doesn't ping under strong acceleration.

If anyone has more information on all this, please let me know. I'm guessing based on the different specs listed in the FSM and could be way off....

[clutchdust]

hey ken, i took some of your advice this weekend and tweeked it some more. it's almost drivable! it's getting there anyway. i drove it around the block a few times to see what kind of issues i would have and a little sputtering and bucking but still ran pretty well.

maybe you can help with this one though. i have noticed that to get the car rolling, i have to slip the clutch at about 1500-2000rpm. being a 4 speed that's not that big a deal. what the problem is though, is from idle, i have to roll into the throttle to bring the RPMs up. if i just "blip" the throttle, it'll bog, sometimes seem to backfire through the carbs. after i get it rolling though, things seem to be pretty good.

still need to change the plug wires but that's about it for the ignition. BTW, since i put the pertronix in, the tach doesn't work. which wire is the tach feed?