What to buy? 1972 240Z vs 1977 280Z

[EuroDat]

Regarding the headers. Always quote the head you are using to the supplier. That way the supplier knows the type of ports you have and can sell you the header with the correct mating flange.

You can find the head type cast between nr 1 and 2 spark plugs.

Chas

[Zed Head]

4 of the cyls are heavily oil polluted, The plugs are covered in sludge, she's tired. I haven't yanked the manifold yet to see the ports. I haven't bought the motor yet, i'm going today to check compression and a closer look.

Oil fouling is a bad sign. Valve seals or rings could be bad. You won't have much time to tinker with the old 240Z engine if you're trying to get the L28 to stop smoking or just run right. You might keep looking. My old L28 had bad valve seals and would only run well after a high RPM run to burn off the crud. Otherwise it just ran "okay". The cylinder pressure numbers were great, you couldn't tell the seals were bad by that test.

[ZcarFanMan]

Oil fouling is a bad sign. Valve seals or rings could be bad. You won't have much time to tinker with the old 240Z engine if you're trying to get the L28 to stop smoking or just run right. You might keep looking. My old L28 had bad valve seals and would only run well after a high RPM run to burn off the crud. Otherwise it just ran "okay". The cylinder pressure numbers were great, you couldn't tell the seals were bad by that test.

Actually the oil fouled plugs were from my 240 motor in the car now. I just got back from looking at the L28 motor and we could only hand crank for a comp test, I don't know if it means anything by these numbers but they were consistent. 3 or 4 revolutions each cyl, the 1st crank all cyls went to 30psi the second crank ended up to be final numbers and didn't change with a few more cranks. The 35psi Cyl 5 you could hear the leak at the exh port. The motor was out of the car. Should I look elsewhere or are these numbers decent for socket wrench cranking..

1 47

2 50

3 50

4 50

5 35

6 50

[Zed Head]

I would say those numbers are pretty meaningless, but at least give hope. Probably not bad for wrench speed RPM. Can't you borrow a car battery and jump it? You could even disconnect the starter from the car and jump the starter directly.

You can tell a lot by looking if you know what to look for. How did things look? Broken manifold studs, sludge under the valve cover, spark plugs from the L28 (this time), etc. They can tell you something about how the engine ran before the car was parked.

[ZcarFanMan]

I told the guy I would bring a battery and my starter from my 240 since he didn't have one. But when I got there there was nowhere to put the starter. It mounts into the trans right? How would I crank the motor? This is all new to me, on the 3CYL 1494cc rotax motors we do the jump trick because the starter attaches to the upper crank case.

No sludge seeping anywhere. The exh ports looked normal except #2 was white. Maybe i'll look for the L28 & trans to swap out..

Thanks!

Edited January 5, 2014 by ZcarFanMan

[Zed Head]

I thought the engine might still be in the car. Yes, the starter mounts to the transmission.

Probably an N47 head if you have a white exhaust port. And that must mean the manifolds are off. So you could look for deposits on the intake valves or oil leaking down from the guides. White is good on an exhaust liner, that means it wasn't overloaded with fuel and oil deposits and was staying clean as designed.

Too bad you couldn't take and post some pictures so the experienced eyes out here could take a look.

[EuroDat]

I wouldn't give up on the L24 so quickly. There can be quiet a few things that can effect a compression test.

Your figures: 75 75 80 150 145 78. Have you tried oil down the spark plugs? If its rings, a threw squirts of oil will bring the compression up a lot.

You could also have some dirty vavles from staning in the open position for years. A leak down test will tell you where its leaking.

It might be worth the effort to start and run and maybe a seaform treatment. If its stuffed what do you have to loose, but the time you spend on it.

Chas

[ZcarFanMan]

Thanks for the "last chance" hope Chas..

I did only 2 cyls and i'm convinced the rings are shot..

#1 cyl I actually only got 70psi and after 4 squirts from the oil can it jumped to 105

#2 cyl 72psi, 110 after oil squirt.

Damn!

I'm going to yank the head today and see what I find. Whats the chance that these cyls will get by on a hone and not going over size? I know it's hard to tell before inspection but lets say it's at 168,000 miles, do they usually need to be bored or would a hone suffice?

Thanks..

[EuroDat]

Thats quiet a jump in compression. Looks like it could be rings. The L-series engines are dam tough for a late sixties, seventies engine and generally go a long time before giving too much trouble. You could very well be suprised and find the bores in good shape and the rings are stuck from sitting so long.

Honing or going oversize depends on a number of things. How much lip it has on the top of the bore and the condition of the pistons could leave you with no other option than going oversize, but its been a really long time since I had one apart.

If you are taking the head off, take some photo's. A photo can say a thousand words...

I would also wedge the timing chain so the tensioner stays put and the chain doesn't slip a tooth. Nice suprise if you decide to remount the head. You never know, it could be something fixable without dismantling too much.

Goodluck and looking forward to the photo's

Chas

[Zed Head]

I would get the L24 running then take it out and run it hard to blow out the crud, wear down the rust, soften up the seals, etc. Some people call this an Italian tune-up (I think the term references the cars, not the people, no offense intended). Not much to lose except a towing fee and you might find that it's actually in good shape. A little bit of surface rust in the cylinders would probably kill your dry pressure readings.

[ZcarFanMan]

OK, got a few pics..

A few broken studs, a few spiders hiding, it was an easy task so far.

Here ya go

[ZcarFanMan]

A few more pics