I just picked up a 70 240 a few weeks ago. It smokes a little at idle but looks like cheech and chong in the car when it's reved. It has the smell of oil, not gas.

What I've done so far- I took the carbs apart and cleaned them and put them back together. It was running rich by looking at my plugs, which were replaced. Carbs were synced. I checked compression and it's 140 across all 6. So it's not the rings. It runs GREAT but just smokes. The only thing I can think of is valve seals or maybe a readjustment of the carbs?

If it's the seals, can they be replaced with the head on the car? The car is in very good condition for a driver, but if I go tearing things apart I might as well redo the engine/engine bay. I'd like to at least drive the car a year before I give it a proper resto.

Welcome. If the smoke is from oil then you need to determine if it's from the valve seals or the rings. It could be from both at the same time but the standard diagnosis is to run a compression test and then add some motor oil to each cylinder one at a time through the spark plug hole and re-run the compression test. If the compression stays the same then the oil leak is through the valves. If it goes up then it's from the rings.

It is possible to replace the seals without removing the head.

Not necessarily. I've seen more than once that these L-series engines have good compression, but that the oil control rings are gunked up and don't scrape the walls clean. Has the engine been sitting for a while? You may want to try soaking the bores (and therefore the rings) with ATF. That can help free up the oil rings. Search the forums for "waking sleeping beast" which haas a good write up to getting one going right after it has sat.

the only other way is to check your valve seals your getting good compresson you might wanna take apart the head

I don't know too much about the history of the car. I know for a fact it sat since May at a repair shop on consignment. The inspection was up this year so I'm assuming it was driven last year, stored winter, then pulled out of storage in May and put up for sale. I did the check with the oil and it didn't change anything. I'll give it one more try with the ATF. If this head comes off I'm going to wind up dumping $5k under the hood.

What ever it turns out being, just remember that it's 37 years old. No matter what you do with the exception of new rings and a bore job, it'll smoke.

Actually, it may be just the head but when you get on it and it smokes, that ussually determins bad rings and oiler ring. Who the hell know what the Previous Owners put that car through before you got it. Mine has smoked for the last 5 years. And I have Great compression on all 6 cylinders and the head has been replaced with an E88 out of a 73' Z and it was in great condition before the swap.

I don't foresee you spending $5000 in the motor unless you plan some serious upgrades.

Congrats on the purchase but remember that the carbs control fuel and have nothing to do with oil other than the burning of it when it's mixed with fuel.

Dave.

Could this Z have a automatic trans by chance? If she does check the vacuum line where it connects to the intake manifold. If you see any sign of oil there in the line . You have a bad vacuum module, or control. They are just a diaphragm that controls the shifting and when they fail they can allow ATF to flow up the vacuum line into the intake. If you have a bad one and change it yours self. There is a small little pin that sticks out of the fitting. Before you install the module put a little grease on the pin to hold it in place when you screw it in the trans. Gary

It's a stick...hate autos with a passion.

This isn't a puff of smoke, it's a plume. I may be buying an L24 w/ E88 head that I could swap in then pull it out and mod it when I restore everything. This is a numbers matching car so I want to keep the original engine and not "ruin" it with mods.

This is a numbers matching car so I want to keep the original engine and not "ruin" it with mods.

I was in the same position several years ago; my car also smoked a lot - most likely because I tried to do a ring job on it myself 20 years ago without really knowing what I was doing. After letting it sit for many years I simply had the engine shipped off for a complete rebuild - for about $2000. I also wanted to keep the numbers matching so this was the best option for me at the time.

Mike what did $2000 get you? I swapped out my L26 because it was smoking and burning a lot of oil and I want to rebuild it then stick it back in. I was just wondering what all I could do for $2-2500. Thanks Chris

I had my engine sent off to Jasper Engines: http://www.jasperengines.com/

Looking at their web page price list it appears that the current price for an L24 is $2087. They currently provide a 36-month, 100,000 mile warranty so consider it as good as new. I believe you end up with your original block, head, crankshaft, and camshaft but everything else is new (not sure about the connecting rods but they do indicate new pistons). Their web page is fairly informative so you can check that out. As I recall the price includes pickup and delivery.

Mike what did $2000 get you? I swapped out my L26 because it was smoking and burning a lot of oil and I want to rebuild it then stick it back in. I was just wondering what all I could do for $2-2500. Thanks Chris

You can also go this route if you have any similar shops in your area. http://www.ctintl.com/ They sell used long blocks imported in containers from Japan. Typically, they'll have under 40K miles, 6 mo/6K mile warranty on internal parts, compression tested/tagged, and steam cleaned. This particular shop sells a L28/F54 long block for $550 + $50 core. I have used their engines in the past and still have one in my 320 pickup (J16) that's been running well for almost 9 years.