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Compression issue/question (L24)


Guest petrol

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Hey all...

 

I just bought a '71 240z from the original owner's family (estate thing). It has been sitting in the garage since 1983. They did me a favor by draining all the coolant and fuel from the tank, and as far as I can tell, purged the fuel lines too. There isnt any built up nastiness in the carbs!! And an empty, clean, silver-inside tank didnt hurt my feelings either. :D

 

Anyway, I went to "fire it up" with some starting fluid just to see if it would light-up, and no go. It sounds kinda flat too. So I proceed to check compression the only way I know how (all plugs out, WOT, etc...) I get a reading of 30-somthing PSI on all cyl's except one (cyl 2 I believe). As far as I know, a blown head-gasket wouldnt kill ALL of the cylinders would it? My lack of experience with the straight-6 shows here. I pulled the valve cover off, and everything seems to be moving/opening/closing the way it should, and there are no signs of a crack history in the block or head. The oil is clean, and the radiator and dipstick both show no signs of coolant/oil mixture. This was an estate thing...left untouched...so there wouldnt have been any tampering to "doctor it up" for more money...so hidden problems arent really going to be a problem here.

 

Anyone have any insight to lend? Anything else I forgot? If the cam/crank timing was off drastically, would this skew the compression like it did? I cant think of anything else to try, other than to swap the motor for one that is good to go. I am in the Dallas/Ft Worth area if anyone is interested in a look-see too. :D

 

Anyone? Anyone?

 

Thanks,

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Guest norm[T12SDSUD]

Quite possiby you just found out why that car has ben sitting there for the last 20 years!!

Anyway, try pouring some Marvel Mystery Oil in the cylinders to loosen up the rings and turn it over by hand a few times and then let it sit for a day.Leave the spark plugs out and turn the motor over the next day and put a towel over the engine so oil doesn't blow eveywhere when you crank it .

After clearing the cylinders of oil do your compression test again and see if it comes up. Also I assume you already checked the rocker arm clearnance but if you haven't then check that as well.

 

if you get it running add the rest of the Marvel Mystery Oil to the crankcase oil and then run it a week and maybe it will help to loosen up anything else that is gummed up.

 

later,norm

 

 

Hey all...

 

I just bought a '71 240z from the original owner's family (estate thing). It has been sitting in the garage since 1983. They did me a favor by draining all the coolant and fuel from the tank' date=' and as far as I can tell, purged the fuel lines too. There isnt any built up nastiness in the carbs!! And an empty, clean, silver-inside tank didnt hurt my feelings either. :D

 

Anyway, I went to "fire it up" with some starting fluid just to see if it would light-up, and no go. It sounds kinda flat too. So I proceed to check compression the only way I know how (all plugs out, WOT, etc...) I get a reading of 30-somthing PSI on all cyl's except one (cyl 2 I believe). As far as I know, a blown head-gasket wouldnt kill ALL of the cylinders would it? My lack of experience with the straight-6 shows here. I pulled the valve cover off, and everything seems to be moving/opening/closing the way it should, and there are no signs of a crack history in the block or head. The oil is clean, and the radiator and dipstick both show no signs of coolant/oil mixture. This was an estate thing...left untouched...so there wouldnt have been any tampering to "doctor it up" for more money...so hidden problems arent really going to be a problem here.

 

Anyone have any insight to lend? Anything else I forgot? If the cam/crank timing was off drastically, would this skew the compression like it did? I cant think of anything else to try, other than to swap the motor for one that is good to go. I am in the Dallas/Ft Worth area if anyone is interested in a look-see too. :D

 

Anyone? Anyone?

 

Thanks,[/quote']

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Good information! I was going to do the oil/cyl thing next to see if the rings were just plain worn-out...but didnt think about the possibility of "stuck" stuff too. ::dummy::

 

Anyway, thanks a lot for the reply!

 

-scott

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