MD_Spencer Posted September 22, 2014 Report Share Posted September 22, 2014 I have a question about engine compression and if I need to rebuild my trucks engine. I have a 1970 521 with the L 16 engine. I ran a compression test yesterday and got theses results. Cylinder 1 = 150 Cylinder 2 = 95 Cylinder 3 = 140 Cylinder 4 = 130 From what I remember from rebuilding air cooled engines this is NOT GOOD! What would the forums advise be. Rebuild the entire engine or just a ring job or get a reman engine. Any help keeping this project going forward would be appreciated. [/url] Quote Link to comment
Z-train Posted September 22, 2014 Report Share Posted September 22, 2014 Time for a new bullet. Quote Link to comment
datzenmike Posted September 22, 2014 Report Share Posted September 22, 2014 Check your valve lash first on #2. If ok... Then pull head and inspect the #2 valves/seats for damage. If ok... Continue with re-build. Quote Link to comment
banzai510(hainz) Posted September 22, 2014 Report Share Posted September 22, 2014 should still run if you have spark and fuel. olddatsuns.com the tech section read this 1st Quote Link to comment
DanielC Posted September 22, 2014 Report Share Posted September 22, 2014 Normal compression on a L-16 single carb engine is 171 PSI, at 350 rpm, wide open throttle. Minimum is 159 PSI. Additionally, each cylinder should be within 10% of the others. Closer is better. Your engine will probably run "OK" but it will run much better if compression was at factory specifications. The cost to rebuild a L-16 is about the same as to rebuild a L-20-b engine, or a L-18. The L-18 is a direct bolt in, the L-20-B is slightly taller, may require changes to the exhaust pipe to connect to the engine manifold. If the truck is running, I would get another engine, and keep the truck running. Use the truck for getting another engine, and trips to get parts, or take parts to a machine shop. Try to find an engine that does not need rebuilding, but Datsuns are much more common on the side of the USA closest to Japan. Be advised, if you swap another L engine into your 521, you will need to keep the 521/L-16 oil pan, and oil pickup. Adjust the valves, and see if the compression improves. You may buy some time before you HAVE to do something, but you need to deal with the engine pretty soon. Make a spreadsheet, with all the costs of rebuilding your engine, the costs of getting another engine, and try to include as many problems you can think of. That will help you make the best, or better decision for you. If you were working with an air cooled engine, commonly from Germany, the most economical and usually the best option is getting new barrels, pistons, and rings, in a kit. With Datsun engines, you do not have that option. If the cylinders are worn to a taper, you have to bore, and get oversized pistons. But Datsun used very high quality metal in the cylinder block, and it is common for Datsun engines to not really need boring, and are within factory specifications, even with a lot of miles on them. Definitely good enough for a daily driver. Quote Link to comment
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