compression test results

[stillnotfinnished]

hi all just done a compression test on my 1200 herald, results were;
169,   148, 145, 168.
re did the middle two with oil added  and got 180 on both.
the car has been off the road for years, but with the engine turned over regularish.
could the improved figures be the result of sticking piston rings??
i remember reading another thread and bill [or sir bill as he should be called!] saying redex should be poured down the bores of an engine thats been stud before starting. i did this. should i do this again? the engine has only covered about 50 miles since getting it on the road again.
any thoughts?
thanks ed.

[Steve Cureton]

Did you try them all with oil in the bores? That's the only way you can do a fair comparrison. I've never experienced sticking rings but I was under the impression that if the compression ring is stuck you will get a very low reading, unlike yours which are reasonably high(ish).  The only way to find out for sure what state the engine is in is to strip it, alternatively just drive it and see how it goes. Unless it's smoking heavily I wouldn't touch it until winter anyway so I could enjoy it through the summer.

[Deleted User]

There are really only 3 places compression can go: head gasket, valves or rings. If you have an air compressor and some junk bits you can make an adapter to connect the air line to the sparkplug hole and pressurise the cylinder. A bit of fun at first because you have to get the crank and piston exactly at the compression/power stroke TDC otherwise the engine spins around.

Listening with a short length of hose to the adjacent cylinder plug holes, intake with throttle open/carb plunger lifted and to the exhaust pipe will identify the source of escaping air and where your compression is disappearing to.

Rusted valve seats are really common for an engine that has sat for a while and will usually come right after a bit. Tight tappets are also a good source of compression loss.

Andy.

[stillnotfinnished]

hi thanks for the replies. the tappets are next on my list of jobs
anyone got any tips??

[Steve Cureton]

I presume you mean tips for setting tappets? If so then rule of 9 applies for a 4 cylinder engine, ie when setting the gap on number 1 valve (counting from the fan end) then number 8 should be fuly open,  set number 2 valve when number 7 is fuly open, etc

To turn over the engine easily remove all spark plugs and turn it over using the fan or a spanner on the pulley nut. Alternatively put the car in 2nd gear and push the car forward to rotate the engine.

[Deleted User]

a real quicky test to see if tappets are your problem is to rotate the engine until each cylinder rockers are 'rocking' which occurs at TDC on exhaust/inlet stroke, then see if the opposing cylinder tappets can be clacked by rattling them. If all cylinders have some clearance that can be heard when rattling the rockers then tappets aren't your problem.

My tip for doing tappets is to back off all the adjuster nuts a 3-4 turns to start with, that way when you are finished there should be no loose tappet nuts. Other thing is watch out for worn rocker tips and trying to get feeler blades into the slot carved in the end of the rocker by the valve stem. If you are unable to cleanly slide the feeler blade into the gap between the valve stem/rocker then the rockers either need setting with a dial gauge or better still they need refacing.

also re the air compressor trick above, I forgot to say listen in the oil filler hole for piston rings leaking. There will always be a little bit of leakage but it shouldn't be a roaring gale out of the oil filler hole.

Andy.