Cylinder Compression

[atkinson40]

When I first got this truck about a year ago I did rings and head gasket. Dumb me forgot to check the flatness of the head. When I started it for the first time I remembered some H2O in the oil problems. I replaced the oil and the problem seemed to go away. I have not driven the truck on the road yet. After the head gasket, I R&R the clutch, rebuilt the carb, and have just finished the brakes. Now I'm back to trouble shooting the engine. I did a compression check and it's crap. From front to rear, 70, 50, 90, 120 PSI. When I did the HG I honed the cylinders, put in new rings, and the valves looked OK . It will start and run like shit with no power. Doesn't overheat. No loss of water or water in the oil. I'm thinking the head may be warped and I need to pull it and check?? Any ideas?? TIA Kevin

[MicroMachinery]

Did you properly break in the engine? 500 miles of varying RPMs, from low speeds to mid range. If not, then the rings probably never seated in correctly, and therefore aren't giving you the compression you wanted.

 

If you DID, however, break the engine in correctly, I'd check the valve clearances next.

 

(Also, you did all that, as well as honing the cylinders, but you never replaced the bearings? Where did all the grit from the honing process go? I think you may have bigger problems then just trying to get your compression back up if you just did a very quick, cheap re-ringing)

[banzai510(hainz)]

If it didnt have a gasket proplem before I would think the head is good. Only you know.

It overheat before?If not I wouldnt worry about it.

 

Ck the valve lash

ck the timming. distributor/oil pump setting

Cam timming, where is the sprocket when crank is @ zero

 

Im thinking oil pump off and valve set too tight.

[datzenmike]

Warm engine and re-check and confirm the compression numbers.

 

Squirt several teaspoon-fulls of engine oil in the plug hole and check the compression again. The oil will seal the rings better. If the numbers go up then you have a ring sealing problem. If they stay more or less the same then the compression loss is somewhere else, likely the valves.

 

Did you measure the bores for wear?? If too worn new rings won't seal.

 

Did you stagger the ring end gaps? top and second ring gaps should be 180 degrees from each other and should not be facing towards the front and back of the motor nor in line with the piston pins. (side to side) This leaves a 45 degree angle to either side of the front or rear. Hard to explain. Compression will more easily leak past end gaps that are lined up one above the other.

[I'm BLUE]

+1 ^^^ Depth gauges + Digital Calipers ( or mechanical ) for bore wear/taper ,,, and were these standard rings put back in ?

 

I always assumed 1 teaspoon was safe to drop in for compression check afer ,,, but IDK ?

 

+1 ^^^ ,,, I would believe a lot of people forget to stagger their rings ( especially above the piston pin is a big no no ) ,,, as much as forgetting to check the ring-end gap ( filing down on piston ring grinder if need be to accomodate clearances ) ,,,

 

timing chain lined up correctly ? ( valve timing )

 

Correct torque specifications ? ( what did you torque it too ? and did you torque in steps ? )

 

Clean surfaces ( have to be very clean , true , and free of oil ! )

 

Valve Lash too tight ?

[datzenmike]

I always assumed 1 teaspoon was safe to drop in for compression check afer ,,, but IDK ?

 

Well the L16 has a dish of 7cc and the 210 head has 38.5cc so plenty of room. Perhaps a tablespoon full just to be safe.

[I'm BLUE]

Well the L16 has a dish of 7cc and the 210 head has 38.5cc so plenty of room. Perhaps a tablespoon full just to be safe.

 

i understand now :)

[atkinson40]

I'll answer everyone's questions here.

 

The HG was blown before changing. Steam out the exhaust. I don't know if it overheated, I bought it with a blown HG. I replaced the bearings. I staggered the rings. I checked the valve clearances. Valves are timed to lower end correctly. Oil pump and Dizzy are correct because timing is correct with a light. I tightened the head in sequence and to specs shown in manual. Didn't check guides. Timing is correct. Starts right up and runs, but runs like shit. Have not broke in the motor other than to start it up once a week to warm it up and circulate the oil. I'll retighten the head bolts and try the oil in cylinder check next. The initial water in the oil after R&R the HG that seems to have gone away is troublesome. -K

[Z-train]

Pull the head and put a straight edge on it.

[yello620]

Did you make sure that the carburator butterflies were open when testing? Like propped open to full throttle? If the cylinders are not geting air through the carb, they have nothing to compress.

[hang_510]

Have not broke in the motor other than to start it up once a week to warm it up and circulate the oil.

does it just idle???

[banzai510(hainz)]

situation like this its always good to have another stock head ready to bolt on to aid in trouble shooting.

 

if water in oil also ck the front cover behind water pump.

 

if looses water and steam out the back also ck the intake bolts as it could suck water thru the water passage(bad intake gasket?

[atkinson40]

Heated up the engine. Redid Comp numbers front to back 80, 50, 60, 110. Not to much change from cold numbers, couple of them got worse. Dribbled oil in holes, front to back 90, 50, 80, 125. Some improvement, Maybe didn't get enough oil in cylinders. Need to score a squirt can at the swap meet Saturday and redo the oil in cylinder test. Heating up the engine didn't improve the numbers. Does this tell me anything?? -K

[atkinson40]

does it just idle???

 

Does not idle correctly. Whatever the problem is, it is not static. It used to idle after it warmed up. Now I need to keep it held at a higher idle with my foot.