Thread: lost of compression on rebuilt engine, need help

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i just recently rebuilt my 1965 289. bone stock 289. i was going to started for the first time today. i crank it it a few times , it sounded weird when it was cranking not normal at all. i checked compression cylinders #1-4,5, and 8 had 0psi. performed cylinder leak down test, all 6 cylinders 90% leaking.
cylinder 6 and 7 150psi. block was rebored from std. 030. new piston, rings, cam lifters,cam, int. and ex. valves, installed, machine shop recondition rods, crank was cut to .010, internal balance, heads rebuild with new valves and seats. A LOT OF MONEY invested, any ideas what's wrong with it. i would hate to remove th engine. i added a few drops of oil in the bad cylinders to see if the pistons ring were bad compression did not raise.

The only time I've ever heard of an engine COMPLETELY losing compression like this is when the assembler didn't offset the rings when they were putting the motor together. You can't align the ring gaps because making a complete circle out of the compression rings is what gives your motor its compression. This could be especially true if all the cylinders are suffering like this because if a builder puts 1 piston and ring set in wrong, they will probably put them all in wrong.

What he said but check your timing gears and chain for proper alignment

I think the guys have hit it. If you put oil in the cylinders and compression did not come up, it is probably your valves not seating. Either timing is off, or they are not closing when they should for some reason.

Don

Listen to Don, Denny, and Charlie on this. It's such a simple thing and it happens more than you know, especially on a first rebuild. Back up and go simple on the valve train check up.

thanks guys for the input. iam going to check this week. hopefully is my valves not seating.

when you did the leakdown test did you bother to listen around and see where the air was coming from... that can point to your problem a lot faster.... listen to the carb for intake valves, exhaust for exhaust valves, oil fill cap for rings, radiator for head gasket, and other cylinders for cracked cylinder walls.... hopefully that'll confirm that you just need to readjust those valves

Hydraulic camshaft?

It's easy to get the clearances too tight on these.

Pick one of your zero compression cylinders, remove the rockers and pushrods then do a compression test on that cylinder.

You guys are the best! Dont know what I would do without all the great input! Finally had a chance to look at the engine today. i loosen every cylinder rocker arm one by one, recheck compression as i loosen a rocker. found valves to tight. So now i have compression on all cylinders and i have 16 rockers loose.
does anyone have any step by step instructions on how to adjust valves?
thanks
SAL

move each cylinder one by one to TDC, as each one is at tdc tighten the rocker down just to where theres no up and down play in the pushrod and then give it a 1/2 to 3/4 of a turn.... once there run it... then you can also do a hot adjustment which you run it with one valve cover off, loosen each rocker til it starts clattering and then tighten it to where the noise goes away, do each one until their all done, and bolt the valve cover back on and then do the next... take note that it is an oily mess and will help if you have an old valve cover that you can just cut a strip off the top big enough to access the rocker nuts

A stock 289 doesn't have adjustable rockers, they just tighten down to a stop. There are different lengths of pushrods. Check that against specs for your engine.

Pope has a good point. Early 289 was a positive stop stud and fulcrum unit. Were the studs changed out? If the OEM studs were retained, It's a possibility that the valve height wasn't compensated when the valves were ground and now the valve stem tips are too high. 62-68 push rods were 6.804" long. 69-85 were 6.886" long (non-H.O. & non roller engines). Possibly later push rods were used creating a .082" interference in length. There is not much material than can be removed on the heads during milling also. This can make the pushrods "grow" in their geometry especially if they were milled once before. Just some info to chew on.

denny's right on that one..... the valves weren't positive stop til 69ish.... bout the same time they went to the 4-bolt balancer i believe

Right, my 260 was adjustable. The memory's the second thing to go, and I forget what the first thing is!
Still, check the pushrod length and installed height of the valves.

OF100man, later ball rockers were positive stop too, not sure of the year that started.