Engine: 1.8 1974.

I tore down the engine to replace Dead gaskets and seals.

Purchased new jugs and pistons reassembled the engine. Fired it up and have 90 lbs of compression on 3-4 125 on 1-2.

Completed a leak down test and all is good as it is holding what compression there is...

Tore the engine down again and measured the cc of the heads and they are all the same. Part number 021.101.371S on both heads.

Measured the deck height of the pistons at TDC and they are all the same....

Head gasket shims are all the same.

What am I missing???

Thanks Jammer!

Fuel injection or carbs ?
If carbs, were the carbs open on both sides ?

Dual 40's and just rebuilt. They were opening. Thanks

ring gap, ring stagger, valve seats, valve clearance, piston to wall clearance, your missing a lot.

Thanks!
But do Brand new Pistons and cylinders leak? If they were bad would that not show up on the pressure test? Also Would the valve seats held pressure during the pressure test if they were a problem?

Valves adjusted by myself and rechecked by another person, and they were good.

Rings haven't seated.....drive it like you stole it a couple days & check again....

When doing a compression test the carbs must be propped open.
"they were opening" doesn't sound right.

And the engine is supposed to be warmed up as well.

Sounds like an aka problem

Compression on a fresh top end-er builds as the rings seat.

So assuming you cut your ring gaps correctly... Here is how I was taught to break in a fresh motor.

Warm it up. When at operating temp, on your favorite quiet road, put the car in second gear and STOMP ON IT. All the way up the rev range. Then foot off and let the car engine brake back down (keeping the car in second gear). Do that two more times.

Your rings should now be seated, and compression should be around 140-160 or so.

Zach

if it were mine and it is out and apart. i would do a light hone on the cylinders (break the glaze), check my ring gaps again, stagger the gaps at 60 degrees and reassemble the cylinders. on the heads, fill each combustion chamber with lighter fluid with spark plugs in the holes and check for leakage past the seats. the chambers should hold the fluid. if they don't, lap the valves into the seats and try again until it seals. reassemble.

Thanks All! I have some Ideas of what to do now! See if I can get this up and running before snowfall!

BTW what is an AKA problem? if your referring to Knowledge then yes... I am a noob.

I agree, it might be why a leakdown will show something like 80/79, but a compression will show 90psig. You need to allow air into the intake system. Prop the throttle to stay open and re-run the test.

Yep will do! But either way the plugs were not firing on 3-4 side unless I had the rpms up. I installed new cap rotor pertonics points coil wire and plugs.....

You may want to check to make sure the case is flat where the cylinders set.
Older cases have been known to sink in the middle and that makes sealing the heads nearly impossible

Also noting you stated 3-4 "side" doesn't fire until the rpm's are up. Sounds like an idle circuit adjustment/issue/vac leak etc. more than compression.

Just a thought.... Is the cam timing correct ? Good leakdown, different compression side to side.... Cams not timed properly
Again, just a thought.

......that would require a Very special cam