No compression after partial rebuild

[Buck]

Hi Folks,
Long time reader and first time poster. I've gained a mass of information from the forum since I've had my car, but am now at my wits end with the current problems and hoping for some advice..

I HAD a perfectly functional 73 Mk2... however I wanted it to be the best it could be. Compression was good all around (around 155) except for cylinder 2 which was down to 100. I decided to investigate..
Anyway, one thing led to another and I ended up removing the heads and replacing all valves, springs and lightly skimming the heads. Cant remember the final measurements of the head but one side needed a thick gasket and the other a shim saver and thick gasket. All valves were well and truly watertight before I put the heads back on.

I also decided while I had the heads off that I may as well replace the rings. I pulled the pistons which were in good shape and gave the cylinders a light hone. The bores were within spec so I just replaced the rings with Grants.

So with it all back together, the compression is a mess.
Cylinder 1 2 3 4 5 6 7 8
Dry 0 0 150 95 40 25 60 30
Wet 0 0 165 110 65 50 75 50

So no compression up front and a real mixed bag elsewhere, with wet results better in all cases. I just cant understand it..

Firstly, with that compression should I even expect the car to start? because its nowhere near starting at the moment..
Secondly, surely the only way I could have such poor compression is if the timing was out?

I did do the timing gear and chains while I had it stripped down. However I visually confirmed that TDC on cylinder 2 aligned with the crank marking. As it stands now the cams are both aligned when the crank is on its mark at TDC. So unless Ive missed something I've got the timing right..

Another possibly relevant piece of information is that the valve clearances are all over the shop at the moment. There was a point before I put the heads back on that I turned a head over and of course all of the buckets and shims fell out. I was in a hurry as was moving house so put them back on randomly and haven't corrected clearances yet.. Could incorrect valve clearances cause the compression issue?

Appreciate any thoughts!

Thanks
James

[GDPR]

The valve clearances could cause zero compression but unless the shim is grossly bigger on those valves it would be more likely the shim is "cocked" and resting on the valve cap holding it open. I would have expected a small amount of compression otherwise as you may be seeing on the ones that are very low

It would likely have to be inlet valves holding open which would destroy all chance of engine vacuum and therefore pulling a fuel mix into the cylinders hence just a dead engine. Take the carbs and pedestal off and spin it over with the plugs in - if the inlet valves are open you'll hear it up the manifold

Alternatively the valves could just be stuck from sitting around for so long, but you won't know that until the cams are out.

I would suggest getting the clearances right will restore it - assuming the cam timing is correct, which I suspect it may be or you would have bugger all on one bank.

Good luck James

Russ

[Staggard]

As I recall the camshafts are sided, so what would happen if they have been mixed up ? I have never done it so I don't know.

[Ian F]

James

I will defer to Russ (Kryten) and Staggard, but would think, everything else being equal that the valve timing is wrong? Is it pushing air back up the inlet when it's turning over. Didn't even know the cams were handed, so learn something every day!

Ian F

[richardthestag]

cams are handed

GRID005152.gif

I would be more worried about valve clearances, get those setup again. would have been easier on the bench but not impossible in the car

[WealdenManinKent]

Hi Buck
Yes Camshafts are 'handed' see below;
Sounds like you had heads sorted so you will have to start over and measure all shim clearances and adjust all clearances as per ROM.

IMG_2474.jpgIMG_2472.jpgIMG_2471.jpg

Roger

[Buck]

Excellent suggestions all. Will try and get out to the garage tonight to check I have L/R cams in the right way..
Valves are not stuck as I had the cams out yesterday to check shim sizes and all popped up nicely as they should. Also shims were all sitting nicely where they should.

Will report back!

[Buck]

So rather disappointingly, the cams are in the correct way.. The grooved cam is in the left hand head which is the correct arrangement. Will follow up on the clearances on the weekend.. fingers crossed.