No Compression/timing Fail.

[coupe72001]

A couple of weeks ago I changed the head/headgasket and bolted a set of triple Dell'ortos onto my L28 skyline. I did the job at a mate's factory, but ran out of time and light. We really rushed the final stages of bolting it all together, but it started up, and it limped home with an exhaust leak and some backfiring. The head/cam had been previously set up correctly by a cylinder head place.

I decided to patch up the things that we had rushed, and I redid the manifold gasket to eliminate the exhaust leak, then I studied up on how to set timing, and bought a better timing light.

When I took the rocker cover off, I found I was one tooth off being timed at TDC. Cant remember if I was advanced or retarded though. I corrected the cam timing, so that the notch in the cam sprocket was aligned with the right side of the line on the cam tower (a la the factory manual/how to build a Datsun engine). Then I statically timed the electronic distributor so the teeth were aligned. Then I turned the engine by hand, then tried to fire it up, but this time, no go. It turned over, but wouldn't fire.

I called RACV, and they had a play, finally doing a compression test, and declaring I had no compression on any of the cylinders. Ergo, the timing is out right along the valve train.

I checked the cam, and tried it at a few different settings - advanced and retarded, but couldn't get the damn thing to fire again. There is a chance that the factory marking for a correctly timed cam is no longer accurate because my cam has been ground.

Any ideas. Anyone want to come have a look? Ill pay for your time with beer and/or some cash, and if you get it running you can have my firstborn child as well.

Cheers, Drew

I'm in St Kilda East, Melbourne by the way.

[coupe72001]

To make matters worse, my aftermarket crank pulley's timing mark, doesn't quite line up with the timing plate on the block. It shows a couple of degrees before TDC when number one IS at TDC!

[Gordie]

i think i rememeber reading about the cam gear having 4 different places that it can go on the camshaft, something to do with adjustment for the chain as it streches. did you get your head machined? might need to change the position of the cam gear on the cam?

[Gordie]

had i quick search

http://www.mail-archive.com/membersozdat@d...u/msg39359.html

[krafty]

could also be 180 degrees out... easy to do... did you make sure it was on compression stroke when you put it all back together?

[OUTATIME]

set the valve clearances? would contribute to it runnin crap..

can check the cam gear position 2morrow if want. cnt remember it off top of my head.

Edited August 5, 2009 by OUTATIME

[V8skylineMAN]

yeah, agreed 180 out. all you will get is popping and farting. wont run.

cheers

Jason

[coupe72001]

Thanks guys. Popping and farting sounds about right! So, I guess I could have it 180 degrees out. Ill have another go on monday. The cam sprocket has three holes to accomodate for timing chain stretch, and I am on number one, as the chain is less than 2000km old.

I like these quotes from the ozdat link:

"Check the position of the rotor i.e. is it pointing towards the front

(true #1 position) or the rear (180 degrees out) - useful to know when

you're trouble shooting."

and

"When satisfied it's in the correct position, check that

valves on #1 are both closed, to be sure you can check that the valves

on #6 are open."

so obvious, but I didn't think to check. If the rotor is on 6 instead of 1 I'll turn the crank 180 degrees without moving the cam and have another go. Valve clearances should still be right, but I'll double check them too.

[blind_elk]

If the distributor is 180 out, then you need to drop the oil pump and position the dizzy drive correctly.

If you rotate the crank 180, then the timing mark on the pulley will be in the wrong position.

PM me if you want a hand - I have all the time in the world at the moment (unfortunately!).

[noddle]

If the rotor is on 6 instead of 1 I'll turn the crank 180 degrees without moving the cam and have another go. Valve clearances should still be right, but I'll double check them too.

I would assume trying to turn the crank with the valves are depressed (since the cams not moving) will bind against some valves,

as mentioned above, drop the oil pump and adjust the gear 180 degrees

Nigel

[coupe72001]

Oh yeah... of course it will bind (slaps forehead). Although, I'm starting to wonder if I am 180 out. The car was driving before I made the adjustment to the timing at the cam sprocket. I was only 1 tooth out, so I don't know how I got it 180 degrees wrong... I am a bit vague though, so it's possible.

[coupe72001]

Ok, so today Mr B. Elk came over and showed me how to set valve clearances and check that everything was timed correctly, which it was. Once we were ready to go we turned it over and found almost no compression on cylinders 1 to 5. Piston 6 was putting out 140 (kpa?). Looks like I must have damaged some valves on this head after all (after an previous over-rev incident). Have pulled the head off to be inspected and any bent valves replaced by Motor Improvements. One of the engineers managed to slip a fingernail under one of the valves and commented that even a minor bend can prevent them from seating right and therefore cause loss of compression.

God only knows how I got the engine to fire up at all for the drive between Deer Park and St Kilda.

Anyway, at least some new valves and another headgasket won't be horrifically expensive, and I have learned some new tricks, thanks again to Mr Elk!

[passin ewe]

Motor Improvements. That's a name I remember, they built my 351 Clevo for my XW when I lived on Dandenong road at the top end of Pahran. They did a really good job. Too bad someone else got to enjoy it more than me after it was stolen on the Gold Coast.

[coupe72001]

They are great guys. They basically talked me through my engine rebuild in great detail, instead of just selling me the parts and sending me on my way. Ricky, that absolutely sucks about your XW, but at least you've got a REALLY interesting car now!

[blind_elk]

Ok, so today Mr B. Elk came over and showed me how to set valve clearances and check that everything was timed correctly, which it was. Once we were ready to go we turned it over and found almost no compression on cylinders 1 to 5. Piston 6 was putting out 140 (kpa?). Looks like I must have damaged some valves on this head after all (after an previous over-rev incident). Have pulled the head off to be inspected and any bent valves replaced by Motor Improvements. One of the engineers managed to slip a fingernail under one of the valves and commented that even a minor bend can prevent them from seating right and therefore cause loss of compression.

God only knows how I got the engine to fire up at all for the drive between Deer Park and St Kilda.

Anyway, at least some new valves and another headgasket won't be horrifically expensive, and I have learned some new tricks, thanks again to Mr Elk!

Glad I was some use

140 psi.

Any telltale signs on the pistons to say they had a "meeting of the minds" with the valves? Only ex or in, or both?

[coupe72001]

Ahh psi! There were tiny burrs on some pistons from a single valve contact. I'll check if it was the intake or exhaust on Monday.