2000TC problem after head refurb

W

Willy Eckerslyke

Well-Known Member
I have a feeling I've done something wrong...
My 2000TC burnt an exhaust valve last week so I took the head off, had the seat (which was savable) and a spare valve recut and refitted them this weekend. All straightforward enough.
As I'd been meaning to switch to HIF6 carbs for a while, I decided to do so while the originals were off so fitted a pair I've had knocking around along with the associated linkages. These carbs looked fairly clean and apart from rather stiff chokes seemed healthy enough to try without rebuilding.
But once it was all back together the car really didn't want to run. Initially sluggish to turn over, it felt as if I'd mucked up the valve timing. It did eventually burst into life but misfiring and backfiring dreadfully.
So I stopped for tea and convinced myself that I'd lost the cam's position. I've just double checked - flywheel on EP, locking pin in place, exhaust valve on cylinder No1 (nearest the front of the car) fully open. At this point, the slot for the camshaft locking pin is about a degree out - not enough to cause such a problem surely?

So could this be entirely down to the new carbs? Obviously I can find out by switching back to the old ones, but is there something else I could have missed?

Any advice appreciated, please!
 
Unknown quantity HIF6s are notorious for causing running problems, mainly due to deteriorated rubber seals of the mixture enrichment device.
If you really want the swap, i would suggest to take them apart, replace all consumable (i.e. rubber) parts with new, and then give them a try.
 
That does sound wise. The backfiring was so serious though, that I'm still convincing myself that it's a valvetrain issue.
I do have a vague recollection of finding once before that the timing marks on this engine are incorrect. So I'd be grateful if someone could suggest the steps to follow to check properly. I.e. from first principles, assuming that the timing has been lost. Piston 1 at TDC ... such and such valves should be rocking... etc...
 
If you don't mess with the camshaft gear vernier, i cannot see how a head swap could affect the valve / ignition timing.
The car was running fine prior to the burned valve, no?
 
Yes it was running fine before, but this weekend I've been dropping things, falling over other things and generally making a mess. I'm seriously wondering if I've refitted the camshaft 180 degrees out. :(
 
Can you not just put the old carbs back on to check? Then if it's still not running properly, it's not them.

I know this is probably a daft question, but you have set your valve clearances, haven't you?

If you want to check your timing marks exactly, i.e. TDC on the pulley, then you need one of these :-



My V8 was 6 degrees out. Just make one up with a bolt and an old spark plug. Make sure your No. 1 piston is nowhere near the top, and screw this in instead of the spark plug. Turn the engine slowly until it stops - as the piston hits the 'piston stop.' Mark on the pulley where this is, then turn the engine the other way until it stops again. Then mark this as well. TDC is exactly between the two marks. Very accurate way of getting TDC.

Richard
 
Thanks, a rough check of TDC would tell me if I've got something completely out of kilter but I need to know what piston to be checking and what the valvetrain should be doing at that point. ( I like the idea of your homemade device for working it out accurately afterwards.) Did I read somewhere that the timing marks on the 4-cyl engine refer to the rearmost cylinder?
At the moment, even while turning it over on the starter it sounds wrong - as if it's fighting against compression.
Valve clearances - yes that was the main part of the job.
Refitting the old carbs is my next step but that does involve quite a bit of work so it would be nice to get a quick indication first that the timing is vaguely within bounds.
Unfortunately the car's outside and the weather is dreadful and promising worse so it may take a few evenings.
 
I haven't done a timing chain on a four cylinder P6 for a while (three decades +) but to tell which one is on firing stroke should be fairly easy.

1 and 4 move together, so will both be at TDC when the timing marks on the front pulley are at TDC. When 1 is on the firing stroke, the rotor arm will be pointing at the position of No. 1 plug lead, and No. 4 valves will be on the rock as it were. i.e. they are changing from exhaust to induction.
No.1 valves should be on the heel of the cam as much as they can be as this is the change between compression and firing stoke - Squeeze and Bang if you watch James May :)

Hope this helps

Richard
 
Thanks! That gives me something solid to check.

I also found one of Harvey's handy pointers in this thread
Cam timing wildly out
"The camshaft locking peg should fit when the rearmost cam lobe is pointing directly upwards."
The key and the slots on this engine look somewhat molested so I've been wondering if I managed to fit it into the wrong one, which shouldn't be possible.
 
Willy Eckerslyke said:
Any advice appreciated, please!
Click to expand...

If you set the engine to EP before you started, and didn't turn it over during the job, then the crank will still be in the correct place, that just gives the chance of the camshaft being pegged into one of the incorrect grooves. If the camshaft is 180 out you can just swap the plug leads 180 on the cap, but they don't tend to run at all when that's the case. Best thing to do is peg the crank again, peg the camshaft, and post a pic of the locked cam peg and camshaft, showing the position of the lobes.

My guess is it's the carbs as they're the only thing you've changed.
 
OK we can discount the carbs, I refitted the old ones and it's still the same - misfiring and spraying unburnt fuel out of the front carb all over the inner wing.
I tried swapping the plug leads around 180 degrees and it would no longer start.
I locked the crankshaft again with the EP mark visible and checked the camshaft. The rearmost lobe pointed upwards and the second lobe downwards (i.e. No.1 cylinder exhaust open). The slot for the camshaft locking key was almost in line with the key as before, perhaps 1 degree out. The rotor arm was pointing midway between plug leads 3 and 4.

I didn't have time to try Quattro's TDC test so I'll try that tomorrow evening.

I'll also recheck all the valve gaps. After putting it all back together yesterday I hadn't rechecked them all, just the one I was working on. I had only checked the others before dismantling and found them within acceptable limits.
 
I don't think I could have as they're all numbered, but I do hope it's something as simple as that.
Also, it's time I got my compression gauge back from the friend who borrowed it a year ago. Perhaps that would tell me something.

Thanks for the words of advice so far everyone.
 
I quickly tried swapping No.1 and 2 plug leads this morning. No, doesn't want to start and is still spraying fuel.
It gives me the definite impression that at least one inlet valve is open during the compression stroke. Or perhaps it isn't closing at all.
I'll check all the valve gaps again this evening.
 
A sticky valve then?
From your description the cam timing does not seem to be wildly out if the marks on the flywheel are correct.
 
Or, I managed to mix up the shims when refitting them. I had them all numbered in an egg box but at this stage I'm ready to believe that I had a brain fart and turned the box 180 degrees or something equally daft. :eek:
 
Ho hum. Well I've found the problem, No.2 valve (inlet) is stuck wide open. 1st prize goes to Demetris!
I don't think it's ever had an inclination to do that before so something must have happened as I was removing and refitting the head or when it was having that burnt seat recut.
What do you reckon, is it likely to be bent or held open by a foreign object? Or might the collets have popped out?
Working outside, with this week's weather forecast, I don't think we're going to find out for a little while. :(
 
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