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1972 TR6 not starting after refitting cylinder head


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This winter's project was to finally refurbish my 1972 TR6 Pi cylinder head with hardened exhaust valve seats. In addition new exhaust valves, and guides for all the valves were fitted and inlet valves cleaned up. The head received a light skim as I was informed it was warped. There was no evidence of any water in oil prior to taking the head off.

So, yesterday with my brothers help we refitted the head and torqued in 3 stages to 65 lb ft with my brand new torque wrench (a Christmas present!). Setting the valve clearance to 0.010" cold as per the Haynes manual. The most time consuming period was refitting the 6 branch manifold (mines two x 3:1 leading to the twin sports exhaust set up) and the inlet manifolds. Those hidden bolts are a real pain. Anyway job done.

Today on my own was the final stages of fitting cables on the injection side and the HT set up. Static timing at No 1 at 10 Deg BTDC. Sparks all good. Though I do point out my No 1 lead is opposite to where all the photos show and where it was until a year ago when the engine was out for a bottom end rebuild. The car had been a good runner after this work albeit with the symptoms of worn valve guides etc.  I primed all the injectors and observed a good spray in the inverted position.

Start up - I knew it would be tricky initially as the butterflies were not perfect and good cable adjustment to follow. The car fired and run unevenly for about 5 seconds, I couldn't keep it going. Thereafter all day I couldn't start the car. I checked the static timing numerous times, spark plugs sparking, and took the rocker cover to make sure I had the No 1 firing when the two valves were closed. I could observe that No1 plug (externally) was firing as the injector sprayed almost at the same time (is this right?). I simply couldn't fathom what was going wrong. I don't like the HT leads in this position, but that's all connected to the metering unit timing, and it was running before. The engine didn't sound like it was even trying to fire.

So help please I need guidance on what to do next. (I have not rechecked compression readings). Apart from that I need help! Thanks in anticipation.

Best Regards Trevor Hughes

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First guess distributor 180' out. i.e. engine not at TDC on the compression stroke but at the end of the exhaust stroke.

Easy test just move each plug lead around in the distributor cap, maintaining the firing order.

If metering unit was 180' out then it would still run. Are the injectors still spraying fuel when engine cranked?

 

With distributor cap off and engine at TDC then brass end of rotor arm is normally between 8 and 9 on a clock face. (pointing at radiator but down a little from horizontal)

Alan

Edited by barkerwilliams
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Thanks for this. Yes the injectors are spraying fuel when engine cranking.

Ref the brass end of the rotor - it is at 180 deg. opposite to what you say - with the lead from there going to No 1 as set up after the bottom end work last year.

I did during the day set the leads up as you say and cracked the engine over, I thought I heard a back fire, so dismissed this and did nt try again.

I had loosened off the distributor when taking the head off so I did think of the possibility it had gone back the wrong way. However with the distributor raised and on turning the drive shaft by hand it goes back in the same way. Its all hard to understand as the engine was running before the cylinder head removal.

Its Wednesday before I can take another look. Thanks again

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Its only a simple engine, no electronics to get in the way. If you have fuel in the cylinder, compression and a spark (at the right time'ish) it will fire - perhaps badly but it will fire. Ignition timing only needs to be close.

You are using new petrol, not some vintage stuff? - A squirt of Easy Start is a good petrol substitute as a diagnostic tool.

Alan

 

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Hi Trevor. 

Regardless of what’s gone on before I’d say that now is a good time to put things right so that you won’t be chasing your tail around bodges to put the previous bodges right. 

Bite the bullet and remove the distributor, put it back in as per the manual and rewire the distributor cap as the factory had it. You will then be in a position to time the ignition as per the manual and if that doesn’t get things running you’ll be able to fault find the problem in a logical manner. 

Best of luck and don’t forget to let us know how you get on. 

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Remove and clean the plugs. They are often the problem in these situations.

I have been working on a 1937 Morgan 4/4 and it ran for a bit then wouldn't. Spark at the plug/lead, fuel and compression were good, but the plugs weren't.

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Hi Trever,

if you remove the rockercover and dizzy cap, you can check if timing is correct:

Put car in say 4th gear and rock fwd until pulley indicates TDC. In this position, cylinder 1 and 6 are in top position, but only one is ready to fire. The one with both valves fully closed should fire. Fully closed means you should be able to rotate the pushrods of the valves of this cylinder.

At this time, the rotor arm of the dizzy should point to the position of the lead for that cylinder. And points should just have opened (some 10 crank shaft degrees earlier.

Job is easier with plugs removed. If in doubt replace the plugs too.

A test light on the ifnition may be helpfull, to see position that the points open.

Waldi

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Thanks guys for the guidance. Wednesdays this week is the day of reckoning. Weather should be good here too. Promise I'll let you know how I get on.

 

Cheers Trevor

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Another day of misery I'm afraid. I reset the distributor and metering unit as per manual; with engine at TDC on firing stroke, and no 6 port just showing in the metering unit. Prior to refitting the distributor the drive looks okay, see photo. I double checked the No 1 valves position with the rocker off.

However on refitting the distributor the rotor arm was pointing direct south and after setting the timing for No1 the unit looks way off to the right. In the photo I've moved the leads along to the right by one to make the leads fit okay and suit static fitting on No1. I really don't understand what's going on here.

I had fitted New plugs, rotor arm and distributor cap. Anyway not a sniff of the engine firing, even turning the distributor left and right to try and find a sweet spot.

One observation today was the spark looked maybe small or weak, or even yellow, not that I've a strong memory on exactly how it should look. I tried a spare second hand coil, but just the same. I have a lumention unit fitted which replaced the points, that's probably over ten years old now.

Recalling the engine was running before the cylinder head work and I did have that mystical rough running for 5 seconds or so last Saturday. My next opportunity to play is late next week.

So next week, I'll refit the points (securely stored in the boot).

Any other ideas out there, especially around the twist in the distributor from what I expected.

Regards Trevor

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Trevor

try changing the plugs - lots of issues currently with dodgy plugs - 

got to be worth s punt- I know you say you have a weak spark but put that inside the cylinder under compression and you could easily get no spsrk

cheers

Rich

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Thanks Rich, on the list! (They were new NGK from Moss) plenty of old ones in the boot!

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Hi Trevor

Sorry to read your woes no fun I'm sure, I had a similar experience with a motor a few years ago.

No expert with these engines but agree I'd replace with new plugs, ditch the electronic ignition for now and give her some Easy Start. From the sound of things it seems to be a timing issue.

Best of luck

Andy  

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In your picture it shows the distributor drive gear with the slots from 12 o'clock to six. The Repair op Manual 12.41.05  shows the slots as being 2 o'clock to 8 at TDC which is what my car is.

If the engine it genuinely at TDC then that drive gear being out will only account for the distributor needing to be rotated an additional 45'ish degrees to "normal".

The distributor drive should not have been removed with the cylinder head work.

Did you remove no. 1 plug and insert a "depth gauge"  to check that when the piston is at maximum rise the timing mark points at TDC or just look at the valve movement?

 

Alan

 

 

 

 

 

 

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Hi Trevor,

You will get there....

did you check the rotor position at the point where the contact points open?

Waldi

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Not sure on why the distributor isn't quite where you expect it to be, but it shouldn't matter as long as the lead to number one is where the rotor arm is at tdc. (Unless it's possible to have the metering unit set wrong in relation to the distributor position? I guess you could check that number one injector is spraying at the point the distributor passes tdc). 

So I would also confirm tdc is where you think it is by checking the piston position at cylinder one and checking the timing mark on the pulley and see where the distributor points to and install the leads from that point. Definitely try the points too.

Gareth

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The garage last year (after bottom end rebuild) has fitted things back with the distributor 180 degree from the norm but correctly wired up to plugs as it had been running okay before I took the head off. I have followed the Haynes manual and ended up where we are. See photo from their manual! That's why I put the leads one along from where you'd expect and set the timing with No1 plug sparking and a 12v light switching on together; so I'll redo this to the 2 to 8 o'clock position as advised by Alan above.

Ref the valves at TDC; I observed the valves in the closed position only and not checked the piston rise. I'll check this for completeness.

So next step; Re do distributor position; double check metering unit timing with No 6 hole eclipse just appearing in the top of aperture.

Fit contact breaker points for now; and use last set of plugs cleaned up.

One question, at starter crank speed should their be a discernible time difference between no 1 injector spray and the plug sparking or is the piston movement just too quick. At what point therefore does the injector spray in the cycle. I had imagined it would be in the induction stroke drawing in fuel and air, then as the piston compresses the mixture, before the spark plug goes bang?

Regards Trevor

 

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Thanks for this Alan, amazing really as I went through this hoop two years ago when I had a leak on metering unit seal to the pedestal and ended up all it should be. I certainly didn't go through this pain. Sounds like age catching up on me!!

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Ouch that could be nasty, last years work included a 'good' second hand CP camshaft to replace my worn one. I do still have that one in my garage.

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  • 3 weeks later...

Right, here's the update after finally getting the engine to fire up after 3 weeks! You'll be pleased to here this isn't after fiddling around every day but I cannot deny its taken far too long. In summary there were two problems identified which once sorted have enabled the fire up.

Firstly checking valve clearances, two (1&7 from the front) were probably far too tight maybe even bad enough for the valves not to be closed; another (6) was very close to this.

Secondly I finally sorted out the distributor drive to the correct position aligned with the metering unit, all good. Though for some strange reason I was still trying to set up the timing with the distributor turned too far to the left. Finally I had a light bulb moment and squared it up so No 1 was sparking correctly. This all sounds basic stuff but when your heads in a muddle with other parameters going odd you'll understand why. More of that later.

So at 4pm yesterday, (Thursday 11th) the engine started and I allowed it to warm up, idling well albeit the valve clearance certainly in need of some fettling, that's understandable. The new valves bedding in along the well. I was driven to run the engine intermittently as the exhaust was smoking off my new carefully installed exhaust wrap; well the red finish was soon turning a gold colour with the heat! the smells not good either!

The backdrop to yesterday was earlier in the day I was convinced in my own mind there was a problem with the head and I'd have to take it off and check the head or the gasket. I had bought a new compression gauge and went ahead to check the readings on a cold engine, throttle wide open. Remembering previous readings prior to taking the head off were not too bad (135-140) I was shell shocked with what I was to witness. Two readings taken in two cycles 1-6 were 135,135  - 110, 110 - 80,80 - 70, 80 - 135,130 - 115,115. (paperwork attached). Crikes what's going on, I then added oil to the low readings 3 and 4 and came back with an increased 125 and 115.  Does this mean the bores are now a problem or is it because the engine is cold.

I phoned a local motor factors here in Southend who has personal knowledge of the TR6 and always nice to chat too. His conclusion was it was still a timing issue and I should persevere as it should still start if set up correctly. So that is what I did and after the checks and adjustments made above, the engine has started.

Today Friday I had the courage to warm the engine up again and burn off some more of that exhaust wrap! (its the binder they use apparently in the manufacturing process that burns off). I think my neighbours were peering out of their windows not too see the engine running but to witness the car catching fire!! After a while, a drive around the block (sorry for the pun!) to prove all systems go. Performance okay, quiet smooth drive, just the clattering of the those mal adjusted clearances.

I still have to tighten down the head to the max torque and set the valve clearances, and I'll redo those compression readings with a hot engine. However there is one more observation to note; there was a slight build up of emulsion on the breather pipe to the air box. Nothing to note on the oil filler cap, or any loss of water in the radiator, nor was the exhaust abnormal. Indeed I was very pleased with the exhaust gas flow as this (twin sports) was much less at idle than before the head was sorted. Maybe some water had entered the block when I took the head off; time will tell.

Thanks for the help to all who have contributed, the Forum is a great asset to our club. I'll update this thread if there are any further observations of note.

Best Regards Trevor

 

 

 

 

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Edited by Trever the rever
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