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Post by dave1800 on Feb 5, 2018 0:52:09 GMT
Are you really sure the valves were set to 0.025"? That sounds like a recipe for hammering the hell out of the valve train and camshaft, with lots of noise. Maybe you were having bad thoughts about Humber rust and misheard - it sounds like the plug gap  David The upshot was that the timing got tweaked slightly, the mixture was enrichened a smidge and the valves got re-set... to .025"! The engine shows the barest ticking and goes like stink. It's never run as well as this in my ownership. From Ron's point of view, the vac gauge had moved from poor to good. "17" is apperenty the number. Chris. |
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Post by tommydp on Feb 5, 2018 17:09:57 GMT
0.025 has got to be the plug gap, I guess?! I can't imagine quiet valves with that gap...
17 is the lowest OK vacuum value for a standard engine at idle, but main thing is that it runs well. They should manage 20 or above if well tuned and in good condition.
T
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Post by Penguin45 on Feb 5, 2018 17:49:25 GMT
Nope, it's the rocker clearance. 015" on the points and .025" on the plugs. 140psi across all four cylinders. The engine is barely making a ticking noise and runs beautifully.
This afternoon I got the garden hose out and flushed the heater matrix repeatedly. It's a bit warmer in there now.
Chris.
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Post by tommydp on Feb 5, 2018 19:35:49 GMT
Well, that's interesting for sure. Rule of nine or tdc firing method?
Would be interesting to hear the reason for this, I mean why it keeps quiet with such clearances and how it makes it perform better. Increased clearance will make the valves open later, so I can't see how this adds up..
But, as mentioned, the main thing is that it runs well!
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Post by Penguin45 on Feb 6, 2018 0:32:29 GMT
I assume that the increased clearance is opening the valves a fraction later. Maybe that's it? The head'll need re-torqueing in a week or two, so perhaps we'll try closing the gap a little and see what the vacuum gauge says. Just remember - I'm the bodywork guy. Chris. |
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Post by dave1800 on Feb 6, 2018 1:02:40 GMT
This is really strange and I worry you are going to rapidly destroy the camshaft. It just doesn't make any sense that it is quiet as just 0.002" can often make the difference between a ticking and quiet tappet.
The Oz TSBs comment on owners complaints of excessive tappet noise from the early Mk1 cars that used the more aggressive exhaust cam timing and a 0.018" clearance. This was reduced to 0.015" for later Mk1 and all Mk11 cars then further reduced to 0.013" for Mk111 cars with the introduction of the smaller tappets and changes to the valve springs and push rods. From what I have found even the hot cams with high rates of lift only require somewhere between 0.014-0.018".
Very odd indeed
David
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Post by dave1800 on Feb 6, 2018 13:23:09 GMT
Some further thoughts! Is it possible that the 0.025" is in fact 0.25mm (ie 0.010"). That would explain why there is no tappet tick and also the reason for the slightly low vacuum and compression readings.
If that is the case then it would damage the valves and head if not corrected fairly soon. It may be worth having s look for peace of mind as it just doesn't add up at all.
David
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Post by tommydp on Feb 6, 2018 16:13:38 GMT
Exactly what I started thinking of too, Dave.
If so, too tight. Remember, if you can't hear them they are too tight. Would explain the low vacuum too, and perhaps the feeling of improved performance as the valves will open earlier. I would check it...
I would have expected higher vacuum and compression, too. Tight valves would make the values low. My (current...) engine has 170 on all cylinders and vacuum is 21 at idle. It's all original and untouched. Found it in a Swedish scrapyard, put in a new clutch and put the engine straight in. Didn't even paint it:-) Amazingly it's the best engine I've ever had.
T
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Post by Penguin45 on Feb 11, 2018 19:30:26 GMT
Further to - Uncle Ron is perfectly aware that the engine settings are not satisfactory and is coming to the opinion that the camshaft timing is incorrect. We will be investigating this possibility more closely. Tommy - you jammy git!  Chris. |
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Post by tommydp on Feb 12, 2018 20:20:15 GMT
Thanks, Chris! I had too google that  I guess I've been lucky with that engine... Finally.. Oh, dear, don't get me into cam timing... My experience is the timing is usually not way off unless someone have been messing with the timing gears. However there can be variations between the rule of nine and the tdc firing valve clearances. And for some reason it seems the inlet valve on cylinder 3 has the largest difference. I've started adjusting them by the rule of nine first, then I check the clearances at tdc firing for each cylinder. If a valve is to tight here, I set it to 0.015. If the gap is too large, as the case is with the mentioned valve on cylinder 3, I leave it as is. It seems to me the feeler gauge should have no real resistance at all, while a 0.016 gauge should not pass without forcing it. If the engine doesn't have any serious backlash, check rotor when turning the engine the opposite way, I'd leave the timing and set the valves as mentioned. It seems to me they have to settle, and a few re adjustments are necessary after a head gasket change. Valve clearances has the biggest influence on engine behaviour, in my opinion. I always try to get those right first, then ignition, then fuel and mixture. Good luck! Tommy
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Post by dave1800 on Feb 13, 2018 7:22:24 GMT
I think the bottom line is that there is something here that needs investigating before any damage may be done to the newly reconditioned head or the cam. If the gap was really set to 0.025" (and not 0.25mm as I suspect could have happened) then there would be considerable clatter irrespective of whether the cam timing was out, too much backlash in the timing train etc. If it was set to 0.025" and the tappets are silent then it would seem they have closed up which means the valves (inserts) have recessed or the head has mysteriously tightened. Neither of these seem likely so I think it's time to remove the rocker box! If it's real you could make a fortune selling the secret to MGB owners worldwide David |
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Post by Penguin45 on Feb 13, 2018 18:06:59 GMT
We will find out on Saturday. Ron's going in properly. I have dug out a new duplex chain, timing case gasket and oil seal, as well as a 360° timing disc.
Chris.
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Post by snoopy11 on Feb 13, 2018 18:38:26 GMT
We will find out on Saturday. Ron's going in properly. I have dug out a new duplex chain, timing case gasket and oil seal, as well as a 360° timing disc. Chris. Major open bonnet surgery. Pics required And details of how that’s done without taking half the engine apart |
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Post by dave1800 on Feb 14, 2018 4:00:16 GMT
I think it was Tommy who warned about some after market timing chains preventing the timing from being set up correctly; hopefully yours is NOS? It would be good to sort out the lack of tappet noise before dismantling. Do you have a replacement tensioner? David We will find out on Saturday. Ron's going in properly. I have dug out a new duplex chain, timing case gasket and oil seal, as well as a 360° timing disc. Chris. |
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Post by Penguin45 on Feb 16, 2018 15:55:16 GMT
Replacement tensioner and gasket added to box of bits.
Don't know about major open bonnet surgery. It's certainly radiator out (antifreeze and new Mikalor hose clips in box) then chain case off (New gasket and oil seal in box). Then it's up to Ron..... I'll see about pics.
Chris.
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I guess I've been lucky with that engine... Finally..
