|
|
Post by dave1800 on Sept 2, 2011 11:26:12 GMT
Kels I have not done this, but the advice is allegedly from someone who has written what appears to be viewed as the best and certainly the most well known book on tuning the MGB. It does make a certain amount of sense to me because once you are actually driving the car then the exhaust valve gets considerably hotter than the inlet so the two will tend to equalise. As you say it could well be noisy and getting the gap right is a balance between it being too large and being noisy and wearing the cam etc and too tight and damaging the valves and losing power. I guess there is no harm in trying these settings to see if the engine runs better and then tightening 0.001" at the time. A vacuum guage should indicate when the clearance is too tight. regards David I would have thought if the tappets were set to the gaps your MG expert is suggesting the engine would be extremely noisy? I suppose a test could be done by adjusting one tappet only and listening to the engine. Regards Kels. |
|
|
|
Post by dave1800 on Sept 3, 2011 0:54:26 GMT
Kels You are right to ignore these "experts" !! Imagine you have set the clearance to zero when the engine is hot. You then drive up a steep hill fast, the exhaust valves will be much hotter than when the clearance was set "hot" at idle or shortly after running and so the valves won't then close fully under these critical conditions! Regards David Read more: landcrabs.proboards.com/index.cgi#ixzz1WqXApFmjIn the BSA car club some experts advise setting the tappets hot and removing the clearance completely? I ignore this advice and am happy with the result. Regards Kels. |
|
|
|
Post by tommydp on Sept 4, 2011 21:20:54 GMT
Hi all!
Well, we have driven the crab quite a lot this weekend and, touch wood, it seems to finally approach a more stable behaviour when it comes to both idling and performance. Though, I don't dare saying it's solved yet.
I've not touched or adjusted anything but replacing the inline filter and rubber hoses for the original steel pipe and I've adjusted the valves again. It seems some of them were too tight again when cold, most likely my previous hot adjustment was not successful:-) I adjusted them cold by rule of nine, so the 0.015 gauge would slide in without force and have a slight drag whereas the 0.016 gauge would not go in without force.
It's noisier, OK, but the fluctuating idle and tendency to stall is no more present. It seems that one valve is causing the most noise, but I'll leave them like this now! The noise is most noticeable at slow idle anyway. It also seems more willing and healthy when revving after this adjustment.
It performs well on the road, but there is still a cloud of blue smoke when accelerating after rolling down long hills, of which we have lots... I'm almost certain this is due to a valve guide issue on cylinder one, at least this piston still appears wet from oil, on piston top and up through spark plug threads. The plug has traces of splash on one side of the insulator and up to the firing end. After long periods of idle it will foul more of the plug, but it seems driving keeps it dry.
Ok, will continue driving it and see how it turns out. I think I will eventually get a cylinder head from Mr Burgess himself, as I can't think of anything else causing the oil consumption than the cylinder head.
Regards, Tommy:-)
|
|
|
|
Post by Penguin45 on Sept 4, 2011 23:59:42 GMT
Hi Tommy,
I've studiously set my valve clearances to .013" (cold), repeatedly over the time that I've owned Eugenie. There was always one tappet ticking away noisily...... In the end, I fitted a nice heavy alloy rocker cover. That shut it up!
Seriously, there is probably one rocker arm with a "dished" (convex) face, so your feeler gauge is lying to you. But, which one? I just live with it.
The "B" engine started life waaaay back in the Twenties as a Chevrolet truck engine and evolved into the engine we know today, so it's pretty ancient, really. Noise is almost inevitable. It's over 50 years since the B engine as we know it today appeared, so the modern tight tolerances of today's engines just don't happen. A degree of acceptance is to be expected.
It's worth tracking down the leaking valve guide though - no-one likes to be followed by a cloud of blue smoke.
Chris.
|
|
|
|
Post by dave1800 on Sept 5, 2011 2:28:27 GMT
The best quote I have seen on how to stop the the B series clatter is...... "the only thing that sorts it out is turning the engine off" Tommy can track down which tappet etc is making the most noise by inserting a feeler guage in each of the gaps in turn (say 0.005") while the engine is running. Sorting it out is another matter! regards David Hi Tommy, I've studiously set my valve clearances to .013" (cold), repeatedly over the time that I've owned Eugenie. There was always one tappet ticking away noisily...... In the end, I fitted a nice heavy alloy rocker cover. That shut it up! It's worth tracking down the leaking valve guide though - no-one likes to be followed by a cloud of blue smoke. Chris. |
|
|
|
Post by tommydp on Sept 5, 2011 20:09:03 GMT
Hi all! Yes, of course the engine design is ancient and ticking is normal for these engines, so I'm not too concerned about the noise as long as it runs ok. However, I'm not living with the blue smoke and fouling of plug one which I'm certain makes it miss sometimes when oil reaches the plug firing ends.
I had a close look at a low mileage Princess 1800 head earlier, and the investigation leads me to believe both heads I've used so far have worn guides. The two heads I've used have noticable end play on all valves. Compared to these, the Princess head has virtually no play. When I block the valve guide with my finger and pull the valve a bit into the guide, there's a vacuum on the Princess valves when I remove the finger, not at all on any of the other head's valves. So the difference is significant.
I have avoided using this Princess head, as it has smaller inlet valves than the 12 H 2709 mark 2 head. It wasn't until now I removed the valves on the Princess head and noticed the significant difference. We'll see, I suppose I'll put in the Princess head sometime, and see if my theory makes sense.
Regards, Tommy:-)
|
|
|
|
Post by dave1800 on Sept 6, 2011 9:42:25 GMT
Maybe it would be better to have new valve guides fitted and reamed with new valves if they are worn? If you put on the Princess 1800 head with the smaller valves you need to check the combustion chambers are the same size; it could mean you need to use a different SU car needle and modify the ignition timing and perhaps a new set of problems to keep us entertained. ;D
Not a good idea to let the carbon build up for too long on your new rebuild.
regards
David
|
|
|
|
Post by tommydp on Sept 6, 2011 13:50:51 GMT
A good point, Dave! I really don't need further headaches:-)
Well, for a start I'm not certain about the CR, and if the pistons in the block, which is a Princess, matches the mk2 head in the first place. Don't now which pistons were fitted when they rebuilt it, but suppose they were the same type as the original ones. Not sure if it matters either, as I understand any head can be used on any block.
You're probably right about sticking to the mk 2 setting, avoiding further mix up issues:-)
I see from the mgb cylinder head identification page, that the mk 2 head (12 H 2709) and Princes 1800 head (12 H 4736) have the same combustion chamber.
regards, Tommy
|
|
|
|
Post by tommydp on Sept 16, 2011 18:06:04 GMT
Friday night on my own, so it's under the 1800 bonnet again after quite a while, as it's been standing.
Took it for a ride yesterday and it worked fine all evening! Took it to work today, and trouble started again:-) I expected it, so not disappointed really:-)
Regarding the oil burning problem, I wanted to check out the oil pressure, as I've never done that. I purchased a quality tester with various adaptors at an autojumble this summer and installed it. With the engine really hot, the pressure will not drop below 50 at idle, even at 600 rpm, isn't this too high? My manual says 15- 25 at idle and 50- 75 running. At fast idle it's about 60 and revving it way up steady it goes up to about 70.
Perhaps there's something wrong with the pressure regulator/ relief valve. I wouldn't be surpriced if they've done something wrong here, did not check it when I got the engine back..
Any opinions appreciated.
Regards, Tommy:-)
|
|
|
|
Post by tommydp on Sept 16, 2011 18:22:06 GMT
John explains:-) "40 - 50 at idle". Suppose that's ok then:-) Time to get that cylinder head off again, I guess:-)
|
|
|
|
Post by tommydp on Sept 26, 2011 19:22:14 GMT
Hi all! Been quiet here for a while, so time to throw in some threads:-) For a start, the troublesome crab has finally become quite stable and reliable. I'm using it every day. Valve clearances are still spot on and not too tight, I'm sure this is essential. Also, I think the inline filter between pump and carb and using rubber hoses instead of the original steel pipe here can cause trouble.
I still had some hesitation at certain conditions, and it wasn't until recently I discovered that the carb needle I was absolutely certain was a ZH, was in fact a TW, which is for one of the carbs on the 1800 S! Well, I've now fitted the correct ZH needle and the improvement was breath- taking, to put it mildly:-)
I suppose I'll get a reconditioned correct head and fit some time during the winter, as there is still some slight traces of oil getting to one plug sometimes. But for some reason the oil smoke after going downhill has disappeared..
Anyway, things look brighter now:-)
Regards, Tommy
|
|
|
|
Post by threelitre on Sept 26, 2011 21:40:57 GMT
Now that was - in fact - a very simple solution. So simple, that I didn't think of it... A colortune should be in your toolbox from now on, as you'd have spotted this problem with one of them almost immediatly.
The car was running lean and the fouled cylinder was probably giving most of the misfire, accumulating more oil than it would have done otherwise (read: now).
Enjoy!
Alexander
|
|
|
|
Post by threelitre on Sept 26, 2011 22:01:03 GMT
Hmm, I just looked ZH and TW up on mintylamb.co.uk - they are very similar, so I doubt they have been fitted to single and twin carb... But I found on my Maxi that running a manual with the needle from an automatic had a very severe bump on the mpg (automatic needle made it use way more fuel). But here TW is leaner in the mid-range compared to ZH, quite notable so... But richer at the tip, so possibly explaining the well running car in full throttle.
Regards,
Alexander
|
|
|
|
Post by dave1800 on Sept 27, 2011 1:10:21 GMT
The ZH needle is the standard (UK) for Mk11 single carb engines with the larger inlet valves and the 9.0:1 CR and the camshaft 5,45,40,10.
The TW needles is the standard (UK) for Mk1 single carb engines with the smaller inlet valves and the 8.4:1 CR with camshafts 0,50,35,15 or 5,45,51,21.
Confused? That's why I am still working on a system to measure carb piston lift in situ while driving in conjunction with a wideband sensor so that I can modify the needle profile to what is needed. I will have to try it out here on a Hitachi - SU look alike - carb on a Nissan "A" series clone but the principles should apply.
Good to hear you found this, as Alexander has noted Colourtune is a good investment, a window into your engine.
Regards
David
|
|
|
|
Post by tommydp on Sept 27, 2011 5:18:45 GMT
Sorry, of course the TW is the mk 1 needle. My SU book has very small printing:-)
Anyway, it seems logical, as the final trouble I had was in the mid range, where the TW is weaker. Typically it would miss on acceleration, and then catch up again. It now performs fabulously throughout the range.
A Colourtune will be ordered!
Regards, Tommy:-)
|
|
