Valve guides/rings 803cc series 2 APHM engine

[JulianW]

Hi,

This engine was running badly when we bought the car 1 month ago. Tested compression, about 120 psi on all four cylinders. The exhaust note did not sound right, as though the engine was firing into the exhaust.

Removed head, two of the exhaust valves were black, two were orangey in colour.

Sent the head away to have new unleaded valve seats put in (Southern rebores, turners Hill), they put in three new phosphor bronze guides, new seats and ground in the valves. They said two valves were in poor condition.

Reassembled engine, new gasket set, adjusted rocker clearances etc. Put on the push on rubber oil seals, but did not use the o-ring seals in the gasket kit from ESM. Compression now up a bit, perhaps 123 psi.

Problem is now, loads of grey smoke at random times and a simultaneous change in the exhaust note when the smoke comes out. Power is not improved at all. If I run at 30mph, take foot off accelerator then back down again, no plume of smoke.

Any ideas please.

Also if the compression ratio is 7.5:1 and atmospheric is 14 psi , would I not expect only 105 psi, or is it more complicated than this?

And another question, please, how should I set the timing? Strobe or adjust for highest idle speed? Will sucking on the vacuum tube with my mouth show up on the strobe timing? Dizzy is a 40299k which is a DM2A4.

Julian Worskett, Horsham Sx. UK.

[bmcecosse]

Welcome to the forum. Have to ask -why did you bother with 'unleaded' seats........and why did they fit only 3 bronze guides? Bronze are NOT recommended for road cars...did they fit new steel guides to the other 5 ?? The smoke sounds like rich mixture - possibly carb flooding, or 'choke' coming on ? If it was 'blue' then it would be oil burning. The pressures you are getting are just about all you can hope for with an 803 engine. Yes - set the timing for smooth idle.....it's about all you can do with an 803, since they 'never' pink due to the low pressures.

[IslipMinor]

Under what conditions does the smoke appear - light loads, heavy loads, cold or hot engine? Does the engine lose power and/or can you hear a slight rattle at the same time? What else has been done to the engine when the unleaded conversion was done? How many miles has the head done since the conversion and is the problem getting better or worse? Has it really got 3 bronze and 5 cast iron valve guides?

Roy knows where this one is going, and I think I have been here before, but for a different reason!! From the symptoms you describe, it could be that one or more of the valves, likely to be exhaust, could be 'nipping' on the bronze guide when the engine is warming up or warmed up and under load.

Apart from the unleaded head, is the engine standard? If so there are a few things to check:

Did you put the valve stem oil seals on the exhaust valves - they should not have them fitted. If so they will need to be removed - with a lot of fiddling it can be done with the valves fitted by cutting them up and removing the bits!

Tappet clearances - normally 0.012" inlet and exhaust, but try 0.015" for the exhaust.

Mixture - set correctly, or one flat 'rich'

Timing - set the static to the standard of 2° BTDC and make sure that centrifugal advance is not allowing the distributor to over-advance at higher engine speeds. If you have a strobe, disconnect the vacuum and check that at high engine speeds the total advance is no more than around 36° BTDC.

Once you have done all this, did it make any difference?

[JulianW]

Thanks for replies and yes, I did put the tube type seals on all the valves. I assumed, as there were 8 o-ring type ones in the gasket kit, all 8 needed seals. I will take them off.

I had the seats done as I assumed with unleaded fuel there was no lubrication of the valve surfaces. I also assumed that 2 of the exhaust valves were damaged because the car has been run on unleaded with just netted lead balls in the tank (which are most likely useless as lead does not dissolve in petrol..) Are you saying cars dont need any mods to the valve seats?

Three valve guides were reamed out and pink metal sleeves put in, with a fine spiral cut in the inner metal surface. I assume these are copper or bronze. I suppose they were not all done as the others were in good condition. I trusted Southern Rebores to do what was necessary as they have been around for 30 years and know what they are doing, hopefully.

OK on the timing, thanks for that.

Also, thanks for comments about the 803 engine. perhaps I should just be done with it and consider a conversion to a larger engine. If I went to a 948 or 1100 would I need a new gearbox or would the old one fit?

Thanks,
Julian.[frame][/frame]

[IslipMinor]

Julian,

Were the 3 sleeves all fitted to exhaust valve guides, or were the guides replaced completely? Were all 4 exhaust valve seats converted to unleaded?

What have Southern Rebores had to say about the problems you have had? Have they seen the problem first hand?

Can you describe the conditions when the smoke appears? Hot/cold/warm up/light load/heavy load?

What thermostat is fitted?

Have any other changes been made to the engine?

There are many views about whether hardened unleaded seats are required for the exhaust valves - many seem to get away without doing so, especially on lightly stressed engines.

[bmcecosse]

An 803 Minor is highly unlikely to do sufficient miles to ever justify any 'unleaded' conversion, and no additives required either... . In any case - The later 998 Mini head is identical and already 'unleaded' and freely available - indeed they are sometimes given away 'free', because hardly anyone wants them on Minis! . As you guess - the lead balls are just another of the various 'con' tricks associated with unleaded running. I have never ever heard or 'reaming' valve guides and fitting 'sleeves' ?? And what ever they did - they should surely have done it to all 4 exhaust guides.....if doing 3. And they certainly don't know what they are doing if they fitted top hat seals to the exhaust guides. These seals will in any case not stay in place unless the later guides with a location groove have been fitted. As suggested - cut off the exhaust seals. I also strongly recommend using 15 thou gap on the exhaust valves.