I'm just about to start re-building my 1971 MG Midget 1275 engine to go back into my convertible.
Having stripped it down and cleaned it, I noticed that (i) it was originally painted in a light metallic green - which I have tracked down to be MGC/Austin Healey green and (ii) it was originally painted inside the block too. (see pics) [frame][/frame][frame][/frame]
Whilst I know it is not necessary to paint the internal surfaces of the block I'm just wondering if anyone else has come across a painted internal surface like this and what, if any, are the problems or benefits of having a painted surface like this would be?
Yes - at first I thought it was just overspray but it is too regular for that - it's not a very thick coat but, like you, i would have thought that over time and having been in contact with hot acidic oil for long periods of time, it would have fouled up the oilways etc. Anyone else seen a block painted on the inside?
it's a long time ago when I heard of this, and forget where I read about it, but the idea was to smooth the inside of the block so the oil returns back to the sump at a faster rate. This was a competition engine. How effective, if at all I don't know as oil at a good temperature is pretty thin.
Yes - the engines often had a thin red coating. I wouldn't be adding any paint now. DO look above the centre main to check the block isn't cracked there..........the major upgrade on the A+ was to eliminate this.
Thanks Roy - yes, I checked the centre main and all appears well. I have not painted the insides either - didn't really seem much point. Lower end is now rebuilt with new mains, big ends, oil pump, thrust washers, new +20 pistons, timing gear and mild road cam. Head in good condition so fingers crossed it will be a sweet engine for years to come!
Yes, its a Piper cam (255) that I have had around for a while - it's a new unit and gives about 8hp more power. It's got a bit better lift than the standard and whilst it will not be breaking any lap records, it will hopefully be a nice mod. They market this verison as a 'mild road' cam, as opposed to a 'fast road' cam and 'comp spec' cam I guess, so it's right at the bottom of the tuning tree.
The problem with 'higher lift' is that it rather precludes the use of the excellent 940 head...... And '255' is barely any more than the standard AEA300 cam anyway.......
The standard cam I had with the engine was starting to show signs of damage on the lobes anyway, a combination of use and having been stood for way too long so rather than buy a new cam, I used the one I'd been given. It seemed false economy not to renew the cam when the chance arose and also to buy another cam when I had a new one ready to go. Agree that the performance improvement is unlikely to be that noticeable and would hope that its 'almost normal' profile will not detract anything significant from the excellent 940 head. I'll keep you posted once the engine is back in the car.....
The extra lift means you will need to pocket the ex valves even more......there is a limit to how well that works, and with the large valves the high lift is not necessary anyway. But I see the point in using what you have... Make sure you have a matching oil pump - and NEW followers for that cam!
Thanks Roy - have fitted new followers - the old ones were terribly pitted and next to useless, new push rods and valves, new valve springs came with the cam shaft and a new spider drive oil pump is in place. How much do you think I need to pocket the ex valves by esp as the cam itself provides only slightly more lift and duration than standard? I was hoping I wouldn't need to do anything else major to the head, having already had unleaded seats fitted.
Oh dear - the unleaded seats were a BIG mistake........ Did we not cover this before? You need to tell me the precise lift of this cam. And the springs - are they definitely for a 940 head ??
Well the original seats were pretty well shot so it seemed sensible to fit new u/l seats at this time. If they were OK, I would have left them alone.
The cam kit originated from the MG Owners Club spares centre in Cambridge so I'm confident that the springs are right for the 940 head and the kit is currently marketed by them as a mild road cam for the 1275 Midget engine.
'shot' seats are just what you want for a 940 head on a small bore engine! It would have been ideal. These new seats will be too hard to cut down to get the 360 thou you obviously need to be safe with that cam.......the gasket thickness will be your only safety margin. It's 'just' enough - and even then we have to hope they didn't include the valve gap in the equation....... . So - you need to assemble the valves into the head and then carefully measure the distance from the valve top face to the head face. Sadly with these seats it is likely to be WELL short of that 360 thou..........and to cut them down (and they are hard!) may make them too thin to be safe. Frankly - you would do better to set this head aside for a 1275 engine, and source another 940 head with 'shot' seats...... Or of course - you can have 'pockets' cut into the top of the block - not an inexpensive process, and they may have to be so deep (because of the new seats and new valves) that the top rings will be exposed.......... Oh dear......
Oh! Sorry -my confusion!! It's great for a 1275 !! And it's not a 255 - it's a 266 so virtually the MG Metro cam - just a little extra lift. Well worth having!! Sorry - been away for a week, and I thought you were one of the 1098 converters ........ You will want an HIF 44 with that engine - and BDL needle.
Don't worry Roy, I have the HIF 44 carb too - thanks for the needle check - it was a question I was going to search for an answer too shortly so you have saved me the time. I must admit I was asking myself how I had made so many errors in my choices of bits etc. I only realised when you said about a small bore engine and to put the head aside for a 1275 that we were talking about different things! I can now scrap all the e-bay adverts I was creating for parts I no longer needed I'll let you know how the unit behaves.... wtch this space
