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MG Midget and Sprite Technical - 1275 bottom end build advice

I'm rebuilding a 1275 bottom end at the present. Can I confirm that with new, standard spec main bearing cap bolts, the torque figure should be 60ftlbs? Is that with no lubricant on the threads or on the bolt head/main cap face? I have hardened and ground plain washers as a recommended tip, as per K Calver.
I intend using Wellseal on the front engine plate gasket. Is that OK?
For the strips that seal around the mains caps, is there any advantage to rubber or cork gasket material? I believe that they should be squeezed into the grooves in the sump and then trimmed about 1/8" proud of the face? Wellseal again or something else?
I have cleaned the sump before paint, with extremely fine glass beads.
I don't want to blast the front engine cover without access to the breather canister, in case I don't manage to clean all the beads out; they're like talcum and get everywhere.
Is there a good way of cleaning the canister, or should I just wire brush the cover and trowel on the paint nice and thick.

Mark
M Crossley

I would replace the metal gauze inside the canister...use the commercial pot stainless steel. scourer

Onbthe main caps....use the manufactures specs and there recommended lubes...if arp...becareful, they changed lube about 2 years ago so mak sure there torque specs match the new lube...there is about 15 psi differance

On the UK side a sealer that seems popular is (holmar??) (hoyermare??) Those are not correct, but if you ask around...a good parts guy will know what your wanting...avoid RTV, appeartly...this is a no no. As the excess gets in the oil galleries

Cork vs rubber...thats personal choice

Im not sure main cap bolts have hardened flat washers...if the bolt kit come with them then yes use them...if not, dont add them

Also check.your new hardware for prestretch or if you have to post stretch your new hardware and the proceddeure for how to do it...on arp it has to be stretched...before final torque

Id say a good powerwash is ideal.to remover the blaster beads as.well as any machine filings in the oil and water gallies

Prop
Prop and the Blackhole Midget

Wellseal yes, and also on the rear main bearing to scroll cover joint face. I prefer cork sump seals but you will need to nip the sump up after a few heat cycles as they do relax. The breather canister can be left in cellulose thinners and then washed out.For the block threads,studs and fastenings I like to degrease them with repeat doses of thinners and cotton buds - making sure they are clean enough to screw in with finger pressure. Aerosol BMC green paint is good - the AH Spares stuff is high on the solids and covers very well.
F Pollock

You're thinking of blue Hylomar Prop. That's what I've used, all my life it seems. Amazing it's still on sale. Either that or gold Hermetite. Which came first, Wellseal or the others above?
Lawrence Slater

Hylomar came out in the 1970's - Wellseal at least 10 years before that, although the formulations may have changed somewhat. Rolls Royce developed them both I believe.
F Pollock

The factory torque settings all assume an oiled thread!
This can just be verry lightly with normal engine oil.
Usualy this is forgotten but the normal oil coat on the botom end is just fine so without knowing it is to correct spec.

What are you using for the rods?
At least use new nuts but consider new bolts (or if budget allows ARP)
Onno K

Thanks for the help everyone. I tend not to use RTV much Prop. I too have occasionally come across lumps of the stuff in motors. I suppose it depends on how much you apply though. Its good for bridging the gaps in Pre-unit Triumph and Ariel primary chain cases.
Blue Hylomar was always a favorite of mine on bike engines, although I've seen Wellseal mentioned, so I thought I'd try it.
I've got some green engine paint, that I used on the block. It's quite old, and smells like the good stuff. It certainly gave me a headache anyway.

I've got ARP rod bolts and their fitting instructions, so I know what to do with them. The mains bolts are standard style from MiniSpares. I wasn't sure about the 60ftlbs manual figure, I've seen 68ftlbs mentioned. As far as oiling or dry was concerned, thanks Onno. The head studs are MiniSpares uprated ones with their paperwork.
For the rear main seal arrangement I've got one of these from Keith Calver
http://www.calverst.com/newshop/index.php?main_page=popup_image&pID=97

Thanks again chaps.
Mark
M Crossley

Mark...thats a great looking kit, I havent seen one like that before....do you put the seam at the top ?

Prop
Prop and the Blackhole Midget

Prop,
Yes the join goes uppermost with a small amount of sealant. There's no going back with the kit, because the main cap needs machining, but in my case the scroll looked damaged, so I had nothing to loose. We'll see how it performs once the motor's up and running.

Mark
M Crossley

I think it's this one - which is the same type I've been using for the past 10 years.
http://www.youtube.com/watch?v=bnOPAlVDcME
There was no machining of the rear cap or flywheel needed on mine, but it was slightly fiddly to do. Two points not mentioned, firstly the crank flange wants to be absolutely flawless as any marks or nicks will chew the seal very quickly - so if you are having the crank ground ask them to polish the flange as well, and secondly crank end float needs to be kept well within tolerance, as any forward movement of the crank will reduce the running clearance. The seal does work - at least as well as the one on the front cover, but you still need to keep the crankcase at atmospheric or lower.The alternative to a worn scroll is either line boring or squeeze casting. Sounds too simple, but all you do is add 2 thou of Sellotape to the rear bearing journal and squeeze cast the rear cover with JB Weld. This brings the running clearance back and allows the scroll to work again.
F Pollock

Furgus,

I don't think its quite the same. The seal holder screws to the main cap using holes tapped into it, after the rearmost part is cut off. The seal itself is split. I'll see how it goes soon enough. If I get my act together...
M Crossley

Yes I think you're right,but machining off the lower part does mean your stuffed if it doesn't work. But I'm sure it'll be fine.
F Pollock

Fergus, could you elaborate on how you do this please. I can't quite visualise it, but it sounds like something worth doing to my engines when I rebuild shortly.

"Sounds too simple, but all you do is add 2 thou of Sellotape to the rear bearing journal and squeeze cast the rear cover with JB Weld. This brings the running clearance back and allows the scroll to work again."
Lawrence Slater

Take the crank and mike up the scroll screw, then add 2 thou of Sellotape or insulation tape radially to increase it's diameter.Take the rear main bearing and rear cover and grind away some of the clearance.Place crank onto fresh bearings adding JB Weld to the ground off area on rear main bearing and scroll cover. Torque down caps and add scroll cover + gasket to squeeze cast the JB Weld against the Sellotape. Remove bearing caps and trim away excess from both parts - but leave the rear cover in place. With the Sellotape removed you will have a 2 thou scroll clearance when the crank is reinstalled.

F Pollock

This thread was discussed between 28/05/2013 and 01/06/2013

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