24 replies to this topic

[Welshminiman]

Afternoon guys, another engine question for you.

The conrods that came with the engine, all the lower half ends were all removed and bagged (don't know why?) prior to purchase, and the pistons were still fitted in the block.

Now that I have removed them from the block, only 3 of the 4 have ident markings, and even those don't all have the corresponding markings showing which way to attach them.

What's the best way to find out which way around these lower half's attach to the main item itself? Or would I be better off getting new items?

[Ethel]

They are machined as assembled units so you'd need to replace complete rods. If you use a magnifying glass you should be able to match up scratches on the milled faces, CSI stylee.

[GraemeC]

If 3 of 4 have markings you can work out which cap goes where.
Orientation is always that the bearing tangs go together

[Welshminiman]

Cheers for that GraemeC, I thought that was the case, but I don't have my Vizzard bible or Haynes manual here at the moment (both at the inlaws) and having not done an engine build in a while, I have forgotten more than what I knew in the first place 

[tiger99]

You can check by feel, the assembled rod and cap should have good alignment in the bore, and if you look after your fingers well (like a surgeon) you will certainly be able to feel a discontinuity of less than a thou at the joint. (Ignore the side faces, they never line up perfectly.) The final check is to assemble with new shells and fit up to the crankshaft (you can do this out of the engine if you wish). Nip up the bolts very slowly and gently, feeling for free movement. You should be able to get them all to full torque without any becoming tight. But do go really slowly and gently, as if one is wrong, the correspomding pair of shells will be damaged if you just torque them up fully.

[Carlos W]

They are machined as assembled units so you'd need to replace complete rods. If you use a magnifying glass you should be able to match up scratches on the milled faces, CSI stylee.

 

They're striation marks!

[Welshminiman]

Would the same rule apply to the crankshaft main caps?

[tiger99]

Yes, and as the two end caps are not reversible, only the middle cap need be considered. Unless, of course, some IDIOT of a previous owner has mixed up caps from two or more blocks..... And yes, it has been seen on this forum. Depressing, because it oftem means that the block is scrap. In theory a new cap can be fitted and line bored, but how do you line bore without removing any metal at all from the upper half of the bearing seating, in the block? The answer would usually involve fitting shells that were over-sized externally, if you could get them easily.

 

When you put the crankshaft in the block, always using plenty of best-quality engine oil, or running-in lubricant if applicable, always (block upside down) sit the crankshaft in the 3 shells, with thrusts in place too, and check that it spins freely. Then add middle bearing and shell, nip up bolts loosely and again check for free rotation. Then one end, and check.... Other end, and check... Then torque them up, one at a time, gradually, checking all the time (it comes naturally once you have done it once, and takes hardly any time in reality). Then, once the fully torqued up crankshaft is known to be good, the big ends can go on, one at a time, following similar procedure. Note that piston drag is not negligible, so it will get stiffer, so check each piston first, they should all feel roughly equal.

 

Check, check, check as you go, and there "should" be no nasty surprises later. Honestly, it really is worth a quick twiddle as you tighten up. Next is camshaft, oil pump and timing chain, it should still be free, right up to the point where you put the head on, and the valve springs mask all allempts at feeling anything.

 

I think you have already guessed all this for yourself anyway, hence the question. But remember, assembling by feel, and even better, by a low reading torque indicator, is no substitute for micrometers, dial gauges, Plastigage, and whatever else gets used to check bearing tolerances and running fits, it is only to detect assembly problems, which it does very well.

 

The cowboy arrogantly assumes that his work is perfect, torques up an entire engine, and only finds out that it will not rotate when the starter motor fries. The competent engineer proves his work at every step. In this context, any Mini owner can opt to apply a high level of competence, as it doesn't in this instance need special skills or training, just common sense. Same of course with hub bearings and such like, twiddle and feel them as you torque up, and consider yourself well satisfied that you have done as good a job as possible. Doing the job properly should be very satisfying.

[Welshminiman]

Cheers for that Tiger99, yes most of it is common sense as you say. The first engine I built (having stripped it first) was during my apprenticeship as an Aircraft Technician, it was a Land Rover engine, couple of years later, my engine in my old mayfair got rebuilt, which shortly afterwards caught fire (not due to engine work I must add) I also built a 1275 for my old Air Cadet sqd to give them an understanding of how engines work.

But move 7 years on, one child down and another on the way, trying to remember the basics was complicated, though now, it's starting to come back to me!

[Cooperman]

If the main caps are not as original, Rob Walker Engineering can machine a few thou from the under deck of the block, machine a few thou from the caps and line bore accurately. In fact he can also make, fit & line bore a solid steel centre cap as an alternative to a centre main strap for a competition engine.

There are other companies who can do this, but I've only used Rob Walker for this.

I believe all the FIA Group 2 race engines have this centre main modification to allow their engines 1275 to rev to around 8000 rpm.

[Welshminiman]

This is something I'm looking at doing, the bottom end hasn't been modified (to my knowledge) and the centre cap is the original from first build.

I've been pencilling down recently what sort of specification I want for this engine, though there are some items I've yet to decide on. My main priority is to do more homework, and ask lots and lots of questions on these pages for advice.

[Cooperman]

We will all help as much as we can.

[Welshminiman]

Well what I want is an engine with good low and mid range torque, plenty of grunt to put a smile on my face  (mostly used around towns, with occasional motorway blasts). I'm not fussed on power, I would much rather have a reliable engine that's fun to drive around on, than have something that will break every 6 months!

 

Starting from the top:

 

Head:

Ported & Polished

Valve sizes (Don't know)

Hiff 44 Carb

Heated inlet manifold (Is there a better one?)

LCB Manifold

Rockers.................... (not got any, what's best?)

Combustion Chamber (Is it worth increasing? read rest of spec before answering!)

 

Block:

Head skimmed

Block bored out to 1312cc

Chemically cleaned (Needs it)

New core plugs (Without question)

Crankshaft (not sure whether to refurb current one, or buy new item)

New Pistons (Hi or Low compression - See Combustion Chamber above)

Camshaft (Kent 266/276? Any others?)

Quality Pushrods & Cam followers (what's best?)

Cylinder head studs (Not sure here, help please, also do I need 11 studs?)

Centre main strap modification/or Steel Strap

Keep Std Oil Pump (unless its better to get new one!)

Mechanical/Electrical Water Pump (any suggestions?)

Electric Fuel Pump (Not sure what one)

S/C Primary/Idler & Input Gears (what teeth though?)

Distributor (No idea, preferably pointless!)

Coil (As above)

 

Gearbox: (Yet to buy one, 4 or 5 Speed?)

Centre oil pickup

Diff (3.4 FDR?)

Kad Quick Shift (Nope Changed my mind!)

Any other suggestion for a gearbox?

 

I don't fancy the idea of a S/C gearbox itself, the noise from the primary, idler and input gears will be enough for me!

 

If I've missed anything, please point it out & suggest, bare in mind, this is all typed up from a scrap piece of paper I jotted on during work!

Edited by Welshminiman, 02 April 2014 - 09:14 PM.

[GraemeC]

Drop gears - go 1:1 however I would go straight cut box before drops.

[Welshminiman]

I would go straight cut box before drops.

 

This is where I stumble a little, The current Primary I have (not sure on number of teeth) the bronze bush? on the inside is heavily scored, now a synchro item would set me back £160, where as the S/C item is £104! would it be worth paying the extra, and just get a S/C gearbox instead?