80 replies to this topic

[maieth]

I keep thinking im ready to start rebuilding my engine and finding something else i dont know. So, following somebody else's lead, I'm going to start putting all questions in one thread rather than having multiple topics open.

Story so far: my mpi chewed up its gears so (with help) I've taken the engine out and split it. The 'box has been fully reconditioned with. New final drive and is ready to be put back.
The engine and internals needed cleaning to be certain there were no basty bits of metal stuck in there (there were) so the engine has been fully stripped and the block, cam, crank and pistons have been dip cleaned. The block has been honed, v.lightly skimmed and repainted. The crank big ends have been reground +10. Mains were fine. On the head, valves have been lapped by a friend, but might need seats regrinding (apparently)*.

At this point I think I have bought everything I need to rebuild, including:
Cam bearings
Cam followers
Big end bearings
Main bearings
Piston rings
Assembly compounds/lube, oils etc
New oil filter
Oil seal
All gaskets
Lock tabs
Spark plugs

So.....

[maieth]

1st question:
Haynes says cam bearings need putting in by a machinist due to special tools and 'reaming' being needed. I have no idea what reaming is and the bearings seem too large at the moment so this will probably mean a 3rd trip to machinist.
A) if bearings don't fit in the holes are they even the right ones? Or is reaming the process of grinding them down to a perfect fit or something?
B) as the block will have to go away again, is there anything else I'm likely to need doing at the same time? (Honing, skimming and crank regrind all done)

Thanks in advance for patient advice ;)

[Nick '91]

I have no idea what reaming is

Google doesn't seem to know either = P

[Old Bob]

Reaming is simply skimming the inside of a hole to get the right fit. This will be included as part of a cam bearing fitment.

Bob

[maieth]

Shameful. Ok, consider myself schooled on that one. So machinist will enlarge holes for bearings or should they already just press in?

[maieth]

Thanks Bob, makes sense.

Please excuse obvious naivety with this build. Trying to do and learn as much as I can without handing everything over to someone else.

[KernowCooper]

Reaming is when a bearing shell or bush is inserted and then reamed to the correct size with a reamer to the specification required, a example is the king pins on a commercial vehicle where the bushes are pressed into the axle and reamed to size of the kingpin.

[KernowCooper]

There will be some degree of interference fit in the bush/shell and then reamed to size.

[maieth]

Anything else worth doing at the machinist's at the moment?

[Fast Ivan]

if you don't have the tools yourself get them to clean out all the tapped holes with the right tap, make sure the holes on the top of the block where it was skimmed, including the bores, have a nice clean chamfer on them, the machine shop can do all of this

[Fast Ivan]

one other thing I would point out is the honing, just to make sure before you put it all back together, did you supply the pistons so that the machine shop could hone to the correct size? how many miles had the engine done prior to the strip?

[Blatherskite]

I have no idea what reaming is

Google doesn't seem to know either = P

A reaming tool looks a bit like a drill as it is spun round in a chuck, but cuts on the edges, not at the tip. It is used to mill out (open out) a hole to precise dimensions, and so is often used after drilling to rough dimensions. You also get a superior finish on the reamed (milled) inner surfaces. Thus, the right tool for completing bearings & bushes.

[Dan]

And it makes a round hole, a twist drill does not.

While it's there, get it cleaned again. Have it cleaned any chance you get.

Get some long thin bottle brushes and pipe cleaners, open all the oil ways and clean it again and again. You cannot make it too clean.

[Cooperman]

From the above, you have missed a new oil pump, a set of oil gallery plugs & a timing chain. Now, with regard to machining, you need to do a 'trial build' (sometimes known as a 'dummy build') by fitting the crank, rods & pistons, nipping up the nuts/bolts and making sure the crank rotates freely. Also check the crank end float and correct this to the correct limit of 0.002" to 0.005" by changing the crankshaft thrust washers. The 'trial build' is normally done with the piston rings off the pistons. Bring the crank to TDC on 1 & 4 and measure how far down the block the piston tops are from the block deck level. Strip again and then check the piston ring gaps. The ring gap needs to be 0.003" per 1" of bore diameter, so over 0.009" for each ring. The block can then be returned to the machine shop for the block deck to be machined to bring the tops of the pistons to block deck level minus 0.002" to 0.005". At this time the cam bearings can be fitted and reamed to suit the cam. Then thoroughly clean the block & crank, fit the new oil gallery plugs using a bit of Loctite to ensure they all seal well. A new set of core plugs is also a good idea.

[AndyMiniMad.]

While its away getting Reamed why not have the centre main bearing machined to fit a main strap. not really required if you dont intend to rev the engine beyond 6000, but it removes any flex in the crank caused by the two centre pistons which opperate on the same stroke cycle. although they are obvously timed to fire on different strokes. It all helps!!

You may or may not also find this of some help.

http://www.theminifo...-just-building/

Cheers.

Andy.

Edited by AndyMiniMad., 17 April 2013 - 03:29 PM.