Author Topic: Engine rebuild supplies  (Read 12690 times)

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Xylaquin

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Engine rebuild supplies
« on: June 12, 2017, 03:08:24 PM »
Hi folks,

I've bought myself a new crankcase, cylinder head, pistons, rings etc
I'm considering that if I've gone to the effort of getting these parts shouldn't I also replace the engine bearings.

My problem is, how can I tell which bearing is correct: there are 8 listed here!

Likewise, for the valve guides, there are three part numbers in the EPC!

Xylaquin

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Re: Engine rebuild supplies
« Reply #1 on: June 19, 2017, 11:25:08 PM »


Everything has arrived. The highlight was getting a brand new cylinder head from Poland for the same price it cost to buy the valve springs from Ricambio  ::)

drcdb15

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Re: Engine rebuild supplies
« Reply #2 on: June 20, 2017, 12:37:22 PM »
Ummm....  you call this thread Engine "RE" build, but it looks as if what you are actually doing is building a brand new engine and then putting an OLD crankshaft, old cylinders, old push rods and con rods etc in it...

Wouldn't it be worth replacing the whole lot? I can't say about the engineering wisdom of mixing (worn) old and new major components like this, but seems a shame not to go the whole way and know that you've got a complete brand new engine. Would raise the resale value too I imagine.


Xylaquin

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Re: Engine rebuild supplies
« Reply #3 on: June 20, 2017, 01:40:17 PM »
Yeah, I'm on the same train of thought really... but my wallet isn't!

The crankcase seems to have came with cylinders installed in it already (although I could be being naïve)
Does the crankshaft really wear out as bad as other the parts which are exposed to combustion? Wouldn't the bearings in the rods be the parts that take the wear?

drcdb15

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Re: Engine rebuild supplies
« Reply #4 on: June 20, 2017, 10:37:46 PM »
Whether or not a bearing will wear out is partly driven by the loads to which it is exposed, as you say, but also by the extent of the lubrication. Arguably a massive bearing like the big-end will continue to run longer than some other more delicate bearing simply becasue it is of simple construction that is tolerant of excessive wear, being out of true etc. Imagine a big end starved of oil - it will pretty much just keep on chugging along. Now think of a needle bearing under the same conditions - it will likely break up with broken pins and rollers spewing out in all directions. Just becasue the bearing is still running doesn't mean it always will, nor that it isn't worn. At the very least it might be worth getting the crank re-ground and new shells etc. Similarly, will there be new liners for the cylinders? (I can't recall offhand if the 126 engine has dry or wet liners to the cylinders but I assume it's got something!). How confident are you that all the oilways in the old engine were always clear and that the oil was always changed at the right intervals, and the correct grade was used... (etc, etc... you get the point, no doubt  :cry:)

Sorry to pee on your chips as they say, but it would be such a shame to spoil the 126 for a ha'porth of 20W40, so to speak.

Xylaquin

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Re: Engine rebuild supplies
« Reply #5 on: June 20, 2017, 11:50:28 PM »
I'm the tenth owner, it's done about 72k. Need I say more?  :P

Basically about a month ago I was diagnosing a starting problem and ended up shearing one of the spark plug holes. The car has had poor compression for quite some time and I reasoned that I might as well replace the cylinder head and a bunch of the engine too. This is how I got to the position I'm in now.

New shells are a definite, as are new pins. As I said, the new block seems to have liners already in it.
I don't quite understand the concept of "re-grounding" the crank... if something is worn, sure that means it has been ground down over it's use? How can grounding further correct it?

To go back to my original post though, what bearing do I get? There's multiple part numbers, I guess they correspond to the multiple bearings available with different allowances. Why sell bearings with allowances?

126blackbird

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Re: Engine rebuild supplies
« Reply #6 on: June 21, 2017, 08:05:14 AM »
If you have a crank re-ground you would then fit oversized bearings. If you take your crankshaft to someone who re-grinds them they will be able to  check it to see if it needs re-grinding or not

Xylaquin

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Re: Engine rebuild supplies
« Reply #7 on: June 21, 2017, 12:54:59 PM »
Ah! It's all starting to make sense now.

Time to start digging around Europe for more parts  :-

drcdb15

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Re: Engine rebuild supplies
« Reply #8 on: June 21, 2017, 11:36:38 PM »
Ah! It's all starting to make sense now.

Time to start digging around Europe for more parts  :-

Understandably cash flow can be an issue at times like this if you suddenly decide on extra expenditure not previously budgeted, and something like a crankshaft is very expensive and very heavy - hence 'heavy' shipping costs too. So it might be worth listing in detail all of the 'old' parts you had been intending to use, and sorting them according to:

1. can I use it for now, and replace later quite easily when I can afford it? - pushrod tubes and even the pushrods themselves come into this group. Also external parts like the distributor.
2. could I use it now if a replacement later is very difficult technically, provided the old part can be checked by experts and reconditioned in some way to be like new? - here the crankshaft is included. Maybe also the camshaft (I can't recall if that's been mentioned earlier or not).
3. this absolutely MUST be renewed, using the old part is totally out of the question regardless of how easy it might be to replace it. This group will include things like O-rings, oil seals, gaskets and of course main bearings and as has been mentioned big ends. You might also want to include small end gudgeon pins, circlips and any other spring clips, end float sprung washers (in my day I recall we used to call these 'Thackereys', never knew why), split pins and the like."

This analysis will not only act as a checklist to ensure you consider every single component of the engine, but also lead on to a bill of materials for purchase and a schedule for the order of work to be undertaken. It will also impress upon you if not already impressed just how many parts there are in even a simple engine like the 126 that make it all work !


drcdb15

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Re: Engine rebuild supplies
« Reply #9 on: June 21, 2017, 11:55:05 PM »
If you have a crank re-ground you would then fit oversized bearings. If you take your crankshaft to someone who re-grinds them they will be able to  check it to see if it needs re-grinding or not
There are several videos on YouTube illustrating crank re-grinding, and obviously I haven't checked them all, but this one seems to me a good illustration to see what's involved. Essentially all the bearing journals are ground circular but as you observed, undersized. The associated bearing shells etc they will be fitted with are then correspondingly oversized. You will hear the engineer explain how once he has made the distorted or worn journal circular, he then has to set about making it a specific amount undersized - 10 thou [sandths of an inch], 15 thou etc, so as to correspond with the standard off-the-shelf sizes to which the shells are made. 10 "thou" is 10/1,000 inch, or 0.254mm.

https://www.youtube.com/watch?v=-7Al0_ihWgs

Xylaquin

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Re: Engine rebuild supplies
« Reply #10 on: June 22, 2017, 11:05:45 AM »
Well I've bit the bullet and purchased a new crankshaft from a shop in Bulgaria!
Also placed an order with 126fan.sk for tappets, conrods, piston pins, clips, main bearings, pilot bearing, pushrods, rod bushes and valve retainers. Now just waiting to hear back from some other suppliers regarding a new camshaft and rocker.

and there was me planning a holiday this year!  :D

Rusty's Uncle

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Re: Engine rebuild supplies
« Reply #11 on: June 22, 2017, 05:20:21 PM »
Dare I ask what the Bis crankshaft cost?

drcdb15

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Re: Engine rebuild supplies
« Reply #12 on: June 22, 2017, 05:44:07 PM »
Well I've bit the bullet and purchased a new crankshaft from a shop in Bulgaria!

Your postie's gonna *love* you ! Generous Christmas box this year methinks  :P

Xylaquin

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Re: Engine rebuild supplies
« Reply #13 on: June 22, 2017, 06:11:12 PM »
Update: the Bulgarian shop refunded me when they realised it wasn't a BIS crankshaft. So I've found one on Allegro.

Dare I ask what the Bis crankshaft cost?

Brand new crankshaft (in original fiat box too) is costing about £160

Your postie's gonna *love* you !
They must wonder... I've had deliveries from Poland, Germany, Italy, Slovakia, France.
The things we do for cheap parts!
« Last Edit: June 22, 2017, 06:13:51 PM by Xylaquin »

Piotross

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Re: Engine rebuild supplies
« Reply #14 on: June 22, 2017, 09:53:03 PM »
I got many engine parts for sell too, from Poland as we know :)