Race Engine Forum UK

Hi. I have a coupe with a hybrid T34 turbo at 1 bar.

With nearly 130 000 miles on the clock, it was running fast and strong. However it had begun using (consuming, not burning) alot of oil. So I decided to rebuild the engine.

So far I have inspected and measured the cylinder bores and the crank journals:

I'd be grateful if you could answer a few question:

• From the measurements and photos shown below, would you say the crank is okay to re-use? If so can I just polish the crank and install new standard-size bearings?
  
  What can you tell from the wear patterns on the bearing shells?
  
  Also. Proabably a silly question but, how do you clean out the oilways inside the crank?

Any other comments would be more than welcome. Thanks

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Cylinder bore measurements(top, middle and bottom). The first set of readings were taken with the bore gauge facing across the crank, and the second set was taken along the crank to check for ovality (is "ovality" a word??)

Cylinder 1: 84.01, 84.01, 84.02
Cylinder 2: 84.01, 84.00, 84.01
Cylinder 3: 84.02, 84.00, 84.01
Cylinder 4: 84.01, 84.005, 84.02

Cylinder 1: 84.01, 84.01, 84.005
Cylinder 2: 84.01, 84.00, 84.01
Cylinder 3: 84.00, 84.01, 84.01
Cylinder 4: 84.005, 84.005, 84.01


Crankshaft Main journals (Two readings taken approx 90 deg to eachother to check for, er, oval-ness)

Main 1: 52.99, 52.995
Main 2: 53.00, 53.00
Main 3: 52.995, 52.99
Main 4: 52.989, 52.985
Main 5: 52.989, 52.989

Crank pins (As above)

Pin 1: 50.791, 50.791
Pin 2: 50.80, 50.80
Pin 3: 50.799, 50.799
Pin 4: 50.80, 50.80

More to come soon!

Very well illustrated post and there is nothing wrong with the crank sizes and no undue bore wear, though that is not to say that the piston rings themselves may not be worn, you should remove from the pistons and measure.

For reference the crank sizes and other data pertinent to your engine are common to other 2 liter units and are published at:

http://guy-croft.com/viewtopic.php?f=1&t=774

Similarly I don't see anything really untoward on the bearings (main and rod very well photographed BTW).

Don't forget oil consumption can come from turbo compressor end and valve guides too.

I would polish the crank with fine Scotchbrite and Jizer or similar. I don't have a picture of this in process because I actually have a lapping tool for this - although if I modify oilways I certainly use that medium for polishing the edges of the modified galleries prior to final polish with an abrasive band. Engine reconditioners do 'lapping' or 'polishing' in the crankshaft grding machine with lapping tongs and if you get them to do it make sure they don't take off too much! Lapping by that method (and mine) must be done contra-direction-of-crank-rotation so it doesn't 'raise the grain'- that is standard practice and violating that rule can cause bearing damage. Contra direction means if the crank (which on this engine - but not all engines - rotates clockwise) is static - the band must be rotated around the crank counter-clockwise.

The 4 x OE crank plugs can be removed with tilting with a drift and levering them out and then the holes threaded out. This is not an easy job if you've never done it before. The tap size is 7/16 UNC and I have threaded plugs (specially made as it happens) for that. If I could ever buy plugs 'off the shelf' that fitted the gallery I'd be very happy to. It doesn't impact materially on crank balance by which I mean a skilled balancer would pick up the difference but it will not lead to amy problems at all.

Hope that helps in the 1st instance.


GC

Thanks for the reply. That's good news on the crank and bores. I'll replace with standard-sized bearings and piston rings.

Unfortunately it looks like the valves are going cost me. I spent hours and decoking the exhaust valves and ports. The exhaust valves were covered in rock-hard coke - I reckon a bit more heat and compression and I could have made diamonds :)

When I tried lapping the exhaust valves I found they were all pitted. The valve seats lapped okay though. The inlet valves are also pitted but not nearly as heavily.

I'm sure the ex. valves will definitely have to be recut, but do the inlet valves have to be recut too?

You'll have to lap for a very long time to get rid of the pitting, and in the process generate deep grooves in valves and seats. Might be best to have seats 'touched up' with a valve seat grinder and valves also. Any local FER reconditioner can do this for you.

I'd just point out that the ex valves are almost certainly stellite faced, a practice (and a far-sighted one) introduced first by Fiat in 1973 (on the 132 2liter series FWIW) and if you regrind that may well be lost. If the ex valve heads are stainless steel (which they usually are on the ex) they will not be magnetic - so test them, and the combo of plain stainless (minus stellite!) against the seats in that head (which have terrific heat transfer properties) is a perfectly suitable combo although not, obviously, as durable. If you want 'as new' - get new valves. That said, new sodium-cooled ex valves (which they categorically MUST BE) are a fearsome price and I would be be for regrinding (if none bent). The stellite thing is a 'non-issue' on the inlet side, it's not used there. The most you are likely to see on inlet valves is plasma coating and then usually only on aftermarket race valves.

GC

Did you clean the tops of the pistons while doing your bore measurements? The top of the pistons look almost like they have signs of detonation. The clean, almost sand blasted surface and small peen / blisters look like detonation damage. All but one piston has no carbon buildup? I would pull the pistons and check for broken rings and or broken piston lands also.
One more thing to check is that the crankcase breather is clean and not obstructed. With that kind of high mileage, especially on a forced induction engine, it is easy to have enough oil residues built up in the breather system that it does not work effectively, especially under boost conditions. If it is restricted, it will pressurize the crankcase and can force oil up past the rings.
Tom

tmvolumex wrote:Did you clean the tops of the pistons while doing your bore measurements? The top of the pistons look almost like they have signs of detonation. The clean, almost sand blasted surface and small peen / blisters look like detonation damage. All but one piston has no carbon buildup? I would pull the pistons and check for broken rings and or broken piston lands also.
One more thing to check is that the crankcase breather is clean and not obstructed. With that kind of high mileage, especially on a forced induction engine, it is easy to have enough oil residues built up in the breather system that it does not work effectively, especially under boost conditions. If it is restricted, it will pressurize the crankcase and can force oil up past the rings.
Tom

The pistons weren't cleaned when I took those photos. The photos make them look clean but they were all in fact covered in carbon buildup.
I've already pulled the pistons and cleaned them. The surfaces are all smooth and I can see no signs of detonation on the pistons or the head. I used det-cans when tuning so I'm confident there was no det. I'll post up some photos of the cleaned pistons soon.
Funny you mention broken ringlands though, because the No. 4 piston was cracked between the middle and bottom rings - along the holes behind the bottom ring. It came apart while I was removing the ring! Can a blocked breather cause this?

Thanks for the heads-up on the breather. I'll pull it and clean it out.

I ordered a 2nd-hand inlet camshaft from a Fiat Tipo 16V to fit to the Coupe. I wonder if it is worn though.

The Coupe inlet camshaft lobes are all shiny as I'd expect. but the Tipo cam lobes are all dark grey except at the tips and bits where they start lifting the valve (I forget what these areas are called). The lobes are, however smooth with no pitting or scratches,

Is this all normal for a Tipo cam?

Anybody??

in my 16V NA coupe engine, there were camshafts with black coating (I´ve also seen "red" coatings especialy on aftermarket cams) - I´ve read that this coating has wear protective function during engine start, when little amout of oil is in the top of the head...But I don´t know whether this statement is true.

here is photo of my slightly damaged cam from my engine

Yup I DO know how annoying it is to wait for an answer to a simple question, sorry!

The answer may surprise you. The shiny cam has been running with the valve clearance too tight and thus the tappet (shim) has been rubbing all over the cam. It should not and the wear (witness marks) on the other cam are from correct operation - the cam contacts the shim at the ramp and the nose region and nowhere else. That said if the cam feels smooth around the lift phase (see below) and nose that is good but if the ramp has been worn away (you should be able to feel it) the shiny cam is, well, junk really. But maybe someone has just polished it..?

The pictures show more-or-less what happens although I'd emphasise that the contact region is very different when the cam is actually acting on the actual shim & bucket assy. I have posted UNUSUALLY LARGE pictures so you can see the areas under discussion.

Read also the related article in the 'GC Virtual Workshop':

http://guy-croft.com/viewtopic.php?f=2&t=837

G

I keep coming back to this thread and admire the workmanship and meticulous organization and cleanliness.
I'd swap my laptop for this desk in a split second.

Congrats as always on the work done here.

And next to the radiator to keep you warm instead of freezing in a cold garage!

Chris

Thanks Chris...

G