Lancia Motor Club

Model Technical and Interest => Augusta => Topic started by: omicron on 20 December, 2021, 04:29:21 PM

Title: Augusta
Post by: omicron on 20 December, 2021, 04:29:21 PM
Does anyone know the internal diameter of the oil restrictor (Tavola 1, part 31-14) that Lancia saw fit to position in the vertical oil drilling that takes oil to the valve gear?   The parts list describes it as a seal, and significantly not a restrictor.   Mine has an 8 mm bore which strikes me as being too large.   My difficulty is insufficient hot oil pressure even with 20W/60 oil and it is only towards the lower part of the normale zone on the gauge at reasonably high engine speeds.    The oil pump gears are perfect as is their end clearance in the pump, the bearing clearances are perfect on the rod journals, slightly large on all three mains, but not, in my opinion, sufficiently so to account for the deficiency, but I will be having them re-white metalled in January.   The tensioner shaft is new so cannot be blamed.     I am tempted to make a new insert with a 5 mm hole unless those with more experience differ.    It is also curious that Lancia chose to take the signal for the pressure gauge at a point far removed from the main gallery which is where it matters and which possibly confirms that the part in question is not a restrictor at all, but merely a way to control leakage through the crankcase to block joint.

As a matter of interest the hydrodynamic wedge in the bearings generates bearing pressures in the order of thousands of p.s.i, and oil pressure is only required to encourage the oil to enter the main bearings against centripetal force on its way to the rod journals.   A good rule of thumb is 10 p.s.i. per thousand engine r.p.m.  So why am I worrying?   This last part is a question for me and not the forum!   The driver's handbook states that the oil pressure regulator is set to 3 kg/cm2 (which equates to 43.5 psi) and refers to the normale section of the gauge without saying bottom, top or half way).   Have people cross referenced the vague gauge to one with trusted calibration?

Thanks for any input, Martin Cliffe

Title: Re: Augusta
Post by: Mikenoangelo on 20 December, 2021, 10:11:31 PM
I did not separate block and crankcase on my car so have not seen the part you mention (by the way it's Tavola 1 31-4 not 31-14) but if you look at Figura 2 at point 18 there is a significant restriction where the oil passes from the passage through the head to the valve gear and also where the oil feed passes through the cylinder head gasket from block to head. On my car the latter incorporates a copper insert which is only about 5mm bore. See attached picture 74. Assuming your chain tensioner does not leak excessively the oil flow is already restricted to less than the 8mm you mention so perhaps reducing the part from 8 to 5mm will not make much difference.

I suspect that the part 31-4 is indeed just a connecting piece between crancase and block so the the paper gasket is no subject to oil pressure. Thus was presumably less of a problem where the oil passes through the head gasket from block to head. If the copper inserts on my engine are original (and they are also fitted in the tiny water (steam?) passages adjacent to the top of the bores) picture 73.Lancia were also concerned about leakages to the outside at these points too.

I'd suspect the pressure regulating valve at the side of the block. I had to reface the taper on the piston and also deburr the rim of the outer end which the spring goes into before it would reliably seat and not sometimes cause pressure to fall.

I also wonder how accurate the gauge is! Mine runs well over the mid point of "normale" at anything over 1500 rpm.


Title: Re: Augusta
Post by: Kari on 21 December, 2021, 09:22:34 AM
Mike already has pointed out to possible locations of leaks. One position which is sometimes overlooked, is the clearance between the excenter (31-293B) and the sprocket (31-300). Excessive clearance here can lead to loss of oil pressure.
I am sure you have checked the oil pressure gauge in the car against a known gauge. IMHO the middle of the "normale" range would be close to 3 bars, the lower end about 2 bars.
I was wondering what oil pressure you get when the engine is cold, by using that 20W/60 oil. As I have no experience running multigrade oil in an Augusta engine, I assume that the cold oil is thin and low oil pressure is indicated?

The oil passage in the block has 6 mm diameter from the tensioner shaft up to the top of block and from there 5 mm all the way up to the rocker shaft.
In my experience the engine will run a good oil pressure with original specs. The challenge is to find excessive play and get it back to factory dimensions.

I assume you have all the necessary data for the engine, if not, let me know.

You mention, that you will have the main bearings renewed. May I suggest, when line boring will be done, the block and crankcase should be bolted together and tightened. The crankcase is not as stiff as it looks.


Title: Re: Augusta
Post by: omicron on 23 December, 2021, 10:00:58 PM
Thanks, Mikenoangelo and Kari,

I'm new to forums and can't quite understand why people have aliases, but I'm sure there is a good reason, but unfortunately it means I can't always identify who's who.

The old saying "engage brain before operating mouth" or in my case, tapping away at a keyboard, comes to mind.   I agree that the 10 mm vertical drilling in the crankcase and block reduces to 5 mm in the head and the oil flow is then further impeded or modulated by the cam shaft front journal before going through a 3 mm hole up to the rocker shaft.   The item 31-4 must just be a way to avoid oil leakage at the crankcase to block interface as you point out. 

I will double check the pressure regulating valve for leakage and I may be able to calculate the spring stiffness knowing it blows off at 3 kg/cm2.    I'll also inspect the clearance of the tensioner sprocket and its eccentric carrier, but i have a feeling it is satisfactory.

Thanks for the tip about using the rigid block to stabilise the crankcase which consists of large quantities of fresh air and not much aluminium.   Over the years we have done literally hundreds of Fulvia engine rebuilds , and in exactly the same way, assembling  the crankshaft into the aluminium crankcase on its own often results in stiffness, which is eliminated as soon as the iron block is attached.

This leads me to a criticism and pet hate of mine regarding Lancia's design philosophy.   So many of their engines use combinations of iron and aluminium that expand at different rates and give the gaskets a hard time.   Even worse, the Fulvia crankcase is non-symmetrical which can only introduce distortion as it warms up.

Each 4 cylinder narrow angle engine seems to be a totally radical departure from the one preceding it.   Did each designer have a NIH syndrome or were they just experimenting to find a solution that actually works?

Thanks, Martin Cliffe   

Title: Re: Augusta
Post by: Mikenoangelo on 24 December, 2021, 07:59:57 PM
Martin – I rather agree with you on nick names but in many cases the real name can be found by clicking on “view profile“at the top left.

I find I can measure the spring stiffness by borrowing the digital kitchen scales (don’t tell her!) and pressing the spring down on the scales through a measured distance with the chuck of my drill press. I did this when I had to replace the minute compression springs which control the non return valves of the front suspension shock absorber units and the result was very close to the stated stiffness of the replacement springs I bought. I could measure my oil pressure relief spring if you like – as I said the oil pressure on my car seems OK.

Using a cast iron block on an alloy crankcase was normal in the 20’s and not generally seen to a major source of oil leaks. I suspect where Lancia went wrong is the limited number of holding down studs which is a consequence of the V4 layout.

I know little about Lancias post Augusta but feel that their persistence with the V4 layout was driven more by company tradition than by engineering needs. The peculiarity of balancing the V4 must have eventually been resolved as the Fulvias can by all accounts rev just like any other configuration but it is striking that few if any other firms followed the same route until the Taunus/Ford engines of the 60’s which used a geared balance shaft to prevent the occupants of the car from feeling the vibration.

Mike Clark