Fiat 131 Abarth Stradale Overhaul

[RedLexus]

Anyways , back to work. Not shown in pictures , but I removed all the ancillaries from the front of the engine block , the front crank seal housing , the water pump , the oil-filter housing etc , and installed new seals and gaskets . The one thing I hte is oil or water leaks on a "fresh" engine. A coat of paint on the front pulleys too , just to tidy them up.
Then , With the head still off , I said I'd better check out the bottom end . The car always had high oil pressure and good flow , so the pump was likely ok , but best to drop off the sump and check it all . I must admit , I was curious to see the crank anyway , and the the Sump gasket needed changing too .
So , unbolt my new engine mounts , jack up the engine to clear the crossmember , and remove the sump...



Happily all looked well , and checked out ok . No excessive piston slap , crank end float well within tolerances , no discernable wear on the bearings , and the Cylinder bores neither worn nor glazed .

Nice crankshaft design , nicely counterweighted from Fiat , typical of the "hotter" TwinCams. Good strong looking Main bearing caps.


So , happy with the bottom end , time to start the clean-up and re-assembly!
A thourough wipe out of the oily bottom end , then , steamclean the sump inside and out , a new Fiat sump gasket , and Shellac jointing sealer on both sides . I gave the Sump a few coats of fresh shiney black paint too.




and after a few minutes to let the sealant cure slightly , back on with the sump . Carefully tightening the studs in stages .

[RedLexus]

.. before I re-fitted the head , I had to fit new Frost plugs... oh what a pain they were! As you can see by the state of the one I removed , versus the new one... I bad to even take the die-grinder to two , and "eat" them out!

[RedLexus]

Then , laboriously plug each and every hole in the deck of the block with cloth/paper , and clean the deck face with fine emery paper . Lots of people don't close the water and oil holes , but I didn't want bits of meal , sandpaper grit , and headgasket mingling with the oil and water! . Also check and clean all the head stud holes. then , a good clean with petrol , and a blast with compressed air .



then , set the number one piston to TDC , re-install the dowels between the block and head , drop on the new head gasket.... and on with the head!

[RedLexus]

So torque tdown the head , in stages , using new bolts . I put a light coating of oil on the threads, and betweeen the headstud and washer , and the between the washer and head. Better safe than sorry , to be sure of a "true" head torque .



then after checking and double checking all the headstuds , out with the shellac again , and on with the Cam boxes.





again keeping everything in the order that it was removed , ie the cam followers going back into the places they were originally fitted to.

[miro-1980]

Most interesting !

I am still mastering my 131 abarth replica, now getting ready to install the whole rear suspension and original diff.

I will have questions for you, once I actually start the process.

Hope you will find time to respond to them.

Miro

[RedLexus]

I would be delighted Miro!

[miro-1980]

FIRST QUEWSTION rE BRAKES:

DO YOU HAVE STANDARD 131 BRAKES ( 227 SINGLE 38 MM PISTON ) ?

MIRO

[RedLexus]

Yes Miro , 227 for the disc , though I don't know about the Brake cylinder size. They are single piston alright .

[Guy Croft]

That engine has the WRONG auxiliary driveshaft pulley - it must have one with a rear flange. If the fuel pump lobe has not been removed and the shaft plugged it needs doing.

The belt must run constrained between the rear of the crank front pulley (or a flange locatged immediately in front of the cambelt drive pulley) and the rear flange of the aux d/s one.

The only exception is where the cam pulleys are the old 3/4" wide ones used on the 8v TC and are flanged inlet front ex rear.

If you have any query about what I have said please ring me on 01522 705222.

GC

[Walezy]

Brake master cylinder is the same as in any other Fiat 131 ( 19,05mm) according to FIA Homologation papers

[RedLexus]

With the followers installed , I then had to install the tappets shims and Camshafts .. First however I rotated the crank a bit to provide clearance between the valves and piston crowns . Naturally I put lots of lube all around all the moving surfaces . I measured all the tappet shims then , aand took note of their thickness and position , so i'd know which ones could be swapped around . I was aiming for a cold clearance of 0.35mm on the inlets , and 0.40mm on the exhausts . Bearing in mind this is a road engine , with normal , mild cams .
Eventually , I ended up with them all pretty close , some a small bit tighter , some a small bit looser . All had clearance however , and I was expecting to have to make some changes once the engine had been started , warmed and cooled.

So , with the cam boxes liberally sprayed with oil , the covers were fitted , then time to fit the timing belt . I used a Dayco item , in retrospect I should have fitted a GC 1 inch wide item , but at the time the owner was in a hurry to hear the engine run! I changed the tensioner of course too.

[RedLexus]

That engine has the WRONG auxiliary driveshaft pulley - it must have one with a rear flange. If the fuel pump lobe has not been removed and the shaft plugged it needs doing.

The belt must run constrained between the rear of the crank front pulley (or a flange locatged immediately in front of the cambelt drive pulley) and the rear flange of the aux d/s one.

The only exception is where the cam pulleys are the old 3/4" wide ones used on the 8v TC and are flanged inlet front ex rear.

If you have any query about what I have said please ring me on 01522 705222.

GC

Well I don't know Guy , it's got the original pulleys , all the exact same as our own road going Abarth , and the same as another one I looked at in Northern ireland . All with a FRONT flanged aux pulley . And the same Camshaft pulley arrangement , rear flanged on the inlet cam , outer flange on the exhaust .I haven't removed the fuel pump lobe as it is in use , operating the standard diaphragm pump on the side of the block .

[RedLexus]

So with the belt on , and the timing marks all ok , I refitted the manifolds . The Exhaust is the (standard?) Abarth long primary 4 branch , the inlet the standard Abarth one too . The filter socks looked quite grotty , with holes etc in them.. so they were junked for new ones . Not the ideal solution , I'm investigating an Airbox or one piece foam filter , as our Abarth rally car also needs one .
The inlet manifold appears to be mildly polished from new to help airflow . Not a brilliant match to the cylinder head however . Some port matching needed!

[Guy Croft]

OK if the cam pulleys are flanged that way!

I have not seen flanged pulleys on that motor, with Gp4 F/L stuff - one lives and learns.

Filter 'socks' are only good for about 30bhp per cylinder and most tuning experts won't use them at all because they are so restrictive and - esp when laden (dirty) - they do get sucked into the rampipe. Sometimes right in though you'll never know formthe driver's seat. You are right to consider something bigger and more suitable.

Here's your Gp4 unit BTW, nearly done.

G

[RedLexus]

Thank you for the pictures Guy .
re the Belt/Pulleys.. perhaps the engines you see are Modiied ones? Vernier Cam pulleys and dry sump drives etc , it's probably rare enough for anyone in this day and age to tune a standard 131 AR?

I must get dimensions and contact your friends in ITG Filters .


Anyways , work must proceed....

So after running the engine (and jumping around happily to hear it run cleanly!) , and checking I had good oil pressure , and my timing etc all correct , there appeared to be a slight tappet rattle . Very slight , and unusually , not constant ! I verified I had no oil leaks or fuel leaks , then left the motor overnight to cool . Sure enough , some of the tappet shims were in need of change , some had tightened , some seem to have loosened , all only small amounts . I admit I took a couple of nights before I was completely happy , that all the clearances were ok , even had to beg some shims from a friend who works in a Fiat dealership .(Thanks Dave N!) . Worryingly , the occasional "tappet rattle" was still there , every now and then , and mostly when the eengine was warm! I even checked the clearances withthe engine Hot , and it was still measuring ok .

After much debate , checking and searching , I found the source of the noise . The Abarth as the previous pictures have shown has the Distributor driven from the Exhaust cam , at an angle .



the picture is very blurry , but essentially the drive gear was the incorrect one! Too small in diameter , not making full depth "mesh" with the mating gear on the exhaust cam . the teeth were rattling off each other , and if left much longer , would have possibly stripped the teeth off . Just as well the Distributor takes practically nothing rotate .