131mirafiori forum

Soon after I got my 124 Sport Coupe CC on the road, I noticed that the performance was way lower than what everybody described so I decided to take it to my workshop.

After removing the cylinder head we found out the following.

The engine is a 1585cc 132 engine and not the original 1592cc one.
Exhaust valves damaged (therefore much lower compression)
A very thick 1.9 millimeter gasket (nobony knows why, as the valves would not touch the pistons in any case)
Low compression pistons.
Cylinder head lowered.
Cylinders in excellent condition and standrad size.

The engine produces 98hp according to specs I found on the internet and I would like a little bit more than this so I was thinking about the following:

I have a set of higher compression pistons from a Lancia Beta which should increase the compression ratio to the range of 9.8:1
Twin Weber 40 IDF's
I also have a cylinder head from a 1608 engine with big intake valves which needs some minor modifications to the water passages according to Guy Croft, but I am not sure if this would actually make an improvement.
The cylinder head currently installed on the engine is a standrad 1585,1592,1995 head which has been lowered and had minor intake port polishing.

Opinions please?






 

Head lowered , meaning its been skimmed to get rid of the warping off the surface .
  and the valve need a good seal on any head so replace damaged one's and chech your 1608 head

I think mine was skimmed not only to get rid of warping but in an effort to increase the compression ratio.
Would it make a difference if the 1608 head would be installed? (which has the bigger intake valves etc)

The pistons on the left are like the ones currently installed on the engine and the ones on the right are the ones I intend to install for the compression ratio to be increased.

Hi!
shouldn't the 124 sport coupe cc 73-75 have the 1756 engine with the 9,8-1 in comp?
Alf

Mine is the 1600 version and should have the 1592cc engine but unfortunatelly it doesn't...
The cylinders of the 1585cc engine current;y installed on the car are in excellent condition so I decided to keep it and upgrade it.

Hi!
The 1585 we have, have pistons with 8mm dome as standard to reach 9,35-1 in komp,the one you have looks like the 5,2mm dome for the 1756 with 9,8-1 standard komp.
Don't you have any regata,Ritmo105,lancia Prisma head, who has 43,5mm inlet valves,and are standard on these models.

Alf

I found a head with number 5936188 with large diameter 43.5 mm valves.
The friend who gave it to me removed it from a 130tc engine, but according to Guy Croft, it comes from a VolumeX.

Any ideas?

Hi !
You will need a head from a 1600tc,the 2l have bigger combustionchambers than the 1600, 48cc and the 2l have 54cc, and if its a volumex even bigger I think.

You will lose a lot of comp with a 2l head, if it wasn't so expensive shipping I could supply you with a head and pistons so you had the 43,5mm intake and 9,35-1 in comp!

Alf

Since the bore is the same on both the 1.6lt and 2lt cylinder heads (84mm), should I assume that my 2lt head has slightly bigger height than the 1.6lt one, thus resulting in a bigger combustion chamber?
If this the case, I could take the head to a workshop and lower it to the desired combustion chamber size  ???
 

Measure it before you cut it. Easy to CC the chambers.

Hi!
When I get time,in between the dipers I can take take some measurements since I have both heads.
But I think they have different chambers just not in height,so don't skim the head so you get valve to piston issues and not alot in gain in comp!

Alf

OK we measured the 130tc head and is is about 52-54 cc as Alf suggested.

With the big dome pistons we installed the compression will be at around 9.35-1.

My standard cylinder head (which has been lowered to the limit) will give compression around 10.0-1.
So the dilemma is, 130tc head with big valves and ports and 9.35-1 comp. or my head with standard valves and ports and around 10.0-1 comp?

I would use the smaller head (ported off course) because 1,6 litre engine does not need big ports of 130tc head. With bigger compression and smaller ports it is more driveable.

Fiat 8v twincam head is actually quite easy head to work with. Here is some pictures from the small port head I ported.
http://vode131.kuvat.fi/#/kuvat/Turismo++Competizione/

Here some porting pictures too. This is from my friends 131 racing engine I did for him. If I do this kind of "street porting" job it takes maybe 6-7 hours.

http://vode131.kuvat.fi/#/kuvat/Sekalaista/131+Racing+moottori/

What about finding a 105 TC head?
It will produce compression around 10-1 and has big valves and ports.
The engine is going to be used for historic racing purposes on my 124 sport coupe CC.

What cams, carbs, exhaust are you going to use? No point upping the compression if everything else remains standard.

I 've got 2lt cams,  adjustable camgears,
twin 40 IDF's,
2lt exhaust manifold and
custom made exhaust system.
I will also install an electronic ignition soon as I find one  ;D

I came across a supposingly 105tc head from a friend.
The number on the casting is 5992169.
We measured the chamber volume and it is the same as the 5936188 head I already got. (Around 52-54 cc)

Is this head really a 105tc head? Any ideas?

Hi 5992169 is Regatta 100S head,
5992303 105/130 tc
4462603 late 105 tc
hope this helps ;)

You have a very useful database there Nick.... :)

5936188 is an Lancia Beta Volumex head, intersting it is with sodium cooled exhaust valves!

It is interesting but the delimma still remains.

Option 1. Volumex head with big valves and ports and 9,3 - 1 compression ratio or

Option 2. The standard head (no. 4371507) with polished ports and skimmed to the limit which produces around 10 - 1 compression ratio.

???

The engine will work with 2l cams and twin IDF 40's...
The car is used for historic racing events.

if you not sure?
here you can found some same questions:
www.guy-croft.com
this is very interesting:
http://www.turbo124.com/forum/viewtopic.php?f=10&t=7743

Read them both, very useful info. Thanks!

I decided to use the big valve ritmo 130tc head but then I found out that the 105tc/Regata 100s head I have, although it also has the big 43.5mm valves it has smaller ports than the 130tc.
The 130tc has 36mm ports and the 105tc has 32.
My engine is 1585cc so I was thinking maybe the 36mm ports are too big for this engine and it would be better if I use the 105tc head?

Hi Stephen!
I would use the 100s head,you will get higher gas velocity and a higher comp with it and still have the same good flow as the 130 head, if you had used race cams I would just ported it as you can do anyway in the roof area and enjoy the raised port centerline!

Alf

Hello Alf.

Thank you for the reply.
I understand why the gas flow will be faster but why is the compression going to be higher?
I measured both heads and the volume of the chambers is the same!

No,if they both are untouched the 100s has a volume of 48cc and all 2l has 54cc so you will gain another 0,5 of comp give and take with the 100s head!
 
A happy new year to you and the rest!
Cheers Alf

So from everything that I have read, I have concluded to the following and please correct me if I am wrong.

- The 130tc head ports are way too big for my 1585 hence the mixture flow will be significantly slower.
- The 100s head provides very good flow characteristics from factory, especially for my 1585cc engine and gives
  higher compression ratio than the 130tc head.
- Unless I replace the 2l cams I have with racing ones, I do not need to port the head in the roof area unless I  
  want to but I will not see much difference with my current setup.
- I can also lighten the valves by grinding off some of the material in the valve face to get better valve spring
  response.

Am I missing something ?

My opinion is that valve lightening is total waste of time. Stock springs are so stiff that it is not necessary with standard cams.

If you want to work with valves back cut them for better flow.

What is the difference between 2.0 and 1.6 cams? I would change the cams, your getting very slight increase if you keep the std cams. 290-300deg or such would give a bit more to go with. Then you ofcourse need more CR. What is the piston head height compared to block deck? You should run with 0,8mm gap between piston head and cylinderhead.

My old rallycar 2.0TC had 320deg cams and they were perfectly capable on street. It was a bit harsh under 2000rpm, but right after it it pulled smoothly.

Marko

The 1.6 cams are 238deg with 9.4 lift and and the 2lt ones are 250deg with 9.9 lift.

I have calculated the compression ratio to be around 9.8

9.8-1 with how long distance between piston and cylinderhead deck?

Ι am not sure about the distance. I'll check my calculations and get back to you.
In the mean time I feel like a convict that has to do hard labour.

Since half of the engine is missing I thought that it would be a good idea to paint the engine compartment.
I would never imagine that I would have to remove tons of the insulation the previous owner had splashed everywhere.

The distance is very important to know, and you must take it to your calculations. 1mm of distance makes over 5 millilitres. So if you should have 0,8 and your having 1,8mm it makes a huge difference. 0,8mm mm distance mean if you have 1.2mm gasket, piston should come 0.4mm over the block deck. Usually in std engines piston is UNDER the block deck = your loosin CR and your not having proper squish. Some experts say if your having the distance between 1.0-2.0 mm it will make engine knock easier, over 2.0mm it wont do it, and if its correct 0,8mm its ok again. But ofcourse, you need to make the CR fit to your cams, and your having pretty mild cams. Propably forexample 10.5-1 may be too high CR with those cams. Cannot tell for sure though.

I found out that the pistons I installed are not the biggest dome available but one size smaller so I will compensate for the lost compression ratio by using a custom made very thin metal gasked.
The estimated CR with the thin gasket will be btw 9.8 to 10.
The Regata 100s head is ready to be placed together with the adjustable cam gears and the twin 40 IDF carbs and I reached to the point where I will have to choose cam setup.
I will send a pair of cams I have for re-profiling so I will be able to set them up as I choose.

Googling on the internet I stepped on the catcams page where they have various setups for all kinds of use so I was thinking something like the 1900314 or 1900316 since the car is used for historic rally events.

http://www.catcams.co.uk/acatalog/Fiat_Argenta__Croma__Regata__Ritmo_90_100_105TC__Tempra__Tipo__1600_-_2000cc.html

Opinions?

Following my previous post, I found some comments from Guy Croft regarding grinded camshafts which are quite disappointing:

"
1. Lousy torque - even compared with standard cams
2. Fuel standoff at the carb (the more radical the cams the worse it gets)
3. Broken valve springs
4. Valves and seats hammered to bits

The best place for 8V TC regrinds is in the scrap bin. "

I would like to know if anybody here has personal experience from regrinded camshafts.
My camshaft options are limited and regrinding a pair of existing ones was the more viable soloution so any comment will help.

Thank you!

You find a good cam grinder who knows his stuff & tell him all that you are using (carbs, head, cr, exhaust, bore & stroke, valvesize etc.) & tell him what you want it to do. ie, Pull low down to midrange or scream its lips off & he will know what to do.
The bad reports on re ground cams have something to do with boy racers who slap some found cams in & expect to go like Stirling Moss. Every thing else is miss matched & badly timed but that does not matter to them, the cams are still shit.
O.

Finally I decided to take the camshafts to one of the two camshaft repair and upgrade shops in my area.
(My budget does not allow me to get new ones anyway)
I was quite satisfied from their attitude.
They took the time to answer all my questions and explain the process.
According to my engine specs they suggested 280 degrees duration for both intake and exhaust and 10.4 valve lift. (I think it is Colombo & Bariani profile)
Depending on the material that will be removed, the clearance will be between 0.4mm and 0.5mm
They also explained how they should be installed and the way they should be timed.
They also provided me details on how to setup the twin IDF  carbs I have for optimum performance.
As for the camshaft carriers, they told me that there was minimum material removal from the camshafts so if I use paper gaskets for the carriers, which are thinner, it will compensate the difference.

Can you tell me the cost?