Repairs and upgrades to a 1585 TC

[124CC]

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  

[124CC]

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?

[sid131]

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

[kev131]

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

[Fiat 131 Abarth#2]

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?

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

[124CC]

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.

[Fiat 131 Abarth#2]

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

[124CC]

Read them both, very useful info. Thanks!

[124CC]

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?

[131 Lover]

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

[124CC]

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!

[131 Lover]

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

[124CC]

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 ?

[vode131]

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.

[131rally]

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