Technical Intresting mk1 valve train differences

[gtirx2]

You guys may already no this but i have never noticed, the differences between the early 85-88 mk1 cylinder heads.
Thats unless they are N/A cylinder heads, but i dont think they are.

I have two cylinder heads(one that i removed from a turbo engine) both dated 1985 and they have slighty differently designed valves and valves springs in them?
These 85 cylinder heads also have fiat 2 stamped on top of the head with the valve springs,where as my 1987-88 cylinder heads have fiat 1.
The cylinder head number on the front left of the head is also a slightly different lay out.

I have not looked closely yet but on quick inspection it seems that the valve springs between the heads are slightly different heights and when compressed and fitted have different spaceing between the coils (later heads more compressed).
Also when the later 87-88 heads are all put together the top of the valve sticks up higher above the spring retainer.
Also on the 1985 heads valves they only have a single groove for the collets to lock into where as the later heads have 3 grooves for the collets to lock into.
The design of the heads of the valves are also slightly different which will also affect the flow in and out of the engine.
This got me thinking maybe this is why its mentioned on the sporting fiats club that
Quote...
The 1301cc version quickly replaced the 1299cc. On paper it generates the same max power (105bhp) in practice the 1301s are noticeably more spritely and torquey motors.
http://www.sportingfiatsclub.com/models/uno/uno.asp

Or am i completly wrong lol?

 

[SteveNZ]

There were 2 different turbo valve designs AFAIK, one had a longer stem. But all turbo valves should have the double retainers. You may have an injected NA head. or someone may have fitted different valves at one stage. All heads should have the same valve spacing too.

 

[gtirx2]

I think all the valves are the same length and the spacing in the heads are the same.
The valve head is the same size but the back of the valve head is a slightly different design.
Do n/a heads have the same size valve heads as the turbo?
They both have double valve springs but the spring lengths are different.
The spring retainers are also different, and like mentioned above so are the collets and the mounting grooves in the top of the valve for the collets.
God knows maybe they are n/a heads?

 

[gtirx2]

Ok here are some pics.
All the numbers on the front of the heads are the same except for a 1988 head that i have? (not pictured)
Also the pic of the exhaust valves is a bit crap but there is a difference in the head design of the valve,not quite sure about inlet valves maybe a very slight difference.

The 1985 head parts are always on the left the other head is a 1987.

1987

1985

Main spring

Inner spring

Inlet valves

Exhaust valves

Collets

Retainers