Intake and carb upgrade

[Testament]

hi. did you measure the diameter of channels on intake manifold? what's the dia. of intake valves? on my 1.8 intake manifold is 42mm, valves 42, and carb is weber42/42dgv. revs like mad, LOTS of low rev torque. if i understood corectly, all should be the same diameter for optimal performance.

It's really alot more complex than that, optimal carb sizing  depends on if its a single carb setup or twin carbs 1 throttler per cylinder. then it depends on cams and RPM range as to what will be the optimal choke and throttle size.  Also I did not know they made a 42/42dgv? what is that off originally?

[djape1977]

whole engine, including carburetor is out of my ex Steyr Fiat 132 1800 special from 1975. bodywork rotted away too badly for repairs but i kept the engine and gave it a new life in another car

[miro-1980]

From my research it looks like the air volume ratio of inlet to exhaust should, be 1: 1,5.

This depends on the carbs, inlets, valves as well as exhaust "channels", exhaust manifols , (4-1 ; 4-2-1, etc. ) as wellas the exhaust piiong and silencers. this is very difficult to actually get it right as it really is a question of very sophistiocated science : how gas behaves in a pipe.     

I have 36 (standard) valves and 44 exhaust valves  ona 130TC head. I was told that increasing the size of the intake does not make much sense except to make sure they match the manifolds.   

[djape1977]

aren't original valves 42 inlet and 38 exaust? at least they are on my 1800. shouldn't the inlet valves always be bigger than exaust?

[miro-1980]

I stand corrected. Obvioisly the in are larger!

Just looked at the date sheet. The standard 2.0 was 36/41.8 ( so called "42's").  The largest ever produced for stock engines were so called "44's" (43,5) for 130 TC . According to Guy Croft the upper size limit is 46 (in) and 40 (out).

 

     

[djape1977]

so there's still room for improvement... 46/40...hmmmmm... would be a nice combo with my abarth cams, twin solex and 4-2-1 abarth exaust...
a question: since you seem to have a much more complete knowlege, and/or database, did all 1608ccm twincams have "dome top" pistons or flat top ones?

[miro-1980]

I am not an expert on 125/1608 but I have a picture of 1608 piston and some data I have collected. 
 
By my data there were several versions made. In US flat pistones delivered compression ratio of 8.2:1 At the same time in Europe the car had a compression between 8.8:1 (for sallons); 9.2: in 125 T and 9.8:1 on 124 coupe and 1973-1974 Coupe , Spider, Beta.

My father had a 125 with 1608 DOHC engine and it was (8.8:1).

Incidentally it is interesting how compatible all those engines are. I have found information that by comparing parts list of 124 and 125 egines the compatibility wtih same size engines of 131 (respectively) is:

124 - (1756 cc) 99%
124 - (1592 cc) 95%,
124 - (1438 cc) 89%
125   (1608 cc) 85%

And we are talking pure numbers of same parts  vs. number of different parts.

It is amazing that essantially the same engine was used in so many cars:

124, 125, Polonez, 132, Argenta, Lancia delta,etc.   

     

[djape1977]

 couple of years ago i scrapped an 1970. (or so) 125 special. red worm had taken it's toll on the car but engine was very good and so i kept it, not knowing exactly what to do with it until couple of months ago when i bought my 131 cl. its sohc 1.6 is a bit tired, oil consumption being around 300g/1000km. that's where that old 1608 comes into the story. it's destiny had been decided. it's going into 131. last week i got hold of some parts for 1608 incl new pistons and head gasket. i'll rebuild it before installing it into 131, perhaps tune it up a bit. i know that there's fiat's tc's that have? much more potential than 1608, but this one will do fine for everyday driving around town.

btw, anyone got any idea what does the B2 on the box sticker of mondial pistons mean?

[djape1977]

my father had 125p in late '70's, i always thought that it was a shame that it was never produced with a twincam in it. what about polonez tc? was there any except racecar versions of it?

[miro-1980]

But they were 125 with DOHC !

My father had a 125 with 1608 DOHC engine bought in Italy branbd new in 1968.  Great car . I remember everybody, once I popped the hood (bonnet) kept asking if this was a  V engine (funny a V4?). They were fooled by the looks of the DOHC engine.

[Robert]

You DO know there were V4 engines? Used by Ford in the 1960s in the 12M/15M models or by Saab in the 96? Actually, if I remember right these were US Ford V8s cut in half; the Americans had no need for these small engines, so they gave it to Ford Europe who in turn gave it to Saab.

[sid131]

i remember the saab with the v4 it had a rear facing seat at the back, i bought one for ?15 irish many moons ago at a charity auction never got it going though engine was seized,  didnt Ford also use the same v4 unit in some transits?

[djape1977]

you mean like this one? http://lada-klub.com/viewtopic.php?t=1971

[sid131]

erm whats that?

[Robert]

This is the mentioned Ford Taunus 12M P6 ("M" meaning "Masterpiece", "P meaning "Project"). Built 1966-70, following the 12M P4 (1962-66), the latter being the first to feature the V4 engine. wow.