Race Engine Forum UK

Hi GC ,
and all members of this great forum.

I have been building my Fiat 131 g4 replica for about 2 years, during this i have tried a lot of engines (other than Fiat) that has more HP than Fiat motors such as BMW M3 4cyl. & opel 16v SFI , they were all ported heads & full rebuild and both fitted with DCOE 40 webbers and headers.

but you know what , they have no torque to get the 131 get fast enough .

i fitted it with a BMW rear suspension with limited slip ratio 41/10.

but NOW :

engine - Fiat 2000cc TC Volumex :
- pistons HC 84mm (Abarth high dome) - not forged. ( i dont know the CR)
- new camshafts (original 2000cc and not Vx).
- Vx supercharger with smaller pully.
- no headers ( i cannot find anywhere and i dont want to customize).
- original Vx webber 34 ADF 150 carb.
- Head ported.
- Marelli ignition with vacume advance.
- bigger radiator from BMW 320i 1995 with electric fan.
- perfect circle rings
- performance bearings FD.
- wide oil pan.
- new water and oil pumps.
- performance head gasket astador.
- all new gaskets and seals.
- good quality disk & clutch
- new gear box 5 speed Fiat 131.

after all that ,the problem is :
i cand get acceleration performace out of this superb engine , it is actually better that the old both engines but still i cannot get more than i think HP 140 only ( no dino just guess ).

after my investigation i found that may be the problem is one of those :

1- not enouph gas (pump is normal interrupter - not performance) , but i switched the pump with high prossure with regulator ( only 1 bar) but the carb wont take it - overflow problem).

2- i tried to fit a DCOE 40 webber and i did actually (i designed an adaptor my self ), but the engine get dead when i open the throttle for acceleration , and i tried the previous setuation with the HP pump with same problem ( overflow).

i am tired and angry about these results after all that work .....

please anybody have an advise about this setuation ...

my best regards to you all

nassim bakir

Easy to answer.

Supercharged engine: Carb too big, well, chokes really but you can't change them.
Blank off the vacuum advance. Fit the 40 sidedraft with 32mm mm chokes, 150 main jets, F16 emulsion tube, 175 air corrector, 55 pump jet, 60F9 idle jet, 225 needle valve. Use a Facet Silver Top 4-4.5psi elec fuel pump in the boot of the car pushing thru a simple fuel filter, no regulator, 4-1 ex better but if you can't get one made on the car with 36" 1.5" bore primary pipes keep the old one and use a straight thru 1.75" bore pipe to the back of the car and 2 big-bore straight-thru oval AX891 silencers from George Polley see:

http://www.polleysport.com/polley/index.asp

That should make you (and engine) feel much happier. That spec (from me anyway) will give 180bhp + at the wheels.
With those pistons it will detonate on pump fuel, get some octane additive in there.

GC

Hi Guy,

one thing i didnt mention is that i changed the cam pulleys (solid with one hole) with lighter weight (for Fiat or Lancia tc from a part store) , it seems that they have different timing that cause engine weeknes as i read your article about that later.
so i fitted back the originals , but the surprise was that the engine is now worse than it was before , as it is running on 3 pistons ( the ignition timing is on number 4 )...WHAT IS THE PROBLEM WITH THAT ENGINE ????????
i checked the timing twice ( crank , piston on number 1 , distributer on number 1, and pulleys on their timing hole )

please HELP...

Unless you have a blown head gasket (which, looking at your HC setup running-badly would not surprise me) or a bent/burned out valve etc my advice above will work for you as it has worked for hundreds of owners of Vx powered units who sought my guidance on setup.

Stop changing things around - READ IT AND DO IT!

GC

thanks Guy,

i'm not blaming anybody here, because thats what i built with my hands, all i'm asking for is your generous support as we are million of milles away from each other , and you are the master here.

i will do complete engine strip down to see what is the problem once the weather becomes good here , then i may change the pistons with LC forget ones , as it seems all that because of HC pistons.

i will post what i found later.thanks again

Hi Guy ,

I promised to post pictures when I strip down the engine , well there is no detonation problem or any evidence of that. The gasket is as good as new, valves are good , pistons and ring are all good like the engine never ran.

Oil pressure was low because of camshaft housing and oil pump drive shaft too much clearance, so the bearings began to wear.

Now, I have changed the whole engine .

I have a ready standard 138AR2000 from 130TC abarth, new bearings, new rings(Total Seal), new oil pump with increased pressure, std Cams (will change later to street race), 43.5 IN & 36 EX Valves on Volumex Head (55cc c.chamber), Volumex supercharger with injectors to fit, and a Megasquirt II ECU to manage.

I'm seeking your advice now : what set up shall I use to have from 180 to 200 HP on wheels?

(I have included three photos of different pistons - or shall you recomend another one? Please advice as I'm comfused here ...
,,,,

Nassim, hi

I wish I could tell you more & quickly! But with the breadth of queries I get I would never get any work done. You need to learn how to burette (cc) the head and some other things and you also need to get the CR down to 8/1 or 7.5/1. I'm just not going to give advice on this project running any higher! You have made some key decisions regarding the engine build in error already, GC Q&A is for competition engines where folk are expected to copy GC 'best practice' so if we're to proceed together, take note!

The BEST initial advice I can give at this time is print off and read about CR':
http://guy-croft.com/viewtopic.php?f=2&t=164
and:
http://guy-croft.com/viewtopic.php?f=3&t=129

You can't just fit new rings to old pistons without prepping them and you can't mix and match pistons between bores/engines, read:
http://guy-croft.com/viewtopic.php?f=3&t=117
and:
http://guy-croft.com/viewtopic.php?t=254

You also need to know that you MUST NOT use pistons like those shown in supercharged applications, you need either bespoke forged (which only I HAVE in stock and which are on special offer see:
http://guy-croft.com/viewtopic.php?f=15&t=1929
or actual Vx OE (because they were never available anywhere else) with thicker crown and wider top and 2nd ring lands and I've not seen a new oversize set (or any other size) in 15 years.

As I said, I am not going to give advice on high CR with supercharged or turbocharged units now or ever because I don't agree with the practice. Insofar as the certainty of how the engine will behave under that regime, you might as well add a tablespoon of nitroglycerine to the gasoline.

GC

Hi Guy,

thank you for your time ...

I have decided to go LC piston but higher than original Vx, I will use standard 84mm flat pistons used in 131 & 132 . they give around 9:1 using original 2L 2000cc head with c.chamber 50cc ....


edited by GC

Sorry, I'm taking this one. Try posting in General Discussions, road cars.

G