Race Engine Forum UK

Hi Guy
Thank you for the 1756 vs 1995 advice, I¢ž¢m going to go for the 1995 it seems like the best solution by far. So now I'm after a bit more guidence

1: The 2.0 is from an auto so I¢ž¢ll have to use the 1.8¢ž¢s clutch and flywheel, therefore I¢ž¢ll need to drill out the flywheels bolts holes to fit the 2.0¢ž¢s bolts. Is this acceptable?

2: I¢ž¢ll be using the standard 124 sport IDFs re-jetted to suit the 2.0 as per your suggested settings on this forum. Cool so far?

3: Years ago I attempted to port and polish a 1756 124 head & manifold with a standard single carb, now I don¢ž¢t know if I actually achieved any horsepower gain, but I Think! I did. All I did was match the head and manifold ports, smoothed off around the valve guides and CCed the combustion chambers and polished the ports and combustion chamber up like a mirror (A very shiny mirror) I am a fitter and machinist by trade but have no flow bench to test any of my mods I know what I did was very accurate measurement wise, but I don¢ž¢t know if it was the right thing to do. If I was to do the same to this motor would I be wasting my time or would I gain a little bit of HP? What do you think?

4: How much will balancing the bottom end do for me? Are the Fiat bottom ends not too bad to start with or do they need to be done as a rule?

5: This should be an easy one. Which pulley set is best to use, the plastic ones or the steel ones?

Lastly the car is for street use and won¢ž¢t be thrashed every time I get in it (If I can resist) So because I¢ž¢m getting too old to crawl under a car every weekend, the car needs to be reliable.

Thanks Guy for all of your help
Kindest Regards
Gill

Thank you for the 1756 vs 1995 advice, I¢ž¢m going to go for the 1995 it seems like the best solution by far. So now I'm after a bit more guidance

Q - The 2.0 is from an auto so I¢ž¢ll have to use the 1.8¢ž¢s clutch and flywheel, therefore I¢ž¢ll need to drill out the flywheels bolts holes to fit the 2.0¢ž¢s bolts. Is this acceptable?

A - Yes you can drill out the flywheel, I assume it is a 124 1800 type originally fitted with 10mm diameter bolts (the 132 1800 has same bolts as 2 liter, 12mm). The bolt holes are 'clearance' (ie: have clearance) on the bolts, the bearing in the end of the crank is used to centre the fw, you must of course use a bearing to support the input shaft - with manual transmission and RWD.

Q - I¢ž¢ll be using the standard 124 Sport Weber 40 IDF re-jetted to suit the 2.0 as per your suggested settings on this forum. Cool so far?

A ¢‚¬Å“ OK, remember my guidelines on jetting need to be proven out by road or dyno testing, but only alter mains and air correctors.

Q - Years ago I attempted to port and polish a 1756 124 head & manifold with a standard single carb, now I don¢ž¢t know if I actually achieved any horsepower gain, but I think! I did. All I did was match the head and manifold ports, smoothed off around the valve guides and cc¢ž¢d the combustion chambers and polished the ports and combustion chamber up like a mirror (A very shiny mirror) I am a fitter and machinist by trade but have no flow bench to test any of my mods I know what I did was very accurate measurement wise, but I don¢ž¢t know if it was the right thing to do. If I was to do the same to this motor would I be wasting my time or would I gain a little bit of HP? What do you think?

A ¢‚¬Å“ You can¢ž¢t go far wrong with the TC head and doing what you describe sounds OK to me, main thing is to smooth out the casting and radius the short-side of the port below the valve throat. As for polishing the ports I have not determined any flow gain from going any finer than 80 grit in the inlet ports, there is an argument for not polishing per-se, for reasons I don¢ž¢t want to go into here. It is worth opening out the ex port both sides a millimetre or so adjacent to the guide boss region, quite restrictive in there. Even modest work like that i've described in the inlet port will yield upwards of 7% increase in bare port flow, to get the best out of the port then you need a nice valve and seat job, 2mm contact face (inlet and ex), 70 degree throat, put a 30 deg back grind on the inlet valves.
You can of course get more flow by going bigger on the ports - say parallel 34mm or 35mm thru, that's fine on a 2 liter, but not esential, and likewise the inlet manifold can be enlarged too, but in your case I'd run it as-is.

Q - How much will balancing the bottom end do for me? Are the Fiat bottom ends not too bad to start with or do they need to be done as a rule?

A ¢‚¬Å“ You should find that the rods if a good original set are balanced perfectly well, both overall and end over end. If the overall weights are the same within a few grams I¢ž¢d say they¢ž¢re going to be fine. Check that they are a matched set, with similar numbering to each other. The crank and new fw need to be balanced though.

Q - This should be an easy one. Which pulley set is best to use, the plastic ones or the steel ones?

A - Makes no difference functionally provided the pulley setup matches my advice on this site, the plastic ones are a lot stronger than they look. For a 1‚ belt you need flangeless steel cam pulleys and a read flanged aux driveshaft one, but modify the fuel pump lobe on the shaft first.

I'd like to write hints on achieivng reliability on the engine build but that will to wait for now.

GC