Race Engine Forum UK

Hello Guy,

Firstly, thanks for all of the fantastic information you have provided on your forum. I love your no nonsense approach.

In Australia, the last of the Fiat twin cams was in the Regata. The Regata 100s had 43.5mm Inlet valves as apposed to the 41.5 I have in my 1756, 124 CC. The valve guides are also 1mm smaller in the Regata head. From this information I would assume (I assume a lot but check more) that the Regata head is in fact a better option to rebuild for my 1756 engine. So my engine combination would be.

1756 124 cc bottom end (Balanced)
Std 9.8:1 Pistons. (will the Regata head alter the compression ratio much?)
Regata 100s Head (with a flow job)
124 BC waffle manifold with 40 IDFs with 34 mm chokes
Cams at this stage would be Std 124 CC inlet and 124 BC exhaust (so I can run the distributor off it).

I hate this question, but I¢ž¢m going to ask anyway. What sort of power and torque do you think this combo …œshould‚ have?

So I suppose the question is. Does this combination work well?
I ultimately will upgrade the cams to finish off the whole thing, but my budget just won¢ž¢t go that far at the moment. I was trying to do all this with a 1995 motor but that one slipped through my fingers.

The head seems like a good idea and any additional information you can give me would be great.

Keep up the good work
Kindest Regards
Gill

Hullo Gill, glad you like the site.

The Regata 100s had 43.5mm Inlet valves as apposed to the 41.5 I have in my 1756, 124 CC. The valve guides are also 1mm smaller in the Regata head. From this information I would assume (I assume a lot but check more) that the Regata head is in fact a better option to rebuild for my 1756 engine.

Yes, good setup that, the 43.5mm inlet valve gives a huge improvement in flow, with a commensurate increase in torque, see flow results for 130TC head:

http://guy-croft.com/viewtopic.php?t=553

1756 124 cc bottom end (Balanced)
Std 9.8:1 Pistons. Regata 100s Head (with a flow job)
124 BC waffle manifold with 40 IDFs with 34 mm chokes
Cams at this stage would be Std 124 CC inlet and 124 BC exhaust (so I can run the distributor off it).
Will the Regata head alter the compression ratio much?

I don¢ž¢t think so, not significantly in performance terms. Remember the 1800 head could be early or late (49/53cc or so). You should burette the new head after valve seat prep and see what you have there. I¢ž¢d be happy with anything over 9.5/1.


I hate this question, but I¢ž¢m going to ask anyway. What sort of power and torque do you think this combo …œshould‚ have?

Well, compare with the 124CSA road version which was basically a 9.8/1 1800 with twin 44 IDF on waffle manifold and 42/36 valves and a decent exhaust layout. That engine was rated at 128bhp at 6200rpm, with 118lbf ft at 5000rpm. I¢ž¢d add on 18bhp from porting and the bigger valves, may be more, deduct 8 bhp for smaller carbs = about 138bhp. As for torque, I guess about the same as the 124CSA, 118lbf ft. You might find peak power and torque a bit lower down with the smaller carbs, say 6000/4800 respectively.

So I suppose the question is. Does this combination work well?

Sure, you've put together a nice spec, it will give a very strong & driveable torque characteristic, making the car faster than many others with more peak bhp.

GC