1756-100s Block Head Cam Combination

[mack124]

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

[Guy Croft]

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