Horsepower estimate after proposed mods.

[ber911]

My current motor with the following specs puts out 178 hp:
66m crank with 85mm JE 9.5:1 comression pistons.
2.4t heads with ported inlets and S cams.
Weber 40 carbs.
Twin plug.

If I change the crank for a 70.4mm one thereby increasing the
capacity and compression ratio and change the carbs out for
MFI any ideas as to how many horsepower I would gain?
Also would a 2.4S MFI pump be sufficient or would I need a
2.7 RS pump?

Robert

[slakjaw]

how much would the compression increase by? 9.5:1 is about as high as you would want to go for a street car i think, unless you have a good source for race gas.

[Tim Walsh]

Slak,
But he's got the twinplug settup. He should be able to go up an additional point of compression with that setup. According to BA your compression will be bumped up about a point.

I would also think that since you're only going from 2341cc to 2397 of dispacement you'd be better off with the 2.4S pump rather than the 2.7 pump.

As for horsepower I'd expect something slightly north of 200 since a 2341cc S engine made was 190 and you've got an extra 50cc or so plus a higher compression engine.

edit:
Is your 178 at the wheels or at the crank?

Just from straight displacement increase you'll be making right at 190 if the power/displacment ratio is still the same, but you've still got the extra point of compression to factor in and MFI is good for a few ponies when set up right.

[petevb]

Hmm, misprint in that math?

I get a 150 cc jump in displacement, from 2247 to 2397. If the piston the head clearance stays the same I get compression increasing to almost 10.1:1.
195-200 hp or so sounds about right. You're about 50cc and 1.5 points of compression up from a stock 2.4 S at 187 hp (SAE). Estimated based on either that or an increase from you current motor I get around or just below 200 hp.