Designing an engine out of a gearbox? Opinions wanted!

[Jon]

I have a habit of doing things in the opposite direction. That's why I have a fully built gearbox and no engine spec to follow.
Maybe some of you more experienced builders could tell me something about what I should aim for engine wise to fit it all.

The car is a full weight 64, I'm 100 kgs, and the gearbox is a 3.88 R/P 4.11, 2.46, 1,65, 1.26. I have 26x6" slicks for it if I need it. It will be used around town and on the strip occasionally. My engine, a 78.4x94 are being redesigned this spring. The crank is a full race Demello with 6 lbs flywheel. I have some new 48x40 CE CNC heads for it, they have received some quality porting in the combustion chamber and a three radius seat job by JPM. CFM should be up to 225-230 now. The 48 IDAs will probably be a bit to restrictive for this engine, but what do I know. I will be running on pump gas, and a CR of 11.3  is possible. I have 5.4 rods now thinking about using longer to reduce the friction on the JE pistons.
I'm not to picky about drivability, for instance I loved to drive this engine around town with an FK89.

I would like to see the car into the mid to low twelve's, and I don't mind redoing the engine every winter.

Any hints on cams or other changes I should make? Were would I need the torque the most with this gearbox?   
 
Thanks!

[BeetleBug]

Dear friend,

Car weight = same
Driver weight = same
gear ratios = same
Tires = MH Dot 205/70

Im doing mid 12`s and I`m using a FK89 in my engine. You will have more power than me and I believe you will go a lot faster. I think my gear ratios suits my car and my use perfectly. Yes, I have experienced problems bogging when the grip is good but then again, maybe I should have launched with higher rpms than 6500 - 7000. My best ever 60ft is 1,66 - not nearly fast enough for a good time.

Keep on with the good work, can`t wait to see and hear your car run!

Best rgs
BeetleBug

[alex d]

me thinks you can run 11s with that engine...what about an FK46?

[Jon]

I hope the engine at least have some potential,  but the relationship between the engine/torque/gearbox is a mystery to me.
To have a quick car you need a engine that gets thru the revs quickly I have heard, but where do you place the torque peak to obtain this?

I guess its almost impossible to do this process the "wrong" way...

[Jon]

By doing some calculations I have came to that the runners lenght, the size of the port, and the capasity of the engine will give a torque peak at 6300rpm.
Maybe not the perfect combo for haulig boats with, but I guess it will do on the street to?

[H67bug]

What was wrong with the fk89 and that spec?

[Petter Carlberg]

I would go for a Fk-89. Easy!

[Jon]

The calculator keeps telling me that my IDA will be to small... and I really don`t want to drill then out. But there are tricks to get the CFM up, like profiling the shafts and such. But it would be a good starting-point to know what a stock italian IDA flows at 25" water column.
Does anyone sit on this data, or could it be on the net somewhere?

Im leaning towards the FK89 as it is "en PERFEKT gat kam" (a perfect street cam) according to swedish street-racer Mats Herrlander.

[Roman]

Keep the FK-89. It's like driving a stocker until you get some RPM on it. That combo should be good for a 11 second ride!
I calculate with 1100 cfm for unmodified 48 IDA:s in desktop dyno. I think you will have max power at approx 7500 rpm.
Take it to at least 8000 rpm when you race, maybe even 8500.

[SOB/RFH]

Go for a FK 46 or a 86C for more drivabillity, they will fit the gear ratio good tooand your car is heavy so it need torque to move...............nothing beats using a car!!!

[Jon]

All I can say is WOW, just WOW, I have been using 600 CFM on the IDA in Engine Analyzer, and in there the elevens seemed remote.  It looks better now, even with my routine a twelve should be possible 
SOB you are right, the car is heavy and Im no light weight either, but I also would like to go with safe old school cam grinds, to help my springs a little, with 48 mm valves they already have their work cut out for them. As you say, nothing beats using a car!!!