Tune to match diff or match diff to engine??

[Piero]

Hi,
what would be the better way to do things?
1: tune your engine, Then match it to a sutible diff.
or match the state of tune to suit your diff.
I am trying to work out what level of tune I want.
although I have the skill and competence to do the work, I lack the experiance and confedence.
I have a Fiat 2l twin cam engine, I am putting it in a triumph spitfire.
I want, (as most poeple do), as much HP and torque as possible from the engine.
a lot of other triumph lads, all use the triumph 2.5 liter engine in there cars and claim about 180bhp upwards.
I dont want to do all the moding to fit my twin cam only to find one day, in a track day event of hill clim etc, that my efforts aint up to the rest.
One issue is what diff to use in my car.
I am useing the Fiat 131 5 speed gear box, and I have a choice of diffs from differant spitfires.
the Fiat diff was about 4.11, my spit with the original engine also used a 4.11 diff.
I will be running 185 60 13 tyres, but as yet still dont know what RPM my engine will do.
I want to get a diff and tune my engine to match one and other.
hopfully chossing a diff might help me chosse a cam.
does that make sence??
is it the best way to do things?
any advice would be a real help.
Ps forgive my spelling, but I was born Dyslexic.

[petert]

If it helps any, it's better to have a smaller cam and shorter diff, than bigger cam and longer diff. You'll never regret having the lower diff, but you will regret a cam that's too big.

[dafnos]

i thing the easy way is to find out what you realy want from the engine hp. and torq do the mods with order and good calculations and then when you have the resaults you will be free to try the dif. conversions and find out what it's better for you or what it satisfies you.
and i thing it's more complicate to tune an engine to fit a diff. from tune an engine and then play whith the diff.


regrds
dafnos.

[Piero]

Hi,
I will be leaving the bore and stroke stock.
I will be using a 2l lump with 130 big valve head, ported ports and seats, stronger pistons, balanced crank, flywheel and clutch.
the flywheel will be Fiat, and light'nd.

Question: Not sure what cams to use :roll: !!!
as I am using a cam mounted ex side distributor, I am limited a bit to what make of cam,
I have spoken to Guy about this (cam type). although it was quite some time ago and I have forgoten his advise.
think it was (depends the type of engine you want)
But as I have never built a twin cam/ nor driven one, I cannot say
also a 2l tc in my lighter and lower down spitfire will be differant again to what others have had.
all I can say is if I build as much power into the engine, WITHOUT the loss of reliability, and at a resonable cost, then I will be happy.
I dont have to use it all if its to much.