jamie956

Hello All new to the site and cosworth tuning,

I 'm now starting a cosworth powerd cortina project and need some help and advice,

I have the running gear from a 3 door cosworth all standard, I want to get the engine rebuilt before it go's into the car and am not sure what way to go.

I'm looking for around 300hp but i want to keep it with as little lag as poisable, becouse its only going to be a light car and im not to interested in hugh top speeds.

Im thinking i dont need to do much more than a standard rebuild if it needs new pistions at what point do you need to move to low compression or 4x4 pistions.

As far as turbos go i have no clue i have spoken to CR turbo's and they are recomending a stg1 hybrid or if i want to reduce the lag further fitting a roller bearing although its not cheap.

Im in the suffolk norfolk area so if anyone could recommend a builder near by would be good also.

Thanks Jamie

Chip

iTrader: (3)

CR are giving you good advice IMHO

4parajon

James @ Grace Engines is'nt a million miles away from you in Reading, built my engine and I can highly reccomend him 07779223001.

jamie956

Yer they seam very helpfull its hard to know weather the Ł400 diffrence is worth it as i have no experence of ether.

Chip

iTrader: (3)

Is there anything actually wrong with the turbo you have at the moment?

Cause TBH, standard is a good option for 300bhp anyway!

jamie956

Fair amount of play in the bearing so guessing its going to smoke like a gooden,

tabetha

A T3.48 will be ideal for 300bhp, CR needs keeping std, lowering will not be needed.
I can recommend Brian Randal, of Hepworth, near Diss/B.S.E. area 01359 251888, for all machining parts etc.
I have a T3 compressor housing machined out with a T34 inducer, and a .48 turbine housing, boost starts at 1400, and full boost by 2500, just to give you an idea.
Got the be one of the easiest engines in the world to rebuild, so might as well diy, got any piccies of the mk3 ?, I love the mk3 tina, esp 2.0 GXL in red with black vinyl roof, and cosmic alloys.
tabetha

Mark Shead

Keep comp ratio stock.

Mark

jamie956

Thanks for the info thats what im after i want somthing that comes on nice and early i also want the engine to rev freely, i had a RS turbo about 10 years ago now that Harvey Gibbs built the engine for that ust to nail 24psi by 2500 and hold it to the red line, i would hate to think what a rebuild by Harvey would cost now out of my budget im guessing.

cossie4i+

iTrader: (15)

You will need a 4x4 exhaust manifold to fit in a Cortina.

Steve

tabetha

Harvey is no magician, seen plenty of mistakes from SCS, just pf's don't have the bollocks to talk about it/them!!
If you are interested in revs perhaps the yb is not the engine for you, the rod angle is not good for a high revver, I limit mine to 7300rpm.
Best thing you can do money wise whilst the engine is apart is a lightened flywheel, so often overlooked, has many many benefits, the std 2wd one is 8.9KG, mine is now 5.8, I wouldn't advise for a road car going much lighter, but the difference per Ł spent is amazing.
tabetha

Papillon

Why not a modern turbo from the mitsu range? I believe they would "outspool" an old t3.

jamie956

Already have it in with a 2wd one just a little dent in the inner wing, although it is going to be spaced framed in the end so should be plenty of room.

axelriet

Why not increase the compression ratio? You can run 8.8:1 or even 9:1 on 98RON fuel without much trouble. Of course this requires proper mapping on a proper engine dyno by a proper specialist. Any attempt on a rolling dyno or on the road will end-up with 4 melted pistons.

Lowering the CR will push the knock limit somewhat further away but also RUIN the thermal efficiency and produce a sluggish engine with slow spool up and terrible response, which ultimately results in a slow car.

Consider that GrA engine (from 1996) were running 8.8:1 which was the maximum allowed by the regulation. Clubman WRC engine ran up to 9.6:1 and top international specs engines were above 11:1 before the water injection ban. OK, they ran on 102RON but 8.8-9.0 on 98RON is very doable and if you care about throttle response, spool up and lag, this is the way to go. Low CR is a relic from the days were ignition curves were rudimentary and difficult (if not impossible) to control precisely.

On the other hand raising the CR requires a good experienced specialist as you need to control the total chamber volume which include the piston bowl, valve pockets, gasket, head skimming etc. For 8.8 you want about 64cc total volume on std bore.

You must also pick some plugs (e.g. Denso IK31), measure the chamber volume with them, map the engine with them and stick to them forever: say your engine shows slight signs of det after hard driving on hot days, upon close examination of the plugs. Common (and wrong) belief recommends colder plugs = more ceramic = less chamber volume and 1cc difference makes your CR jump from 8.8 to 8.9 = more det... better add 5% toluene on track days.