Ford Zetec race engine

[Bob Gray]

I'm looking into building a 2.0 Zetec for circuit racing and wonder if anyone has experience of both the SE and ST170 (badged Duratec), which gives more power in naturally aspirated form on carbs/itbs and which is a better base to start with? We're looking for 230-250bhp btw.
T.I.A

[Notso Swift]

The ST170 has larger inlet valves as standard, always a good start, I am working on memory but 33mm vs 32mm

Do you have to use a Zetec, Duratec is a better base with 35mm inlets, though I think Zetec has a steel crank (someone can confim) so will do the revs on the standard bottom longer

That power is a pretty simple formula:
Proper ECU
ITB's
Cams
around 11:1
decent extractors
Shouldn't need any head work for 230, but a little for 250

[BertMk2]

Originally Posted by Notso Swift

Do you have to use a Zetec, Duratec is a better base with 35mm inlets,

If you have the choice then a Duratec is a better option. We ran a 2 litre Zetec in our old rally car but when we built the new one it was a straight choice between Duratec and XE - it worked out easier and cheaper to get power out of either of them than getting the Zetec to 230bhp.

[knighty]

Originally Posted by Bob Gray

I'm looking into building a 2.0 Zetec for circuit racing and wonder if anyone has experience of both the SE and ST170 (badged Duratec), which gives more power in naturally aspirated form on carbs/itbs and which is a better base to start with? We're looking for 230-250bhp btw.
T.I.A

Bob, I say this having done alot of race work on both engines about 10 years ago, formerly at Weber-Alpha.......then at Mountune as a design engineer.......really, just dont waste your time and money with the old iron block zetec engine, the valves are too small for high power NA engines, its also a very heavy engine, and it needs alot of work for 250bhp NA, its OK for a turbo engine, but not for a normally aspirated item pushing 250bhp........get yourself a 2.0 all aluminium Duratec engine, which are now common as muck in any scrap yard, with carbs and cams you will be well over 200bhp immediatley........you will not see any power difference between carbs or fuel injection, the advantage in fuel injection is better emissions and drivability and the fuel wont surge in the carbs if you are considering high-G circuit racing......dont fall into all the BS of whats better, if I was doing it I would get a set of secondhand carbs plus a new ignition kit from WebCon, as there is no distributor on either engine......but be careful of your emissions requirements!!!!

When at Weber-Alpha (WebCon) we developed the new 45mm and 48mm weber carbs from Spain for the 4 valve per cylinder engines very wel, and there is no appreciable "flat spot" if your carbs have the 5 progression holes drilled in them, this basically bridges the gap (flat spot) between the idle and main fuel circuits inside the carb........older versions only have 3 holes, hnece the horrid flat spot, which got the carbs abit of a bad name........Alan Collins at WebCon can redrill with a special carb-jig if you have older carbs for a small fee!

[Bob Gray]

Whilst I appreciate the input I have to say that the point of my original question is to find which is best for power output between a 2.0 cooking model Zetec and a ST170 Zetec (which has bigger valves, solid lifters etc)with vvt deleted.

[Notso Swift]

If it has to be a Zetec then go for the biggest valves
If you start with the small one you are going to cut bigger ones any way and you will need to modify the bowl and inner radius to suit, less time spent will save a fair bit of money from a good head guy (as opposed to the average stick a flap wheel in there type.)

Using the Zetec will drop about 30 hp from the basic formula above and the head will be key