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Author: Subject: Duratec variants - N4JB vs. CJBA
pjay

posted on 2/10/11 at 05:34 PM Reply With Quote
Duratec variants - N4JB vs. CJBA

I'm hoping that from the superb collective wisdom here someone can explain the technical differences between the N4JB (Fiesta ST150 Duratec) and the CJBA/CJBB (Mondeo 2.0L - may also be Focus etc).

I understand that the N4JB has a different cylinder head but what technically are the differences - other than EGR valve blanked as standard, inlet manifold butterflies not fitted and blanked, different coil pack (if not COP) etc. Also what technically are the differences in the block.

Thanks
Pete

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flak monkey

posted on 2/10/11 at 06:31 PM Reply With Quote
No technical differences in head or blocks. No extra machining or anything like that that will make extra power.

The differences you list are the only things, all the bolt on stuff

If you want to make a little more power you can do a bit of blending on the short turn of the ports, bot inlet and exhaust have sharp edges. There is enough material in there to put a nice radius on. Theres some pics in my archive, duratec folder.





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pjay

posted on 2/10/11 at 06:57 PM Reply With Quote
Hi Dave - thanks you've hit the nail on the head with extra power. Had heard that the ST150 head was better flowing etc. etc. but just got a engine (thankfully cheap) and can't see any specific differences in internals of the head or the block.

Any idea why Ford made the different part number on the head etc?

I'll have a look at your archive at the flowing mods (although couldn't stop being distracted by the supercharger the last time I looked...).

I guess I'll have to look at fast road cams since I can't afford piston mods at the mo. Currently 192BHP on balanced but standard internals so I'm hoping I might get another 12-15BHP with Fast Road cams (Newmans FR cams have been recommended). Any comments would be appreciated.

Cheers
Pete

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big-vee-twin

posted on 2/10/11 at 08:05 PM Reply With Quote
As I understand it the Duratec has quite large valves which don't open too far. If you put a high lift cam into the engine you may also need to install pistons with pockets machined into the top, as they may collide with the valves.





Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016

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flak monkey

posted on 2/10/11 at 08:39 PM Reply With Quote
Yep, I cant remember the highest lift with stock pistons off the top of my head. Any aftermarket pistons will have decent reliefs for higher valve lift. Most of the more moderate cams will work with standard pistons though, but just check clearance before bolting the head down finally.

There's no difference at all in the heads in stock form, for definate. The CJBA is the engine code, so the ST150 has a different engine code (N4JB) as its got different ancilliaries.

[Edited on 2/10/11 by flak monkey]





SJ Engineering - custom engineering

http://www.saltflashracing.co.uk/

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pjay

posted on 2/10/11 at 08:57 PM Reply With Quote
Many thanks for the responses. Off to talk to the piggybank...
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OwenSP

posted on 5/5/16 at 07:28 PM Reply With Quote
Apologise for digging up an ancient thread but i've been reading some conflicting info regarding certain heads flowing better and could do with some help clearing up

For example: http://www.sbdev.co.uk/Duratec/Cylinder%20Head.htm

Am I right in thinking the heads with 'RF 3S4G' and 'RF 6S4E' stamping appeared on the st150 and later mondeo/focus models but only post 2008? None earlier? And do these heads definitely flow better?


Numbers on the side of this head say 1S76, so this is one of the earlier heads that did not flow as well:

FORD MONDEO 2.0 PETROL CJBA 145 BHP 5 SPEED MANUAL ENGINE 2000 - 2007


Thanks in advance

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