Miltz

Hi all,

I'm currently working on a MK1 Escort 4x4 conversion and am currently looking into engines. One I'm considering is the Cosworth FB (BOA/BOB) series V6 to do something different.

The main issue is making it work with the 4x4 driveline, more specifically fitting the front diff through the sump. Is it possible to use the sump from the 2.9 L Colongne V6 in the Sierra XR4x4?

The next issue is which engine is best, BOA or BOB with the main consideration being strength in a turbo application? Is there any major structural differences between the 2 engines that would make one a better choice than the other?

I'm aware of the main differences between the engines and the only advantage I can see in the BOA over the BOB is that the BOA can be fitted with a Jenvey throttle body kit without having to use a custom manifold which I am prepared to fabricate myself.

Any advice would be much appreciated and for those that are interested the link to my build thread is below.

https://passionford.com/forum/restor...onversion.html

Marc sierra

iTrader: (1)

You can use the 2.9 sump from the XR4x4, but you have to fit the drain hoses from the cylinder heads to the 4x4 sump.

The BOB engine is a stronger casting and can take slightly more revs, but the BOA engine is easier to install since it runs on the EEC IV instead of the EEC V of the BOB. The EEC V uses PATS (anti-theft system) and needs the automatic gearbox to be present. Although on Fordpower a few people are working on trying to remap the standard EEC V to ditch the autobox and PATS. The BOB engine also has slightly more power because of different cams (which can be fitted to the BOA too) and a different inlet manifold that has a variable lenght.

If you're going for a turbo I'd use the BOB because it's stronger. The ECU doesn't really matter anymore then since you need a remap anyway.

Miltz

Hi Marc,

Thanks for all that info, especially regarding the block etc, it looks like the BOB will be the way to go for me, especially as I don't intend on using the factory ECU.

Just one question regarding the intake that you might be able to help me with. I'm aware that the BOA and BOB used different inlet manifold mounts but is it possible to use the readily available intakes for the BOA (e.g. Jenvey) with the BOB by using an adaptor plate or similar or will I need a custom lower section to mount the throttle bodies? This is something I can sort out myself but if it's been done before and there's adaptors available it will save me both time and money I'd otherwise use 3D modelling a new lower section and having a 1 off item cast for me. That said I've actually already started the 3D modelling, with information from Jenvey I've got the top half of the lower manifold modelled and only need the dimensions for the head mounts and ports to blend in the lower half, this may still be the best option to minimise any under bonnet clearance issues I can imagine I'll come across.

In regards to the 4x4 conversion, what you've said reinforces some infomation I found a day or 2 ago on another site, link below.

http://www.maddoldbugger.supanet.com

Marc sierra

iTrader: (1)

I'm not really sure on the intake. I think it would be best to ask here:

http://www.fordpower.org.uk/forum2/index.php

There's loads of info on the 2.9 24v engines on this forum, including throttle body, supercharger and turbo conversions.

dojj

iTrader: (3)

Don't forget you will need the harder and harder to find 2.9 flywheel to go with it so its almost a no brained to require a 2.9 xr4x4 as a donor vehicle for the mechanicals as you will need the box and props and all the running gear and the loom in order to make up one for the boa

Unless I've got the wrong end of the stick and you are thinking of mounting he engine sideways

In which case the mondeo v6 is a much better option but you will probably have to donate a jag x type for the parts cause

Miltz

Thanks for that Marc, I'll have a look through their site and see what I can find.

Miltz

Hi Dojj,

No plans on mounting the engine sideways, I can't imagine trying to get an X-Type floor under an Escort, I'll leave that for someone else!

I've actually come across a complete XR4x4 a bit closer to home, just trying to sort out the import paperwork at the moment and with any luck should have it on its way within 3 weeks, well that's how long the government says it will take to say yay or nay to its import anyway.....

Miltz

Hi all,

Was just wondering if anyone knew the size of the exhaust ports at the flange for the BOB engine, or better still the the complete dimensions for the exhaust flange?

Cossiemainful

iTrader: (1)

This crossed my mind....

BOA: strong chain drive (and strong loom)
BOB: weak chain drive til '98 (make sure this weak point is already cured on pre '98 engines, then all is fine, besides the weak loom)

but all in all both engines are technically strong and reliable.

Miltz

Hi all,

Could anyone tell me if the 2.8l XR4x4 sump is the same as the later 2.9l sump. Looks like I'm going to have a fair bit of trouble getting the 1991 2.9l XR4x4 into the country and may have to make do with a pre 1989 car as the donor due ti import restrictions on cars less than 25 years old.


Cheers.

Miltz

Also, does anyone out there know the overall length of the BOA/BOB versus a YB series 4 cylinder?


Cheers.

Miltz

Hi all,

It's been a while but I'm starting to get back into this after leaving the company I was with and setting up my own among other things.

I'm still leaning towards using a twin turbo FB series engine over a YB series so have a few questions coming up, if anyone can help it would be much appreciated!


Cheers,

Miltz

Miltz

I ended up getting the 1991 2.9 XR4x4 after jumping through a few hoops so that sorts out the flywheel and driveline issues, will also take the sump from the OHV 2.9 and see if I can't sell that engine with the RWD sump to be fitted to a Capri or similar.

Miltz

What was the difference between a '98 BOB cam drive and that found on earlier engines? I believe '98 was their final year of production so finding an '98 engine might be difficult. Factory loom isn't an issue for me as I'll be running motorsport ECU and custom loom.

Miltz

And does anyone know if the inlet ports on the BOB are the same size and in the same location as the BOA? Looking at pictures they appear the same with the only difference being the BOA using a single fixing bolt per inlet while the BOB has 2 fixing bolts per inlet on the the head.

dojj

iTrader: (3)

don't forget you'll need to use the 4x4 oil pick up pipe as it's a different shape to the 2wd version

dojj

iTrader: (3)

got both sets of heads in the garage but won't be going there till later this week

can measure up if you like

robrs2

Inlet is totaly different si and BOB uses side feed injectors the BOA uses top feed.