Jump to content

Has anybody done a diesel to petrol FV432 custom conversion?


Recommended Posts

Hi Folks,


I was wondering if any of you have ever taken on the job of converting a petrol FV432 over to a diesel? I am not too concerned about the factory diesel "bulldogs" and other models because of the lack parts here in the States. We've converted vehicles from petrol to diesel and petrol to propane just because I hate the residue that petrol fumes leave on clothing and skin after driving around.


I have four 432's and they are all petrol. Two of them run "pretty" good and other others are just OK and it's always something to do with fuel system. If the parts were over-the-counter I guess it wouldn't be such an issue but all the spare parts require months of paperwork for us. I have to submit an import form to our BATF office to ask permission to import the parts and that usually 6-8 weeks and then we have to have the seller in the UK file an EUC form as well as and export permit.


One pack has been pulled and the footprint looks as if a Cummins 4BT or 6BT could be used but I will do some measuring later today to confirm.




Link to comment
Share on other sites

The Bulldog (FV432 Mk.3) uses a Cummins 6BTA but also changed the separate gearbox and steering units for a combined Allison setup. If you want to keep the existing gearbox and steering unit I suspect you'll have problems with gear ratios as the B81 (and K60) are higher revving than most modern diesels.



Link to comment
Share on other sites

Hi i put a K60 pack in my MK1, had to make a prop spacer 60mm i think from memory also you only use 4 of the 5 mounting bolts and there is a bit of fab work to be done regarding pack covers inside and outside, there was a lot of messing around and it's far from standard but this thing was destined for the scrapyard, and now its alive again. If you need to know more give me a call.




Edited by threewheeler
Link to comment
Share on other sites

I think the RR B80 max rpm about 3500, the K60 about 2500 to 3000 Max and the Cummins 6BT ranges from 2800 to 3100 depending upon power setting.



Not quite true, as far as I know. The B81 was I think 3750 rpm, from my recollection of the cut out speed on rotor arm and the K60 had a max crankshaft speed of 2400 rpm, but both cranks were geared to the output flywheel which ran at a max of 3750rpm, bringing it into line with the B81 engine output speed to match the transmission when the FV432 was updated to Mk2

Link to comment
Share on other sites

I stand corrected. Did RR not up the RPM on the B81 when they did the redesign increasing the power output and swept volume over the B80. When considering an engine swap it the useable rev range that matters I think, and when the revs drop how will the replacement engine recover to cruise. Where is the green band in the rev range for each engine. How many times do you run a vehicle flat out and for how long. I remember being told by a Daf salesman that to get the best braking effort from the exhaust brake you had to run the engine up to the blue range that was over 4000 on the CF and XF range. I never had the nerve. It has been some time since I have driven anything large but I remember mostly running in the 1100 to 1500 range most of the time.

Edited by john1950
Link to comment
Share on other sites

  • 4 weeks later...

the B81 went for larger pistons and volume, bigger jets, taking power from 160 in the B80 to 240 in the B81...and yes max revs 3750, if you go over you will throw a rod, not that I have ever done that gov'nor or not...I also heard that the transfer box bearings fail at 4000 rpm but no idea how true that story is...


the output of the K60 is supposed to match the revs of the B81...

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...