8BA & 8RT engines in LP Bren Gun Carriers

[cletrac (RIP)]

For the "best" forties flattie with all stock parts start with a 46 to 48 Canadian truck engine. They had higher compression and a better camshaft for operating at our higher altitude. Then get a 49 or up 255 Merc engine and put the crank and pistons in the truck engine. You need to change to the 239 crank gear so it'll work with the 48 camshaft since the gears are cut the opposite way. Bolt all the older accessories on and you'll have a 140 hp flattie that looks and sounds original. Oh, and Ford didn't use a 12 volt system until 1956 so flatties wouldn't have got them.

[Richard Farrant]

Originally Posted by cletrac

. Oh, and Ford didn't use a 12 volt system until 1956 so flatties wouldn't have got them.

Except the wartime British Ford WOT series of military trucks, the full 12 volts on their flatheads !

[RichardT10829]

I thought the speed was limited by the gearing not the engine ? if you want to go faster put a taller final drive in the gearbox... or a taller crown wheel in the diff...simple...your gauge will no longer be accurate but hey ho......... remember folks the speed limit in the UK for carriers is now 20mph.... would hate to stop one in a hurry at 40...it just wont happen. personally if i was going to build a modded unit for a carrier i would aim for something that has plenty of bottom end grunt and plenty of torque for static neutral turns etc..... thats just me though

[Darrin Wright]

Thank you all for the wealth of information.
It has shown me that I still have a lot to learn.
It is a bit hard to find info on wartime vehicles and engines, I had a thought that the V8 in the carriers was 100hp but could not find a reference to/for it.

In hindsight I should have mentioned why I was looking at the later engines. I thought a little more hp would really help the carrier, I also wanted something that was more maintainable with the distributor easily got to for timing and adjustments.

I think my way forward is to get a 100hp wartime engine (whick my Dad has several) and rebuild it with some internal improvements from Flatattack racing (adjustable cam followers/lifters, modern water pumps, thermostats) and also an electronic distributor (Pertronix electronic ignition is one of many out there). Also an upgrade to a 12 volt system for starting and lighting would assist.

Thanks

[shaun]

I fully agree with Richie, I dont see what the need for speed is with carriers, power and torque to pull you through the mud and up hills yes !!! but carriers are not good at speed things soon get out of control, as my old father says "any fool can drive a big car fast in a straight line" . may as well chrome the heads at the same time. ive probably said to much

[RichardT10829]

if you want adjustable followers i think you need to strip the block back to bare bones as the block needs a hole drilled where the followers sit (or so i have read) if you want cheap and easy oomph then i would suggest the following:-

1) port and polish the head and block around the valves (just slight relief not full flow or it gets pricey... you can do this yourself with a die grinder and stone mandrels)

2) change out the cast exhaust manifolds for stainless ones (with better flow) OR port the cast ones out with a die grinder to match the exhaust ports on the block

3) centre main strap (stops blowing out the centre main when you over rev)

4) change the carb.


should point out that none of the above should even be attempted until you know the port velocity limits etc for the unit ! otherwise you take too much out and jigger the engine.

when you get into the realms of adjustable followers and cams it gets pricey you then need to consider high flow oil pumps etc etc... then its a case of why stop here i might aswell lighten cross drill and balance the crank and rods, and pop a lightened flywheel on whilst i am there.... KACHIIIIING !

if you want more CR then simply facing the head and deck will achieve this.. now remember when the CR goes up the quality of fuel or octane should go up too otherwise you blow holes in pistons.


from my own meager experiences in a carrier i have driven 60hp and 85hp units.... even the lowly 60hp unit was more than enough ! and the 85hp unit was very good more than enough to do what you need. so if you get a 24 stud 99a (100hp) you will have more than required...


i am afraid I have the "BHP" T shirt i spent just sickening money getting a 1300cc mini engine to exceed 200 BHP.... i got there in the end but my was it costly



and finally whilst i ramble on... you need to consider the tollerences of the running gear.. will it take greater BHP and torque... and if so how much ? i have seen diffs stripped clean of teeth and they never go quietly something always gets taken out at the same time...

[cletrac (RIP)]

That 255 Merc with the longer stroke gives lots of bottom end torque where you need it but the engine won't rev any higher than any other flattie. You don't want much more speed out of a carrier anyway. Think about how long those tracks would last at 50 mph!

[Mike Cecil]

Darrin,

I built up a 99A 239ci engine with (1) late pattern crank with two oil holes per journal, and (2) 8BA rods with fixed shell bearings and 4 ring pistons. Had it balanced. Everything else was standard. Worked fine: it's still in my (former) Blitz 15cwt. From the outside it looks the same as standard.

Mike C