8BA & 8RT engines in LP Bren Gun Carriers

[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

[Lynn Eades]

Some extra cubes give some low end gain. better breathing is for the higher end of the rpm range, and is not what you'll want. Save that one for your hot rod.
Being able to turn the thing, and get it rolling is where the problems lay.
Not much point in making it breath better (stainless manifolds, port job, cam etc.) wont help if its still restricted at the exhaust elbows.(and what else are you going to mod?)
The truck cam is probably as good as it gets, as cams go. The adjustable tappets will work with std cams, and the extra cost here is somewhat offset by the extra labour costs of the standard setup.
With an oversize set of pistons to increase the cubes, I'd say the last two posts have completely covered what is nessesary, for a great performing carrier power unit.
As with any motor job, just do it all well. (and yes Rich you do have to drill the block to use adjustable tappets, but it is also easy to make a minor adjustment later)

[cletrac (RIP)]

On some of the adjustable lifters you can get a special wrench to do the adjusting without drilling any holes. It sort of looks like a 90 degree snap ring plier that goes down from the top to hold the lifter body while you tighten the adjusting nuts.

[Philliphastings]

Hey guys,

Don't get me wrong, I can see the merits of many suggestions on this thread and I know the satisfaction of modifying and improving the performance of collectible vehicles (when I used to restore Model T and A Fords I had all the cool accessories)

But I thought the point of most Military Vehicle restorations is to preserve the vehicles as they were during the world's most devastating conflict. My hope for the Scout Carrier is that it will eventually look, sound, smell and feel just as it woukd have for the hapless RAC troopers who crewed them in France and Belguim with the BEF, or with British and Australian forces in the Middle East and North Africe.

I'm not criticising those modified carriers - they are yours to do as you please, but how noble an ideal it would be to demonstrate to my grandson in years to come what his great grand father and might have experienced all those years ago...

The old gutless late 30's English spec engine is what my carrier had and what I hope it will have again.

Cheers