Stroking a 4.0L

[Fozwanger]

Hi,

I've got a rover 4.0L cross bolted block with large mains journals and I'm going to fit a buick 300 crank, apart from the flywheel andy pitfalls?
Has anyone had any experience with over boring from 3.7" to 3.766"?
The Des Hamil book and V8 tuner claim you can go to 96mm (3.78") although the conversion in the book is wrong (imperial conversion too small), again, any pitfalls?
I'm going to use forged 305 chevy pistong with a 0.110 dish and 64 300 heads, and running twing turbo's and nitrous, any experiences?

Thanks in advance

Jeff

[mgb260]

Why not just go 3.736/stock 305. Only .036 over. I heard they don't like more than .040 over. You need the D&D flywheel and rear seal conversion for the 300 crank, or you could offset grind a 4.6 crank and use stock flywheel with no seal mods.

[minorv8]

Factory liners will not take 3,766 bore. All 96 mm bore blocks have top hat liners which allow boring up to 96or 96,5 mm.

[cgill]

I'd be curious to see how you are fitting the twin turbos given the limited engine compartment space. I thought of a turbo but decided to just increase displacement.

[Fozwanger]

It's in a morris minor

[minorv8]

You could fit a supercharger on top of the engine still keep everything stock looking :-)

Which tranny and rearend have you got. I suppose you have some kind of a fabricated chassis  ?

[roverman]

Jeff, "twin turbos and nitrous", so... 600-1,000 hp. ? Drag racing or sustained ? Problem is, stock cranks start getting "iffy" around 400-500hp. ?  Good Luck, roverman.

[Fozwanger]

Oh no, nothing that serious. At the moment I've got a 4.0L HC TVR motor with the twin turbos, so looking for about 350hp plus the 100 / 150 shot for short bursts. I'm building the stroker in the back ground for when I wreck the 4.0L. I was at Prescott hill climb earlier in the year and was watching the tvrs racing and the 4.0L were quick but the 5.0L just had so much more torque and pulled much quicker out of the bends. The 300 crank I'm led to believe is a lot stronger than a 5.0L crank, and I like a challenge of making things fit that aren't meant to.
350hp plus the NoS will be fine, I want more torque for drivability.
It's a road car btw, I drive my rods as much as I do my regular car. What's the point of building it if you're not gonna use it?

[BlownMGB-V8]

> stock cranks start getting "iffy" around 400-500hp.

Why is this Art? Has someone been breaking cranks? Why haven't we been hearing about this? Who have been trashing these cranks and under what circumstances please?

Jim

[minorv8]

TVR 5 litre cranks are not the best looking items and are known to break. I believe most if all are externally balanced, too.

[Fozwanger]

5.0L cranks are shite. They break between the front main and no1 generally. They break under normal use so don't wanna huff one. That's the reason I want a 300 crank :-))

[DiDueColpi]

This isn't a crankshaft, but it does look usefull!
They also advertise their own cranks.
Might be worth a look.

http://www.boostperformance.co.uk/
Cheers
Fred

P.S.
The dimensions of that LS block sitting beside the Rover block look really interesting.
Probably just a dream but is the LS crank a close fit?

[roverman]

Jeff, Whichever crank you choose, make it internal balanced,(better durability).  roverman.

[Fozwanger]

It will be. I tried to upload some pics bug they are too big.
If you want to see the build go to
Www.rodsnsods.co.uk and look in the garage section for twin turbo Moggy. Probably easier if you put it into the search box on the site rather than sift through the pages.
:-)

[Wotland]

Hi Jeff,

Main problem with TVR 500 crank is not the crank itself but how TVR factory assembled engine.

It is externally balanced with low level tolerances.

Also crank brakes because the front damper is not correctly bolted.

[Fozwanger]

Hi dimitri,

I was under the impression it was because there was no journal overlap between front main and no.1 big end, with the OOB forces from the external balancer causing "whip" I the crank at the point.
I'm going down the Buick route as I can't find anyone here to offset grind a 4.6 crank!!

[minorv8]

I tried to find a shop locally to offset grind a crank but it is simply too much slow grinding. Nobody was interested... and the cost would probably been the same as new longer stroke crank.