Stronger rods for my 4.6 ? Advice please :)

minorv8 · Post by **minorv8** » Tue Aug 14, 2012 8:25 am

What are the dimensions of the 4.6 rod ?

4,6 rod length is 149,8 mm
4,0 rod length is 155,2 mm

Can´t recall the big end width, have to check when I get home

mgbv8 · Post by **mgbv8** » Tue Aug 14, 2012 8:30 pm

I dont think I'm going to bother repairing the engine now...

http://s205.photobucket.com/albums/bb27 ... 1QQtppZZ20

Ian Anderson · Post by **Ian Anderson** » Tue Aug 14, 2012 9:06 pm

Chebby time then?

Ian

mgbv8 · Post by **mgbv8** » Tue Aug 14, 2012 9:16 pm

Nah!!

I'm sticking with British leyland I think.

With a stronger bottom end I think I can have a good go at a 9 second pass on the 1/4 mile.

JSF55 · Post by **JSF55** » Tue Aug 14, 2012 9:26 pm

Bad luck there perry

mgbv8 · Post by **mgbv8** » Tue Aug 14, 2012 9:28 pm

Shiit happens mate!!!

You cant make an omelette without breaking some eggs eh ??

I'm looking for a 9 second omelette with a Rover V8

topcatcustom · Post by **topcatcustom** » Wed Aug 15, 2012 7:30 am

Shiit! Looks like the conrod has buckled under cylinder pressure with all your N20 and fatigued on compression then snapped at the start of the intake stroke, time to find some H beam rods I think Perry!

Dare I ask- if that is/was your brand new top hatted block...?

ian.stewart · Post by **ian.stewart** » Wed Aug 15, 2012 8:22 am

Pel, You are a dab hand with Devcon, just need to buy a bigger tub,
As you want to keep to BL, If it was me, I think I would be looking as a pseudo BL short engine, there must be a few smaller capacity engines laying about within the drag racing circles.
I know this will run against the ethos of the car, but where do you go with this, you are probably pushing the envelope of reliability of the 4.6, to a point where it will start letting go in other places, and costing a small fortune to keep on top of it., Rovers are not cheap, By the time you have built a bullit proof short engine, --- Sorted the liners, New pistons, new rods, machined the crank to take new sized rods, possibly with an offset grind, quality fixings, a second hand Wildcat block is starting to sound like a good deal. I think most of the internals are off the shelf so you would be making a saving there on consumables, like pistons and rings on a NO2 engine.....

kiwicar · Post by **kiwicar** » Wed Aug 15, 2012 9:17 am

Hi Perry
I am with Ian on this one, to me it looks as if the block has failed around the base of the liner allowing the liner to move off line as the piston has gone past BDC. Unless you had hydrolock on the cylinder I can't see how else you would get enough force to put that S bend in the rod. . . you did do a propper job there. . .
It also comes back to my particular thing about the large bearing rover block, I am still convinced the larger bearings significantly weaken the block casting aroud the bottom of the cylinders.
Nascar engines make 850 plus bhp and use bearing sizes smaller than the 3.5/3.9 blocks and although they have engine failures they are at power levels highter than you are at.
I would surgest building an engine based around a 3.9 block, one with the cross bolt bosses, get a 1" thick girdle made up with intigrated caps that locate the walls of the block to the rest of the bottom end and drill it for cross bolts. Then get a 4.2 crank, a set of Nascar corrillo rods with the honda acura big end bearing size and off set grind the crank to fit (should give about 1/8" extra throw, and use chevy 305 forged pistons I think you will end up with about 4.4 or 4.5 litres (you could even go for a TVR 4.5 crank in small rover main bearing size and off set grind that) forget the cooling system, fill the block with block filler then stick some buick 300 heads on the top, you dont then have to worry about the 300 heads cooling passages as you dont have any water in it.
Or as Ian says build an engine around a wildcat bottom end. . .
Best regards
Mike

ChrisJC · Post by **ChrisJC** » Wed Aug 15, 2012 5:14 pm

Got a vid of the run in which this event occurred?

With regard to the 4.2 crank, I believe that Land Rover could break them in the stock 4.2l Range Rover engine on the dyno by running it at high speed & load. Perhaps why they went to the larger bearing size for the P38 engines.

Chris.

Wotland · Post by **Wotland** » Wed Aug 15, 2012 7:28 pm

Well 4.2 and 4.5 engine should share same Iceberg casting.

I don't no if LR continues to use Iceberg cranks on their 4.2 production engine.

But Iceberg crank are the strongest crank you can find.

You can push it to 8000RPM and I know at least one guy who broke one carillo rod before to damage crank.

Wotland · Post by **Wotland** » Wed Aug 15, 2012 7:34 pm

kiwicar wrote:Hi Perry
I am with Ian on this one, to me it looks as if the block has failed around the base of the liner allowing the liner to move off line as the piston has gone past BDC. Unless you had hydrolock on the cylinder I can't see how else you would get enough force to put that S bend in the rod. . . you did do a propper job there. . .
It also comes back to my particular thing about the large bearing rover block, I am still convinced the larger bearings significantly weaken the block casting aroud the bottom of the cylinders.
Nascar engines make 850 plus bhp and use bearing sizes smaller than the 3.5/3.9 blocks and although they have engine failures they are at power levels highter than you are at.
I would surgest building an engine based around a 3.9 block, one with the cross bolt bosses, get a 1" thick girdle made up with intigrated caps that locate the walls of the block to the rest of the bottom end and drill it for cross bolts. Then get a 4.2 crank, a set of Nascar corrillo rods with the honda acura big end bearing size and off set grind the crank to fit (should give about 1/8" extra throw, and use chevy 305 forged pistons I think you will end up with about 4.4 or 4.5 litres (you could even go for a TVR 4.5 crank in small rover main bearing size and off set grind that) forget the cooling system, fill the block with block filler then stick some buick 300 heads on the top, you dont then have to worry about the 300 heads cooling passages as you dont have any water in it.
Or as Ian says build an engine around a wildcat bottom end. . .
Best regards
Mike

Mike,

I am curious no know if Iceberg crank will be strong enough to use 2.3"main and honda rod journal ? Safe overlap ?

mgbv8 · Post by **mgbv8** » Wed Aug 15, 2012 8:49 pm

ChrisJC wrote:Got a vid of the run in which this event occurred?

With regard to the 4.2 crank, I believe that Land Rover could break them in the stock 4.2l Range Rover engine on the dyno by running it at high speed & load. Perhaps why they went to the larger bearing size for the P38 engines.

Chris.

I asked Ian Blackett if he got the run on vid and he was in the photo booth downloading stuff so he missed it

I'm searching the web for anyone who may have filmed it.

mgbv8 · Post by **mgbv8** » Wed Aug 15, 2012 8:53 pm

topcatcustom wrote:Shiit! Looks like the conrod has buckled under cylinder pressure with all your N20 and fatigued on compression then snapped at the start of the intake stroke, time to find some H beam rods I think Perry!

Dare I ask- if that is/was your brand new top hatted block...?

It was Tom...
My new top hat block.... Boo hoo!!!

But at least it proves that the arp top end and cometic gaskets did the job they were supposed to do eh ??

And the bottom end is all the original 110,000 mile stuff with stock con rod bolts. Non of them let go did they??

Cobratone · Post by **Cobratone** » Thu Aug 16, 2012 2:55 am

Well Pell, if you're going to f**k an engine you may as well f**k it big time! Good job my friend