Stronger rods for my 4.6 ? Advice please :)

kiwicar · Post by **kiwicar** » Thu Aug 16, 2012 12:59 pm

Hello Mr Wotland
I think the issue of too little overllap of big end and main journals is not the issue with the rover, rather too much stiffness relative to the block. How often do you here of rover cranks snapping? how often do you get block failure?
As I said in that rather long post the crank on a Nascar engine uses smaller main and big end journals than the Rover, the big ends are around 1.8" diamiter and they run standard SBC (2.3"), not 400 mains (2.45") you can even get after market blocks with 302 mains (2.2"). The then drill all the big ends out and hack off metal until they weigh about 32lb, down form about 48lb for a standard 350 crank all on a 3.25 stroke crank.
The biggest common long throw chevy crank is 3.75", it has 1/8" less overlap than a stock 350, mine is also bored out on the big ends to reduce weight this is again less journal overlap than a small bearing rover, I would not worry about reducing the overlap on an iceburg rover crank by only .20" especially on a crank that I think is relativly too stiff for the block it is in (as I also said in the post).
Best regrads
Mike

mgbv8 · Post by **mgbv8** » Thu Aug 16, 2012 1:31 pm

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

You said it Big Tone

Have it large !!!!

stevieturbo · Post by **stevieturbo** » Thu Aug 16, 2012 6:32 pm

mgbv8 wrote:I dont think I'm going to bother repairing the engine now...

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

It's a plain and simple rod failure.

Sticking to a budget. Buy a cheap 3.5 with nice thick cylinder walls and liners. Buy the chevy rod/piston combo for it, use a suitable CR, and fire as much boost and gas into it as you can.

Yes it is nice to have a larger engine, to make the power with less stress etc etc. But IMO that more applies to road cars, where we want more torque, nicer to drive etc.

For a race car, engine capacity is less important over engine strength. And a 3.5 will be the cheapest option by far.

ChrisJC · Post by **ChrisJC** » Thu Aug 16, 2012 8:30 pm

I wonder if anybody has measured block flex at high power levels. Particularly >400BHP wot I bet Perry was running. Ultimately of course it will all bind up and catastrophically fail.........

Chris.

stevieturbo · Post by **stevieturbo** » Thu Aug 16, 2012 9:04 pm

ChrisJC wrote:I wonder if anybody has measured block flex at high power levels. Particularly >400BHP wot I bet Perry was running. Ultimately of course it will all bind up and catastrophically fail.........

Chris.

400hp isnt exactly high. And just exactly how would you measure block flex ?

Certainly rod failure such as this, would have nothing whatsoever to do with the block.

A rod failed, there is no other reason than they are not up to the job. It has nothing to do with the block, the crank, the anything else. Just the rods.

I did run my 4.6 for quite a while with std rods and pistons, at a guess I was maybe around 500bhp. Doubt it would be much more. But I'd say my TT setup would have been easier on things than Perry's blower and lots of gas.

Cant remember how many miles I'd have had on mine, but lots of them were easy road miles. I eventually melted a piston and resigned the RV8 in favour of an LS.

JC. · Post by **JC.** » Thu Aug 16, 2012 11:28 pm

I suppose it'll be a nice addition to the collection of broken engine parts.
Makes a change to have something snap rather than melt, eh!

minorv8 · Post by **minorv8** » Fri Aug 17, 2012 5:49 am

Cant remember how many miles I'd have had on mine, but lots of them were easy road miles. I eventually melted a piston and resigned the RV8 in favour of an LS.

Yes, and the same rods have seen plenty of action after I bought the engine from Stevieturbo. And why not since they have been stress relieved with TT setup

sidecar · Post by **sidecar** » Fri Aug 17, 2012 6:34 am

Rods can fail not just because of a large load being placed on them, they can fail due to a small load being placed on them a million times. A bad load is placed on them during the end of the exhaust stroke but I guess that would not bend the rod like what has happened in this case.

mgbv8 · Post by **mgbv8** » Fri Aug 17, 2012 7:12 am

stevieturbo wrote:
mgbv8 wrote:I dont think I'm going to bother repairing the engine now...

http://s205.photobucket.com/albums/bb27 ... 1QQtppZZ20
It's a plain and simple rod failure.

Sticking to a budget. Buy a cheap 3.5 with nice thick cylinder walls and liners. Buy the chevy rod/piston combo for it, use a suitable CR, and fire as much boost and gas into it as you can.

Yes it is nice to have a larger engine, to make the power with less stress etc etc. But IMO that more applies to road cars, where we want more torque, nicer to drive etc.

For a race car, engine capacity is less important over engine strength. And a 3.5 will be the cheapest option by far.

Rod failure due to more load than they can handle was my thought Stevie. When you look at the damage on the engine itself rather than in pictures you can see the pattern of damage where a broken rod has been flailing around and punching things

I'm going window shopping for parts today !

mgbv8 · Post by **mgbv8** » Sun Aug 26, 2012 7:34 pm

Crower rods seem the way for me now.

Got a good deal on block, crank, rods and pistons. I'm going to bolt it together this week and I hope to be fitting the block next weekend

With a bit of luck I'll have it running in 2-3 weeks

stevieturbo · Post by **stevieturbo** » Sun Aug 26, 2012 7:38 pm

custom set, or do they make them for the 4.6 already ?

mgbv8 · Post by **mgbv8** » Mon Aug 27, 2012 1:57 pm

stevieturbo wrote:custom set, or do they make them for the 4.6 already ?

Custom made kit Stevie.

ChrisJC · Post by **ChrisJC** » Mon Aug 27, 2012 3:25 pm

stevieturbo wrote:
ChrisJC wrote:I wonder if anybody has measured block flex at high power levels. Particularly >400BHP wot I bet Perry was running. Ultimately of course it will all bind up and catastrophically fail.........

Chris.
400hp isnt exactly high. And just exactly how would you measure block flex ?

No, but two things make me think the rover block is pretty floppy:
1. Project Iceberg (the Diesel project) cast little cast-iron stiffeners into the block to try to make it stiffer. I believe the project failed because of inadequate block stiffness.
2. The higher power engines (4.0 / 4.6 litres - 190 / 225BHP) required cross-bolted mains to enhance block stiffness. Perry is now at twice those power levels.

Dunno how you'd measure it though, and I don't know at what level it becomes a problem.

Chris.

minorv8 · Post by **minorv8** » Tue Aug 28, 2012 7:23 am

Custom made kit Stevie
More details please !

Wotland · Post by **Wotland** » Wed Aug 29, 2012 6:27 am

If ever Eales has some 5.7" rods and + 0.020" forged pistons to work with 82mm stroke.