4,6 block main bearing cap side bolts?8,8 or 10,9 hardness?

[kokkolanpoika]

Hi..

I wonder that why rover 4,6 block main bearing cap side bolts are std 8,8 hardness bolts.. And 2 of bolts are 12,9. Back of the engine (near flywheel)
I just think that is there any proplem to fit 10,9 hardness bolts to replace original 8,8 bolts..
My "main" bolts are now ARP studs, and i need need new side bolts anyway.. I think side bolts are not available at ARP stuff?
And because 10,9 bolts are slightly harder that std 8,8 bolts, then i will think that those are slightly better then if build a performance engine?

Experience of bolts?

[RoverP6B]

The use of studs and nuts for securing main bearing caps is advantageous if the block that you have is a 2 bolt type, with only minimal main bearing cap to register fit.

The 4.6 block has totally different register fit, so the entire verticle length of the cap is secured by the register within the block. Using 4 bolts instead of 2 secures the main caps with considerable security, with no chance of movement even under the most severe racing conditions.

"The standard bolts as supplied by Rover for securing the main caps in cross bolted 4.6 litre blocks are suitable for all applications including racing"... as advised by Des Hammill in his excellent text.

Ron.

[stevieturbo]

I would imagine the side bolts wouldnt matter. They arent exactly under huge stresses.

The ones on my LS1 certainly arent anything fancy. Id say prob 8.8
Only an M8 fastener on the LS, circa 24lbft.