cross bolting

[matt28]

Does anyone know why 450s are cross bolted but 500s (and 400s) tend not to be? What would be the logic behind only cross bolting the 450?

[Jay Ayegees]

As I understand it:-

TVR obtained all their engines direct from Range Rover - so they had to take what was being used on Range Rover and modify where necessary.

The RR 4.6(450) was a later development and had cross bolts as part of the RR spec whereas the 400, 430 and 500s were based on earlier non-cross-bolted blocks. TVR could have but choose not to cross-bolt the blocks as part of their modifications.

I believe that some later 500s were cross-bolted.

Somebody wiser will be along shortly to give a more definitive answer.

Jay

[Boosted LS1]

It's probably more to do with block/crank availability at the time of production.

Boosted.

[matt28]

Thanks guys

So does this mean the 450 is a better bet than the 500 if you're planning on tuning, especially going down the supercharger route? Or are there other parts that become the weak link prior to the cross bolting becoming necessary?

[spend]

Are X-bolted engines proving more reliable? It seems to me that there are many more occurences of slipped liners with these later engines. I am not convinced either that the X-bolting should be used without the stiffer aluminium sump - else you could be stressing the edges of the block to crack? I'm sure an Engine builder would advise a well balanced engine with stronger internals (to suit your pocket) whether x-bolted or not. There seem to be rumours that the later X-bolted engines were better balanced out of the box (ie tolerances of rotating masses) I do'nt know how true this is.

You should also remember that many of the 'pros' that folks quote about the x-bolted blocks are already present in the common TVR 'intermediate' blocks (ie the serp engines).

Dave

[GreenV8S]

Cross bolting is basically a good idea, but it's a case of 'a bit better' (better bearing support, stiffer block) rather than cr@p without it / bullet proof with it. I have never heard of it leading to stress damage on the bottom of the block.

[Boosted LS1]

Cross bolted engines come with stronger cranks, superior rods and pistons compared to stock earlier rover parts so would be better for a blown application. You may be able to find an export version on 8:1 c/r which would be a bonus. Try land rover places for export units.

Boosted.

[spend]

Why then did LR switch to a rigid cast sump at the same time as the changeover to X-bolting? The extra stress on the bottom 'flange' of the block might be causing the cracking across the valley as seen in a few later engines that I have seen described. It certainly seems to me that slipped liners are far more common in these later engines, far more so than with the intermediates. As far as I can see it is only the X-bolting that is the difference hence my personal hypothesis.

Dave

[Boosted LS1]

spend said:

Why then did LR switch to a rigid cast sump at the same time as the changeover to X-bolting? .

Dave

I can't answer that fully but iirc the rigid alloy sump allowed it to be tied into the bell housing more positively. Think they bolted together, not so easy with a tin sump and a metal plate underneath it.

Boosted.

[spend]

Boosted LS1 said:

Cross bolted engines come with stronger cranks, superior rods and pistons compared to stock earlier rover parts so would be better for a blown application.

Are you comparing X-bolted against pre-serps Mike? Unlike LR's TVR (Chims & Griffs) are predominately serpentine 'intermediate' engines, which I thought had the newer crank/rods & pistons already.

Dave

[The AJP Griff]

Cross bolting was done by Rover to overcome the problem of block/cap fretting primarily.As they wanted to run higher and higher temps for emmissions reasons,the damage caused by fretting became more of a problem,as over 80oC causes the fretting(hence it's better to run the 74oC stat,even all year around).The last of the griffs and also all 4.5 chimaeras usually had rover crossbolted blocks.

[Boosted LS1]

spend said:

Boosted LS1 said:

Cross bolted engines come with stronger cranks, superior rods and pistons compared to stock earlier rover parts so would be better for a blown application.

Are you comparing X-bolted against pre-serps Mike? Unlike LR's TVR (Chims & Griffs) are predominately serpentine 'intermediate' engines, which I thought had the newer crank/rods & pistons already.

Dave

Yes I am Dave. Intermediate engines have the early 2.3" cranks and early rods/pistons afaik. They just got the serp front end but with a dizzy before the full switchover. They had cross bolt bosses on the side of the block but the caps weren't big enough to accept cross bolts so the side bosses were never machined. Prior to intermediates the factory did limited cross bolting along with twr for race/rally applications. To stop cap shuffle as mentioned above. They were called 'X' blocks, some didn't have the lifter oil ways bored in order to run solids and add strength.

Oh, patterns on it's way

Boosted.