Sand cast blocks, right? Pretty minor variances there over time.

For the liners to fit, the cylinder bores are going to be real close to original factory spec.

Sure, tooling and dies and jigs can age and wear, but most of the time that wear reduces the size of the tool so you would expect more clearance between sand-cast block areas versus the milled/drilled areas in the block, I would think.



...and even if there is a case where the coolant or oil tunnels in the block were larger than factory spec (making them closer to the cylinder bore, for example), then those larger coolant passages would yield a cooler running motor which would negate the main problem with Disco motors (overheating).


Well, I could be wrong about all of that, but that's just how I think about things.

 

 

Correct, but your head gaskets won't be torn!

 

 

Alloy heads and iron blocks = differential expansion rates that aren't absorbed by steel head gaskets, hence composite gaskets absorb more movement laterally and vertically but are prone to failure if overheated. Alu expands at approx twice the rate of iron.

Thermal Expansion Coefficients at 20 C
Material Fractional expansion per degree C x10^-6 Fractional expansion per degree F x10^-6

Aluminum 24 13
Brass 19 11
Copper 17 9.4
Iron 12 6.7

8 more rows
Thermal Expansion Coefficients
hyperphysics.phy-astr.gsu.edu/hbase/Tables/thexp.html

 

 

Thanks for the info! I used arp studs when I did the hg's on my current 4.0 and I use studs with engines at work. There's no way I would ever use bolts unless I had to.

I think I get it; MLS is better for iron block/Alum heads bc of the different expansion rates, but not really necessary with alum/alum?

What is this easy-pin job you speak of, by removing the heads? I'm aware of the standard procedure others have used. Is it just better access with things out of the way?

 

Price.

 

 

The last time Rover recommended the use of the Cometic style of gasket was back in the days when 14 bolts secured the heads to the block. When Rover (1995 for RRC and 1994 for DI if memory serves me) switched to composite gaskets is was to address the perpetual problem of leaks being created towards the back of the heads. There was a third row of four head bolts (with the furthest back bolt being the culprit for leaks all too many times) that were eliminated with the introduction of the composite gasket. At the time, nearly everyone involved with the Rover V8 felt that FINALLY Rover was doing something to address the issue of head gasket leaks. People bitched and moaned about the technique for tightening the new head bolts into place but for the vast majority, the change was viewed as a positive.