The V8 Owners Forum -

Hi, I ve heard of cracked bloxx and slipped liners in RR.
I´m intended to buy a RR 4.6 with THOR efi system and until now, never heard of these probs on these engines.
Any ideas?
Why are all my old topix gone?

One of the main links is to the old forum, where all old posts are archived for searching (topics can't be added to).

didnt you notice this is actually a new forum??

Yes the 4.6 is prone to the block cracking behind the liner. Its a well known problem.

katanaman wrote:didnt you notice this is actually a new forum??

Yes the 4.6 is prone to the block cracking behind the liner. Its a well known problem.

That´s not new to me, but are there any differences in experiences with the blocxx with the THOR system, all probs I heard of, were with bloxx with GEMS efi?
Any ideas? Am I right or not?

Any 4.0 or 4.6 block regardless of inlet or management system can crack. Even the 3.9 blocks can do this. Any block with a 94mm bore.

The 4.0 motors seem to have the most problems closely follwed by the 4.6 motors.

There are a few theories as to why this happens. Some believe the high engine running temps of the later management systems are to blame, some believe the high stresses involved with the angular torqued head bolts are to blame and some say they're just plane rubbish and will crack no matter what. No matter what the reason though they can all suffer from it so its something that needs to be checked or you could end up paying out more to get things repaired or replaced.

If you're checking an engine thats out of a car and in bits try to get a look at the pistons. If any of them look very clean when compared to the rest which would in theory be black (if the engines covered some miles) then run away. I believe its the rear cylinders that are most prone to this however i'm not sure on that but it could happen to any cylinder i suppose. If the engines running in a car look for head gasket type symptoms .

There are different grades of block though. They are graded on the thickness of the alloy of the block behind the liners. The grade is a colour, one of three i believe but i don't know what they are or where the colour marking is on the block. This could be worth looking into to get an idea of the blocks quality.

Hope this helps!

IMHO block cracking is down to a number of factors, I believe high running temperature experienced due to RR being used in town traffic and inadequate cooling, higher temp themostates, I plan to use 82c.I think the largest part is down to the casting process not being perfect, sandcasted and being more suseptical to coreshift leading to the water jackets not running parallel to the bores, and of course the larger bore sizes of 4.0 and 4.6 which further reduces the thickness of the material between the bore and the water jacket. Rover did grade the blocks according to the minimal distance between the jacket and the bore into three categories identified by red, yellow or a blue dab of paint in the lifter gallery. Red is the best and blue the worst. Rover Tended to use red where possible for 4.6 and if no red were in stock then yellow but never blue. 3.9/4.0 they used blue and if none in stock then used yellow.

Red grade had a minimum thickness of 2.8mm. Yellow 2.5mm and blue 2.2mm. I think this grading process performed using ultrasonic equipment from 1997.

So you can just see the colour dots, when you remove the efisaystem and the valley gasket!??

Here is one of my old topics, just letting you know what you're into worst case

http://www.v-8.org.uk/snitzforum/topic. ... IC_ID=4761

my 3.9 is blue.

Haven't got a clue what mne is lol! T'was black when i got it!

Yep!! On my block I have a single red dab of paint on the Passenger side of the lifter gallery. Ignore dabs of paint in other places.

desertrover wrote:So you can just see the colour dots, when you remove the efisaystem and the valley gasket!??

i got no paint inside my block, only blue dabs on the front of the block on each bank

you probably have something else Tony or done a different way as your block is too old to be what Adam is on about.

Cheers M

thev8kid wrote:i got no paint inside my block, only blue dabs on the front of the block on each bank

the same on my block and it was a factory fitted RR engine.