FOR ALL YOU GUYS WHO HAVE WONDERED ABOUT ROVER V8 ALUMINUM BLOCKS CRACKING BEHIND ONE OR MORE CYLINDER LINERS, ALLOWING COOLANT TO ESCAPE FROM THE WATER JACKET, BEHIND SAID LINER(S), TURNING TO STEAM, AND ESCAPING UPWARD INTO THE CYLINDER(S) STEAM CLEANING THE TOP OF PISTON(S), ETC., AND/OR ALSO ESCAPING DOWNWARD INTO THE OIL PAN, EVENTUALLY LOOSENING THE LINERS, CAUSING THESE SLIPPED LINERS TO MOVE UP/DOWN WITH THE PISTON WITHIN THEM, CREATING BANGING AS PISTON MOVES AGAINST THE HEAD AND/OR THE LOWER END OF CYLINDER BLOCK, READ THIS:

WHAT CAUSES THE ALUMINUM BLOCKS TO CRACK BEHIND CYLINDER LINERS? LITTLE OR NO CRACKING SUCH AS THIS, WAS ENCOUNTERED DURING THE TIME WHEN GENERAL MOTORS, BUICK/PONTIAC/OLDSMOBILE, AND LATER ROVER, ONCE THEY BOUGHT RIGHTS TO IT FROM GM, IN ITS ORIGINAL CONFIGURATION 215 CU. INCH ALL ALUMINUM BLOCK. AT THAT TIME, THIS ENGINE HAD APPOX. 89 MM BORES. ONLY WHEN ROVER INCREASED THE CAPACITY OF THE ENGINE FROM 89 MM BORES TO 94 MM BORES, IN THE 3.9 L VERSION, DID THE CRACKING PROBLEM RISE. NATURALLY, IT CONTINUED UP THROUGH THE 4.0 l, 4.6 l, VERSIONS, BECAUSE THE BORE DIAMETER REMAINED THE SAME THROUGHOUT THE RANGE, 3.9 L TO 4.6 L WHAT HAPPENED IS PRETTY OBVIOUS, THE LARGER CYLINDER BORE DIAMETERS CREATED MUCH THINNER ALUMINUM WALL BETWEEN THE WATER JACKET AND THE CYLINDER WALLS, BEHIND THE LINERS. CRACKING WAS CAUSED BY WALLS WAY TOO THIN, SOMETIMES AS THIN AS 2 MM, ALSO BY EXCESS HEAT (A HUGE CONTRIBUTING FACTOR), AND EXCESS STRESS IN CRITICAL AREAS BETWEEN WALLS BEHIND LINERS, BY THE HEAD BOLTS (I SAY THIS, BECAUSE OF THE UNUSUALLY HIGH NUMBER OF CRACKS THAT TAKE PLACE QUITE OFTEN RIGHT AT THE BASE OF THE HEAD BOLT THAT IS BETWEEN CYLINDERS 1 AND 3 OR 2 AND 4, OR BETWEEN 5 AND 7 OR 6 AND 8. THIS HEAD BOLT STRESS IS RELIEVED SOMEWHAT THROUGH THE USE OF ARP STUDS RATHER THAN THROUGH COMMON HEAD BOLTS.

Some have alleged that replacing the original equipment liners with TOP HAT liners will solve some or all of these issues. The TOP HAT liners, for sure, will prevent slipped or loose liners from moving up/down, and banging against the head and against the lower end of block, BUT THEY WILL
NOT PREVENT THE BLOCK FROM CRACKING BEHIND ANY LINERS, TOP HAT OR OTHERWISE, AND THEY WILL NOT PREVENT COOLANT STEAM FROM THE WATER JACKET ESCAPING UPWARD AROUND THE TOP HATS, AND INTO THE COMBUSTION CHAMBERS.

FOR EXCELLENT CLOSE UP PICTURES AND VIDEO OF ALL THIS, FROM RPI ENGINEERING, IN ENGLAND, SEE THEIR POSTING ON YOUTUBE. YOU WILL SEE HOW BLOODY THIN THE WALL IS BETWEEN SOME WATER JACKETS AND THE LINERS; IT IS NO WONDER THAT THEY CRACK.

 

Good info... and yes its true that top hats won't prevent a block from cracking, but top hats can allow you to run the engine with a cracked block. Top hats (WITH o-rings at the bottom) effectively convert the cylinder to a wet sleeve in the event of a crack. The coolant will be unable to travel upwards as its sealed by the flange and head gasket, and won't be able to travel downwards into the crankcase due to the o-ring.

 

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Yes, that is what we are told is true, but RPI engineering in England, that has rebuilt, on average, 150 to 200 of these V8 engines per year since 1993/1994, SAYS TOP HAT LINERS DO LEAK STEAM UPWARD, AROUND THE TOP HAT AND AROUND THE HEAD GASKET INTO THE COMBUSTION CHAMBER (AGAIN, BASED ON THEIR YOUTUBE VIDEO ANYONE CAN SEE), AND A FRIEND TOLD ME THAT HE HAD THIS SORT OF THING HAPPEN WITH HIS TOP HAT INSTALLED LINERS, SO WHAT IS THE TRUTH HERE? PERHAPS RPI HAS RECENTLY COME TO THIS CONCLUSION, FROM WHAT THEY ARE EXPERIENCING?

 

Okay, I found the video you are talking about.
Interesting claim. I think I will forward this to Richard Turner @ turner engineering and see what he says... I suspect they have rebuilt many more rover v8's than RPi. They don't cover o-rings in the liner either.

 

I can't see coolant leaking around a properly fit top hat liner and head gasket unless the coolant is boiling. At that point I suppose the pressure might get high enough to do the job but....

If coolant at normal pressure (around 15psi?) Can't make it from the water jacket to the nearest cylinder (obviously assuming a good gasket and flat surfaces) then how could it do it in this scenario?

 

Yeah I agree, I don't see how coolant could possibly get around the flange.

Response from turner:
I suspect Turner rebuilds a load more of these motors than Rpi.

 

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Interesting; thanks for the additional information on this subject. From this information, I surmise that it is vitally important as to the type of material liners are made from, AND how tightly they are fit into the bores in the block. RPI Engineering was talking about STEAM leaking around the upper flange, and around the head gasket, which has nothing to do with the o ring at the base of the liner, which stops leakage into the oil pan. Thus, I would imagine that having liners made of good material, fit very tightly into bores, would prove a blockage to steam escaping upward to the head, into the cylinder. Apparently, all liners for this purpose, are NOT created equally, and I know that all liner fitting is not done equally well by all machinists, so you get what you pay for, or the quality of work you do; no surprise.

 

I just watched the video. Sounds like these guys are full of **** and are just attempting to justify tossing blocks in the scrap heap in order to sell new ones to customers.

 

Either way interesting information.

 

So we screwed up by punching out the old buick based casting. I am here in the US and might just be able to come up with a vintage Buick 215 ci block. Can I put it in a disco by hanging all the bits on it? And, if so, can I add a stroker kit, etc. all the old school hop up items?