Hi All,
IMHO the one of the ways of dealing with the issue of Rover V8 engine blocks cracking is aluminum liners. Some modern all-aluminum v8 engines actually have these cast-in. Even though the liner and the block are both made from aluminum, it's a different alloy. The liner is coated with Alusil which allows for better friction pair (aluminum-over-aluminum makes for a very poor one). The original coating back in the day was Nikasil (invented Porsche IIRC). BMW learned " the hard way" that Sulfur in gasoline washes this coating off and ruins the engine which is why today Alusil is used instead.
Does anybody make these liners for Rover v8? No wonder the thin-walled rover blocks crack, the thermal expansion coefficient of cast iron and aluminum is very different. If the liner and the cylinder are both aluminum alloy the problem could be solved.
Also, does anybody make a main cap girdle for the 89-93 3.9 blocks (non-enclosed main caps)?
Some of the aluminum engines that I have seen had steel hollow pins (visualize them as a piece of pipe) pressed into the block, around the studs for the main cap. The main cap was machined to fit tight on the pin. this way the main cap movement was eliminated. Due to simple physics of leverage, a small pin at the mating surface where main cap meets the block prevents movement much better than super-stiff stud or bolt. A bolt or a stud will flex and allow the cap to move. This will eventually allow the crank to break.
Has anybody pinned the main caps on Rover v8s before?
Questions about aluminum bore liners, main girdles and pins?
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juha_teuvonnen
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Re: Questions about aluminum bore liners, main girdles and p
juha_teuvonnen wrote:
Has anybody pinned the main caps on Rover v8s before?
I don't know about the other stuff apart from I used to run a racing 2 stroke that had coated bores!
As to the dowels that are used to locate engine components, well the RV8 main bearing caps use "registers" at the sides of the caps to locate them. Infact the block can be knackered in this area if the caps are just fitted then pulled down by the bolts.
Pete
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juha_teuvonnen
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IMHO the registers on the side of the caps are a bad idea, especially when implemented the way they were in the non-enclosed RV8 main caps. The longer distance between the registers (as opposed to the difference between the centerlines of the dowel pin) means more play when the aluminum block expands and consequently more fretting. I am thinking about adding dowel pins as a way of reinforcing the bottom end on a non-crossbolted block (1992 3.9). The other way would be a girdle over the main caps, but that's probably a more involved project. I am going with ARP studs anyway, I am wondering if this bottom end will hold up when I drop in a stroker crank. I am planning to build this engine for Range Rover LWB classic, which is a heavy car. It will put more strain on the crankshaft when compared to a lighter vehicle.
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Boosted LS1
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The chevrolet ls7 has dowels to help locate the main caps and that's not a bad thing, not perfect though.
Alloy girdles for the rover have been produced before and I've used them with a longer stud kit and individually machined spacers between the girdle and caps. Works well.
As for alusil bores the porsche has these and they are very good until you scratch them. Then the block could be written off. I've managed to salvage some but only just. Thing with alusil is that the whole block is silicon rich, there isn't a liner as such. Nicalsil is a different thing all together, it's a plating treatment. An alusil liner in a rv8 may be so thick that it screws or weakens the block making the efforts pointless.
As for the crossbolts on a rv8 any stretch/flex is taken up by the threads. It's what bolts do to maintain correct tension. I think a crossbolt is better then just a dowel pin but crossbolts and pins are even better.
Alloy girdles for the rover have been produced before and I've used them with a longer stud kit and individually machined spacers between the girdle and caps. Works well.
As for alusil bores the porsche has these and they are very good until you scratch them. Then the block could be written off. I've managed to salvage some but only just. Thing with alusil is that the whole block is silicon rich, there isn't a liner as such. Nicalsil is a different thing all together, it's a plating treatment. An alusil liner in a rv8 may be so thick that it screws or weakens the block making the efforts pointless.
As for the crossbolts on a rv8 any stretch/flex is taken up by the threads. It's what bolts do to maintain correct tension. I think a crossbolt is better then just a dowel pin but crossbolts and pins are even better.
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juha_teuvonnen
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kokkolanpoika
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You can buy 2nd hand unit and fit new top-hat liners in it.. I think it is cheaper/better solution in long term? And you may get 4,6L engine then.. I agree with "boosted"...ARPS on their own will be fine. Or better still ARPS and a cross drilled block.
I don't think that dowels will do much to stop the cap moving, they are used just to locate one component onto another. They would have to be quite long before they actually helped to stop the cap moving, and quite thick. You would then have to drill out the bolt holes to a bigger diameter and to quite a depth, this might weaken the cap. What's worse is that the block is slightly weak in the area that the bolts/studs go into, drilling this area is not a good idea. (Plus you'd be drilling out the thread!)
I don't think that the weight of the car will make much difference to the load on the caps, you'd be better off spending your money on a really good balance job as it's the vibration at high revs that frets the caps.
AJMHO!
Pete
I don't think that dowels will do much to stop the cap moving, they are used just to locate one component onto another. They would have to be quite long before they actually helped to stop the cap moving, and quite thick. You would then have to drill out the bolt holes to a bigger diameter and to quite a depth, this might weaken the cap. What's worse is that the block is slightly weak in the area that the bolts/studs go into, drilling this area is not a good idea. (Plus you'd be drilling out the thread!)
I don't think that the weight of the car will make much difference to the load on the caps, you'd be better off spending your money on a really good balance job as it's the vibration at high revs that frets the caps.
AJMHO!
Pete
Last edited by sidecar on Fri Oct 31, 2008 12:40 pm, edited 1 time in total.
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juha_teuvonnen
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