4a block strength

[30psi 4agte]

What are peoples thought on this.... You may or may not know that the 4age is prone to splittng bores on big boosted/ high hp engines. -- i havent broken one yet, touch wood

I have a mate in the states (wil from club 4ag) who is making some good grunt from his 4a and he has split two bores in two seperate blocks. Now he has gone down the route of fitting sleeves in the block to give the bores some strength...usually this would be a good idea...but in a 4a with its siamese bore arangement??

This is what im getting at.. There is not meat / strength left in the upper part of the block due to having to machine it all out to fit the sleeves in ??

Do you think it will be weaker ???

[fixeruperer]

really, cool as, so the hex bolt has a hole in it so its acting like a sleeve it self.
big boost without o-rings, nice.
the sleeve's would be stronger anyway, then with the cast block around it you'd think the sleeve couldnt split. The cast block can split becuase its cast and not super strong.
sleeve's for the win.

i spoze there alot of room for improvement on the galleries you could reinforce them and make them stronger.

[jezza323]

couldnt u just grout fill the lower part of the block for strength?

[30psi 4agte]

really, cool as, so the hex bolt has a hole in it so its acting like a sleeve it self.
big boost without o-rings, nice.
the sleeve's would be stronger anyway, then with the cast block around it you'd think the sleeve couldnt split. The cast block can split becuase its cast and not super strong.
sleeve's for the win.

i spoze there alot of room for improvement on the galleries you could reinforce them and make them stronger.

There is no doubt that the sleeves are stronger than the original bore but what im talking about is the block basicly pulling apart as there is nothing holding it together anymore

IE: between cyl 2&3

If any f you have actually fitted sleeves into a block before you woill know what i mean.... The force needed to actually get a sleeve into a block is alot !

I can see the top half of that block wanting to pull/spread apart just fitting the sleeves.

[fixeruperer]

ooooo i see your point, yeh that could look nasty.
some sr20's are getting around with big sleeve's like that and there an ally block.
pitty the studs doesnt go further down the block and were a snugger fit becuase besides the block the head studs would give some strengh.
tap the core plugs and replace with steal plugs just to help.
time will tell with that one.

[oldcorollas]

he mentions it is a 2 step sleeve... i imagine that means it is thicker at the top than the bottom... such that there is still some block, near the top, to hold it together?

the head and hedbolts will help to hold it together i guess but to answer your question, you'd need to see how far down the thickest part of the sleeve goes...

[30psi 4agte]

Yeah you are right stu.......... I had thought of that but even if there is "some" form of original material left there it would only be 2mm (prob less) as the bore on a 4a is soooo close together.??

I still think it will be weaker but weather or not that is a stress ( splitting apart) that will be seen in an engine like that or not i dont know..


Like fixer said ( which is also my favourite saying ) "Time Will Tell"

[30psi 4agte]

The more i think about this.............

You would want to have a decent gurdle setup on that block when boaring it out that far let alone putting in the sleeves

[Ben Wilson]

The thing to think about is the loads on the block. There really shouldn't be any lateral load on the sleeves, all the load should be internal.

There are a lot of open deck blocks out there and they survive.



I have heard about people putting in spacers into open deck blocks to stop the cylinders shifting. I'm sure a cast iron top deck does a better job.

[oldcorollas]

i think he was more referring to the installation...

since sleeve is not a loose fit.. and if, due to the siamese nature of the block, there is no material at all holding the sides of the block together, then when you press the sleeves in, the block should split, just from the sleeves being installed...
in the pic above, there is at least metal all around the sleeve..
in that example, if the sleeves were bigger, and there was no block between the sleeves, then surely the this block that is supposed to hold the sleeve would push apart and the sleeve would be loose?

[Ben Wilson]

I see what you are saying, but other than the shrink fit of the sleeves, there is very little lateral load on the block.* There is also still a lot of strength in the lower section of the block with the mains caps etc. I'd assume the sleeves are welded together through the welsh plug holes while the engine was being assembled, that would give a nice load sharing effect as well. I think that once you've bolted a head on there, it should all hold together.

* - The only lateral load I can think of is the side loading from the pistons, if a sliding aluminium piston can survive the load, a cast iron block should be able to cope.

[takai]

Especially with the sleeves present as a load spreader.

[LeeRoy]

Im aware of the costs in what im suggesting but its still another option. You could always offset the bores and pistons to either end of the block ie front and back but this would require some modification of either the big ends or the crank or both. If you were to do this it would give you a bit more meat between the bores and hopefully a little more strength. Alternatively some kind of external bracing?

Whats the cost of getting sleeves like you have suggested done anyways?

[Ben Wilson]

Yeah, but the head/combustion chambers would get nasty..

I was thinking about this earlier. If you were paranoid about the cast iron strength around the top deck, you could always grind the whole deck off and replace it with a machined steel plate. I can't be stuffed going out to the shed to measure it, but I think you could you could probably go to a 5mm or so plate.

This would also give you the chance to adjust deck height to get the exact compression ratio you want.

[Mr Revhead]

i want to know how hes splitting blocks!
i have NEVER heard of anyone doing that.
even on 400hp+ engines running 25+ psi.