4a block strength

[30psi 4agte]

/me quickly shovels brain matter back into his ears. +rep

He is just a freak isnt he...He reminds me of the magic 8 ball -- You ask a question and always get an answer..

Top stuff stu.... Cant rep ya anymore though.


One thing im yet to find out is... If the bore was std on that block or not. If it was bored out that would make it a bit weaker to start with and more prone to splitting too.


The king of the 4a's Mr norwood never split a block in a 10,000 rpm, 40+ psi boost destroked 4agte. He was making something like 600+hp from 1.5L.
i have always wondered why he never split one and people running far less boost do ???

When i spoke to wil ( guy who's block that is) awhile back....I asked was it detonation that was killing the bore ?
He assured me the A/F was fine and it was just excessive cylinder pressure that did it.

So what are the general thoughts on this anyhow.... Worth it or stick with a std bore ?

Im skeptical...... and not sure if i like the idea yet. Unless there is something there that i cant see and dont know about holding the thing together....... Hmmmmmmmm

[Ben Wilson]

Could he have used a thick block. There are a lot af variations of 4AG block out there, unless you go through and sonic test all of them, you don't know. There might be a thicker wall one out there.

Someone on club4AG was talking about this, but of course he wouldn't tell what the thicker wall blocks were...

[LeeRoy]

How about the possibility of doweling or running bolts/studs through the whole block all the way down from the head to the mains? Ideally some bolts though the middle between the bores would be ideal but by the looks of things not an option.

[fixeruperer]

there big cut outs for the valves, must have quite a bit of compression.

[TC1600]

they are flat top pistons, I'd say they are more for high lift from the cams

[jeffro ra28]

Has anyone ever considered the fact that splitting bores CAN also be caused by a improper tune condition. ie. Detonation. So what is the right A/F under such extreme conditions?

The Darton liner is tough as, if you have actually had any experience machining or honing them you will know what im talking about.

Currently we are using Darton liners in aluminium race blocks because we couldnt get the race spec cast iron blocks to stop splitting next to the head stud. This would happen at around 250hp per cylinder. We havent had any drama's with the aluminium race blocks factory fitted with Darton liners.

I suspect the aluminium block itself probly isnt as strong or rigid as the cast iron one but the liners are certainly more resistant to cracking. Which is why it may still be benifitial in the 4A. The question is, can you sacrifice block strength and rigidity for cylinder wall strength and crack resistance?

On the naturally aspirated engines with aluminium blocks and darton liners, we find that the engine will make the most power in the first 2 dyno runs. After that, we have to wait for the engine to cool down again. The thoery is that the aluminium moves around that much with the affects of heat it gradually deform the shape of the liner, it effects the ring seal. Go figure

This is probably occuring in the blown engines aswell, but there is that much fuel being pushed past the rings anyway, its not really a concern. Plus you dont really chase 20hp around the street on somthing thats already making 2000hp.

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.

Have you ever actually tried welding cast iron!? It basically has to be cherry red before you can weld it without it cracking under the bead, or next to it. This would be a disaster in a cylinder sleeve!

[30psi 4agte]

Could he have used a thick block. .

even if it were a "thicker block" it wouldnt matter as there will still be the same amount of material between the bores because of its design.

If you look at the pics closely you can see the liner through the coolant gallery in some pics. There has been that much machined out.

[jeffro ra28]

Depending on bore size, but as a ballpark a liner is fitted with .001" of interferance. Would you think this would be enough to split the bore whilst fitting?

[30psi 4agte]

Depending on bore size, but as a ballpark a liner is fitted with .001" of interferance. Would you think this would be enough to split the bore whilst fitting?

Well if you look at how much material is left on the outer of the sleeve linings ,,,,Id take a pretty good guess and say there will only be 1-2mm left in the center of the block. IE between cyl 2 &3

Will putting a sleeve in crack that amount of material with a .001- .002" interferance fit ??
Cant tell you that ...... But i wouldnt put money on it not cracking, put it that way

[Ben Wilson]

Have you ever actually tried welding cast iron!? It basically has to be cherry red before you can weld it without it cracking under the bead, or next to it. This would be a disaster in a cylinder sleeve!

I was talking about steel sleeves (like RMS was talking about). At the time, I wasn't aware you could get cast iron sleeves.

even if it were a "thicker block" it wouldnt matter as there will still be the same amount of material between the bores because of its design.

If you look at the pics closely you can see the liner through the coolant gallery in some pics. There has been that much machined out.

Look at the picture where the block is cracked - It hasn't cracked between the bores...

[jeffro ra28]

I was talking about steel sleeves (like RMS was talking about). At the time, I wasn't aware you could get cast iron sleeves.

If the boring was done in the correct manner there SHOULD still be virgin cast iron all the way down the bore. If this was taken away, it would be even weaker.

[oldcorollas]

you need some big G-clamps

[30psi 4agte]

If the boring was done in the correct manner there SHOULD still be virgin cast iron all the way down the bore. If this was taken away, it would be even weaker.

Did you see that they have gone through to the coolant gallerys ?

[terryo]

I have sleeved 4A blocks, both std and race ones, but its not a fun job and some blocks end up as scrap. There is a special material that is stronger than the parent cast iron. There is absolutely no point in putting back "standard" cast-iron sleeves. Sleeves are stopped from moving up or down by a machined step at the top or bottom of the bore depending on the block design and you certainly cannot press a sleeve into a water jacket. You need about 1.5mm thickness of parent metal to hold a sleeve properly, so mostly you sleeve blocks back to standard bore size . The stronger sleeve material can be a bit thinner than conventional sleeves, but they still end up about 1.5mm wall thickness. When you grind the top deck flat again after sleeving, you can hardly see where they are, so it does not effect the gasket surface. Most 4A block splitting I have seen is when they are bored beyond 1.5mm. We have plenty of 200hp race engines without any such problems. boosted is a different issue of course, and mostly that relates to deck stability which Toyota motors are not renounded for. In fact, they are quite crappy.

[jeffro ra28]

Did you see that they have gone through to the coolant gallerys ?

Thats the problem.

I will go to work today and take some photo's to show you some of the affects a split bore can have on pistons.