Marcus it looks like with 79mm youll have the following measurements

start of bore 1 wall will be 4mm (5.5mm original as in you pics)
siamesed 1 and 2 will be 4mm (7mm original)
while the midle bores will be 3mm each (4.5mm original)
and all side wall around 4.5mm which is where the stress is

Sounds like a 280hp A series with 79mm is going to be perfect!
The dyno figures DDgonzales posted earlier if they are yours? means
your old setup had the most power at 4000rpm and tapered off?
What turbo was it you used if that was your beast?

I´m amazed by how popular this thread is, it feels good that you guys haven´t abandoned the A-engine yet! In Finland it´s impossible to build a street leagle Cherry or 1200 with ca18 or sr20 engine so we have to stick with the old A-engine!

I will take the engine parts to my machinist and ask if the wet sleeve is an option for me, I can post his comments later. I think that a arp-bolts and a bearing brace is a must when using sleeves, especially in high rev engine! Oil nozzles under the pistons is also a good investment, a bloke here in Finland has mounted nozzles from a Bmw in his A-engine, the nozzles cost 12€ each.

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I have made the same conclusion, 79mm is not a problemeven in a boosted engine, and now I understand why there is 80mm headgaskets available for N/A setups.

I used a tiny IHI RHB5 turbo when i went on the dyno, that´s why hp drops of after 4000rpm! I can put up a vid on the youtube if you wish so!?

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I agree full bearing brace would be needed with arp bolts

If you go wet sleeve and want to remain 79mm there are renault 16/17/18
cars with the 807,843 and 841 engine that have the 78 and 79mm sleeves.
These sleeves are often boosted after 300+ thousand kms with a re-hone
or 1mm overbore. You should be able to get them for cheap.
I used to be able to get these engines easily for 80aud but havent seen
the mentioned rens for about a year now at wrecking yards.

Would love a vid of the beast with the rb5, Just love the thought of
something so responsive to frighten all those big capacity sheep :)

The pic below shows that the offset will have to go towards the
one side of the block also to avoid the camshaft area
essentially giving a tdc at perhaps 2-5 degrees much like on
modern engines where combustion occurs on the downstroke
past crankshaft centre.

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Here is a vid of one of my dynosessions as requested, hope you enjoy!

http://www.youtube.com/watch?v=49GELRO_yd8

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Sometimes I'm an idiot - I only just realised (and it should be obvious to me considering your username!) what this engine is in. Shooting for 280hp at the FRONT wheels - man that's my kind of crazy.

Is the bearing brace a girdle that goes across the bearing caps? Good idea I say, how would you go about making it? I made a rough one up a while ago but had a few clearance issues.

Chris

Nice job with the block Marcus, that helps me a lot with my wet sleeve project.

Gary, what do you think 83mm ca18de pistons will fit?

Yes Chris but would be good to use existing ca18de, L series
or Z series bolts. Something a tad longer with same thread
will save from using custom Arp bolts.

Anyway anyone knows the thread pitch and length?

Marcus knows he is crazy, lucky he has cold weather to slow him down :)

to make a stud girdle, you basically just get a sheet of approx 10mm thick steel, and mill out the 'slots' to make clearance for each rod/crank/counterweight, and get longer than standard main studs.

you then machine down 'top' of the main caps if necessary - to make them flat across the top, so the girdle can bolt down evenly across the cap (and this actually makes it stronger as there is more support of the main cap with the girdle on top. You don't just machine the main caps as is, as theoretically some could be a little taller than others (since for a std application all that mattered was that the holes/crank tunnel were all aligned . So you mill the whole lot to get them even so the girdle fits

Obviously the holes drilled through for the studs to go through on the girdle - do them slowly and accurately so that you keep them a firm fit (not too tight that it jams or sticks, but just enough room to allow it to be fitted)




sorry for using a pic of an inferior motor :) (the holden red 6) and further to that, although I've done a bunch of holdens over the years, this was not mine, I actually got the picture from someone else on the net years ago (and I can't remember who it was anymore!)

Anyway that gives the basic layout.




Obviously with stuff like this, you might have to make the front or rear one a little narrower to fit, or you might even have to make a custom sump (sometimes you can get lucky and get 2 stock factory sumps and cut them and join them back together to make more clearance, but you also have to find (by trial and error) whether you can get that to fit inside your engine bay/cross member.

Still, if you're chasing 280bhp, that might just be the way you have to go.

There is another 'stage' you can go to with stud girdles. You basically still do the one like in these pictures, but then you add 'legs' that go from the 'boundary' of the main girdle, and reach out and up to two new rails that go where the sump bolts on to, and you then use countersunk socket headed capscrews (bolts using an 'allen key' to tighten them, and a countersunk head so the bolt will fit flat with the 'new' sump rails. that ties the mains to the outside of the block as well (this is actually more important on holdens, potentially, as they tend to break the mains around the area where the cam is, as it isn't as well supported as the other side).

I don't think that this would be necessary - a 'regular' or standard main stud girdle should do just fine. But if you did go to wet sleeves, then I'd definitely be suggesting the one that goes out to the sump rails as well. That actually ends up taking a few hours to build right, so it won't be a super cheap solution, but you might just need it with wet sleeves on an A block.

there's an old story or joke about a young boy asking his dad 'how do they know what signs to put on bridges that say 'maximum vehicle load 30 tons' or whatever weight. And the father says something as a joke 'well son, they just build the bridge, and then drive heavier and heavier trucks over it until it breaks and then they rebuild the bridge and know the right limit.' Now of course that's mostly a joke, but I think in this case, you are getting to the stage where you might just have to test the limitations of the block etc, and might face engine damage that can only be prevented with a stud girdle (of whichever type)