Block sleeves?

[E30_Crazy]

Finally got my hands on a spare M20 to rebuild after my last one let loose. VAC has sleeves for both the S52 and M52/M54 starting at 84mm and up. With the diameter matching up fine, I could have the machine shop cut them down if they are too tall. I plan on using 86mm pistons and a Rotrex supercharger, hence wanting to resleeve with stronger/newer metal. Anyone see any flaws in my thought process, or have suggestions/experience?

[maggspower]

That is going to cost a sh1t load of cash, and gain you nothing. If you are supercharging then that will outweigh the couple of extra cc by far. The super/turbo charger gets rid of all the volumetric efficiency problems you will encounter. It makes a smaller engine behave like a large one.

You want to keep the block as stiff as possible, so keep as much metal in it as possible. A bendy block (yes they do bend) causes sealing problems with the rings and will lose power in the long run.

I would suggest going 84.5mm bore with new custom pistons so you have fresh bores and compression ratio of your choice.

I am building one to this spec now, last seen on a dyno running 505 bhp.

[E30_Crazy]

Will 84.5 still be strong enough to handle boost? The new Rotrex chargers are getting into some pretty high numbers boost wise. IIRC close to, if not on, 20psi.

Since I'll be running an M52B28 crank, I was just seeing if I could safely reach a full 3.0 L engine with sleeves. But if you suggest that 2.8 (slightly more due to .5mm bore) will behave similar to 3.0, then Ill stick with the sleeves already in it.

Thanks for the advice. I will definitely take it into account.

Is your build using a turbo or supercharger?

[maggspower]

Will 84.5 still be strong enough to handle boost? The new Rotrex chargers are getting into some pretty high numbers boost wise. IIRC close to, if not on, 20psi.

Since I'll be running an M52B28 crank, I was just seeing if I could safely reach a full 3.0 L engine with sleeves. But if you suggest that 2.8 (slightly more due to .5mm bore) will behave similar to 3.0, then Ill stick with the sleeves already in it.

Thanks for the advice. I will definitely take it into account.

Is your build using a turbo or supercharger?

The 505 bhp on the engines last incarnation was using the standard pistons so 84mm bore.

An m20 block has no liners its is a solid one piece "block" the holes are machined out, the more you machine out of these holes the weaker the block becomes.

Not a problem for moderate N/A builds with 6000 rev limits. But for high power F/I builds with higher rev limits then you need to keep the block as ridged as possible.

Not only that, you are giving yourself less and less head gasket to seal with, not ideal with F/I. This is why I have the above engine (its a customers) it eats head gaskets. It has a Rotrex supercharger too.

Don't aim too much for specific numbers, 3 litres (you can't with an m52 crank) , 500 brake.......... Just aim to get a good running, strong motor.

[E30_Crazy]

I take it that you are working it to not go through head gaskets then? Not too promising for my case if it's still 84mm and blowing gaskets. What do you plan on doing/recommend me to have done to prevent the same?

Don't see a lot of supercharger builds, and even less with Rotrex. How is it mounted up, if you/the owner don't mind me asking? I don't have PS or AC, so there's two spots to consider. Exhaust side would give a better linear path for air/piping. Just have to consider the heat. Even with an intercooler, you don't want to heat up the charger unnecessarily. And it would be a relief to know that hr found somewhere to order the mount... if not, I have a place that can fab one up, whichever side I choose to mount on.

And yeah, number are all flexible, even if I like to throw them out, haha. A reliable engine is my first priority, after going through my second.

[maggspower]

The problem with the one I have on the workshop is the static compression is too high. Which means it goes well with little lag, but is producing too high cylinder pressures.

So lower static compression, and a Cometic MLS gasket.

I have not built the charger outfit, I am just preping the engine internals to cope with the added stress put upon them.

I will however say, it is of up most importance to follow the Rotrex manual to the letter. In particular, the orientation and relitive hights of each component in the charger system.

You will have to make a custom mount.

[reggid]

heaps of guys running a lot of boost on 85mm bores

[E30_Crazy]

heaps of guys running a lot of boost on 85mm bores

No doubt there. I just want the build to be as strong/reliable as realistically possible. I seem to have bad luck with engines. I've gone through 2 in the E30, and the 5.0 in my Ford has lost compression in a cylinder, and is pushing exhaust and fuel into the oil system, blowing all the seals.

Nonetheless, I appreciate the input, makes me feel a little better about 84.5mm or 85mm bore.

[E30_Crazy]

Maggspower, what are the CR and PSI/Bar numbers that engine was running when blowing head gaskets? And what CR are you planning on making it to not blow them anymore? Just so I have an idea for specs on a set of pistons.

[E30_Crazy]

Maggspower, what are the CR and PSI/Bar numbers that engine was running when blowing head gaskets? And what CR are you planning on making it to not blow them anymore? Just so I have an idea for specs on a set of pistons.

[reggid]

a proper tune is more important than anything, poor tune will kill you always but just lowering the CR wont help much if the tune is still crap....heaps of info on r3v and e30tech forums. lots of turbo guys

[morerevsm3]

as reggid says, it will be detonation blowing the gaskets, drop compression, and/or pull timing or go to E85 fuel. I o-ring the blocks and use stock gasket for FI rather than use cometic gasket, gives a window for bad fuel etc, but is not a substitute for a good tune