Turbo M20 2.8L Stroker w/ 135mm rods

[ForcedFirebird]

Hit up google for the intermediate shaft. Peerless (member at e30tech) did a write-up I believe.

N/A I put them at .013" top .016" second, boosted .021" top and .023" second. With boost, err on the large side.

I read a HotRod Magazine article a long time ago (remember magazines? lol) where they tested ring gap on an engine dyno for power, oil consumption and leak down. They followed the multiplication rule, ran it, then kept opening the rings, test, open rings, test, until they were stupid large gaps (IIRC 3x the norm). The final test consumed marginally more than the first and the power didn't change much. That was on a solid state dyno and don't recall if they did engine braking to crate extra vacuum etc during the test. I have never personally dyno'd ring gaps, just follow the standard rules based on bore size.

Grumpy went into detail on his page. http://garage.grumpysperformance.com...ing-gaps.2837/

[SLEEPYDUB]

If the solder is more than .037" by a good margin, shave the head to match.

So are you saying the "quench" needs to be 0.037"?

[ForcedFirebird]

Yes. Head to piston clearance.

[apostate]

If the solder is more than .037" by a good margin, shave the head to match.

Another "great" idea.
@EngineBuildingBird -> as already mentioned in this thread (by digger) it is much more wise to use a custom thickness head gasket for these "corrections". I see that you have a special appetite for milling, shaving and decking but these are irreversible (and costly) operations that make the engine unusable for any other purpose. Furthermore, the chance of a mistake made by the user or the machine shop is also irreversible while the chance of choosing the wrong gasket thickness is expensive but remediable. Finally, it is highly probable that a block and a head that are not decked, milled or shaved will retain a much higher demand and selling price, especially the rare they get.

[SLEEPYDUB]

Thank you ForcedFirebird, you've been a big help.

My machinist is a long time V8 and domestic engine builder, he is the most qualified person in my area for any kind of engine machine work with the best reputation. This is however, his first BMW engine, although I do believe that he is completely competent in his work.

With that being said, are there any key notes that I need to bring up to him? Ie; Bearing clearance, deck height, etc? I see that the oil pump intermediate shaft bearing needs to be at about 0.015" clearance for optimal oil pressure, I see the rings need to be gapped 0.021 and 0.023. Am I missing anything else? Any other tolerances that need to be brought up?

[ForcedFirebird]

Another "great" idea.
@EngineBuildingBird -> as already mentioned in this thread (by digger) it is much more wise to use a custom thickness head gasket for these "corrections". I see that you have a special appetite for milling, shaving and decking but these are irreversible (and costly) operations that make the engine unusable for any other purpose. Furthermore, the chance of a mistake made by the user or the machine shop is also irreversible while the chance of choosing the wrong gasket thickness is expensive but remediable. Finally, it is highly probable that a block and a head that are not decked, milled or shaved will retain a much higher demand and selling price, especially the rare they get.

LOL! Are m20's made of silver in Guiana? Built properly, they are going to last another 30yr, so it's not like they are going in the garbage. So, you go build your m20 the way you like, put it on the dyno (or 405), then come back and show how wrong we are doing things here in "America".

[digger]

Another "great" idea.
@EngineBuildingBird -> as already mentioned in this thread (by digger) it is much more wise to use a custom thickness head gasket for these "corrections". I see that you have a special appetite for milling, shaving and decking but these are irreversible (and costly) operations that make the engine unusable for any other purpose. Furthermore, the chance of a mistake made by the user or the machine shop is also irreversible while the chance of choosing the wrong gasket thickness is expensive but remediable. Finally, it is highly probable that a block and a head that are not decked, milled or shaved will retain a much higher demand and selling price, especially the rare they get.

He's using solder to check the piston to head Squish band clearance during mock up.

You can still get a custom set of 3.1l Pistons 135mm Rod with a block decked 0.5mm from previous adventures. Note that MM use a 138mm rod with 89.6mm stroke work out the compression height on that

[ForcedFirebird]

Thank you ForcedFirebird, you've been a big help.

My machinist is a long time V8 and domestic engine builder, he is the most qualified person in my area for any kind of engine machine work with the best reputation. This is however, his first BMW engine, although I do believe that he is completely competent in his work.

With that being said, are there any key notes that I need to bring up to him? Ie; Bearing clearance, deck height, etc? I see that the oil pump intermediate shaft bearing needs to be at about 0.015" clearance for optimal oil pressure, I see the rings need to be gapped 0.021 and 0.023. Am I missing anything else? Any other tolerances that need to be brought up?

Are you planning on upgrading the main cap fasteners? If so, they will need to be align honed - people think they don't need to, but the bore does measurably distort. Main bearings set to .002" and rods .0015, .005" thrust.

Make sure you have the pistons before he bores, as each MFGR will have a clearance standard based on material.

[ForcedFirebird]

He's using solder to check the piston to head Squish band clearance during mock up.

You can still get a custom set of 3.1l Pistons 135mm Rod with a block decked 0.5mm from previous adventures. Note that MM use a 138mm rod with 89.6mm stroke work out the compression height on that

Not to mention BMW built machining into the design for future rebuilds. I don't do the full .5mm on the budget 2.8's, ~2.5mm (.010" to my tooling) which leaves the block still within factory rebuild limits.

If you purchase a reman from BMW, I can't see them NOT decking both the block and head, it's standard rebuild procedure.

[apostate]

Yeah.
Could you quote an offer from MM for a block decked 0.5 mm?
No.
It is hard enough (and expensive) to get pistons that will work with 89.6 mm crank and 135 rods.
Get into the real world.
EngineBuildingBird will tell you that through all these years of engine building of his, he will deck the block and the head to achieve CR or quench.
I admire his reputation over this forum but sometimes you have to go with commonsense.

[SLEEPYDUB]

Are you planning on upgrading the main cap fasteners? If so, they will need to be align honed - people think they don't need to, but the bore does measurably distort. Main bearings set to .002" and rods .0015, .005" thrust.

Make sure you have the pistons before he bores, as each MFGR will have a clearance standard based on material.

I am using ARP Main Studs. When you say it will need to be align honed, what exactly needs honed? The bore of the mains where the crank sets in? Sorry for the noob questions =(

As for needing the pistons before he bores the cylinder, I was under the assumption that I need him to tell me what size bore I need first? Basically to determine if the engine even needs to be bored out? I am trying to stick with stock size bore, so what is the proper sequence of events here?

[apostate]

Sticking with the stock size bore is a lottery.
Wait... EngineBuildingBird will say the final word, of course. ;)

[digger]

Yeah.
Could you quote an offer from MM for a block decked 0.5 mm?
No.
It is hard enough (and expensive) to get pistons that will work with 89.6 mm crank and 135 rods.
Get into the real world.
EngineBuildingBird will tell you that through all these years of engine building of his, he will deck the block and the head to achieve CR or quench.
I admire his reputation over this forum but sometimes you have to go with commonsense.

It's common sense of you take say 0.5mm from the block then you are going to be stretched slighty further to get the ring pack within the compression height avoiding the pin and valve reliefs. Most use 135mm rods so its not a big deal in the real world and it's not a show stopper at that point. A thicker gasket is fine to compensate, though not ideal on turbo engine especially is max effort is required. You can actually design a 3.1L piston with 135mm rod with oil ring not into the oil ring if you want.

[digger]

I am using ARP Main Studs. When you say it will need to be align honed, what exactly needs honed? The bore of the mains where the crank sets in? Sorry for the noob questions =(

As for needing the pistons before he bores the cylinder, I was under the assumption that I need him to tell me what size bore I need first? Basically to determine if the engine even needs to be bored out? I am trying to stick with stock size bore, so what is the proper sequence of events here?

He needs to tell you how much he needs to remove to get the bores good. I'd just order 85mm that's enough meat to true it up to keep it simple

[ForcedFirebird]

Without question bore it at least .25mm, but .5 is more common, +1 gives you matching gasket size to bore, which is great to avoid edges and hot spots. I have had blocks measure out for reuse of stock replacement pistons after deglaze, but no quality machinist will hone a used block the extra few thousandths for forged replacements. The bores will not be round. Don't forget to rent a torque plate, your local v8 shop probably won't have an m20 setup. These long siamese engines will move when the head is bolted.