Turbo M20 2.8L Stroker w/ 135mm rods

[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.

[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]

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".

[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?

[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.

[ForcedFirebird]

Yes. Head to piston clearance.

[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]

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]

It has upgraded rods as well. Sadly, though, he thought my engines were too expensive, so he purchased a rotating assy elsewhere and it's already pressurizing the crank case after a month of daily driving. I have a feeling the builder set the ring gap too tight since his previous engine (also from same builder) chipped the ring lands. We put a 3.15 from a z3 in it so top of 3rd is 120mph, and boy does it get there quickly. Forgot to mention it does have a t4 back housing and ball bearing journals.

Yes, the intermediate shaft bearings are what the oil pump shaft rides on in the block. They don't press in like standard cam bearings in a pushrod, they need to be pressed in square, then burnished to size as not all pump shafts have equal diameters, and the beatings themselves collapse during installation. Don't forget the needle bearings in the distributor dummy and block.

Use the solder method, yes, simple. Don't even need to be at TDC when you place the head. If you rotate the crank 20° clockwise, all the pistons will be below the deck. As mormal, put the head on the mark, mount it, then you can back the crank to TDC and it will mash your solder. I personally prefer to put the belt on and check them all as I have found many heads that were not heat-straightened before they were shaved and the chambers will vary on the quench band. These ~30yr old heads have gone through a lot lol.

Well that sucks about the rings, do you have a specific gap that should be used for this application? Do you have any links on how to proper install the intermediate shaft bearings?

[ForcedFirebird]

"Use the solder method, yes, simple. Don't even need to be at TDC when you place the head. "

And scrap everything.

Yes, prostate, that is correct except for the scrap part. I don't know about you, but every in-line engine I worked on the last 22 years, you set number one to TDC, then rotate the crank an extra 20° and all of your Pistons will be far below the deck. The only way the valves would touch them would be if you took the retainer off and drop them through the guide.

[apostate]

"Use the solder method, yes, simple. Don't even need to be at TDC when you place the head. "

And scrap everything.

[ForcedFirebird]

It has upgraded rods as well. Sadly, though, he thought my engines were too expensive, so he purchased a rotating assy elsewhere and it's already pressurizing the crank case after a month of daily driving. I have a feeling the builder set the ring gap too tight since his previous engine (also from same builder) chipped the ring lands. We put a 3.15 from a z3 in it so top of 3rd is 120mph, and boy does it get there quickly. Forgot to mention it does have a t4 back housing and ball bearing journals.

Yes, the intermediate shaft bearings are what the oil pump shaft rides on in the block. They don't press in like standard cam bearings in a pushrod, they need to be pressed in square, then burnished to size as not all pump shafts have equal diameters, and the beatings themselves collapse during installation. Don't forget the needle bearings in the distributor dummy and block.

Use the solder method, yes, simple. Don't even need to be at TDC when you place the head. If you rotate the crank 20° clockwise, all the pistons will be below the deck. As mormal, put the head on the mark, mount it, then you can back the crank to TDC and it will mash your solder. I personally prefer to put the belt on and check them all as I have found many heads that were not heat-straightened before they were shaved and the chambers will vary on the quench band. These ~30yr old heads have gone through a lot lol.

[apostate]

lol

digger and forcedfirebird talking about built m20s is nonsense?

GTFO brah

Absolute nonsense.
Believe.
Goodbye.

[SLEEPYDUB]

A basic stock b25 rebuild with factory matching forged pistons, Bimmerheads dual pattern regrind, and a p6267 just pulled 518whp/550tq at 19psi locally, so don't sweat obtaining those numbers with your stroker.

As far as quench, with a boosted engine, it is more important than N/A as it reduces hot spots and potential detonation. To get a good quench, square and deck the block, bore it, replace the intermediate shaft bearings (be cautions and make sure your machinist understands the procedure). Then you will fit your pistons/crank/rods. Finally you will want to use a sacrificial head gasket (only thing VR gasket is good for lol) and torque it down with used bolts, but before mounting it, place a pieces of solder on the angle part of the piston. Some people like to use clay, but I find the solder is easier to measure (not a bad idea to also do the piston to valve clearance at this time). If the solder is more than .037" by a good margin, shave the head to match.

For pistons, just use the factory style with the raised wrist pin to compensate for the longer rods, and factory dome, you won't need anything special. Many piston MFGR's already have the files to avoid a custom piston fee.

Did you have a MFGR in mind already?

EDIT: Missed the part about compression. Go with as much as your tuner feels comfortable with, but I haven't had an issue going as high as 10:1. Local here has an e39 m5 with stock compression (never opened, 11:1), and is making 780whp @1bar with only meth for charge cooling (no FMIC).

Wow that is impressive for an otherwise stock B25. I was running 25psi on my B25 and my B27 on a 6266 and E85 using the Bimmerheards 280/274 dual pattern, Id like to assume I made close to that same power. My engine held the power fine, but it let go while riding the limiter, so I'm assuming that is the reason for the damage...I hope...

As for quench, my machinist shouldn't have a problem with squaring, decking, and boring the block.

As for the intermediate shaft bearings, these are the ones that the oil pump shaft sets into, and where the snout of the crank and the rear of the crank set into? Is this the part you said to make sure the machinist understands the procedure?

So when I fit the rotating assembly, I need to go ahead and buy a VR gasket just to use for this procedure, set the cam and bottom end to TDC, torque the head down with the solder, and that pinch in the solder will give me my measurement. I think we can handle that part.

Piston wise, I've had good luck with JE and was going to see what they have to offer. I am also open to suggestions on MFGR and CR.

Thanks again

[MrBurgundy]

Have a good time.
I will get out of the way, so you can discuss all this nonsense you discuss anyways in this thread.

By the way:
Real info is on the 402 meter strip.

lol

digger and forcedfirebird talking about built m20s is nonsense?

GTFO brah