S50B30US NA rebuild for track car

[bimmerboy318]

The only thing that I've contested my machinist on is that he wanted to take .010" off the deck of the block. I was worried about piston to valve clearance, further increasing CR, more slack in the chain, etc. .010 was already removed from the head so .010 off the block is .020" total. With the stock head gasket CR might rise beyond 93 octane.

Would .020 be an issue seeing as I used 11.5:1 pistons? I guess the tuner could fix that and/or retard the cams. How does one retard the cams anyways? Move it a tooth on the gear or just use the slop in the slots.

[bluptgm3]

The VaNos/chains are not an issue. Accounted for in the VaNos set-up steps.


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[ScotcH]

20 thou would not be an issue. But the block almost never needs work, unless there is rust pitting or some damage. I would just have him lick it ... if that, unless it has issues, but unlikely.

[Allona]

The only thing that I've contested my machinist on is that he wanted to take .010" off the deck of the block. I was worried about piston to valve clearance, further increasing CR, more slack in the chain, etc. .010 was already removed from the head so .010 off the block is .020" total. With the stock head gasket CR might rise beyond 93 octane.

Would .020 be an issue seeing as I used 11.5:1 pistons? I guess the tuner could fix that and/or retard the cams. How does one retard the cams anyways? Move it a tooth on the gear or just use the slop in the slots.

Going from memory .020” will get you another .5-.6 or so increase in static compression, you will get noticeable slack but the tensioner will keep it in check. I have a similar situation in my race engine.

[Allona]

Glad I found this thread, a lot of good information shared. I am also in the process of doing an S50 race engine build. I would like to get feedback from you guys on max bore.

Race class rules allow me up to 1mm overbore. I just ordered custom pistons for 87mm bore to take advantage of rules and use the max allowed, it all adds up, but I also want a reliable build. I have done several 2.8L builds, and all have been bullet proof, but this is my first 3.0L.

I had been undecided on bore and finally decided to go with 87mm, that seemed to be the consensus in the BF including the turbo guys. I also checked with a local BMW mechanic and he told me that 87mm was ok as Iong as I used a Cometic head gasket. I still have time to change the bore on my custom piston order, so I would like feedback from the group. I just read in this thread not to go beyond 86.5.....Is this true even if I use a Cometic gasket? I don’t want to open up the engine unless it blows up

I plan to use the aggressive cams.

Hoping to get a killer power band near 300hp like ScotcH posted!

Am I looking for trouble with an 87mm bore on this build?

[bimmerboy318]

Paraphrasing what others have told me and it makes sense. The reason to go with 86.5 pistons is to be able to use the stock head gasket. The stock head gasket is the same for S50 with 86mm std bore and also S52 with 86.4mm std bore. However, going with a cometic gasket allows 87mm bore.

Please post a photo of your wiseco’s when you receive. The wiseco’s I’ve seen were 11.5:1 but were a flat piston instead of a dish piston. Not really sure the difference but curious if this is the case. JE and Wiseco and others are owned by the same company so interesting if they are different.

[Allona]

Thanks for the response on the bore limit, makes sense. Wiseco will send my pistons in 6-8 wks, but they have promised to send me a 3D diagram in a week which I will share.

[Talperian]

Thanks for the response on the bore limit, makes sense. Wiseco will send my pistons in 6-8 wks, but they have promised to send me a 3D diagram in a week which I will share.

Allona, I would recommend a good ATI damper from GDM. If your spinning that high with a cam that big, I would also recommend a decent port on the intake. There is a CNC port in progress with a bunch of development time into it by a renowned porter, should be complete in a couple of months. Might be worth looking into.

As I'm sure you know, you will also need upgraded valvetrain and solid lifters to use that particular camshaft profile.

The way I see it, after fixing the known bottom end issues. Is that the flow potential of the head is the next big item to work on.

Message me if you need more information on the damper, etc...

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[aeronaut]

I went through the same set of questions re head and block refinish. As stated, 0.02" total is about 0.5% increase in static compression ratio, very likely less dynamic.
I had some light pitting in a few areas of the block, but far away from the headgasket seal rings around the cylinders. My machinist said, no worries. I measured the flatness of the block with a machinists straight edge, and all looked good. 1 full season on the engine and so far engine is behaving as it should (stock pistons).

[ScotcH]

We stuck with the 86.5mm bore, just didn't feel the need for the extra .5mm, and the cometics have been a bit of a hit and miss. They say can be reused, but really, they should not be ... and they're not cheap (but not horrible either).

The ATI damper is a great idea, though the s50 crank is much better balance than the s52.

- - - Updated - - -

I have ordered 12:1 custom Wiseco pistons, for 140mm rods.

I plan to use the most aggressive cams available, used Catcam 290 with 12.5mm specs for valve pocket on the piston order.

I use race gas and was planning to spin it to 8,000 rpms. Hoping to get a killer power band near 300hp like ScotcH posted!

Am I looking for trouble with an 87mm bore on this build?

I'm curious to see the piston design as well. The 140mm rods would make for a really good rod ratio, and you could probably spin it even beyond 8000, and with the huge cams, it should make power up there. I didn't think it was possible to get the 140mm rods in there, it would put the pin too high in the piston. Maybe that was with the s52/m54 cranks ... we have 137mmm rods on our m54 builds, and the pins are pretty close to the top.

[Talperian]

A little side note, I got this to fit the other day. Should be really fun, I plan on comparing m50 manifold, s54 itbs with stock airbox, and csl airbox on the dyno here shortly

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[aeronaut]

Cool!!! Interested in the dyno results, that'll be fun.

[ScotcH]

I'm sure that CSL box won't make any more power. Sell it to me for cheap please.

[Talperian]

I'm sure that CSL box won't make any more power. Sell it to me for cheap please.

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[Allona]

Allona, I would recommend a good ATI damper from GDM. If your spinning that high with a cam that big, I would also recommend a decent port on the intake. There is a CNC port in progress with a bunch of development time into it by a renowned porter, should be complete in a couple of months. Might be worth looking into.

As I'm sure you know, you will also need upgraded valvetrain and solid lifters to use that particular camshaft profile.

The way I see it, after fixing the known bottom end issues. Is that the flow potential of the head is the next big item to work on.

Message me if you need more information on the damper, etc...

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thanks for the recommendations. I will definetivley PM you about the ATI damper and port work.

Agree on the valvetrain, I have solid lifters on my current engine, it takes a lot of patience to set the cam lash corrrectly! I am using fresh OEM springs with a S50 reground cams . Very happy with this set-up, getting really good performance out of it, but I cannot add any more cam because of the OEM pistons.

[ScotcH]

thanks for the recommendations. I will definetivley PM you about the ATI damper and port work.

Agree on the valvetrain, I have solid lifters on my current engine, it take a lot of patience to set the cam lash corrrectly! I am using fresh OEM springs with a S50 reground cams . Very happy with this set-up, getting really good performance out of it, but I cannot add any more cam because of the OEM pistons. Already have a set of 80lbs Supertech springs waiting to get to work on the new build.

Just FYI ... you don't HAVE to use solid lifters. We have hydraulics on ours (M50 NV, so larger diameter). For sure the solid would be better optimized and lighter, but it does work Spring on the other hand, definitely.

[Allona]

We stuck with the 86.5mm bore, just didn't feel the need for the extra .5mm, and the cometics have been a bit of a hit and miss. They say can be reused, but really, they should not be ... and they're not cheap (but not horrible either).

ScoTcH, so you are using the OEM gasket on 86.5 mm bored engines? even on the high compression 307hp engine that you posted the dyno chart? (BTW I am very impressed with the power band on that engine) Does it eventually break down or it is not an issue at all?

I still have time to call Wiseco and make changes on my order....

[GG///M3]

I'm sure that CSL box won't make any more power. Sell it to me for cheap please.

Yes yes, or to me.

[Allona]

I'm curious to see the piston design as well. The 140mm rods would make for a really good rod ratio, and you could probably spin it even beyond 8000, and with the huge cams, it should make power up there. I didn't think it was possible to get the 140mm rods in there, it would put the pin too high in the piston. Maybe that was with the s52/m54 cranks ... we have 137mmm rods on our m54 builds, and the pins are pretty close to the top.

Yes thats the idea, improve the rod ratio so I can spin it up there. I had used M54b25 pistons on a prior 2.8 build and these had a compression height of 28.3mm, about .008" down from the block deck at TDC. I was using 140mm rods and 84mm crank. So with the S50 crank stroke of 85.8 the compression height on the new pistons only needs to come down .9mm compared to that prior build. It will be tight fitting the pin, but doable. Let's see what Wiseco come back with.

[Talperian]

Yes thats the idea, improve the rod ratio so I can spin it up there. I had used M54b25 pistons on a prior 2.8 build and these had a compression height of 28.3mm, about .008" down from the block deck at TDC. I was using 140mm rods and 84mm crank. So with the S50 crank stroke of 85.8 the compression height on the new pistons only needs to come down .9mm compared to that prior build. The new pistons should have comp height of about 27.4mm, and a dish top designed to get me the 12:1 compression. I am also specifying thinner rings used in the more modern BMW pistons to help with the short compression height. It will be tight fitting the pin, but doable. Let's see what Wiseco come back with.

Are you using a 140mm rod with 22mm pin? I would honestly be less concerned about rod/stroke ratio and more concerned with reciprocating mass, inertial loads to me is what will help with high rpm durability.

There is a balance to consider with ring stability and rod length. The s54 has a rod/stroke ratio of 1.53 and spins to 8000rpm, for example.

Just some food for thought.

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[Allona]

Are you using a 140mm rod with 22mm pin? I would honestly be less concerned about rod/stroke ratio and more concerned with reciprocating mass, inertial loads to me is what will help with high rpm durability.

There is a balance to consider with ring stability and rod length. The s54 has a rod/stroke ratio of 1.53 and spins to 8000rpm, for example.

Just some food for thought.

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Agree,Yes on the 22mm pin. I am trying to keep reciprocating mass as low as possible. Rods I am using are similar to the Eagle/Molnar rods, so lighter than OEM. I have specified thinner wall and shorter wrist pin, and asked Wiseco to keep the piston as light as possible....we will see. On the ring thickness I have used Totalseal's recommendation....I have had good luck with them on prior builds. I am not an expert by any means, just sharing what I have in process.

[Talperian]

Agree,Yes on the 22mm pin. I am trying to keep reciprocating mass as low as possible. Rods I am using are similar to the Eagle/Molnar rods, so lighter than OEM. I have specified thinner wall and shorter wrist pin, and asked Wiseco to keep the piston as light as possible....we will see. On the ring thickness I have used Totalseal's recommendation....I have had good luck with them on prior builds. I am not an expert by any means, just sharing what I have in process.

Awesome! Sounds like you have a good plan!

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[ScotcH]

I think the next time I build one of these, I'll use the 137mm rods, with 21mm pin. They are off the shelf Honda rods, and we used them in our M54 builds with custom 13.5:1 JE pistons. I think a nice 12.5:1 custom set with teh 137mm in an 86.5mm s52 would be very nice

[GG///M3]

I think the next time I build one of these, I'll use the 137mm rods, with 21mm pin. They are off the shelf Honda rods, and we used them in our M54 builds with custom 13.5:1 JE pistons. I think a nice 12.5:1 custom set with teh 137mm in an 86.5mm s52 would be very nice

When it comes time for me to do an engine building I’ll be shooting you a pm lol

[Talperian]

I think the next time I build one of these, I'll use the 137mm rods, with 21mm pin. They are off the shelf Honda rods, and we used them in our M54 builds with custom 13.5:1 JE pistons. I think a nice 12.5:1 custom set with teh 137mm in an 86.5mm s52 would be very nice

I like this approach.

I have (2) builds I'm starting, both using 138mm Honda rods with 21mm pins. One is a 11.5:1 S52 for a street car, going in an e30 (for a client).

The other is for my road racecar "race engine", 89.6mm crank, 14:1 87mm bore (E85), CNC-ported head, 13.5mm lift cams, etc...

The nice thing is for an NA engine you can use a nice lightweight 70-80g 21mm pin. Coupled with a 270-280g piston, its a dramatic difference in reciprocating mass.

Here's a pic of the s54, honda 138mm, and s52 135mm. From top to bottom, for comparison.

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