Jelmer's 538iS *sold*

[wkohler]

If you religiously adjust your rockers for a few tanks (Order 6-8 cam cover gaskets and go to town after every fill up), you can do cam for like $800 US. And to raise compression, you can get the shop to cut a bit extra off the head and run stock thickness gasket. It should be able to raise it at least 0.5 CR before you need to worry about clearance. And at that point, you'd just be running 91 octane equivalent with a tiny bit more ignition.

This is an S38B38, which you obviously know nothing about. It's not a Chevy 350. If I had a question about an S38B38, I'd ask Jelmer.

[Jelmer538i]

@Gazm3: I can get 102ron in a town pretty close to me so that is what i'm going to use only in the future. I will consider raising the compression.

@Owndapwn: ??!?

@Chris: x2

[Owndapwn]

This is an S38B38, which you obviously know nothing about. It's not a Chevy 350. If I had a question about an S38B38, I'd ask Jelmer.

Just checked the price of S38 cams. Thought the $2-3k was for machine work to fit new cams, not $2800 for two cams with no shims or springs..

[gazm3]

I would just change to a larger intake cam.
The b38 exhaust cam will be fine for well over 400bhp. You will probably find getting the Schrick cams cheaper ex Germany than locally. I'd also slot the cam wheels so u can dial them in to optimum. It makes a good case for changed pistons with the relief pockets so u don't run into clerance problems.

With that great head big 90mm stroke and large throttle bodies, going for high 11's or very low 12's in the comp and a higher lift intake cam, you would easily make 420bhp+ Only have to rev it to the low 7's and have reasonably streetable manners. The high comp will give you great response everywhere in the rev range and the big intake cam lift will make the power. If inning on the ron102 u can feed lots of timing into it. You could make a switchable map when running the ron95 with reduced timing and slightly richer but you would lose plenty of power.
Most modern engine management systems(aftermarket) will allow you to run a flex fuel sensor which works very well so u can have a blended fuel octane and it will map it according to the final octane number

Good luck, it's exciting building an s38 as it's basically a race engine detuned for road use

[Jelmer538i]

What about stock compresssion and a bigger intake only?

[gazm3]

Definetly worth going for a bigger intake cam even on stock comp but if you go big with the cam you may run into piston to valve clearance issues. It would be fairly straight forward for a machinist to grind in some small relief pockets into the pistons.

The higher the compression the better the low to midrange power will be. Bigger cams on stock compression make them a little like a 2 stroke. It will make moderate power (around what u had before or slighly less) then at 4500 it will be like some one rear ended you. Even as little as 11:1 it will feel like someone rear ended you at 2500. High comp engines give that glorious angry character and that insane throttle response where u just touch the throttle even at low revs and the engine just launches forward. It also gives better fuel economy you get more 'bang' per unit of fuel.

You could squeeze some extra comp out of the engine with using a thin 40thou MLS head gasket (stock is 70 thou for memory) and perhaps take off 20-30thou off the head. You may be ok with te std cams but with a larger intake would definetly need relief cuts.

I can understand the financial side if the build. I have 4 builds going and house renovations so it ain't easy.

With the std s38b38 if u gave it 11:1 comp it would probably make 20-25bhp more but it would have power everywhere.
If u gave it a bigger cam u may make 40-50bhp but lose a little down low but it would scream at the topend.
If u done the intake cam and 11:1+ comp it would make say 70 bhp more and have power everywhere with an even more topend rush.

[Jelmer538i]

What cam would you suggest with stock compression:

http://www.bar-tek-tuning.com/Sportnock ... /index.htm
https://www.pureperformancemotorsport.c ... hafts.html

[gazm3]

Hey Jelmer
choosing a cam is tricky, but there is not that much choice. Im not an engine guy per se, but I have an engineering background and have researched and lots of long discussion with my engine builder (normally with alcohol)


The OEM cam has 264deg duration and 10.7mm valve lift with OEM compression being (higher than I thought 10.5:1)

Schrick only now seem to do the 280, which has 280deg, 11.0mm lift, and 2.7mm lift @TDC
it seems they used to do a 284, based on the S14 cam, but its not officially avaliable.

CatCams supply more variety (PPM in Australia do exactly same cams - which is probably where Ill get mine from.)
291deg, 10.75mm, with 3.05mm@TDC
293deg, 12.45mm with 4.00mm@TDC
299deg, 13.25mm with 4.45mm@TDC
303deg 13,45mm with 5.10mm@TDC

The key numbers to look for are the lift, and the lift @ TDC. Lets say the B38 head flows 309cfm @ 12.7mm lift, which Matt has tested on the flow bench, equivalent to 470bhp @ around high 7k rpm.

A simplistic view would be to assign a valve lift per hp based on the flow bench results. The lift VS power is most likely not linear but for the exercise its a reasonable guide. All going well and fully optimised (good exhaust, tune, no cats, no air meter, etc etc), with the OEM head, with a guide to comp and fuel and rpm needed:
OEM cam 395bhp, 10-11.4:1, RON95++, 7000rpm
Schrick280 407bhp, 10.5-12:1, RON98+, 7250rpm
Cat291 397bhp, 10.5-12:1+, RON98+, 7250rpm
Cat293 460bhp, 11.8+, RON98+ 7750rpm,
Cat299 490bhp, 11.8+, RON100+ 8000rpm
Cat303 497bhp. 12.8:1+ E85, >8000rpm

Its only a very rough simplistic guide and suitable for b38 head. Obviously for b35,b36 and M88/3 head would need some head porting and oversize valves, and the smaller throttle bodies would somewhat restrict power.

The bigger the cam the more compremise, and more strain on the valvetrain. One of the important items is valve lift at TDC gives an insight into how grumpy a cam will be, where lifts in the 2's are pretty streetable, where in the 5's are really race only.

The Schrick 280 seems to be popular and pretty streetable, with a reasonable increase in lift. It will work with the std comp of 10.5:1, or with a thinner MLS gasket most likely still be ok with piston to valve clearance, and give a nice lift in comp close to 11:1. You could slot the cam wheels to optimally dial in the cams to get good effect, and you would only need the intake cam. The cat 291 is not really much bigger than OEM in lift, it would have better top end than OEM, but you could just slot the cam wheels and dial more duration into the OEM cam so probably not worth considering over OEM for the cost.

I was looking at the catcams 293 or 299, but I already have custom pistons with valve relief pockets, and will run around 12:1 comp (initially). I need both intake and exhaust cams as have M88 that only has 10mm lift with OEM. You could run the cat293 with the OEM exhaust cam, but at very minimum, you would need valve relief pockets milled into the std pistons, but compression even with a thin gasket probably wouldn't be high enough to make it streetable and take the full advantage of the cat293, and your tight clearances would mean you may not be able to dial in the cam to optimize it. The cat293 would make sensational power on 12:1, well over 400, especially with those big throttle bodies, and nice OEM tuned length headers, on high 11's low 12's comp, it would be pretty streetable, would idle a little grumpily but once off idle it would be great. It would also need upgraded springs/retainers (which you should do for all cams).

Sorry for the long winded explanation, but I thought its better at explaining (in laymans terms) why to use a certain cam rather than just saying use the schrick 280 if std pistons or the cat293 with custom high comp pistons.

[Jelmer538i]

Thanks! I really appreciate your input!

Exhaust wise I will do the next: Cut both the M88/3 headers at the point where they will be 2,5" and go 2 x 2,5" all the way back.
Intake wise, I have 2 carbon airboxes, a smaller one and a big one. I'm sure the big one is the one to use here.

Ill have the cam sprockets machined to make them adjustable, a friend of mine is engineer that is capable of this.
Another friend (the one that did my brothers S38 turbo) will help me with the engine and told me that we need to see how much the head can be milled.

[Jelmer538i]

@Gazm3: This is what I found about Schrick 280's on M5board.com:

I called Schrick and VAC about camshaft choices. While schrick only sells 280/280 for the S38, they also said the 272/272 for the M88 will work also, if the circle diameter is compensated.

VAC sells schrick and catcams, the rep said the schrick 280/280 is like adding 38 cam gears. If you added the gears you wouldn't need the 280 cams, and vice versa. The catcams he recommended 291/291, and is tad bit more aggressive but is a step up from the schrick 280's. It all depends on what the motor is used for.

Any thoughts??

[gazm3]

Both the cat291 and the Schrick 280 are not much bigger than OEM in the 3.8. In the m88 and b35 they are a fair but bigger. The 280 has slightly more lift that's probably the one I would go for but it's probably better money spent on other areas and use the OEM cams and max the comp and perhaps machine small pockets so u have greater range to adjust the OEM cams. Eric Bannifors (red shark racing ) made 387rwhp with the crane 280 11:1 comp and the scat 92mm crank. He spun it up to 8000rpm which is fine with an upgraded crank hub.

Matt my engine builder built a stock spec s38b38 everything OEM except forged pistons that made 11.2:1 comp. it was compromised by no cam gears and the stock ecu/chip and air meter. Boy it went like a rocket from as little as 2000rpm and was faster than my superchaged 540i. It made just on 300rwhp on a conservative dyno and probably had 30-40 hp left in it with slotted cam gears and aftermarket ecu.

It's a tricky one but unless u were chasing big power going for the bigger cat293 and prepared to change pistons if prob stick with the OEM stuff, stick adjustable gears on it and get the comp as high as u can put the upgraded hub on and rev it to the mid/high 7's. It will probably make close to 400bhp. If u want 50more bhp u have to open up that wallet more. For a Dutchman that can be a hard thing LOL

[WilNJ]

VvVv q

[Jelmer538i]

For a Dutchman that can be a hard thing LOL

Thanks for all the advice!
What modified hub is there for the B38? They already have the hub with 4 M12 bolts instead of the one M22(?) nut that the B36 has.

[tig]

Jelmer, have you considered contacting Paul Burke?

[Jelmer538i]

No. Is he still in the BMW business?

[tig]

No. Is he still in the BMW business?

He was a terrific help for me last year on my M30B35 build. He's tricky to get a hold of, but once he sees you're not a bozo he seems willing to take the time to offer advice and input.

[Jelmer538i]

Since I'm Dutch, the fact that there will be second baby next year and that my girlfriend want to marry some times near I decided not go go all they way with cams, pistons and conrods.

This is what I was thinking of:

Cometic 1.01mm headgasket which will give a 11.4:1 comp ratio but than the squish band will be only 0.5mm which will cause detonation/knock so by milling the squish band 0.29mm the gap will be 0.8mm which is the minimum I've been told.
This would give a 11.1 comp ratio.

[Jelmer538i]

I worked on the 538iS again.

First the engine. Took the head apart and put it all on a clean work bench. After work I covered it up with a blanket. The head has been done in 2007, 15000km's a go so I don't mess with it.


The block. I'm going to replace the rings. The cilinder wall look good with no signs of much wear but they are a tad to smooth so some honing and new rings will do.



All bolts, nuts and brackets will be re-plated. I'm not sure if I want the pulleys plated or powder coated black. I kind of like the look of the M88 engines in the BMW museum.



I also looked at the famous M88/3 "puddle of snakes" which I'm going to hack up so that the secondary pipes will be 2,5". As a center muffler I'm going to use a Magnaflow stainless muffler and 2 magnaflow resonators. The rear muffler will be custom made by me due to limited space in a E28 and the lack of slim double 2,5" stainless mufflers. I ordered 2 caps and 2 lenghts of perforated tube. What wool would work best for this?






Next is my carbon airbox. I have 2 of them, a big one and a smaller one. The big one was on my S38 for a couple of years before it failed. It had to much stress on the 6 tubes to the throttlebodies and broke loose the resin. My engines didn't suck in this resin but I was very lucky on this! I've cut the 6 tubes out and ordered some 3mm aluminium sheet, a 84mm alu tube and a hole saw so that I can make a new section that i'm going to glue on. It will be secured by some screws.





Why not use the second, smaller one? Cause I like them big!

[e38740imd]

great work

[Jelmer538i]

Sold it yesterday!

[wkohler]

Uhhhh...uhmmmm...what?

[cddallara]

Uhhhh...uhmmmm...what?

This.

[stoney]

Permanent BAN

[Owndapwn]

Did someone hand you a briefcase with $50k or something?

[tig]

This thread is bullshit. If he sold it, it's no longer "Jelmer's 538iS", is it?

[bkbimmer]

Congrats, bigger and better things.

[wkohler]

Are you saying there's a Jelmer's 738is?

[Jelmer538i]

I sold it to the E28 meister himself. This would be a big project again and with the E12 turbo, the 1st Gen Cummins, my Patrol and my brothers E28 turbo we just have to many projects and we both have our family's so we get less and less time for projects.

[gazm3]

I here u about too many projects.

[stoney]

Just let me know when you've had enough Gaz