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Thread: Turbo E36 GT94r, Schrick Cams, 8.5.1 pistons - Compression

  1. #1
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    Turbo E36 GT94r, Schrick Cams, 8.5.1 pistons - Compression

    Hello Members been a while since I posted... Wanted to inquire regarding vacuum and cylinder pressure readings... Just got the old girl back on her feet after years of being in the garage; and upgrading the cams .. Noticed some oddities with my setup...

    I have:

    1. E36 Turbo M3 w/S52 engine
    2. 87mm pistons
    3. 8.5.1 compression
    4. GT/94r Turbo
    5. Schrick Cams 276 intake / 270 exhaust
    6. M50 manifold
    7. TurboSmart Eboost2 with 4 port solenoid.
    8. Gen1 SteedSpeed CNC 2-piece exhaust manifold.
    9. Tail 50mm gate with 14.7 spring
    10 ECU - Vic Sas - Tec3r / ODB2
    11. Ferrera Valve Train +1 mm oversize valves/ double springs

    Prior to the upgraded cam installation - I was using Schrick Cams 264 intake / 256 exhaust. My vacuum reading at idle hovered between 17-18; with summer ambient outside temps between 75F-90F. In the winter months it would be 18-19.. To add all cylinders read 185 psi...

    Now with the upgraded cams - 276 intake / 270 exhaust - The vacuum readings are 14 - 15 at idle.. I also had to increase my idle from 750 rmps to 900 - 1000 rpms otherwise she will loop up and down... Question; considering the cams are larger with lift/duration - is the vacuum readings correct??? I would assume the compression numbers should be lower with the larger cams?? I will do a compression test to see what it should be since these cams are in place... Maybe I have a small vacuum leak??? May need to do a smoke test... Wasn't sure if anyone experienced this.... Otherwise the car drives great and pulls hard.. No misfires... No issue with driving... Any feedback would be great. Thanks..
    Last edited by Morfeus17; 09-12-2022 at 09:03 PM.

  2. #2
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    Makes sense you would get less vacuum with the more aggressive cams. You could experiment with cam timing. Someguy2800 might have ideas. I use the cam blocks he recommends for 264/256, which were based on Chikinhed’s actual degreeing. I recall having to retune when going to just the 264/256 Schricks. Maybe some tuning would smooth out the idle a little.

    How do you like the cams other than idle?

  3. #3
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    Hmmm. I was told by VAC, and others that the 276/270 and my previous 265/256 did not require degreeing.. They were meant to drop in as OEM factory... Anything bigger will require Degree Cam timing... So what you are saying is surprising to me... Also to add since my pistons don't have deep valve relief - the vanos unit required a 3mm shim just to ensure non-interference once activated.. Now; you are very correct.. my tune needs to be redone; for sure....

    Outside of idle.. The cams are great... The turbo pulls harder through-out the rev ban especially upstairs.. And since my final drive ratio is 2.79 - I can keep the turbo loaded longer on all gears; without mashing on the gas pedal... These cams do make a noticeable difference... The turbo is very responsive with them...

    Otherwise TBD on tuning... Thx for the feedback...

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    I am not saying they require degreeing. Just that it is possible a different cam timing spec could help. The hard part would be finding that spec — if you knew it, Someguy2800 could print up a set of modified blocks to make retiming easy.

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    Gotcha... I will look into it....

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    It is normal for the idle vacuum and compression to go down with bigger cams, so nothing surprising there. The schrick cams can indeed be installed with the factory blocks without any special degreeing, but the default settings on them are not very aggressive, so there is quite a lot of power to be made by degreeing them to a more aggressive angle.

    The tricky part here is there are two different versions of the 276/270 cams, and I don't think there is any markings to tell the difference. The older ones were timed to have the centerlines the same as stock S50 cams, so they were like 120 degrees LCA intake and about 113 degrees LCA exhaust. This varies from cam to cam though by a few degrees. At some point they revised them and now the new ones I've profiled are 110 degrees LCA intake and 121 degrees exhaust.

    The dyno graph below is an NA S52 with a ported head and built bottom end with 11.5:1 87mm pistons. The red line is schrick 276/270 cams with stock timing blocks, which the owner said he measured at 117 deg intake and 114 deg exhaust. The orange curve is with the cams timed to 112 degrees on the intake cam and 108 degrees exhaust.


    Last edited by someguy2800; 09-13-2022 at 11:11 AM.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

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    Wow that is a difference.. Good info regarding the two type of cams and more power can be made from them and that's on a NA motor. Very Impressive... Now that being said... I just did a compression test on all cylinders.. I had the car running till warm up temp.. Shut it down for about 30min.. Then ran my checks.. Crank the motor for 10 sec x 3 on each cylinder..

    Not sure if this is normal or not??? The stock compression is what 200-205? I'm running 8.5.1 low compression pistons/ with 276/270 cams -
    The below results show a drop in PSI per cylinder...

    Cyl1 - 135
    Cyl2 - 125
    Cly3 - 130
    Cly4 - 130
    Cly5 - 125
    Cyl6 - 130

    Let me know.... The thing is we don't have any charts on this stuff as a reference point?

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    Your idle vaccum definitely changes with cams, I am about 1.5 psi less vacuum than I was with stock cams.

    To Perry's point, they can be timed for improvement, and yes there are more than one set (annoying) that they have sent out. The same can be said for the 264/256 which I recently put in my car. The normal on center orientation and even with the blocks he offers were both wrong to make a long story short...schricks fault they don't make this clear or noted anywhere.

    ~Ken~ '99 M coupe THE "original" TT Stage 3 - HTA3586R; 701 whp 672 wtq @ 26.5 psi ; NeverSell - CoupeCartel

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    Wow. Very Very interesting... This is news to me.. My question though; if I decided to degree time these will this cause interference with my pistons?? Im running CP pistons but there is no valve relief on them.. Would this pose a problem?

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    Quote Originally Posted by Morfeus17 View Post
    Wow. Very Very interesting... This is news to me.. My question though; if I decided to degree time these will this cause interference with my pistons?? Im running CP pistons but there is no valve relief on them.. Would this pose a problem?
    I haven't run these cams but you would think that if you were to degree your cams you would put them in "optimal" position, which, if designed to not smash into pistons, would be maintained. The fact that they are not centered w/ the blocks means that perhaps they're more likely to interfere because "who knows".

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    That cranking compression is due to the valve events. I would start by advancing the intake cam. 150 to 160 would wake it up a bunch. Roll it over and put 100+ psi to the vanos line and hit the plug with 12v+ and gnd to advance the cam. Spin it over a couple times and you will know if there's contact. Or use an override in the software, not sure if tec 3 has that functionality.

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    I realize this is pretty difficult to follow, but here is how to measure the piston to valve clearance on an assembled motor. Even if the valve don't touch when spinning the motor over by hand, they can still hit when the engine is actually running because the connecting rods stretch a little bit and when the engine isn't running, the hydraulic lifters will bleed down.

    https://studio.youtube.com/video/4Y6qbF0v8OE/edit

    - - - Updated - - -

    Quote Originally Posted by Morfeus17 View Post
    Wow. Very Very interesting... This is news to me.. My question though; if I decided to degree time these will this cause interference with my pistons?? Im running CP pistons but there is no valve relief on them.. Would this pose a problem?
    One of my biggest pet peaves about this platform is all the companies selling pistons with valve reliefs too small for even relatively mild cams. Its just idiotic how often I run into that.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

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    Quote Originally Posted by 5mall5nail5 View Post
    I haven't run these cams but you would think that if you were to degree your cams you would put them in "optimal" position, which, if designed to not smash into pistons, would be maintained. The fact that they are not centered w/ the blocks means that perhaps they're more likely to interfere because "who knows".
    Optimal for one motor is not necessary optimal for another engine. Displacement, head flow, intake manifold, ect... all change that. Every single cam sold for these engines, and pretty much all aftermarket cams really, are just timed at an arbitrary angle, usually just copying the lobe center angles of one of the stock cams, or copying what seams to be popular on other engine platforms. I've profiled almost every M5x cam availible and there just isn't any rhyme or reason to any of them. They should really all be considered mystery cams until you profile them, because a lot of them don't even match the duration on the spec sheets, let alone the lobe center angles.

    I've been selling these for years and I hoped having easy to use tools would encourage more people to experiment, but not much progress has been made in the general bmw tuning public. In an effort to make better use of these I've been profiling every set of M5X cams I can get my hands on.

    https://www.alien-engineering.com/pr...-timing-blocks


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

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    Quote Originally Posted by someguy2800 View Post
    Optimal for one motor is not necessary optimal for another engine. Displacement, head flow, intake manifold, ect... all change that. Every single cam sold for these engines, and pretty much all aftermarket cams really, are just timed at an arbitrary angle, usually just copying the lobe center angles of one of the stock cams, or copying what seams to be popular on other engine platforms. I've profiled almost every M5x cam availible and there just isn't any rhyme or reason to any of them. They should really all be considered mystery cams until you profile them, because a lot of them don't even match the duration on the spec sheets, let alone the lobe center angles.

    I've been selling these for years and I hoped having easy to use tools would encourage more people to experiment, but not much progress has been made in the general bmw tuning public. In an effort to make better use of these I've been profiling every set of M5X cams I can get my hands on.

    https://www.alien-engineering.com/pr...-timing-blocks
    Not saying optimal in terms of "dialed in" I mean optimal in terms of interference.

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    I bought off the shelf JE pistons about 8 years ago and I think they added 1mm clearance over stock. Have seen some pictures of other pistons that look like they add even more, but don’t know how much.

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