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S38 cams upgrade opinon is needed ! Cat Cams vs Shrick cams.

14K views 21 replies 13 participants last post by  GiorgioM5 
#1 ·
HI all S38 Enthusiast and Colleges, hiha:checkeredflag:

I got very, very, very, good deal on running S38-B36 engine. I want to build up for street abuse and track fun ! Its going to my 3rd E30 M3 chassis with worked fire wall and engine pushed in for better weight distribution..but that is another topic.. lets not discus that now.

I need your opinion for cams choice

1. Cat Cams 283 / 278° - Max lift: 12.45 / 12.00mm
2. Cat Cams 289 / 281° - Max lift: 13.25 / 12.75mm


1.Shrick Cams 280/280° - Max lift: 11.00 / 11.00mm
2 Shricks may be I can order 280/272° 11.00/ 11.00mm

Also very Important is Valve Adjustment options on both choices cams! I want to be able to do valve adjustment

I think choise 1 Cat Cam is the best for what I am looking for 283/278

Power band 4000-7500 rpm

To me makes more sense to go with Cat Cams but since I never had the experience to try.

My idea with this engine is.

1. Massive Head work
2. Copression raised to 10.5 not more I dont want to go crazy like 11.0+...
3. Cams ????????
4. Increase displacement bore to 3.7.
5. Haltec Platinuim2000 Stand Alone
6. Stock intake with early flapper round 3500rpm.
7. 7500rpm max not more.

I am not chasing crazy power. Just to have fun.

Thank you guys
 
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#6 ·
Maybe because dyno numbers dont depend only on the camshaft itself but a lot of other factors as proper ECU tuning, timing etc
 
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#8 ·
At the risk of getting flamed I wouldn't have thought the cams would offer any large advantage over stock particularly when you consider the bang for bucks angle. I heard that one of the E34 M5 24 hour racers did extensive chassis, brake tuning but left the engines virtually stock.

:cheers:

ralph (vadas1)
 
#10 ·
Im about to buy an old M5 that needs the cams replaced anyways so Ill spend at least 1200 either way. After I looked into it I wouldnt want to do the job unless I could do the springs as well and maybe even rocker arms which pushes the budget well over 3k.

So the census is the cost outweighs the power benefits then?
 
#19 ·
Hello!
What did you choose afterall? On the catcams site they say the cams you were considering needed to be used with shim under bucket
Did you do that?

What if i only changed the intake cam for the 12mm lift 278 cam, would i still need to go shim under bucket?

Thanks
 
#20 · (Edited)
Hi,

Damn how much I have learned from this 6 years old post.
And continue to learn...
I love challenges...

I sow your post on the M3 forum as well...

I would like to give you my advice because its important to prevent
someone from taking wrong direction.

First of all Ask yourself what is your Priority, what do you want (share with us!) ?

Why are you so abbesses with Shim Under the Bucket ?!
Consider pain in the dot valve adjustment!
TimConrad with his real DMT E30M3S14 was running at one point shim over and had no issues at 8500rpm
Valve springs Must be replaced due to aged and fatique material.


What will be your RPM achievement ?
I would not pass 8000 rpms wth your 3.8 90mm Storke.
(for reliability purposes)
What CR ratio are you planing to do ?
Exhaust is critical point.
If you want to change the Intake only as you mentioned 12mm lift,
do you have custom pistons already ?

What is the purpose of your car ? One to do it all ?

What engine management are you planing to use ?
The stock DME with custom burn dyno/live eprom chip or stand alone ?
What fuel are you planing to use Pop Corn ? (as I call it)

The secret dressing for the salad is how the cams will be Dialed.
The main goal is the Torque Curve to be as flat as possible.

At the last ~300rpm your power curve should start dropping.
The reason is you don't want the max power from the cams to be above your rev limiter.
We can see how BMW did great job from the factory. 3.6 version 315hp at 6900rpm.
and the rev limiter is 7250+/- a very good working formula and concept.

Bellow I am attaching you a dyno from E24M6 stock is 260hp(at the engine)
After 3.6 cams and Original 9:8CR and other tweaks I was able to pull 265RWHP
pay attention how flat the toque is and this engine does not have intake flapper.
At the end of its power the torque curve drops but never drops bellow
from what it started.
HP ended flat.

I would say think carefully what are your priorities.

From your post question. Indeed you wanted to upgrade your cams.
and because Vac recommends Shim Under and now you are confused...(which I understand).

Hear is cam timing I have dialed and dyno tuned.
 

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#21 ·
Hello!

I want what you were talking about, flat big wall of torque, power increase from what i have now, and will use on street and track

I am obsessed with NOT having to use shim under bucket hehehe and not having a shim flying of the bucket with too agressive cams
I have almost the same spec as Passos , big pocket custom pistons (+13mm clearance) 12:1 compression running on ethanol( little less than passos)
Head has bigger lighter valves and higher rate springs by supertech, and correct port/polish

While talking to my mechanic we were trying to choose a cam that had a real increase in lift but not necessarily too big duration
We saw schrick 280 11mm lift , but we wanted more lift to use the bigger flow of the prepped head (oem 10.7, not that different)
Catcams exhaust cam 276 12mm seemed perfect for my intake cam (keeping oem exhaust + installing adjustable gears), but they recomend shim under for the set (set: intake at more than 12mm lift, we did not know if it was needed if only exhaust were to be installed)
We wont run more than 8000rpm, 7500 at max...
After a lot of research i found out about schricks 284/276 set for the s38 (same specs as s14 cam), seems like a custom cam, with 11,5 and 11,3 lifts. This set they say i dont need shim under, just what i already have ( higher rate springs, live map etc)
I would get just one, but can only buy the set... So thats what i am after...
We will do a live map after instalation on oem ecu
Intake and headers will be oem..., de cat exhaust, oem final muffler...
Lets see what i end up with

Thank you for the grafs and insight
 
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