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View Full Version : Custom made rocker arms? 8000+ rpm rev limit?


Dan Pinder
07-05-2004, 05:22 PM
What do you guys think about building an m20 that could hit 8000 or more rpms?

Has anyone considered having custom rocker arms made? They are apparantly the weak point. I know I have broke one before.

How high can we rev the bottom end if it's balenced? At what point do the piston speeds become too much?

swartz
07-05-2004, 05:26 PM
a couple of my friends hondas rev over 8grand its crasy. it feels liek it goes forever.

2000civic si turbo. the car pulled forever never stoped. if our cars could it would be silly

x628x
07-05-2004, 05:38 PM
that would be badass. S2000s and RX8s rev to 9000.

some bikes rev to like 18000. :)

Dan Pinder
07-05-2004, 05:41 PM
So what do we need to do then? I'm mostly worried about the piston speeds.

Let's do something about it.

nitro325is
07-05-2004, 05:46 PM
Not really a good idea from a performance perspective.Since most M20 fall on their face after 6000 or 6500 with a modest cam.Im sure its the same for FI.
From a durability stance..yes someone please bring them out.Korman charges an obscene amount.Broken rockers are such a pain since you have to pull the head most of the time to replace them on the M20.

Dan Pinder
07-05-2004, 05:51 PM
I think my short runner intake manifold will help out in the high rpms.

Are the korman rocker arms any different? Arn't they just shot peened or something?

x628x
07-05-2004, 05:55 PM
Not really a good idea from a performance perspective.Since most M20 fall on their face after 6000 or 6500 with a modest cam.Im sure its the same for FI.
From a durability stance..yes someone please bring them out.Korman charges an obscene amount.Broken rockers are such a pain since you have to pull the head most of the time to replace them on the M20.

what about with a turbo?

TriFlow
07-05-2004, 06:03 PM
I've broke 2 sets of factory rockers.. I now have the korman and there working so far..

Dan Pinder
07-05-2004, 06:13 PM
I've broke 2 sets of factory rockers.. I now have the korman and there working so far..Do they appear any different than stock?

nitro325is
07-05-2004, 06:43 PM
[/quote]what about with a turbo?[quote]

Same thing applies.Talking M20s here. A turbo only makes more power thoughout the cars entire powerband versus its NA version.
If you add a cam to an NA it moves the power band up and usually gain a few HP(lose some TQ) at least on NA M20s.
I dont personally know anyone running a cam with their M20 turbo but seems to not work well from what I have read on other sites.Another issue on its own.

There is no performance gain in putting the rockers on a NA or FI M20.The cam is the deciding factor of the powerband.Adding a cam might get you a few hundred more RPM but it still falls on its face after 6500 even with a turbo..Unless you have a really wild cam like 300+.At which point the car is virtually undrivable in city driving even with a turbo.Turbo with 300+ cam will probably be a nightmare.Remember our cars DO NOT have variable valve timing.That is how those other cars mentioned can rev sky high and yet still be civilized in the city.
Put them on for durability.Same reason I got HD valve springs.

Digitalwave
07-05-2004, 06:47 PM
I agree, I don't see the need for an 8,000 RPM M20, a bone stock M20 falls off before 6,000 RPM's anyway.

Dan Pinder
07-05-2004, 07:30 PM
There is no performance gain in putting the rockers on a NA or FI M20.The cam is the deciding factor of the powerband.Adding a cam might get you a few hundred more RPM but it still falls on its face after 6500 even with a turbo..Unless you have a really wild cam like 300+.At which point the car is virtually undrivable in city driving even with a turbo.Turbo with 300+ cam will probably be a nightmare.Remember our cars DO NOT have variable valve timing.That is how those other cars mentioned can rev sky high and yet still be civilized in the city.
Put them on for durability.Same reason I got HD valve springs.

The problem with a NA high lift cam in a turbo car is that the NA cam has a lot of valve overlap. On a turbo car air gets forced out the exhaust this way.

I don't know about anyone else, but I am running a custom made turbo high lift cam, with minimal overlap. More flow without the negative side effects of a NA cam on a turbo system, and probably more gains because I would think it has less overlap than the stock cam.

I just made a short runner intake manifold that should raise my power band up a lot.

I think I could really benefit from a higher RPM limit.

swartz
07-05-2004, 07:32 PM
dan mega squirt doesnt have a rev limitier.....

Dan Pinder
07-05-2004, 07:39 PM
lol.. but the engine does.

When the piston hits the firewall, you're at the rpm limit.

decay
07-05-2004, 09:19 PM
with even a slightly more aggressive cam, i think the m20 head is going to need a lot of opening up to make 7000+ rpm worthwhile.

Dan Pinder
07-05-2004, 09:23 PM
You don't think shorter intake runners would do the trick?

Giga Shadow
07-05-2004, 09:52 PM
Deffinatly.

decay
07-05-2004, 09:59 PM
they'll help, i'm sure, but not as much without headwork. airflow goes by the "weakest link" rule...

i'm betting that's how all the crazy swedes get their #s on stock bottom ends-

TriFlow
07-05-2004, 10:47 PM
I've broke 2 sets of factory rockers.. I now have the korman and there working so far..Do they appear any different than stock?

Ya they did look different.. I hope there stronger cause I cant afford any more head removals..

Dan Pinder
07-06-2004, 10:13 AM
I just talked to korman. They run a 325i race car that runs 8,800rpms with thier stress relieved rocker arms. Although he says they change them after every race.

Stock rockers are good for 7,500rpms and the valve train is the weak link on this motor for rpms.

I would say that 8,000 rpms with korman rocker arms and good springs is resonable.

Digitalwave
07-06-2004, 10:18 AM
Well I guess the best you can do is dyno your car and see where you powerband ends, and set your rev limit a few hundred RPM behind that.

Dan Pinder
07-06-2004, 10:20 AM
I still think my short runner intake will help a lot.... but I do plan to port the head.

Yeah, that's what I will do. For now I'll set it at 7000rpms.

Jay Stock E30
07-08-2004, 11:19 AM
I'd be worried about more than just the valve train, that might be the weakest link, but you are going to be putting alot more stress on the crank,rods and pistons. I don't really rember exactly what corky bell said about engine rev's vs boost, but reving the engine higher is harder on it than boosing it to a degree, so I'd imigen that reving it that high, plus boost is a good formula for enigne failer. Props to you if you get it running good at that high of an rpm though.

kyle325
07-11-2004, 10:49 PM
I thing harder valve springs and the stringer rockers would take care of the top end. If you are having the bottom end balanced, ask the tech what he thinks the max rpm would be, I think as long as the bottom end can take the momentum change at top and bottom dead center, it should handle the boost. Does any one offer ligher (without sacrificing strenght) rods? I know you can get lighter pistons. You coud probabyl even have the crank lightened.

By no means will yuo end up with an s2000 engine's longevity, but if you stay below 7500 I would think the engine would last as long as the s50 will.

decay
07-12-2004, 02:50 AM
i've heard pauter makes rods for the s14 and s50- i'd be pretty surprised if they didn't support the m20 as well.

x628x
07-12-2004, 03:29 AM
I just talked to korman. They run a 325i race car that runs 8,800rpms with thier stress relieved rocker arms. Although he says they change them after every race.

Stock rockers are good for 7,500rpms and the valve train is the weak link on this motor for rpms.

I would say that 8,000 rpms with korman rocker arms and good springs is resonable.

8800 rpm on an M20? thats crazyness!

DevInAz
07-28-2004, 07:41 PM
dk, dk where are you in phoenix? i'm in mesa. there are acouple of us with e30's but i've never seen anyone else around the valley. i'm building a turbo motor right now. drop me a line if you want. 480-250-7004 Devin

decay
07-28-2004, 10:04 PM
Dev: pm'ed you.

straight6
07-28-2004, 11:55 PM
Hey Dan,

Where did you get that turbo cam?

JSF252
07-29-2004, 12:14 AM
I dont think that an 8k rpm M20 would NOT be very pleasing (at least off the track). You would have to put a pretty big cam in, so the engine will make power that high. When you put a cam in like this, you've effectively removed some torque from the bottom end, and replaced it with HP at the top end (in most cases). The low torque on the bottom will be apparent when leaving stop signs/red lights. By the way, how many of you drive at redline 75%+ of your time behind the wheel? I know some of you beat on your cars pretty hard, but I drive my car "resonably" most of the time, so I enjoy not having rev the daylights out of my car in daily traffic, just to make power.
Has anyone read the article about the 2004 Honda S2000? Honda upped the displacement from 2.0L to 2.2L in order to get more torque out of the engine. Customers were complaining that the car was no fun to drive, unless you were in the mountains. Car and Driver mag. called it a "special car, for special circumstances". They meant that the "old" S2000 was a pleasure to drive on the track or in the mountains, but in stop-and-go traffic, it was a pain in the ass. They also said that the wail of a 2.0L turning 5k @ 70mph for a couple hours was annoying also. So Honda upped the displacement, got some much needed torque (down low), and made a MUCH more pleasant car to drive.....everyday.
So if you are planning on making a dedicated track car (as Korman did), then 8k rpm will be more than welcome. But for a daily driver I think you'd be dissappointed.
Just my $.02, I hope to hear other's oppinions.
Josh F.

Giga Shadow
07-29-2004, 12:53 AM
Has anyone read the article about the 2004 Honda S2000? Honda upped the displacement from 2.0L to 2.2L in order to get more torque out of the engine. Customers were complaining that the car was no fun to drive, unless you were in the mountains. Car and Driver mag. called it a "special car, for special circumstances". They meant that the "old" S2000 was a pleasure to drive on the track or in the mountains, but in stop-and-go traffic, it was a pain in the ass. They also said that the wail of a 2.0L turning 5k @ 70mph for a couple hours was annoying also. So Honda upped the displacement, got some much needed torque (down low), and made a MUCH more pleasant car to drive.....everyday.

We're talking about a 2.5 turbo charged 6cyl.

Torque is always going to be there. :)

swartz
07-29-2004, 01:03 AM
i got some torque for ya :jack14:


yo donkey what happened to the smiley u had with the smiley gettin it all over the face i cant find it on this site?

Giga Shadow
07-29-2004, 01:15 AM
I got it from that UK e30 site.

:fart:

swartz
07-29-2004, 01:20 AM
what site would that be?

Giga Shadow
07-29-2004, 01:35 AM
:lol:

www.e30zone.co.uk/

Dan Pinder
07-30-2004, 05:56 AM
I just priced out custom made billit rocker arms with some of my engineering and CNC connections.

It would cost about $1500 to set up, but after that they would be about $15ea or less depending on quantity.

Hmm... If I had the extra cash right now I would do it. Maybe I will when the body kit is done.

Giga Shadow
07-30-2004, 06:16 PM
So after you pay 1500 to punch in the specs on the cnc it'll cost $15 each after that? :lol:

Will the rockers be heavyer you thing? Did you change anything on them
or are they exact copys?

Ask them how much for a roller system :o

Dan Pinder
07-30-2004, 08:35 PM
I think a hardened cam or something like that would be neaded for a roller system. Wouldn't it?

I havn't actually designed anything. My brother is an egnineer, so he could do it.

Billit is stronger than a cast stock part, so I would assume it could be made lighter. Just getting it not to break would be a great accomplishment.

Giga Shadow
08-02-2004, 05:23 AM
http://www.opeltuners.com/rollerlifters/roller%20cam%20parts.jpg

Yeah, you need a spacific roller cam, rockers and lifters...
It'll be lighter and wont create nearly as much friction
Nobody would every offer that for a bmw though. :cry:

Here's some basic for people that don't know what hell were talking about. :lol:
http://www.mustang50magazine.com/techarticles/18679/




What do you think about these?
"Rocker Arm Retainers" :idea:
http://www.bmpdesign.com/assets/productfoto/113174.jpg


On all early single-cam, 4 cylinder and chain-driven, 6-cylinder engines the rocker arms are held in position by a tensioner spring. In high R.P.M. situations these springs permit the rocker to move laterally. Rocker arm failure is the result. Once the rocker leaves the valve stem contact area the rocker will bind against the retainer resulting in broken rocker arms. The BMP retainers will stop high R.P.M. rocker arm movement. The two-piece billet aluminum construction permits installation without cylinder head removal.

http://www.bmpdesign.com/products/acc/engine/rockerretainers.shtml