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Old 09-16-2010, 01:06 PM   #1
renosubby
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Default How high can you rev????

I am doing BC 280 cams with springs and retainers, What would be the highest i can rev it with this? i was hoping for 8000 rpm
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Old 09-16-2010, 01:21 PM   #2
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"Revving" the engine is a function of the limiter setting... It can be whatever you want it to be. You need to get more specific as to what you are looking for. Do you want to make peak power at 8K? Do you want to have a power band through 8K? What do you want to do with 8,000 RPM exactly. What turbo are you using as well?

Getting high duration cams is one way to make more power at higher RPM, while sacrificing low end too. If you want a more flexible power band moderate duration and high lift makes more sense. Porting and polishing of the heads also makes for a more "rev happy" engine. Larger valves should also be a part of a high rev 2.5L build.

High lift cams (+10.5 mm) will also require modification to the heads, higher seat pressures and stronger valves.

If you are talking about running an EJ257 past 7,500 RPM a balanced rotating assembly and oiling mods are definitely necessary.

Unless you have a very purpose built set up peak power will happen well before 8K on an EJ motor. If you want and 8K power band you have to do much more than just some mediocre cams with lots of duration.



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Old 09-16-2010, 01:21 PM   #3
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Quote:
Originally Posted by renosubby View Post
I am doing BC 280 cams with springs and retainers, What would be the highest i can rev it with this? i was hoping for 8000 rpm
It depends on what your motor is balanced to. Some will say that you need a dry sump oil pump but with 08 STi pump you should be fine.

I have met people that rev to 8k with stock valve springs...
You should be able to rev to 8k

GL
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Old 09-16-2010, 01:46 PM   #4
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As far as your valvetrain is concerned, you are fine.
As for your shortblock, we don't know the components or quality and specs of your machine work.
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Old 09-16-2010, 04:24 PM   #5
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sorry for not giving specifics.
What Im looking to do is while drag racing I want to shift 1st and 2nd somewhere around 8000...This way I fall into my power band a lot better.
I have stock bore 8.9:1 wiseco pistons. no porting or anything to head. just putting valve train in there.
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Old 09-16-2010, 06:00 PM   #6
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Get a good balance on the crank, and get some valve springs and you'll be pretty well off right there (assuming you're doing the pistons, rods, bearings). That's about the minimum though, and I can't say I'd want to keep the engine at 8k for a very long time with just that work done. Drag racing, sure, road racing, I'd do more work.
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Old 09-16-2010, 10:17 PM   #7
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I spun to 8k rpm almost everyday for 40k miles =)

I just ported all of the oil galleys, 11mm 08 pump, bigger oil filter (yay!) andddddd ... ported the crank / rod bearing oiling holes a bit so they "scoop" oil IN. Lasted pretty long, with a LOT of abuse.

I'm pretty sure one of the arp bolts on the eagle rods came apart, as the top of the block is half gone and I can just about fish out an relatively un-damaged rod cap!!!!

I still have to tear it down and inspect though
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Old 09-16-2010, 10:53 PM   #8
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Its not that cams that will have the trouble. Do proper clearances for the block if you wanna rev. If you are revving your motor to 8k RPM it means the heads are revving to 4k....They spin at half speed.
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Old 09-17-2010, 01:34 AM   #9
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Quote:
Originally Posted by bhhamblin View Post
If you are revving your motor to 8k RPM it means the heads are revving to 4k....They spin at half speed.
And Subaru designed the valve train with a "3600 RPM" rev limiter in mind, so what difference does that make?
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Old 09-17-2010, 08:08 AM   #10
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OP, you got a decent size turbo??

I know what you mean about getting the RPMs up there. My motor is a 2.2L and my rev limiter is set like... 8200. It's mainly for gearing because I track the car and run the JDM 6spd tranny. Just need to hold a gear longer sometimes. Currently on a 20G turbo, Crower valve springs and Ti retainers, stock cams, unported heads, stock valves. My engine displacement helps as well as getting the internals all balanced from crank pulley to the clutch and FW.
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Old 09-17-2010, 01:55 PM   #11
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Quote:
Originally Posted by AKSubieDubie View Post
I spun to 8k rpm almost everyday for 40k miles =)

I just ported all of the oil galleys, 11mm 08 pump, bigger oil filter (yay!) andddddd ... ported the crank / rod bearing oiling holes a bit so they "scoop" oil IN. Lasted pretty long, with a LOT of abuse.

I'm pretty sure one of the arp bolts on the eagle rods came apart, as the top of the block is half gone and I can just about fish out an relatively un-damaged rod cap!!!!

I still have to tear it down and inspect though
Same here. I spin to 8k daily and do a lot of road racing.

11mm pump, balanced rotating assembly, fully built heads, etc. If your heads are not ported, over-sized valves, etc. your power is going to fall off way before 8k rpm.

Lots of revving out here:
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Old 09-17-2010, 04:01 PM   #12
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I have "built" heads too minus cams, which are stock 04 sti. I ported them MILDLY as in blending in the valve seat overhang. +1mm manley valves, dual valve springs, ti retainers etc.

Full race lower, home made upper twin scroll 83 75. Holds same power from say 4-4500 -> ~8000 +-100 rpm ..... at least according to my butt dyno with ~25 psi on pump + meth.
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