How high can engine rev safely? [Merged 12-7]

[Eagle 5]

How high can the 420A engine rev safely on stock springs and retainers without worrying about valves floating or what not? Also, what is needed to get rid of the rev limiters ? (7200 and 7800 fuel/ignition cuts) would a msd ignition work? just wondering. Im rebuilding my engine and Im trying to decide what to do head wise. Originally i was going to get stainless valves, crower springs, retainers, pt cruiser lifters, rockers but someone said I should get cams and get port work done instead of getting the wprings, retainers and lifters since the stock ones are fine. anyone know?

 

[4geze63]

why would u want to?

 

[Mirage2LTurbo]

why would u want to?

Powerband.

 

[1fast97gsx]

why would u want to?

yup ... large turbos tend to spool at a higher rpm but keep making power to a higher rpm. On a 16g or even smaller turbo reving that high is pointless.

 

[pneumo]

Stiffer valve springs help keep the lifters from pumping up because the spring pushes harder on the lifter.

When I built my motor I ported out the oil pressure relief valve hole so it will bypass more oil when it sees high pressure. I made sure the relief valve spring was up to spec so oil pressure was not reduced at idle.

 

[anomalyinva]

I disagree. I'm running 3g lifters, ss valves, crower springs/retainers, hks 272's, wiseco/eagle bottom end (and ANY motor should be balanced!! It's not just a performance thing!!) and I'm regularly shifting at 9000, and have taken it to 9500 a few times with no issues. I don't see the need for a dual spring setup unless you are going regularly to 9500-10000.

Interesting. I've always heard it suggested for 9000+ to go with a dual spring setup. I guess I should revise my thinking. How often do you go up that high?

 

[Awdboost]

I'm not sure if the springs will play that big of a role when the lifter are seeing 130 psi.. that is just too much oil pressure.. But Stiffer springs couldn't hurt. I like the porting oil pressure relief idea.

 

[Mirage2LTurbo]

Interesting. I've always heard it suggested for 9000+ to go with a dual spring setup. I guess I should revise my thinking. How often do you go up that high?

Whenever I ream on it

 

[rdrkt]

Ive gone through this thread and read most of the posts. I notice that a lot of people have anecdotal evidence about high revs but I haven’t seen a lot of concrete evidence about the reliability or the gains of revving up that high.

Have you guys gone over dyno sheets or reviewed boost logs on your DSMlinks or standalones? I have a Magnus 2.4 with a gt40 with a t350 with a 4 bolt .82ar exhaust housing, SM intake manifold, 272 cams, ported head etc. Take a look at my dyno chart slightly over 30lbs nothing special just two different runs on two different days with two different intake manifolds. This is the same setup that that a lot of you are talking about. Take a look at that power curve. Why in the world would I want to rev to 9k or higher? The power just isn’t there up top. Even on a 2 liter you wouldn’t need revs like that unless your are looking at a BIG turbo like a T04r or greater and some really big cams. The only place where you would really want to rev it up is on the 1-2 shift. That is the one place at the track where you will experience big time lag on your turbo.

I revved my bone stock tranny to 9000-9500 all last season, it came out of the car in perfect shape. It wouldn't shift well that high, but it's fine. Shifts excellently at 8500.

Dude I’m putting you on notice. I’m stealing your tranny watch your back

 

[HighPsi91]

The more power you put down over the course of the 1/4mile the quicker and faster you will go. If your turbo is that large that your shift recovery RPMs drop below the power band then you need to rev higher. In extreme cases (and I mean extreme) you may have to rev to 9500. This is not the case for anyone running slower than mid 9s, unless of course your setup is just so mismatched you have a 9sec turbo on a 13sec car as seems to be the case more often than not. There really is no need to rev past 8500rpm for 98% of us. I only rev to 8200 and my turbo is bigger than any of yours I guarantee it. I have no balance shafts, the stock valves, and the stock 1991 lifters that came with the car. You guys are getting way too carried away.

Valvesprings... yes they are important, I run a dual spring setup still with the "stock" retainers. What springs you need to rev to "X" RPM is totally dependant on what cams you are using. The lobe lift and ramp rate of the camshaft is what dictates how much spring pressure is needed. Keep that in mind.

Also keep in mind if you want to rev top 9500 and actually make it worth your while you will need ALOT of airflow. Both the compressor and turbine side will need to be very sizeable... much more than a 50trim or 60-1. Also the cams are a limiting factor to the top end power.. more so than even the intake manifold regardless of whats popular. With the right cams the stock intake will make plenty of power past 8500rpm. Im not saying that there are no gains to be had with a sheetmetal, Im just saying that the stocker isnt some big brick wall in the way of top end power. 272s are great cams and work awesome because they focus our power in the RPM band thats is usuable to the large majority of us. They are however far from optimum for big high rpm power. Enough boost can help overcome this though

As far as oil pressure goes.. I dont see why it should be a problem. A few folks do suffer from excessive high rpm oil pressure. Possibly their bearing clearances are real tight and everything else in their motor is just so to cause this. The oil pressure relief valve that is on all our cars is whats responsible for limiting maximum oil pressure. Obviously if the oil pressure is going too high then that valve is not doing its job. You may need to dig out the die grinder and bump its flow capacity up bit.

 

[rdrkt]

Any where from 100-130 psi at the head witch the lifter can not bleed out fast enough and end up with bent valves.

People would see that much pressure at the pump where your oil pressure sender is located but that much pressure at the head is damn near impossible.

 

[Mirage2LTurbo]

That tranny is sold New *non-stock* drivetrain is going in for next season. IE new everything from the rear-end to flywheel (or should I say flex plate)

 

[Awdboost]

rdrkt, 2.4 Motors have a different air consumption then a 2.0. So your VE consumption is much higher then a 2.0. And your intake man, head, port and etc. will run into flow issue at higher RPM's before it will happen to a 2.0. 2.0 Can make lots of power higher up because it will not run into restriction problems, because of the motor being physical smaller. It's all about moving the RPM band up when you have all the extras to do so. Also on a 2.4 your power band moves down because of the extra displacement so you make power sooner and loose power sooner too. On a 2.0 we make power later and lose power later. I really wish people would stop question why.

Also for the oil pressure in the head.. Lot of guys will see this and just don't monitor it.. I talk to FRH and they have told me that they have seen 110 at only 6.5K in the head. It's not impossible it's happened.

 

[pneumo]

Also for the oil pressure in the head.. Lot of guys will see this and just don't monitor it.. I talk to FRH and they have told me that they have seen 110 at only 6.5K in the head. It's not impossible it's happened.

But is that much pressure bad? How much is too much?

If anyone is really worried about lifter pumpup, and you've already ported the oil bypass hole, then get an oil distribution body off an early '90. This part is bolted on the left side of the head under the valve cover and distributes the oil to the various galleys in the head. On the '90 car it has a spring loaded oil bypass port, just like in the oil filter housing. Later model year cars didn't have this, they just had a part with distribution passages and no bypass.

 

[Awdboost]

But is that much pressure bad? How much is too much?

Rule of thumb.

For every 1000 RPM you must have 10 psi of oil pressure.

SO.... if your are at 9000 rpm you should have 90 psi of oil pressure.

 

[aves911]

When you guys are talking about porting out the oil return. That is where it gets bled back from the oil filter housing into the pan correct?

Where are you enlarging the hole?

Thanks,
-Jacob

 

[Awdboost]

I have done a few mods to control the oil pressure.
-porting out the hole on the bypass, on the oil filter housing.
-adding an extra washer on the bypass valve to allow it to open sooner.

extra washer

-I kept the back balance shaft in. (The counter weight was machine off.)

pic here

-In the head I have 3rd gen lifters. I ported the oil holes. just the one next to the lifters.

My car will be staring in 20 days.. I'll keep you guys updated on the oil pressure stuff.

 

[aves911]

When porting the oil bypass, how much did you guys take out? Just a little?

Sorry to pester, but this may be something I will be doing soon.

-Jacob

 

[Awdboost]

The Machine shop did it. I'm not sure how he ported it or how big it was. Sorry.

 

[blueberry_dsm]

i am trying to build my motor so i can derive as much power as i can from high rpms. so for the top end of my motor, i will be running the HKS 272 Cams, intake and exhaust, HKS valve springs, HKS adjustable cam gears, and a Kevlar timing belt, along with a balance shaft emliminator kit. i will also be porting my own head.

i am running all HKS, because i know they will compliment each other, and a super strong kevlar timing belt. is there anything i am overlooking for the top end, aka the head.

is there anything better than this setup? the motor is from a 1990 mitsubishi eclipse, 2.0 turbo, 5 speed, fwd. to be used on a 1993 eclipse

### is the highest i can possibly rev my motor? i know you can raise the rev limit by swapping the cams, springs, and gears.

thanks for any and all help

 

[Old Mitsu Tech]

Converting from n/t to turbo? I'm not sure if you want to know at which point will it let go, or how far up will it pull hard reliably.

Obviously you know the regular redline. I've not heard of anybody talking of running over 8,500. The bottom end is just as important as the top end. If you have forged everything, balanced everything and ARP everything. Then you certainly would be more reliable than stock everything.

Now, when you say you are porting your head. Are you using known formulas and using a flow bench or are you hand porting and gasket matching?

If you get a runner too big or miss a hump, you can actually hurt your flow by creating turbulence or dead spots where none should be.

I would contact a good shop with flow bench and tell them what you are wanting it to do and follow their recommendations. They can do all the work in house and save you a lot of time and headaches.

I'd also say that some of the guys in here that are pulling 9's and 10's can help a lot if they are willing to share their secrets. Never mind the bench racers. I'm talking dyno and track time slips. Those are the ones you want to learn from if you want maximum power and speed.

Follow someone who has proved successful and you will find it the easiest road to follow.

Good Luck

 

[dsm-onster]

If you plan on raising the rev limit then a SMIM will definately benefit you. The 1G intake mani and head combo does not drop off as much as many think in the higher revs but it can be significant by 8500 rpms. If you plan on reving to +9K, I suggest lighter forged internals as the rotating mas will be incredible and you will not only keep a little power for the drive shaft, but you will save yourself from possible breakage... This is what was recommended to me. In fact read this thread I posted recently. It has put me on the right track. You'll need a very, very large turbo to rev very, very high.

FP2s and 10,000 pms

What are the specs on the HKS springs? are they dual springs? I wouldn't touch 10,000 rpms w/ out duals. But I'm doing great on my Manley singles and an aggresive ramp rate from my FP2Xs at 8500 rpms.

EDIT: Plus what Old Mitsu Tech said . . . he posted a second before me.

 

[91-gsx]

I just wanted to know what some of the people on this site rev their setups to with the stock cams? A lot of people upgrade their turbo before cams, so i just want to know what type of turbo you run with the stock cams and how high you rev? I want to upgrade my turbo soon and just wanted to know what some of you are revving to with the stock cams.
thanks for the info

 

[fwdeclipse]

When I was running my e316g I would shift at 6500.Now I have a t4 60 trim and its hard to keep off the limiter at 7500 .I would say with stock cams the motor will stop making power at about 6500.

 

[MyBeatGSX]

ditto, 6500 and the power just isn't there (with an E16G).

 

[SBstar]

normally with a 14b or 16g and stock cams shifting at around or near 6800 is considered the norm (drag racing of course)