Valves

Brent · Post by **Brent** » Wed Oct 19, 2005 6:54 am

I was just wondering what advice you guys could offer me when it comes to selecting valves for a 200-250rwkw 4G63 DOHC? Motor has forgies and rods.

Brent · Post by **Brent** » Wed Oct 19, 2005 11:54 am

So stainless valves are an overkill?
I am enlarging the exhaust valves,
so I will need custom ones made.

2000_turbo · Post by **2000_turbo** » Wed Oct 19, 2005 3:15 pm

The DSM guys are often using the 1mm oversized valves, but the stock valves are more then enough for your application. Are you doing your headwork yourself? If so, be warned you could easy ruin your head. I did my headwork myself, I only removed the casting inperfections and made the transitions more smooth.

Gr,

Martyn.

blue1 · Post by **blue1** » Sun Apr 16, 2006 8:11 am

Bigger valves will give you more flow without going up in the cams, so if you can work out the tech side of the size gain of a bigger valve over more lift of a cam.

Post by **DJpowerHaus** » Mon Apr 17, 2006 11:32 pm

I'm going to see how much of a bottle neck this stock head is. I'll have bolt ons but no porting. When my cousin / uncle and I looked at it when it was appart last summer we couldnt find much casting to clean up. Mitusbishi makes some good parts.

Mike · Post by **Mike** » Wed Apr 19, 2006 12:04 pm

DJpowerHaus wrote:I'm going to see how much of a bottle neck this stock head is. I'll have bolt ons but no porting. When my cousin / uncle and I looked at it when it was appart last summer we couldnt find much casting to clean up. Mitusbishi makes some good parts.

AKA HKS

Post by **DJpowerHaus** » Wed Apr 19, 2006 6:52 pm

Not dual springs.. just Crower stuff.

I'm from the school of thought that you want to use the least valve spring you can get away with or else you're just throwing away power to valve train friction.

I'm NOT an engineer so I dont know the ins and outs of this stuff.. but I do know that companies will sell you kits with 2, 3 or even 4 springs because you'll think more is better and you'll pay more for having something "better" even though its marginally so.. or even if it will hurt performance. Sort of like buying a Tornado. Hell, I was willing to try stock springs but Crower stuff is pretty cheap and it sure beats 15 year old valve springs.

Or I'll float valves... so we'll see. Crower Springs and Titanium Retainers with FP3 cams at 8K... who knows. I'll probably need something alot more extreme with my 2.1L if I ever build it.

As for valves which is what was asked about. If you really want to upgrade your valves (which you wont need to do until over 500hp) Evo valves might be a slight upgrade. No need to go with oversized valves until way up there... yet again something that has benefits but you dont really need.. but salesmen will not tell you that if they dont have to.

carguyf545 · Post by **carguyf545** » Fri Apr 21, 2006 11:32 am

i took a head and cut it in half, then i ported my head. i will post pics asap(computer is down), well i might not post the pics in the next year. but i do have the pics.

4G63Turbo · Post by **4G63Turbo** » Tue May 16, 2006 1:57 pm

DJpowerHaus wrote:
I'm going to see how much of a bottle neck this stock head is. I'll have bolt ons but no porting. When my cousin / uncle and I looked at it when it was appart last summer we couldnt find much casting to clean up. Mitusbishi makes some good parts.

AKA HKS

this is new info to me, is HKS associated with mitsu?

Post by **DJpowerHaus** » Tue May 16, 2006 3:23 pm

Rumor has it that HKS designed the DOHC head for the 4G63. Not sure where this came from or if it is true or not. HKS did design a DOHC head for the G54B as well as countless other majorly reworked parts for other engines.

Hard to verify though. HKS seems to be hiding everything about its history from 1980 - 1988.

Here is a cool little car you can read up on that wasnt a collaboration but shows the interest HKS had in the Starion at one point:

http://groupbrally.com/mitsubishi.shtml
(Scroll to the bottom.. and yes its a work in progress... converting from google translated japanese is a chore)

(NA)turalyRWD · Post by **(NA)turalyRWD** » Tue Aug 01, 2006 11:45 pm

Ok maybe a little late but if u havent upgraded yet i highly discourage any major enlargening of the passages and 1mm oversize valves heres my train hop on if you like. Alright a larger head may flow more on the flowbench but the major thing the flow bench lacks is the piston starting compresion before the valves are 100% closed. So the easier it is to get in its just as easy to get out correct. Its all about velocity hence the smaller diameter but smoother flow*this is where polishing comes into play. Next we have the ovesize valves and until recently i was on the sweet bigger must be better road. But no longer. Your valves only have soo much space around them for the air to come out correct. If you look at the valve placement on the 63 head the bigger valve would have air slamming into the cylinder walls on ruffly one quarter of each valve. So my theory is to debur both sides of the head and slightly enlarge/smooth intake side towards the middle of the cylinders and polish the hell out of them. And to enlarge the exhaust side all the way around and polish it a little. Make any sense to anyone?
I do my best to keep it short i swear.

Garrett

rarson · Post by **rarson** » Wed Aug 02, 2006 2:36 pm

So, your first point is reversion, right? It is easier for air to get in and thus easier for air to get out (the very reason why DOHC engines typically breathe better at high rpms and produce less torque at lower rpms) and making the valves bigger would hurt this, right? Well, I pretty much agree with that, but I think you'd just be shifting the powerband a bit higher, potentially making more at the top end.

Secondly, you're talking about valve shrouding, correct? Which would get worse with larger valves. I agree, but here is where the total setup comes in. One of the big reasons Marco used 2.4 blocks in his strokers was for the larger pistons. The bigger the bore, the less the valve shrouding.

So, I am agreeing with you with an asterisk: yeah, with a stock bore, larger valves probably aren't such a great idea, but if we optimize the entire setup, I think they can be a benefit.

Now there is something else interesting I noticed the other day: the KA24DE has some huge valves. Along with it's huge rods, it seems like this engine was built to rev and then choked by possible the intake manifold (and probably exhaust, too). The intake valves are 36.7mm and the exhaust are 31.3mm. That's pretty big! But the bore is also larger (than the 4g63) at 89mm. Ironically, the SR20 and KA24 share the same bore spacing (obviously the SR20 is a much shorter engine though) and yet, while you can get 90mm pistons for the SR pretty easily, I have yet to see any KA pistons in 90mm. My guess is that 90mm would require sleeving the KA and that the .5mm extra bore wouldn't be worth the cost of sleeving.

Anyway, the size of the KA24DE valves really surprised me.