ported head and bigger valves

[dsmjay]

hey guys ive got my motor tore down for all my new parts going in. And i figured that while i had the head out i might as well do it right with comp cams, manley springs/retainers...and so i got the bright idea to do the 1mm oversized valves and getting the head ported and polished.

my question is what kind of gains hp/tq did you guys that got your heads done?

i'll be running a 50 trim, the cams are the mid ones that sbr sells.

 

[dsmjay]

50 people looked and no one has an educated guess...i know there are dsmers with bigger valves and ported and polished heads on their cars

 

[nanokpsi]

I'm sure for a lot of peopel, its a tough guess. Personally, I am doing so many changes at once it would be hard to see what the head is worth. Cams themselves are proven to be a great mod Usually worth about 30-40whp in the big end. Cleaning up the head will probably buy you 10-20 more whp but that is very hard to prove/say.

hth

 

[dsmjay]

i understand that...im doing so many things right now too...my motor is getting completely rebuilt as we speak with forged internals head work..cams..turbo..etc. just curious if anyone had done it and had any dyno proven results

 

[fourreGsixty3]

I cant be exact with hp/tq gains but I would first say which comp cams? the 101200s same as hks 272s which are proven to ad 35hp to fly, and as for porting/polishing that allows for better flow and technicly doesnt add hp...just free's it up, and the +1mm valves for both intake and exhaust I would say add 15 whp and 9 wtq but those are just an estimate from an article I read that had exacts from an rb26dett head.

 

[dsmjay]

was that a dsport tuner mag?

 

[Verticaljump1]

Personally I wouldn't go with the 1mm oversized valves, you have no need for them. It's going to cost you around $250-$300 to get the valve seats cut to fit the larger valve, and you have to get the "valve pockets" ported to take true advantage of the 1mm oversized valves. I'm not saying they are a waste of money because with the right moves they can make some good power, but I think it would be more of an advantage to you to spend the $500 (between the acutal valves and machining) somewhere else. I would definately agree with you to get the head cleaned up a little bit though. The exhaust ports could use a tad bit of work, you can leave the intake ports or knife edge the divider, but definately smooth out and port out the valve pockets. Don't go crazy because velocity gains you power not size. If you smooth out the casting flaws in the valve pockets and maybe move a tad bit more material, get your exhaust ports worked and polished, you'd have a damn good head.

 

[dsmjay]

i got a good deal on the valves (185) and i only will have 150 into the labor from a local friend that does this shit for a living...so really for what i have into it...its not bad at all

 

[GVR4592]

You won't see much if any gain from going to oversize valves. Porting will net you a small gain, but these heads flow pretty well stock. Are you planning on porting the head yourself?

 

[dsmjay]

You won't see much if any gain from going to oversize valves. Porting will net you a small gain, but these heads flow pretty well stock. Are you planning on porting the head yourself?

please stop posting your oblivious opinions on dsmtuners. this is the reason this place gets the tag of MISINFORMATION.

how the hell are you going to try and sit here and say that bigger valves and get the head ported and polished isnt going to net me any gain?!? thats where the power is made...air and fuel. no im not porting myself, im having a reputable shop doing it.

stop the maddness of your post

 

[GVR4592]

I didn't say a ported head wouldn't help you out. I said you won't see much if any gain from going to bigger valves and a ported head would net you small increases. With a turbo that only flows 50 lbs/min porting the head will give you some mild increases on the top end but nothing to write home about. I've had used heads with oversize valves and my 60 trim and I didn't notice a thing. Not 1 lb/min increase from the dsmlink logs. I know a few semi-local guys that tried the same thing and saw no increases. One of them is evil_eagle on here, check out his mod list and 1/4 mile times.

Without unshrouding the valves (which is very difficult with the 85mm bore) you will probably be hurting flow more than anything.

 

[dsmjay]

what cams we're you guys running when you had this done. other people that i have talked to had nothing but good things to say about getting it done...they we're on other cars, but still the same basic principal is there.

 

[GVR4592]

I was using stock cams, evil_eagle was using 272's. There are a few threads on NABR and dsmtalk about it.

 

[krummel21]

I'm basically in the same boat I am taking my head off to do some work to it the only difference is I plan on going to a 2.3 or 2.4 stroker later and I don't know if this will make a difference on what I should get. Here is what I was planning.

BC 280 cams - $330
BC Springs and retainers - $219
Revised Lifters - $140
1mm oversized valves - $273
machine work for the 1mm valves - $?
3 angle valve job - $?
JM Fab intake manifold - $475
gasket match intake and exhaust - $?
Miscolanous - $?

My question is with my current mods do you guys recommend removing some things (i.e. the oversized valves) and what things might you recommend adding. I really want the greatest performance gains the cheapest route when it comes to the machining work.

Also if you guys could fill in estimates on the places I don't have prices that would be awsome.

Thanks,
Krummel21

 

[all_motor_mike]

I'm basically in the same boat I am taking my head off to do some work to it the only difference is I plan on going to a 2.3 or 2.4 stroker later and I don't know if this will make a difference on what I should get. Here is what I was planning.

BC 280 cams - $330
BC Springs and retainers - $219
Revised Lifters - $140
1mm oversized valves - $273
machine work for the 1mm valves - $?
3 angle valve job - $?
JM Fab intake manifold - $475
gasket match intake and exhaust - $?
Miscolanous - $?

My question is with my current mods do you guys recommend removing some things (i.e. the oversized valves) and what things might you recommend adding. I really want the greatest performance gains the cheapest route when it comes to the machining work.

Also if you guys could fill in estimates on the places I don't have prices that would be awsome.

Thanks,
Krummel21

bore for o/s valves 50.00-75.00
3 angle valve job with assembly 180.00-250.00
gasket match intake- it should be close if your getting a JM intake if not then anywhere from 50.00-100.00............... and u dont want to gasket match the exhaust manifold (assuming your exhaust ports are gasket matched)


AMM

 

[krummel21]

How bout the list do you think I need it all or will i get close to the same benefits without some of things?

 

[all_motor_mike]

How bout the list do you think I need it all or will i get close to the same benefits without some of things?

i think a race ported head with o/s valves those cams and that IM is going to do wonders for that engine............. i would not take anything away from that list but thats just me. now what are u doing about the exhaust side of things.......... including the turbo?


AMM

 

[krummel21]

I should have everything in my profile but I have an evo exhaust manifold (wish I had the new fp exhaust manifold), fp3052 turbo and 3" downpipe and exhaust. So then you think with that turbo I should be using a lot of the potential from that head and there is nothing there that is over the top? Lol souds like I don't want everything, thats not true it's just that I don't want to spend more money than I need to and have an over the top head that I will never see the full potential with out a bigger turbo or something else.

 

[TunaTalon]

Larger valves will allow higher air flow. If your engine is bottle necked by air flow then larger valves will help. According to the Mechanical Engineers handbook (http://www.ongcreports.com/HR MANUAL/mech_eng_handbook.pdf) Peak volumetric efficiency is at about 0.5 mach number through the intake tract and sonic limiting hits hard at 0.6 mach number. See Wallace Racing - Mach Index Calculator for a mach number calculator but, but, but... it's based on one valve per cylinder so enter RPM/2.

If your engine is limited by something else like turbo capacity or fuel flow then bigger valves will just move your peak torque up to a higher RPM and provide no more horsepower.

For a simplified explanation see page 5 of my StrokeOrNot document at http://www.kidzuku.com/StrokeOrNot.pdf.

 

[krummel21]

I guess does anyone know how many lb/min you would have to be flowing to actually need the os valves? I read the article but it really doesn't give a definative answer from what I saw.

 

[TunaTalon]

I guess does anyone know how many lb/min you would have to be flowing to actually need the os valves? I read the article but it really doesn't give a definative answer from what I saw.

The limitation of flow through valves discussed in StrokeOrNot is velocity measured in mach number. Your question about pounds/min is a mass flow rate.
At any velocity and valve size, mass flow increases linearly with boost measured in atmospheres.

For any VE, valve size, and displacement, velocity through the valves increases linearly with RPM.

For the very narrow range of sizes in question for any given VE, and RPM the mach number decreases linearly with valve open area.

For any given lift valve open area increases with the square of the valve size.

Hmmmm I’m beginning to see why there’s no profit in bench racing.

Or you could go to Wallace Racing - Mach Index Calculator intake port mach index calculator and check out the conditions you are interested in. The calculator assumes one valve per cylinder so enter RPM/2 for the 4G63.

Also see Automotive Converters and Calculators for calculations of other engine features including effects of boost and VE.

 

[4pistons]

One of the best reasons for going with oversize valves on 1G 4G63 head is to correct for the ugly bowl area caused by core shift that's prominent on a lot of these heads. I've seen at least 6 of them that were terrible!

The bowl area ends up "larger" than the seat, especially on the long turn side, and the stock seat ends up being a "wall" or "ramp" that screws up airflow right at the valve. Good thing we all run boost and just cram air in anyway but it hurts flow.

If the head is cut and oversize seats are installed along with some minor porting, the transition from the bowl to the seat is alot smoother.

Now, are ALL 1G heads suffering from core shift? I doubt it. But oversize valves will correct for the core shift and you'll get a power increase across the entire rpm range.

Rick - '91 GSX