I have a few LS heads laying around, so I decided to practice porting them, and will evenually have one flow tested to see how well my work is.

My question is the intake ports on the LS head are 48mm wide, and I have opened them up to 52mm wide. Should I open them up more or is 52mm enough? I do not want to go too big. I am trying to optimize the 4K to 8K rpm range of my powerband.

 

I always thought the old saying held true:

"It's what is on the inside that counts"

Meaning that opening the face of the port (any technical jargon escapes me at the moment) beyond a port match is just going to hurt performance. It's more about reworking the inside of the port to get a straighter shot around the face of the valve more than anything.

This is just what I "think" as I am by no means a cylinder head guru.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EKhatch &raquo;</TD></TR><TR><TD CLASS="quote">I always thought the old saying held true:

"It's what is on the inside that counts"

Meaning that opening the face of the port (any technical jargon escapes me at the moment) beyond a port match is just going to hurt performance. It's more about reworking the inside of the port to get a straighter shot around the face of the valve more than anything.

This is just what I "think" as I am by no means a cylinder head guru. </TD></TR></TABLE>

I know what you mean. I have done a lot of research, and looked at many pictures of other porters work. I have also measured my P8R head and my B16 head, which have 50mm wide ports. The head I am porting on is a PR4 and only had 48mm wide ports. I decided to open them up. I have also taken care of the bowl work already. I have narrowed the splitter too, but did not knife-edge it. I believe in leaving a small airfoil.

My head needs a lot of work as the PR4 head only flow 197 cfm in 28" of water and at .450" of lift. Thats weak ****. I definitely need some more flow to get me past 172 whp that I am currently stuck at.

 

bump for answer to my question.

 

anyone got anything for me yet?

I will post some pics of what I have done so far later this week.

 

the mouth of the port is only 1 point or segment along the path.

I'm no headporter but it's my understanding that the whole port from start (IM velocity stack) to finish (seat angle and valve) determines whether that is big enough.

Everything is related back to your valve diameter and cam lift.

The cross sectional area along the path of the port is described as a percentage of the valve diameter.

Then you decide how much flow improvement you want at each cam lift point.

They describe this using the term "flow efficiency".

Flow efficiency = Lift/Valve Diameter or Lift/Valve Area.

So on a flowbench, they take flow volume (cfm) measurements at each raw cam lift point or they work out the Lift/Valve Diameter and choose to lift the cam at increments to get a series of L/D points . If you do it the second way, you know how efficient the port flows at various raw cam lift which is an indicator of flow speed effects. Flow speed (by affecting in cylinder mixture motion and burn efficiency) is what dictates driveability at part throttle and mid rpm WOT.


So the overall shape of the port (from start to finish along the length of the port) and the efficiency at various cam lift points dictates whether 52 mm is big enough for that powerband width that you want.

There's been debates and voodoo talk about reversion at low cam lifts and whether it's worth optimizing low lift over mid to high lift points. No need to get into that now.

But lets face it, just looking at the mouth size and ignoring the rest of the port isn't a good idea. You have to have a rough idea of the overall shape.

Where the headporters are ahead of you is: because they've done a ton of these, their experience kind of tells them what size (cross sectional area) combinations that they need along each segment of the port's length to get a certain flowbench curve shape that they want. They kind of know by experience that a certain range is good enough to deliver the flow quality at low to mid rpm without giving up the peak flow for peak hp.


So the IM runner diameter, port mouth opening (what you've zoomed in on), SSR steepness, bowl, seat angle, valve area all combine to give you a net effect at each cam lift point. They usually describe the cross-section along each point of the port (including the IM runner btw) in terms of % of the valve diameter or % of the valve area.

I kind of described this over at Team-Integra.net but the server is down, so I can't link the image to show you what I mean.

But that's the context that you have to put your question under.

You pretty much have to let everyone know your peak hp goal too (so that they know the peak cfm that you need at max lift), you max cam lift, IM runner diameter, seat angles, and valve diameter so that the experienced guys can say, yeah...52mm is good enough or not (or close enough).


It's the big picture not the tunnel vision focus into 1 segment only.


btw 4000-8000 rpm is a pretty wide powerband. I don't think that's realistic. Do you? I mean Erick Aguilar's powerband is only 3000 rpm wide and he's a pretty good tuner. Most of us all motor plebs jump for joy if we get 2000 rpm wide powerbands.






Modified by Michael Delaney at 12:55 PM 12/27/2005

 

Thanks! Do you have any formulas that may help me? i like crunching numbers!

I have done more than just open up the mouth. I have done some work in the throat and bowl area as well. Whether or not it is beneficial or not, only time will tell. For reference to how I approached teh head to port, I looked at photos on port work on LS heads by various porters. I have multiple angles of teh ports to give me and idea of what areas to work.


Some measurement that I can give you off teh top of my head:

-My Intake valves are 31mm, but may be upgraded to 33mm if I can not find it possible to use my P8R head. A valve job is a must on teh list before teh head will be used.

-My cams are 62404-2 made by Crower. They have a max lift of .445" on the intake side, and .434" on the exhaust side.

-My Intake manifold is made by Skunk2, and is similar to an ITR IM. The runners are close to 7" in length. The IM will be port matched to the head or left slightly smaller. Before porting the head teh runner ports were larger then the Intake ports. Port mouth is 52mm wide on the Intake side and 45mm wide on the exhaust side.

-Valve Angle in relavence to the piston is 27 deg.

-How do I measure SSR steepness?

-My current powerband is from 4300 rpms to 7100 rpms where I peak at 172 whp and continue old that power to 7600. I honestly do not care about peak numbers, I just want a stronger powerband. If I gain 15-20 whp in the midrange and only 10 whp at peak, I would be more than happy. If I had to have a goal peak wise, 200whp would be nice to hit.

Give me a formula and I will crunch numbers! I will take pics and post them so my work can be critiqued. Like I said in the first post, this is more of a learning experience for me. I have many heads that are given to me for free(b/c no one wants an LS head) so I can practice all I want!

 

no formulas.

just run the flowbench and have them do a flow efficiency calculation run as well to see where you're hurting: i.e. low, mid, or high lift.

I'm not the guy to ask...you have DonF, RLZ, omniman, Max_CFM here...those guys can give you more insight than me.

here's an example on the net with a domestic port where they choose specific diameters in cross section along the length of the port from the IM to the seat and express it as a %age of the Valve Diameter:



they also run the steady state flow at various test vacuum pressures for a specific flow/valve area and actual measured flow velocity (after it's been converted using pressure probes and pitot tube measurements)

 

Still no feedback from the pros, so I have decided to take pics of my work....so far.

I am no pro by any means. I am just practicing and I am looking at getting some feedback from some people to see what I can improve on. As you will see in the pics, I increased the port size from 48mm wide stock to 52mm's wide. I didnt gasket match, but wonder if I should. All work so far has been done with a Tungsten Carbide bit. The ports still look a little messy, but I have not cleaned the head yet. Please leave me some feedback and tell me what I need to do.

 

you will need bigger valves for the bigger port

 

There several approaches to porting a B18B. If you are staying with lower lift cams and don't plan to run alot of rpm (less than 8500), I would just focus on a good 30-45-60 VJ with a 0.050 wide 45. Blend the bowl into the seat and the short turn into the seat.

 

there isnt really a restriction at the port entry. there's gains in narrowing the divider, knocking down those guide humps some and at the valve seat. the gasket manufacturer doesnt care about port flow.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MAX_CFM &raquo;</TD></TR><TR><TD CLASS="quote">you will need bigger valves for the bigger port

</TD></TR></TABLE>

So basically I didnt need to go bigger on the port? I just try to make it similar to those found on the Vtec heads.

Well If I cant find a way to make the chamber of my P8R head smaller(I was thinking welding it up, and then milling), then I will most likely go at least 1mm os. There is only one company that makes 2mm os and they are very very expensive.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rocket &raquo;</TD></TR><TR><TD CLASS="quote">There several approaches to porting a B18B. If you are staying with lower lift cams and don't plan to run alot of rpm (less than 8500), I would just focus on a good 30-45-60 VJ with a 0.050 wide 45. Blend the bowl into the seat and the short turn into the seat.</TD></TR></TABLE>

I am currently running Crower 62404-2's which have .445" lift on intake and .434" on the exhaust. I plan on staying below 8500. Right now I peak 172 whp at 7100rpms and hold it until 7600.

Thanks for teh valvejob advice. If I decide to use this head, that is where it will be going once I clean it up is to the machine shop.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lohatch &raquo;</TD></TR><TR><TD CLASS="quote">there isnt really a restriction at the port entry. there's gains in narrowing the divider, knocking down those guide humps some and at the valve seat. the gasket manufacturer doesnt care about port flow.</TD></TR></TABLE>

I do not want to narrow the divider too much. I want to leave an airfoil. If you look at an airplane wing, the leading edge of the airfoil is rounded while the trailing edge comes to a sharper point. Do you think I should take out some more in that area?

 

I have seen quite a few ported heads and regardles of who did them, they all seem to have 2 things in common. 1) The intake port splitters are always narrowed and moved back. I beleive this is to reduce the turbulence created when incoming air hits the splitter. I'm not 100% on that though. 2) The short turn into the port is always straightened where it leads into the valve. This allows the shortest and straightest path in to the combustion chamber. I want to make it clear, I am not a expert, I am only sharing what I have seen done to many of the ported heads from KG, DPR, Portflow, Endyn, Alaniz, etc. I am sure that the real head porting experts can explain why these seem to be the standard mods. Good luck.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybrid_vtec &raquo;</TD></TR><TR><TD CLASS="quote">

I do not want to narrow the divider too much. I want to leave an airfoil. If you look at an airplane wing, the leading edge of the airfoil is rounded while the trailing edge comes to a sharper point. Do you think I should take out some more in that area?</TD></TR></TABLE>

yah you can take more out of the divider without actually knife-edging it.
heres a pic for reference. dont mind the X's or filler in the injector notch.



Modified by lohatch at 8:17 PM 3/6/2006

 

Thanks! I have the rest of the week off from work. that should give me time to work some more on it. I'll post new pics when finished.

 

Ive found that the key to getting good flow out of an LS head is to concentrate on the throat and the areas leading into the throat. Ive done several LS heads and this is definately the way to go. I had my first LS head flowed by Brad at RLZ and it did 228cfm with a stock valvejob. On this head i only opened up the mouth of the port to 50mm. This just goes to show that all of your gains with porting come from the throat of the port. Its all about getting more air around the valves.

Look at it this way. Lets say you have a boosted car with a 2 1/4" dp and a 2 1/4" exhaust. You can put a 3 inch dp on it and see some gains....but youre still restricted by the 2 1/4 inch exhaust. When you put on a 3inch exhaust youre not only gonna see the gains from the exhaust...but also the full potential of the dp. I hope you got this analogy...im not usually too good at them.

Heres a pic of the first LS head i did...i blew it up a little so you can see where i took most of the material off.


And heres the flowchart



Hope this helped a little

 

damn good info

 

Thanks. I got the analogy. I also plan to have the head flow tested to see what it flows out of curiousity. I have plenty more heads to practice on. Eventually I will see a pattern and catch on.

 

Yea practice is the best teacher in this case. Ive only been doing it for a little over a year and ive gotten alot better since that head that i posted the pic of. Youll start to learn what works and what doesnt. When you get the basics downs you can start focusing on other things such as port angle and how to increase VE in certain areas for higher lift or lower lift cams. I never knew it was as technical as it really is. Ive learned alot and there still a ton that i dont know.

BTW-That flow chart i posted is my port work(228cfm) with stock valve job, versus brads valve job(231cfm) with a stock port. That goes to show you how important a GOOD valvejob is...and Brad has one hell of a valve job

 

Any updates? Im interested in seeing how this turns out

If you need any help shoot me a PM!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sCeRaXn &raquo;</TD></TR><TR><TD CLASS="quote">Any updates? Im interested in seeing how this turns out

If you need any help shoot me a PM!</TD></TR></TABLE>

I will keep this up ro date, and keep you informed. No new progress, yet. I have been off all week, but I have been working on my suspension, and trying to think of a way to modify my new H-brace to fit. Right now my exhaust manifold hangs too low! I may have to custom build one.

I should be able to get some more done on the head this weekend, so keep an eye out.

 

in for the progress

 

Hopefully I will have some more pics up this week!

 

&lt;---patiently waiting...