Porting/Polishing question......
Thread Starter
Le Mans Master
Joined: Mar 2002
Posts: 5,889
Likes: 2
From: Castro Valley Calif.
St. Jude Donor '03 thru '26
Porting/Polishing question......
I just had some work done on my heads and intake, and I got to thinking.....
Just what the hell are the effects of this money I've just spent? I don't mean in actual numbers, but in generalities......... Logic tells me that increasing the flow on the exhaust side probably gets me additional HP/RPMs since backpressure is reduced, while increasing the intake side would tend to improve the torque.......
Am I thinking in the right direction, or am I all wet? And,...... maybe it's not good for a guy like me to be doing all of this thinking stuff in the first place :lol: Maybe I should just take my better numbers and run........ :jester
Just what the hell are the effects of this money I've just spent? I don't mean in actual numbers, but in generalities......... Logic tells me that increasing the flow on the exhaust side probably gets me additional HP/RPMs since backpressure is reduced, while increasing the intake side would tend to improve the torque.......
Am I thinking in the right direction, or am I all wet? And,...... maybe it's not good for a guy like me to be doing all of this thinking stuff in the first place :lol: Maybe I should just take my better numbers and run........ :jester
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: Porting/Polishing question...... (Caboboy)
You guessed it, increased flow capacity. There are certain areas of the ports which cause a bottle neck effect. The molocules running down the sides of the ports strike these inperfections and get bumped into the crowd in the middle. Think of it like a 4 lane highway and suddenly the cars in the two outer lanes decide to turn into the traffic in the center lanes. What happens? Well one thing for sure, everyone has to slow down. By removing small amounts of material in the right areas, it can insure a more even pass for all the air/fuel molocules to pass thru without having to collide with one another. Polished combustuon chambers helps rid spent fumes fron the cylinder for a fresher charge the next round, as well as greatly reducing the chance of carbon buildup.
Thread Starter
Le Mans Master
Joined: Mar 2002
Posts: 5,889
Likes: 2
From: Castro Valley Calif.
St. Jude Donor '03 thru '26
Re: Porting/Polishing question...... (Jvette73)
Jvette, thanks for the response :cheers: I may not have worded my question well enough though. What I was really after was info on the net effect on each side of the head.......
ie: does porting on the exhaust side affect the HP more so than torque, while the opposite would be true for the intake side (torque more so than HP)?
Maybe I've got too much time on my hands, I dunno, but it occurred to me that we all seem to be hung up on intake flow too much when we talk about heads (this head flows blah blah blah; that head flows blah blah blah), when in reality we need to be concerned with the relationship of flow to the type of motor we want to build.
For example, I'm doing a torque motor with a superram and a cam that runs out of range at 6000K.............do I need to be looking at a specific side of my heads to enhance my objectives? And, how valid is the flow % (intake to exhaust) that you hear so much about?
Like I said, maybe I just have too much time on my hands :lol:
ie: does porting on the exhaust side affect the HP more so than torque, while the opposite would be true for the intake side (torque more so than HP)?
Maybe I've got too much time on my hands, I dunno, but it occurred to me that we all seem to be hung up on intake flow too much when we talk about heads (this head flows blah blah blah; that head flows blah blah blah), when in reality we need to be concerned with the relationship of flow to the type of motor we want to build.
For example, I'm doing a torque motor with a superram and a cam that runs out of range at 6000K.............do I need to be looking at a specific side of my heads to enhance my objectives? And, how valid is the flow % (intake to exhaust) that you hear so much about?
Like I said, maybe I just have too much time on my hands :lol:
Drifting
Joined: May 2001
Posts: 1,329
Likes: 12
Re: Porting/Polishing question...... (Caboboy)
There is no relationship between exhaust port and HP or torque, same for intake port. The fact is that depending on your engine ci, you will need a certain amount of flow on the intake side to fill the combustion chamber. Proportionally, you will need a certain flow on the exhaust to get rid of the fumes. Your cam will take a role in your port size too and this depends on lift, duration and overlap. I won't try to describe the effect of each caracteristics as I'm no expert in cams (and very few are). Another point to consider is velocity: The smaller the port, the faster the flow which is important at low RPM. This will give you more torque at low rpm.
I'm sure you heard all this before and you're trying to find the magical reason for this but you're not looking in the right direction.
I'm sure you heard all this before and you're trying to find the magical reason for this but you're not looking in the right direction.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Porting/Polishing question...... (Caboboy)
On the exhaust side you have to look at the total system valve to exhaust pipe tip. Exhaust back pressure will ruin the best designed port & full length headers. Because it won't have the high and low pressure waves. The higher the E port flow in CFM the less durration you need to make a certian power level. Your big ci is going to need lots of port flow. especially if you have N2O in mind. I have spent alot of time on DD2000 and it seems that once the exhaust port gets up around 230 cfm the motor is maxed out on TQ Your can vary the exhaust duration 16-18 degrees @ .050 and the max TQ figure never really changes much. Just the RPM where it occurs.
So the intake is where you want to invest all the money.
My heads are at the race shop getting new wimpy springs. I'm down sizing to 165-175# closed for up to .700 lift. Better 8620 heat treated steel Crane Pro lifters and CC Billet roller cam with extreme profiles. I'm going to make this one last longer
So the intake is where you want to invest all the money.
My heads are at the race shop getting new wimpy springs. I'm down sizing to 165-175# closed for up to .700 lift. Better 8620 heat treated steel Crane Pro lifters and CC Billet roller cam with extreme profiles. I'm going to make this one last longer
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: Porting/Polishing question...... (gkull)
Check this out, pretty informative.
http://www.ws6transam.org/afrflowdata.htm
http://www.ws6transam.org/afrflowdata.htm
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: Porting/Polishing question...... (Caboboy)
I think you're hinting on how the runner size affects the engine. Take two heads that flow the same blah,blah,blah but one has a 210cc runner while the other has a 185cc runner.
The smaller head should/will make more torque and HP at a lower RPM if all things are kept equal. The larger head will hit it's peak(similar) numbers at a higher RPM.
More cubic inch will make the larger head trend towards the smaller head. The manifold tunning should fall within the heads range.
That's it in a nutshell as I understand it and apply.
KM
The smaller head should/will make more torque and HP at a lower RPM if all things are kept equal. The larger head will hit it's peak(similar) numbers at a higher RPM.
More cubic inch will make the larger head trend towards the smaller head. The manifold tunning should fall within the heads range.
That's it in a nutshell as I understand it and apply.
KM
Le Mans Master
Joined: Jul 2001
Posts: 8,183
Likes: 3
From: Santa Maria, CA
Re: Porting/Polishing question...... (Caboboy)
Cabo, I called your engine shop in Newark today. I asked the gal about porting the kind of manifold we have. Right away she knew what I was talking about and gave the definite impression it wasn't fun! Quoted me six bills and I politely said thanx; that's all I was wanting to know at this point. And then your
crossed my mind immediately!
:lol:
Sticker shock. Thank you tho for providing the contact info, I appreciate it. :cheers:
Just what the hell are the effects of this money I've just spent? maybe it's not good for a guy like me to be doing all of this thinking stuff in the first place :lol: Maybe I should just take my better numbers and run........ :jester
:lol:
Sticker shock. Thank you tho for providing the contact info, I appreciate it. :cheers:
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Thread Starter
Le Mans Master
Joined: Mar 2002
Posts: 5,889
Likes: 2
From: Castro Valley Calif.
St. Jude Donor '03 thru '26
Re: Porting/Polishing question...... (gkull)
George, I was in your neck of the woods last Thursday in the Vette and I wanted to stop by soooooooo bad! Problem was I had an early appointment at work the next day and I just couldn't wait for you to get off work :sad: I really wanted to see how things have gone since you tore the motor down.
Larry, what a terrific site. It really illustrates the step by step improvements to be had when you start spending your money :lol: Good luck on your project!!!
Kelvin, I think I'm pretty dialed in with what I want this thing to be, but the proof will be in the pudding when it goes together. I'll be ready to take you up on that offer with the diacom when I get back from Mexico. I guess it's about time I got into the new millineum :lol:
Paul, yeah, I think she's had it with S/R work, she complained the whole time! Did you ever see the flow numbers she got on my heads though? Incredible!!
Geeze, the thought just occurred to me we could buy a house with all the money we've spent on our motors and stuff! See, I told you I should stop thinking :lol: :lol:
Larry, what a terrific site. It really illustrates the step by step improvements to be had when you start spending your money :lol: Good luck on your project!!!
Kelvin, I think I'm pretty dialed in with what I want this thing to be, but the proof will be in the pudding when it goes together. I'll be ready to take you up on that offer with the diacom when I get back from Mexico. I guess it's about time I got into the new millineum :lol:
Paul, yeah, I think she's had it with S/R work, she complained the whole time! Did you ever see the flow numbers she got on my heads though? Incredible!!
Geeze, the thought just occurred to me we could buy a house with all the money we've spent on our motors and stuff! See, I told you I should stop thinking :lol: :lol:
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Porting/Polishing question...... (Caboboy)
When your here I have 1100 hundred some hours of sick time on the books and I know where we could go! :lurk:
Every cam company said I had the set up for high 8000's at a loss of life because of high spring pressure. I think ER friction add and light oil kept it going. I always raise hell. I never did have anything last that long. I must have done all right because the bore still has all the cross hone markes. Not bad for a garage motor
Every cam company said I had the set up for high 8000's at a loss of life because of high spring pressure. I think ER friction add and light oil kept it going. I always raise hell. I never did have anything last that long. I must have done all right because the bore still has all the cross hone markes. Not bad for a garage motor
Le Mans Master
Joined: Mar 2001
Posts: 9,464
Likes: 1
From: Modesto CA
Re: Porting/Polishing question...... (gkull)
Tim,
The motor that's going in to my vette is all based around a 180cc Head that flows 230/118 @ .560". The intake is matched to flow 230cfm at the same thing. I'm trying to keep the passages as small as possible (but keep the flow up) becuase I want as MUCH torque as I can POSSIBLE squeeze out of a 383. The headers I'm using, MANY people will say that using 1 5/8" headers are too small...but in my opinion, if you're not making over 400hp, they're perfect. (I plan to make probably EXACTLY 400bhp...but torque is what wins races :D)
The motor that's going in to my vette is all based around a 180cc Head that flows 230/118 @ .560". The intake is matched to flow 230cfm at the same thing. I'm trying to keep the passages as small as possible (but keep the flow up) becuase I want as MUCH torque as I can POSSIBLE squeeze out of a 383. The headers I'm using, MANY people will say that using 1 5/8" headers are too small...but in my opinion, if you're not making over 400hp, they're perfect. (I plan to make probably EXACTLY 400bhp...but torque is what wins races :D)