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#1
10-31-2021, 05:09 AM
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intake manifold porting
Hi,
I've ported my RPM intake to the Felpro 1233 gasket size, which is a little smaller than my ports on the D-port E-heads. I also ported the runners maybe 3" into the intake when I did the gasket match and now I'm wondering, if I should make them a little bit rougher than they are, since some say the intake needs to create a little turbulence. I also smoothed the plenum to make it easier for the mixture to travel into the runners. Again, will it need to be a little rough here as well? I used a 80 and 120 grit and it feels pretty smooth, but maybe this isn't even considered "smooth". What do you think? Thanks! Chris |
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#2
10-31-2021, 06:36 AM
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you can get away with a smoother thqn cast finish but definitely NOT POLISHED. TOO smooth of a finish will let the fuel drop out of suspension causing raw FUEL droplets to form...this is BAD. Surface texture helps KEEP the fuel atomized in the intake track which the carburetor tried so very hard to make possible.
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#3
10-31-2021, 06:48 AM
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I don't know if this makes a difference, but I use a Holley Sniper...
What would be considered polished? I could go over with the 80 grit again or use some 40 grit by hand... still looks rather smooth, but somehow I can't imagine that this is "smooth" in terms of polishing. |
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#4
10-31-2021, 07:14 AM
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Quote:
Even with Port Injection, there is always a bit of reversion and some amount of fuel attached to the plenum walls. This is not necessarily a bad thing but you do get a small spike on the EGO Sensor when you do a "tip-in" be it a carb or EFI system. JME (Just My Experience doing emissions work and carb work) Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#5
10-31-2021, 07:27 AM
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The sniper efi still uses a wet intake unlike a PORT injection model so it would still be considered same as a carb. Clean up the casting, smooth out the radii and blend all edges...runit.
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#6
10-31-2021, 07:32 AM
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Basically I already did this, but I used 80 and 120 grit, which feels rather smooth.
So I need to know if this is still rough enough not to cause fuel droplets to form, or maybe I should make it a little rougher, maybe with a stone or 40 grit on the Dremel tool? (or even by hand) |
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#7
10-31-2021, 07:37 AM
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I suppose the straight walls can be smooth, while the tight side of any turn can remain rough.
In theory the rough surface causes a "no flow" to "low flow" boundary layer which loweres the physical CSA. You'll want to compensate for that. |
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#8
10-31-2021, 07:42 AM
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NO STONES ON ALUMINUM.....= DEATH
you can not use a stone (aluminum oxide) grinding wheel on aluminum it will load up , explode and you will die!!! go here...down to myth 8 look at the head port...that looks pretty nice http://speed.academy/10-myths-of-cyl...21545410156250 |
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#9
10-31-2021, 08:09 AM
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Quote:
 thats actually good news since I only worked on the straight paths... and maybe 80 grit isn't even what some would call "polished surface" which seems to only be a good thing on dry intakes when the runners start to make a turn, I left all the roughness since I also wouldn't be able to reach it with my tools |
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#10
10-31-2021, 08:12 AM
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Quote:
would you use a 40 grit paper by hand to make it a little rougher again, or is my finish still not smooth enough to cause any trouble? my goal was to clean up casting imperfections and help flow, but not to mess up fuel atomization |
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#11
10-31-2021, 08:36 AM
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You want a finish just like the raw manifold casting but without the pimple and casting seam/ ridge Imperfections every where you can reach in the Plenum, it’s runners and in the head if you happen to be working on that also.
I use a 80 grit roll in my slow speed grinder ( 12,000 rpm ) that I can throttle back a bit to less then 1/2 that speed. Even with a 60 or a 80 grit roll if you move it fast enough and in different directions you will end up with a finer finish then the grit of the roll you are using, so do not do that! This does not really apply to intake manifolds unless your removing a lot of material, but many times I will end polish after a 80 grit session with 120 grit. This near more mirror like finish allows me to see imperfections better, so once all is good I go back with the 80 grit roll to get the as cast texture I want. Air flow will always take the path of least resistance, just like water. This means that in following curves in runners a greater percentage of the air mass will ride on the outside wall of a curve. Also since fuel riding in that air has more mass it will at a certain air speed and turn radius try to stay on a straight path a then drop out from being suspended in the air and just slam against the outside radius of a curve. This action takes place even with the air in a runner itself. Once port air speed gets high enough and a turn gets to be a tighter radius then 15 degrees the air mass itself wanting to as posted follow the path of least resistance will try to hug the outside wall of a curve . The much heavier weight of fuel in a runner will want to take that path of least resistance much sooner then the air will! In short it’s most important to have that 80 grit finish on the outside of curves if your doing any work at all! If your doing any kind of porting work other then clean up, keep in mind that once high speed air is asked to go around even just a 30 degree bend in a port you could loose as much as 18 % of the air flow you once had!! This all hinges on the shape of the port/ runner in the bend area. If your talking about for example basically rectangular shaped intake runner then you want that outside wall to be taller, as in more like a Trapezoid. If your working with more of a oval or round shaped runner then you want to try and make that outside wall flat as if starting to form the runner into a rectangle.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! Last edited by steve25; 10-31-2021 at 09:07 AM. |
| The Following User Says Thank You to steve25 For This Useful Post: | ||
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#12
10-31-2021, 08:43 AM
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thats interesting... at the moment I can see that I removed all the imperfections like you said, because it is smoother than I initially planned
so it would be the best idea to get the 80 grit roll and use it with slow speed to get the as cast texture back... I'll do that, thanks! |
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#13
10-31-2021, 09:39 AM
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I like Steve 25's advice and approach. My mentor, Joe Mondello, (RIP) was arguably the best hand porter of cylinder heads with thousands of winning combinations from Indy Car, to Land Speed, Top Fuel and more. While the article of the 10 myths has good information and is backed by flow bench and experience, there are still disagreements of the "one way" to do things. That's why we race! From Joe Mondello's school, I learned: Street, mild performance, 800 RPM-6000 RPM, central fuel distribution through manifold, 60-80 grit finish, open texture on aluminum such as manifolds, 10,000-15,000 RPM grinder cartridge roll. Combustion chamber roof: Smooth and shiny, 120-150 grit, wet cartridge roll, 15,000+ grinder. Exhaust port, as smooth as you can get it. No disadvantage to a mirror finish other than the time it takes to get there. The smoother you can get it, you are just mimicking a longer port runner in the header. For the OP's application, I would think a smooth 120 grit finish with a wet cartridge roll or flap paper would be very nice. FWIW.
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#14
10-31-2021, 10:20 AM
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Quote:
Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
| The Following User Says Thank You to Tom Vaught For This Useful Post: | ||
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#15
10-31-2021, 10:21 AM
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I just tried to use a 80 grit roll with 8000rpm and it is now a little less smooth, but still feels smooth to be honest.. it's not feeling like it felt as cast
Am I doing something wrong? Even 40 grit by hand will not give it a rough touch in my opinion... If 80 grit or even 120 grit roll is fine, I'll just make a last round and leave it be. |
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#16
10-31-2021, 11:23 AM
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Your simply spinning the cartridge roll (1) to fast , or (2)!staying in one spot too long, or a combo of both.
If need be go back in with a Aluminium burr very very lightly and then give it a 80 grit Passover a few times. Many times once I get my shapes right I just go over areas with a fine cut cast iron burr lightly that is well lubed up so it does not load up! Also if you are using the small 1/2” diameter Dremel tool size rolls they in effect are spinning faster for any given rpm used then a 3/4” diameter roll. If your Dremel is battery powered then unfortunately there’s no other chooses of speed but 2. With a plug in type you can put it on a veriable speed box on the motor. or make one out of two wall light dimmers wired in parallel to handle the current needs of your plug in grinder. Yes, you would adjust both dimmers! The right tools for the job will always provide the best results in the least amount of time should that be a concern.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#17
10-31-2021, 11:33 AM
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I have a Dremel that can do 5000-30000rpm. I also have small rolls, so maybe I should run it as slow as possible
By hand with just a 80 grit paper wouldn't make muche sense? |
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#18
10-31-2021, 11:47 AM
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this is how the runners look after 80 grit... it feels smooth but not sure if you would call it smooth
 this is the plenum, when I did one side before redoing it with 80 grit (this is 120 grit)... not sure if this is too smooth as well, but it's smoother than picture 1 
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#19
11-01-2021, 02:28 AM
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Quote:
That thing lets go and you could have a 5lb chunk of that wheel go through your gut and you would die. I took it out of service and my boss spent 3 hours picking aluminum chunks out of the wheel with a carbide tip scribe. It made me so mad I went and found the shovel and had the guy brought in. Made him sign a grinder safety sheet, next time he is gone. For those that do not know the aluminum in the wheel creates a potential difference in heat spot on the wheel where it could crack and fail. |
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#20
11-01-2021, 06:32 AM
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Over night I now finished the intake with 80 grit at slow speed.
It may feel rather smooth but it surely doesn't look smooth. Can you tell, if this is fine, too rough, too smooth? this is how it looks:   and I seperated the water crossover: 
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