Intake Manifold finish

[WeingartnerRacing]

I have been wondering about intake manifold finish and a post on yellowbullet got me thinking. I try to give customers a manifold that has a relatively smooth finish (60grit) but on my personal stuff I usually don't bother to make it look beautiful, I just leave it as the carbide leaves it, as long as it performs. However I had alway thought that the ruffer surface of the manifold helps with atomization of fuel and some other things related to air until I saw the post on yellowbullet. The thread has since been deleted but it had a picture of intake that Slick Rick had done for one of the Texas Pro Stock motors. It was beatuiful and was smoother, not ruff, definetly cartidge rolled. I am cetain that Rick's customers could care less what the intake looks like as long as it performs. Those motors where looking for the every last horsepower but he still choose the smoother finish over the ruff. Does anybody have any thoughts on the matter or has done any A to B testing? I have done intakes both ways but never on the same engine.

Notalent if ATK is up to it I would love to do a comparison.

[cv67]

Be curios to hear opinons also
notice speirs leaves his rough
Am going to have my intake flowed..may/may not do more work on it thinking about leaving a carbide finish

[jacksoni]

Our own "Me Speedtalk", Don Terrill says in his book that a rough surface is worth power over a smooth polished one. Or maybe he was talking about the ports. Don't have it handy to check.

[Old School]

Go to the forum on Maxracesoftware if you have purchased Pipemax.

[BOOT]

Been wondering this myself. Say for example you have a small runner hi-velocity, I would lmost think a smoother finish would be better. Where in a large lazy runner you need ruff to help keep atomized more. Or in non street driven where you launch at higher rpm, I would also think smooth.

[rookie]

Read this article about Larry's test. http://hotrodenginetech.com/pipemax-cre ... d-porting/

[Olefud]

If it helps, think of surface finish as influencing the boundary layer –a thin layer of air attached to the wall that gets thicker with surface roughness. The boundary layer works to attach flow to the solid surface and can be helpful in getting the flow to turn a tight radius. On a starlight shot it adds a bit of drag and reduces to effective X-section a very small amount.
Wet flow is another consideration. In most ports the flow is such that, while the boundary layer is attached to the port wall, it has a bit of internal turbulence within. The turbulence serves to keep fuel entrained rather than wetting the wall as it may do with a high polish.
As with most things, roughness/polish is a tool not an answer.

[BOOT]

Read this article about Larry's test. http://hotrodenginetech.com/pipemax-cre ... d-porting/

When you look at his ruff finish, how is that not the same as casting finish? Doesn't that create a lot fo sharp edges in the chamber?

[bigjoe1]

I have never seen where a high polish is better,but I always do a 60 grit final with the cartridge rolls. Something that has worked real good for me is to sand blast ( glass bead ) over the cartridge rolled surface. I alway sand blast over any polished surface. I know for a fact that the ultra smooth finish on new pistons can be improved by the sand blast finish


JOE SHERMAN RACING

[WeingartnerRacing]

I understand why it should work. However I would like some comparison testing. I just don't see why if ruff surface makes more power Rick wouldn't do it on that type of manifold. I would love to leave it ruff it would save about 3 hours of work on the manifolds when I port them.

[wyrmrider]

would carb vs efi make a difference above the injectors

[rookie]

I understand why it should work. However I would like some comparison testing. I just don't see why if ruff surface makes more power Rick wouldn't do it on that type of manifold. I would love to leave it ruff it would save about 3 hours of work on the manifolds when I port them.

I would guess that with the cold induction of Prostock with all their coatings and high RPM they are probably not as beneficial as total air flow...these types of induction systems need a leaner and better atomized mixture than what your average 5500 to 8000 RPM Racer would ever obtain.

[Lasher...]

Way back in the day Clay Smith wrote about testing the polished port theory on a Flathead Ford ....... when the intake ports were polished the engine lost power over a textured finished when talking about wet flow. He said the exhaust seemed to respond to a smoother finish but that was dry flow........ he said that he put some gasoline on a flat piece of smooth glass and shot it with a blast of compressed air and all it did was spread the gas over the glass..... but when he put some gas puddled on sandpaper and hit it with air the fuel blasted off the rough texture of the sand paper..... so he theorized the rough surface on the intake ports helped keep the A/F in suspension and the mirror polished surfaced would hold onto some of the fuel on the ports and not letting it all into the cylinder.

[F-BIRD'88]

BigJoe1: are you bead blasting the piston tops to reduce the sharp machined edges of the valve reliefs? ....or some other purpose?

[bigjoe1]

I de burr all the sharp edges before I bead blast the tops. It will make the carbon film stick to the piston faster and better than the ultra smooth CNC machine finish


JOE SHERMAN RACING