Keep em, loose em, or trim em: Injector Bumps

nodestiny · Post by **nodestiny** » Fri Sep 16, 2005 4:45 pm

I have heard a lot of people say that filling in the top of the magnum intake manifold with JB Weld till hard, then filing down the injector bumps smooth will help give a bit more airflow in there. The other side says it helps mix the air/fuel (where its fuel injected, so how much does this actualy help?)

What do you guys say?

Ifixyawata · Post by **Ifixyawata** » Fri Sep 16, 2005 4:51 pm

I know that a basic principle of port and polish work is to avoid making the intake passages, on the head or intake, smooth because supposedly the a/f mixture benefits for it. This applies to both F/I and old carbed engines.

nodestiny · Post by **nodestiny** » Fri Sep 16, 2005 7:49 pm

yeah, i can sand it most of the way, then sandblast

That would give it a decently rough surface!

nodestiny · Post by **nodestiny** » Mon Sep 19, 2005 10:15 am

Sooo.... injector bumps? Figure this is a decent size resistriction... anybody have reason to keep em?

Baal · Post by **Baal** » Mon Sep 19, 2005 9:29 pm

Ifixyawata wrote:I know that a basic principle of port and polish work is to avoid making the intake passages, on the head or intake, smooth because supposedly the a/f mixture benefits for it. This applies to both F/I and old carbed engines.

wtf?

rice_eater · Post by **rice_eater** » Wed Sep 21, 2005 2:36 am

Baal wrote:
Ifixyawata wrote:I know that a basic principle of port and polish work is to avoid making the intake passages, on the head or intake, smooth because supposedly the a/f mixture benefits for it. This applies to both F/I and old carbed engines.
wtf?

yeah no kidding...the point is to make them smoother not rougher so air flows faster and straighter

Ifixyawata · Post by **Ifixyawata** » Wed Sep 21, 2005 2:45 am

Nevermind, I don't know shit. Do whatever you want to, I'm just relaying information I've heard over and over again. I've never port/polished anything so I can't speak from experience. Again, just relaying information.

Baal · Post by **Baal** » Wed Sep 21, 2005 4:11 am

Well probably what you mean is that if the polished is excessive.. (mirror quality) the fuel sometimes condensates on the surface of the ports.

That used to happen more in carburated engines tho.

BlackRoseRacing · Post by **BlackRoseRacing** » Wed Sep 21, 2005 6:46 am

The theory of the rough surface is for better atomiztion of the air and fuel. The problem is, it mostly pertained to carburated vehicles due to the lack of technology and crappy design.
With newer injected systems there is no need for the roughness because the fuel injector design is to aid in the atomization, hence the fine spray. Where as a carb would just dump fuel into a manifold and it would puddle up.
On injected vehicles smoother is better. More air flow in and out.

nodestiny · Post by **nodestiny** » Wed Sep 21, 2005 9:07 am

DOH!

I appreciate the help on P+P, i have already decided to do a minor job of porting (just ridding of the nasty rough casting)...

But what im trying to find out: Fill the Injector Bumps with JB Weld and file down the inside so it gets more airflow, or leave them for whatever purpose they serve?

Baal · Post by **Baal** » Wed Sep 21, 2005 3:00 pm

BlackRoseRacing wrote:

The theory of the rough surface is for better atomiztion of the air and fuel. The problem is, it mostly pertained to carburated vehicles due to the lack of technology and crappy design.
With newer injected systems there is no need for the roughness because the fuel injector design is to aid in the atomization, hence the fine spray. Where as a carb would just dump fuel into a manifold and it would puddle up.
On injected vehicles smoother is better. More air flow in and out.

lol why the "im with stupid" smiley, i sad what you said -.-

Post by **Diablo0** » Wed Sep 21, 2005 6:04 pm

If you wanna get rid of the bumps you must fill them somehow... with actual welding or JBweld...

http://www.nrgyheads.com/projects/sohci ... take20.jpg then to make it look better, grind and sand it smooth.

http://www.nrgyheads.com/projects/sohci ... take21.jpg

Resulting in no bumps

http://www.nrgyheads.com/projects/sohci ... take13.jpg

I don't have any dyno numbers but based off word of mouth the bumps are what cause the most loss in the intake system. I'd know for certian if I had my Intake Mani back from NRGY to test it.

Baal · Post by **Baal** » Wed Sep 21, 2005 7:19 pm

WTF... isnt that an outside pic?

Post by **Diablo0** » Wed Sep 21, 2005 7:48 pm

Yes but it shows what needs to be filled ontop so you can grind down in the inside and not grind through.

Baal · Post by **Baal** » Wed Sep 21, 2005 8:24 pm

whats the purpouse of those bumps anyway?

talking about bumps... anyone have seen the exhaust port, they have a bump in the lower part totally obstrucring the way out of gas, is it a cooling passage or WTF is that.

nodestiny · Post by **nodestiny** » Thu Sep 22, 2005 9:15 am

The only thing i could see the bumps doing is keeping the incoming air from hitting the spray of fuel instantly. Instead, it seems it would create a small "dead zone" so the fuel can be pushed a bit further before hitting the incomming air.

Could be totaly off, though!

so filling them would probably be the best way to go? Might take a bit more time on my manifold then

BTW, here is my mild P+P job. Didnt open it up much, but VERY smooth compared to the rough bumps. Used a brake hone from NAPA to do this. Faster way it to wrape the hone in 60 grit first, then smooth out with hone itself later. Obviously, the right side is done where the left side is the OEM casting.

BlackRoseRacing · Post by **BlackRoseRacing** » Fri Sep 23, 2005 5:41 am

still needs a lil more work