I have been wondering if anyone has ever polished the runners on thier intake plenum (upper and lower). I read an article that talked about intake runners on wet intakes, such as carbeureted and throttle body injected engines. Also about dry intakes such as the ones on port injected engines. The article said that wet intakes could benefit from a grainy texture as it helped with the atomization of air fuel mixture. On the contrary, dry intakes could benefit from smooth walls on it's runners, improving air flow all the way to the cylinder head. I've been thinking a lot about this. There is a procedure called Extrude hone, where they push an abrasive paste like goo through the passages to be polished. I don't even know if any of the machine shops around here do this.

 

Hmm im interested in this as well. I talked to a gm shop owner a few years ago about it. He said its Not the greatest idea since they were designed for it for fuel atomization.

 

In a cpi intake, the fuel injector poppets are at the end of the runner, right before the intake valve. So, the runner is dry all the way up until then. There isn't any fuel atomization going on. I mean, thats how I see it. What do you think chris015? Anybody else have any input or theories on this?

 

Well,what im thinking is since the 1st gen is like a oldschool manifold with a carb,the fuel is dumped with a little more volume into the center of the intake,which then is pulled to each intake by vacuum. So the motor needs to work with more fuel atomization for better air fuel ratio for better performance. poppit valves spray more of a finer mist then a tbi injector since you have 6 injectors to power the engine,instead of just 2 big injectors. Plus i think a factor of having better flowing heads (vortec) helps with fuel mixture for the poppits too.


I think i said all that right..

 

I can get an intake plenum set up from a junkyard pretty cheap, I just don't have access to an extrude hone or a flow tester. Plus, I don't have a dyno to test the rear wheel horse power once the mod is complete. I guess I'll leave it alone unless someone knows some definite results

 

Man, I was just on bonehead performance site. They are the ones who do the extrude hone process. Forget it. The prices are way to high for me. They have some impressive numbers and pictures. I am not building a racecar or anything, so I guess I'll just keep it as it is.

 

Most guys that port and polish simply use tootsie rolls on a die grinder. You can remove what needs to be and get the texture you want just fine by using the correct grade of sandpaper. Personally I've done a few wet manifolds and never had any problems.


The exhaust you still want smooth as you can get on either type so you go down even more with the sand paper.

I'd leave the high priced fancy stuff to the full out race cars unless you just have money to waste. That the case I can give you my pay pal info.

 

That would be my suggestion. The difference between the fuel being introduced prior to the intake runner versus the end of the runner has already been covered, so I won't get into that. Smoothing the runners out in the intake of an engine that introduces the fuel prior to the intake runner is a bad idea for a street driven vehicle. The smooth walls will actually promote fuel drop-out. This will result in uneven distibution of the air/fuel mixture and you'll end up with come cyliders running rich, some running lean and overall poor performance. On an engine built strictly for racing (high rpm for short distance) you would have potential for an increase in performance, but not a street engine that is subjected to constant stop and go traffic. If you want to experiment you could gain a couple hp and a slight improvement in mpg by port matching the intake to the heads, and the exhaust ports to the exhaust manifolds, but I wouldn't go any further into the runners than about an inch when you blend them.

 

This was rhe confirmation that I was looking for. I will probably never get around to it, but I could actually handle a port matching job myself. I have actually done them on other engines. This motor in my Jimmy runs, and don't think I want to tear into it just to do this one mod. Maybe when I rebuild it someday.