SilverTibby

Some people here might know that I installed bored intake manifold last week, but had problem with smoke coming out from bottom of the intake manifold. Today, I took out everything again, and found something that could be the problem maker.

After looking around for the solution, I found out that the bored intake manifold's four runners are much larger than the engine port openings and little bit bigger than gasket openings (just the bottom part). The smoke came out from the bottom so I thought that this could be a problem.

To prove this, I took some pictures.

This picture shows the engine port with the gasket. You can see that the engine port is smaller than gasket opening.


This one shows stock intake manifold runner with the same gasket. The IM runner is smaller than the gakset.


This last picture shows bored intake manifold with the gasket. Although it is little bit hard to see, the IM runner is little bit larger than gasket opening (especially the bottom), thus it is much larger than the engine port.


Please post your opinion on this... I really want to drive my Tiburon with this new mod.

Thanks

Jon

This shouldnt cause the problem as long as you get a good seal. But it will disrupt the airflow going against the whole purpose of the larger bore so they need matching

Red

Jon has it spot-on...

The entire reasoning behind boring the intake manifold is to provide a more fluid airstream. If the lip is mismatched AGAINST the flow, then it will cause more problems than solutions.

In nearly all cases, places where components like this match up (TB -> IM, IM -> Head, Head -> EM) the ''sending'' side should be smaller than the ''receiving'' side. Otherwise, you will get either disruption, or worst-case, flow reversion in those locations. Not good.

A properly ported head will be gasket-matched, so your intake manifold runner openings should not be larger than the gasket.

MechaniX_034

Boo yah, time for an Extrudehone port match! If you run the intake too big(like this)you'll start getting resonation in the airstream in the port(kinda like air at a certain density and certain velocity tends to bounce off of things set at a certain angle)and because of this the port needs to be re-chamfered for best flow characteristics at peak RPM. Yeah it's gonna cause velocity drop at the lower RPM range. It's a trade off, but if you wanna make power you can't make an omlette without busting some eggs you know how it goes!

Good luck.

DESIGN

It has been stated in the past that a real danger in porting our IM's is that it is real easy to go too far up the runners and mess up the injector seats. Is it possible that whomever you had do that port job had done that?

Red

The injector seats are almost on-top of the cylinder head; they are not *way down* the runners. Take a look at the third picture, see the big-ass hole dead center above the runner opening? That's the injector bung right there.

Not much to screw up smile.gif

DESIGN

Thanks RED. BTW what are the things to metion to your shop if your having the IM done locally vs. shipping it to Onpol?

Jon

To be honest from what u can see on the pics i dont think that there is a problem with the component parts on that side. Although the ports on the block side do need matching so as not to disrupt air flow. If there are no deep gouges on the block side and the gasket is in as good condition as it looks in the pic, then the only other option is that u fitted it back on wronge.

Its real easy to do because there are so many studs with the holes not much wider than them it is easy to get it on a little wonky when it looks fine(i did it). All that happens then is you end up tightening the manifold into the threads on the stud and it feels as if its bolted down but there may be a 1mm gap at the bottom that you would never see.

When you put it on put all the nuts on but dont tighten them then wiggle the manifold really hard in the direction of the block then nip them all up. This is not taking the mickey its just dead easy to get it slightly wonkey.

HRD_Tiburon

With a sharp abrupt edge or a raised edge impeading air flow, a event can occur called reversion of flow caused by turbulence. Reversion is where the air flow will change directions and flow in reverse. Reversion is counter productive. It creates vorticies at that edge.

onpol

Try to match the gasket to the IM by cutting the excess.Check if the gasket is in good condition.Install everything again and check all the hoses are in place.Tight all the bolts equally.Let me know if you still have the problem to send you another IM or give your $ back.