I know that gasket matching the upper plenum of the 2 piece creates an aneurism (bubble) in the runners, but what would happen if you port the crap out of the upper manifold? There's plenty of material to open it up all the way to the plenum, it looks like enough to actually taper down to the gasket. Any thoughts and/or has anyone done this?
Sorry I posted under the wrong category
Last edited by moparloper; 06-17-2009 at 01:49 PM. Reason: Wrong category
'70 340 Swinger
'72 Ralley Charger - 440 Air Grabber
'87 Shelby Z - 2.5 TII
'88 Pacifica - 2.2 TII
'02 2500 - Cummins
I know somone that ported the crap out of, then had to add weld where they broke through and then ported it some more. Seems doable and if I had a stock upper I might think about it.
The upper piece of the manifold is smaller so that when it goes into the larger lower portion it doesn't hit a stepped wall.
Flowing from small to large non gasket matched doesn't hurt flow much but going from large to small with a step (non gasket matched) is very bad. I am betting that is why they made the runner on the upper half smaller than the lower half to avoid this in cheap high volume production.
If you are going to port it you need to either have it the same size throughout or go from small to large where they connect. It is also important to have a nice even flow path rather than an inconsistent one with bubbles.
This is one of the last areas to mess with on our engines anyway. The heads and exhaust should be done first.
-Rich
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well the upper half was opened up all the way to the plenum, then the lower half was matched. I didn't say that because I thought it was a given.
If the overall cross section of the port is consistent all the way through the runners to the plenum (and the head port is also matched) then it should be a successful porting job and increase flow.Originally Posted by GLHNSLHT2
If you are inconsistent in the area (as would be the case with simply port matching) or have bad bends then it will be much less successful.
-Rich
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Slight taper, large to small, tightening all along. Use inside calipers to measure ID, to avoid bulges, and to keep the degree of taper consistent.
John Laing
"The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
-- Alexis de Tocqueville
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
--Ayn Rand
"To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
-- Justice Antonin Scalia
The taper should be something like 4 degrees. If you go 6 or more it starts to hurt things.
For an 8 inch runner that means you could be about 1" wider at the top than the bottom if you could keep a constant straight line angle throughout. It would require an awful lot of work to get the taper right but John is right it would help slightly.
When I made my sheet metal manifold I had a 3 degree taper cut in the runners but then the runners got shortened so much it became pointless.
-Rich
Offering Custom/Niche FWD Dodge Products!
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- DOHC 2.0/2.4/Hybrid products
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I would also be wise to pin them (or install dowels around two bolt holes) to make sure they line up properly during assembly as there is some slop.
Thank you gentlemen, this is the information I was hoping for. The remaining question is, has any tried this?
'70 340 Swinger
'72 Ralley Charger - 440 Air Grabber
'87 Shelby Z - 2.5 TII
'88 Pacifica - 2.2 TII
'02 2500 - Cummins
Yes. Works well but then no comparison or dyno . . . . . and I added a 3/8" phenolic spacer between the upper and lower with two hand cut gaskets. In addition to keeping the upper cool, it helps in making the turn, in keeping equivalent ID above and below the joint.
John Laing
"The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
-- Alexis de Tocqueville
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
--Ayn Rand
"To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
-- Justice Antonin Scalia
You may find that with extensive porting of the upper manifold you are probably going to weld up areas on the outer wall or long turn (the side facing the firewall). That's what I had to do anyway. Don't wait until it is paper thin to weld as the welder will just blow holes through the paper thin metal. Figure out where to weld before removing too much. A used manifold will also have lots of impurities in the casting which will also give your welder fits. You may need to get the flange resurfaced after all that welding too. Mine wasn't too straight after the welding.
Good luck,
Todd Nelson
I ported the lower half and gasket matched it where it joins the upper and never noticed any issues.
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weld it....port it....then reflange it.
that is the proper way to go about things.
ive taken out the lower runners to max capacity, and then some lol....if your going to work with the top you definately need to weld the back (firewall) side of things to help keep the port consistent and funnel. altho as much work as you do to the 2 piece Topper, your still stuck with small plenum volume
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