what's the story with manifold porting ? - Mopar Forums
 


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Old 02-02-2009, 01:13 AM   #1  
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what's the story with manifold porting ?

my friend says because of our **** poor port size ( 906 ) i should port my manifold & use a 2 in spacer to get more flow ?????
mmm wouldn't it make bottom end power drop off ?
i thought our stock ports choke ( stall ) around the throat area leading into the bowl .?
how dose spacer plates work ?
what dose manifold porting do .
i have a holley street dominator manifold on 383 cid & stock heads .
i am planning on doing a mild number on my heads . template port & blend bowl , port valve boss & web , short end radius , & roof & walls to open up the throat area . & open up port window to fuel stain . any thoughts .
( i used to port 2 stroke moto bikes for 7 years so i won't be just digging in . )
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Old 02-02-2009, 03:07 AM   #2  
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Spacer plates? You talking about a carb to intake spacer? It raises the carb off the intake to allow more air and fuel in the intake. Depending on the setup you go with (4 hole, 2 Hole or open) you can gain power in different RPM ranges. I've got a 4 hole 1" spacer on my J10 for more low end power since my motor will never see anything higher than 5000 rpm.
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Old 02-02-2009, 09:24 PM   #4  
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not gasket match

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Originally Posted by 66sportfury View Post
really 78d200?i thought all spacer plates raised the rpm curve? even four hole cool thanks, and only gain 7-12 horse right? porting the manifold. gasket matching is what i think he is talking about?, matching the intake gaskets to the manifold, and maybe raidius porting. thats when you smooth the runners where they split to the heads so gas dont hang up.
my friends talking about full on guting out the inside runners . i have a engine masters magazine on page 63 there talking about a 730 hp chevy oval port iron headed thing & theres a photo of the manifold plenum & its razor edged. ( they are flowing over 400 cfm each runner )
now i have already taken the edge off my manifolds runners & but ol mate says its no where near enough . he says its gota be knife edged ( sharp )
my spacer plate is only 3/4 in & i have it open because i have a single plane manifold . ol mate also says i need a 2 in spacer plus ported manifold & ported head to be in the competertive ball park mmmm ???
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Old 02-02-2009, 11:04 PM   #6  
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yeah i to love the b engine

well iam limited to a 1 in spacer anyway because my air cleaner hits my hood . aleased till i put a hood scoop on . hemi dart or hemi belvedere type , mopar type only . my mate also says a 2 in spacer would work similar to using a 850 cfm carb . ( i have 750 ) i think i'll just use what i got port my manifold a bit more around the plenum end of the runners so it tappers down for good velocity & pulls hard @ around 4800 -6200 rpm .
i am gona try for some more cheap power by using cold air ducting & cooling my fuel & wraping my manfold or using a heat shield under it . ???
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Old 02-03-2009, 02:12 AM   #8  
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Originally Posted by 66sportfury View Post
when on the track. take the air cleaner off.
already do mate
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Old 02-03-2009, 03:47 AM   #9  
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I understand now what you mean by porting the intake. It is just like porting and polishing the heads, the smoother the surface is the more air/fuel you will get and the faster you will get it since there is no rough surface to catch it.

As far as the spacers go, They will increase your power a little (single digits) and may raise your RPM curve, depending on the amount of the spacer. The larger the spacer, the larger more it will raise it. The size of the holes do have an effect on where it adds power too, not much since the power increase is so small. I drove my J10 with a 1" 4 hole spacer for a month then took it off and drove it for a month. I felt no difference. On a race car, you may though.
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Old 02-03-2009, 10:19 PM   #10  
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from what I've been told about porting inlets , its actually better to have a slightly ruff surface . like a golf ball , sharks skin ect it creates a low pressure zone which speeds up air flow . on 2 stroke motorbikes we polished the inlet ports just so you could easily clean them at the next re-ring with kero . AND FOR **** APPEAL so you can show ya mates .
when i port my heads i will only polish my exhaust ports , chambers , piston tops , exhaust valve & first 4 inches of header pipes .
that's just so carbon doesn't stick as easily that's all .
my inlet ports i would leave a stone finish . mmm does that through a spanner into the works on porting .
I'm not a porting expert though . i don't know the technical side or have never used a flow bench . I'm self taught & i use my river bend theory .
IE the out side of the bend is deeper & flows more volume & the shallower & inside of the bend flows less but faster & so dose tapering a port it will also pick up speed to a point . until the smaller end dams too much ( lags ) . it all about blending & balance . i hope you guys can make sense of that . all i can say is of the thousands of port jobs i done only one person complained about my work & that's because he needed a different pitch prop for his outboard boat motor . & he came back with a 6 pack of beer & said it now hammers with a big smile .
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Old 06-12-2009, 04:07 PM   #12  
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well as you may have scene my little number on my heads went right out the window . they are all out race jobs now . hehehe .
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Old 03-29-2010, 07:38 AM   #14  
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well i suppose porting is to help open up the restriction as best you can with what you got . so really the sh#tier the manifold the more porting will help ( same with heads ) if you have then you buy better heads & inlet manifold . if ya a poor *** or average Joe like me you have to make sacrifices . so a missus & kids is just out of the question .
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