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Intake manifold porting

General engine tech -- Drag Racing to Circle Track

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steve cowan
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Intake manifold porting

Post by steve cowan »

I cut up a old team G intake that I bought off fleabay a few years ago,my idea as a science project is to port manifold and tig weld it back together,i bought a new electric bandsaw on the weekend so I am cutting stuff up until the novelty wears off :D .
I have ported a couple of intakes over the last couple of years and they are a pain to say the least.
One thing I noticed was the team G had been gasket matched to a 1205 felpro,the issue here is at the gasket flange the CSA is 2.61".
At the opening at the plenum the long runner is 2.36" and short runner is 2.48" so straight away I see a problem with gasket matching.
I have 4 other intake and they all have taper from plenum opening to flange.i think the intake manifold does not get much discussion either through lack of knowledge or secret squirrel stuff.
My 383 chev stuff runs a intake cylinder head port of around 2.3" average CSA to try and peak at 6500rpm or so,i want to port,weld runners so there is very little taper,will port plenum and thinking of runner extensions in plenum area,maybe also weld a tapered spacer to plenum as well,then also tig intake back together,this could be a total fail but will be fun to try and learn something, will also bolt to head on flow bench and test up to 40" depression, feedback,comments tips all welcome.
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steve c
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Re: Intake manifold porting

Post by mag2555 »

As with anything flowing something you want to work on the main restriction point(s).

In that Intake you want to address the tightest part of the bend in each runner from the exit of the Plenum to the head flange.
This at the runner to head flange interface on this Manifold and what you want to do there is raise up the roof of the outside wall of the runner and naturally bend that height increase back in across the runner roof.
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Re: Intake manifold porting

Post by Biteme »

I’ve ported my team g 7532
Mcsa as cast was quite small, iirc 1.9”
They have plenty of meat for porting though.
I mostly worked the area from just up past the sharp turn, all the way up to the plenum, mostly concentrating on the outside wall.
Runners # 4 and 5 needed the most work, as they are the tightest turns.
Then worked the plenum over.
There is hardly any taper in the runners.
Finished up with around 2.35 mcsa.
Heads are 2.25.
Haven’t flowed or dynoed it yet.
GARY C
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Re: Intake manifold porting

Post by GARY C »

From everything I have seen on this subject most single plane intakes are sized for a 4500 to 7000/8000 ish rpm range so any cross section increase will only favor upper rpm ranges. Maybe CGT or randy331 will chime in on their EMC rpm range intake testing.

I am sure you know that with out a before and after dyno test then all modes will just be a time consuming theory.

I called DV several years ago about cutting the spider off of an intake so that I could get the first 1" perfectly aligned with the head and after a 2 hour explanation on the meticulous intake testing they did on this very subject it was worth 1.5 to 3 hp over a normally ported intake. But he did tell me to not let that stop me from doing my own testing. :)
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steve cowan
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Re: Intake manifold porting

Post by steve cowan »

The biggest thing is the runner at the plenum is trapezoidal in shape and goes to rectangular at the flange,makes it difficult to measure correctly.
I have had intakes bolted to cylinder heads on the bench and pitot probed,its something to be mindful that you are looking for minimal flow loss but just making the runner bigger may not be the right answer.there have been threads in the past where just changing intakes as cast from one brand to the other has netted minimal torque increase,a intake that has been sized and correct length,taper and proper plenum size and entry shape has to pay dividends.
I have all Don's CDs and I have listened to Nascars Phill Martin saying the trend was they used to cut intakes in half ,port and weld back together.
I have a high plenum team G intake but it sizes close to super victor.
I would like to hear if anyone has welded a intake back together, there are a couple of areas that will be hard to get to final finish.
Thanks guys for the feed back so far.
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Re: Intake manifold porting

Post by cgarb »

What's the plan or welding it back together? Going to weld the plenum area from the inside and the valley area from underneath? Might be a little tough getting a torch and filler rod down in the plenum at the same time.
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Re: Intake manifold porting

Post by steve cowan »

cgarb wrote: Tue Sep 15, 2020 1:31 am What's the plan or welding it back together? Going to weld the plenum area from the inside and the valley area from underneath? Might be a little tough getting a torch and filler rod down in the plenum at the same time.
thats the thing cutting was easy,again this a experiment and i am not worried about junking the intake,i think it will be difficuilt in some places for sure,i know trying to port a intake is a tough deal as well :D
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Re: Intake manifold porting

Post by cgarb »

Maybe cut a window out of the valley pan area so you can gain access to weld the bottom easier. Then you can weld the plate back in after the plenum has been welded.
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Re: Intake manifold porting

Post by maxracesoftware »

that SBC Team G was a very good Intake Manifold in its Day !

won out in TQ + HP over other similar Manifolds many times .
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Re: Intake manifold porting

Post by smeg »

steve cowan wrote: Tue Sep 15, 2020 1:19 am The biggest thing is the runner at the plenum is trapezoidal in shape and goes to rectangular at the flange,makes it difficult to measure correctly.
I have had intakes bolted to cylinder heads on the bench and pitot probed,its something to be mindful that you are looking for minimal flow loss but just making the runner bigger may not be the right answer.there have been threads in the past where just changing intakes as cast from one brand to the other has netted minimal torque increase,a intake that has been sized and correct length,taper and proper plenum size and entry shape has to pay dividends.
I have all Don's CDs and I have listened to Nascars Phill Martin saying the trend was they used to cut intakes in half ,port and weld back together.
I have a high plenum team G intake but it sizes close to super victor.
I would like to hear if anyone has welded a intake back together, there are a couple of areas that will be hard to get to final finish.
Thanks guys for the feed back so far.
Steve, check out Marcella intake manifold pics on YB he is the man.
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Re: Intake manifold porting

Post by mt-engines »

steve cowan wrote: Tue Sep 15, 2020 1:19 am The biggest thing is the runner at the plenum is trapezoidal in shape and goes to rectangular at the flange,makes it difficult to measure correctly.
I have had intakes bolted to cylinder heads on the bench and pitot probed,its something to be mindful that you are looking for minimal flow loss but just making the runner bigger may not be the right answer.there have been threads in the past where just changing intakes as cast from one brand to the other has netted minimal torque increase,a intake that has been sized and correct length,taper and proper plenum size and entry shape has to pay dividends.
I have all Don's CDs and I have listened to Nascars Phill Martin saying the trend was they used to cut intakes in half ,port and weld back together.
I have a high plenum team G intake but it sizes close to super victor.
I would like to hear if anyone has welded a intake back together, there are a couple of areas that will be hard to get to final finish.
Thanks guys for the feed back so far.
I have cut and welded my fair share of intakes in the past and haven't had to in probably the last 6 years. its very time consuming, and if you want it to look nice after its welded back up you need to have a friend that owns a wheelabrator with stainless shot.

with so many off the shelf intakes out there that save us 40 hours of plenum porting why bother. unless you are looking for 2hp/ci+ the gains wont be much. And if that were the case you should really just buy a different intake.

there are a few ways you can go around welding it back together. with it bolted to a mock engine and you have the ports close to where you want, notch the sides of the plenum so you can get your tig torch in and start welding. there is so much to this i cant really explain. because depending on if you are modifying the pad for a 4500 or going back to 4150 depends on where i start or if i even patch it that way or start from the bottom. but typically i am adding material in certain spots anyway so cutting and adding flat stock gives me the room to weld the plenum floor first and grinding it flat.

are you filling the floor? if so. epoxy, round stock, sharp flat stock etc.

the only advice i can give you is, be patient and good luck. be prepared to machine, drill and tap new carb stud holes, spot face bolt holes etc. aluminum moves and shrinks alot.
steve cowan
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Re: Intake manifold porting

Post by steve cowan »

mt-engines wrote: Tue Sep 15, 2020 11:56 pm
steve cowan wrote: Tue Sep 15, 2020 1:19 am The biggest thing is the runner at the plenum is trapezoidal in shape and goes to rectangular at the flange,makes it difficult to measure correctly.
I have had intakes bolted to cylinder heads on the bench and pitot probed,its something to be mindful that you are looking for minimal flow loss but just making the runner bigger may not be the right answer.there have been threads in the past where just changing intakes as cast from one brand to the other has netted minimal torque increase,a intake that has been sized and correct length,taper and proper plenum size and entry shape has to pay dividends.
I have all Don's CDs and I have listened to Nascars Phill Martin saying the trend was they used to cut intakes in half ,port and weld back together.
I have a high plenum team G intake but it sizes close to super victor.
I would like to hear if anyone has welded a intake back together, there are a couple of areas that will be hard to get to final finish.
Thanks guys for the feed back so far.
I have cut and welded my fair share of intakes in the past and haven't had to in probably the last 6 years. its very time consuming, and if you want it to look nice after its welded back up you need to have a friend that owns a wheelabrator with stainless shot.

with so many off the shelf intakes out there that save us 40 hours of plenum porting why bother. unless you are looking for 2hp/ci+ the gains wont be much. And if that were the case you should really just buy a different intake.

there are a few ways you can go around welding it back together. with it bolted to a mock engine and you have the ports close to where you want, notch the sides of the plenum so you can get your tig torch in and start welding. there is so much to this i cant really explain. because depending on if you are modifying the pad for a 4500 or going back to 4150 depends on where i start or if i even patch it that way or start from the bottom. but typically i am adding material in certain spots anyway so cutting and adding flat stock gives me the room to weld the plenum floor first and grinding it flat.

are you filling the floor? if so. epoxy, round stock, sharp flat stock etc.

the only advice i can give you is, be patient and good luck. be prepared to machine, drill and tap new carb stud holes, spot face bolt holes etc. aluminum moves and shrinks alot.
Thanks for you reply,some good info there,I understand what you're saying about effort expended for results given,i don't work in the industry but I enjoy finding things out for myself even when it's a fail.
I have read all your posts on the forum,i like your no nonsense attitude it reminds me of a couple of guys who don't visit the forum much,
Like most people I have lots of little projects on the go most of the time so I will put some photos up every now and then.
steve c
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