Intake Manifold Porting Show ‘n Tell

[Lloyd klem]

Lloyd,
Really appreciate your input and photos etc,you do really nice work.
I have a question for you or anyone else who wants to answer -
My engines are 550 - 600hp 383 sbc stuff I run
Street/ strip car 3600 pounds.
I have done a few single plane intakes
Vic Jr
300 - 25
SV
and I have several others.
When I size a intake and decide on what I think is close I make the CSA of both runners the same only length is the governing factor.
I always open carb pad and have lots of spacers.
The question regards keeping the intake manifold runners the same size.??
I currently run at 6000 - 7500rpm window but one combo will go 8000rpm next year hopefully using the big trickflow intake manifold.
Thanks in advance
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I will give you my opinion on where I would be if trying to peak say 7500 and run out to 8000ish.If mine I would have intake valve about 52 percent of bore being used.I would leave my throat 91 to 91.5 of that valve.I measure my runner length from valve seat to say about 3/8" back from radius in plenum opening.So imo for that rpm I would be wanting right at 11" total runner tract.So if head port average is 5.5" then that leave same 5.5" avr of runners in intake manifold.This is my opinion and just something to think about and look at.If you had say 2.55" csa at upper runner area in head I would be looking at about 3.6" on my long runner in plenum for csa and 3.25ish on my short center runners.This can be changed with other variables as cam events etc used .Again this is just where I would be and roughly what I have used in that similar area.I like 2" 4 hole radius into open spacer for general tuning.I like to have carb blades away from floor of manifold etc.

I wish I could get my 350/360hp Super Stock engine at 11" total. The E is the only manifold that fits under the hood. So I'm at 5.140 head and 5.000 manifold, But it has a ton of taper from 3.500in at plenum to 1.95 at head opening and 1.85 at PR. I shrink the manifold and it kills power. These peak at 7300 and trap at 8800 with 10.140 total.

Chad
That is great info.Nice of you to explain and share that..

[1980RS]

I just pick up these vintage dual planes to maybe do some porting to. Neigher of them have been run both are new. The 2101 Eddy one is so old it doesn't even say Performer on it yet. I am thinking 1978 model.

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[Lloyd klem]

Does anyone have any experience with the Weiand Track Warrior for a BBC in a 496? I'm sure curious about the pro and cons. Some of the negative reviews I've seen were about the runners being too small and that's about perfect for what I have in mind which is a high-torque, 6k rpm peak hp application with a Terminator X Stealth. I just don't know anything about it.

I think you would like that manifold for what you described.If you only had 4.00" stroke I would probably go with a dual plane but I think you will be happy with that choice.

[Lloyd klem]

There is a good thing with constant taper and that is that it keeps the boundary layer thinner.
But there is a bad thing too.
The reflections för stuffing air into the engine are used before they are needed.
And you will never be able to pull a really deep depression before maximum piston velocity.

Erland

I understand fully your points.I work with pretty tight or short rpm spans.Big taper seems to be lesser of the evils.Everything we deal with is a huge compramise,all we can do is test and go with what works for us on that given project.I don't have allot of time to read on this site .I do appreciate your knowledge of engine dynamics and sharing.

[juuhanaa]

There is a good thing with constant taper and that is that it keeps the boundary layer thinner.
But there is a bad thing too.
The reflections för stuffing air into the engine are used before they are needed.
And you will never be able to pull a really deep depression before maximum piston velocity.

Erland

Good morning,

I dont get it. When the the calculated frequency match the given rpm, over scavenging doesnt have to be a problem and when taper is used to increase CSA, it changes the reflections on lower rpm to happen higher rpm.



-juhana

[steve cowan]

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Work in progress...

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My opinion is the taper at the carb pad will probably work well,I would run with a shear plate

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[steve cowan]

Here is a pic of imo the most common mistake made.And getting paid for the hours to correct this is tough.Guy paid for this once and now I get to redo it correctly Look at fair left runner which is number 3.Its a shorter runner than number 1 next to it.It has a bunch more csa than number 1 runner.So I can only go up on number 1 to get csa and taper fixed.It won't have much of a round radius left going into the roof.I will have to add 1 inch spacer and incorporate into that.This will get plenum opened a bunch with shear plate also.IMG_20221127_120751130.jpg

Lloyd,
Really appreciate your input and photos etc,you do really nice work.
I have a question for you or anyone else who wants to answer -
My engines are 550 - 600hp 383 sbc stuff I run
Street/ strip car 3600 pounds.
I have done a few single plane intakes
Vic Jr
300 - 25
SV
and I have several others.
When I size a intake and decide on what I think is close I make the CSA of both runners the same only length is the governing factor.
I always open carb pad and have lots of spacers.
The question regards keeping the intake manifold runners the same size.??
I currently run at 6000 - 7500rpm window but one combo will go 8000rpm next year hopefully using the big trickflow intake manifold.
Thanks in advance
20220224_162126.jpg20220224_162138.jpg

I will give you my opinion on where I would be if trying to peak say 7500 and run out to 8000ish.If mine I would have intake valve about 52 percent of bore being used.I would leave my throat 91 to 91.5 of that valve.I measure my runner length from valve seat to say about 3/8" back from radius in plenum opening.So imo for that rpm I would be wanting right at 11" total runner tract.So if head port average is 5.5" then that leave same 5.5" avr of runners in intake manifold.This is my opinion and just something to think about and look at.If you had say 2.55" csa at upper runner area in head I would be looking at about 3.6" on my long runner in plenum for csa and 3.25ish on my short center runners.This can be changed with other variables as cam events etc used .Again this is just where I would be and roughly what I have used in that similar area.I like 2" 4 hole radius into open spacer for general tuning.I like to have carb blades away from floor of manifold etc.

I am going to throw a spanner in the works here -
Lloyd, I don't expect you to give me all the answers here so a yes or no is fine.
Current project engine is out
383 sbc 4.030" bore
11.45 comp hope to bump close to 11.8 ish.
MS 109 fuel.
1.94" intake valve 89% throat
50 degree seats.
2.27 throat with stem taken out.
Going to try to make throat the minimum CSA.
Using big trickflow intake
Looking at 2.4 at head/ intake flange.
Have not measured properly yet but let's say 3.4" approx at runner opening in manifold, plenum will get Work.
266- 272@ 0.050 " comp roller
With the undersized intake valve would you still work on your csa at manifold opening?that you mentioned.
I have never run a throat bigger than 90%.
Considering 52 degree seat on exhaust.
As far as the small valve situation, it is just a personal goal to see what I can/ can't do myself with the learning process.
If I can make 600hp or a shade over that,my aim is to try and run my 3600lb streeter down to 10.0s if at all possible.

[Erland Cox]

There is a good thing with constant taper and that is that it keeps the boundary layer thinner.
But there is a bad thing too.
The reflections för stuffing air into the engine are used before they are needed.
And you will never be able to pull a really deep depression before maximum piston velocity.

Erland

Good morning,

I dont get it. When the the calculated frequency match the given rpm, over scavenging doesnt have to be a problem and when taper is used to increase CSA, it changes the reflections on lower rpm to happen higher rpm.



-juhana

As soon as there is a discontinuity in area in the port the outgoing rarefaction pressure wave will reflect back to the cylinder.
If there is a larger area it will reflect a pressure wave.
So if we taper the head the ports reflections will help with filling the cylinder and on most engines this will prevent the cylinder
to draw a really deep vacuum.
That vacuum is what we need reflected at around BDC and forward to fill the cylinder with a late closing inlet valve.
So 3 things will happen, the vacuum pulled will be less, the returning pressure waves will be spent to early and they will also be weaker.
So where in the port the intake starts to taper up has a lot to do with at what rpm you want maximum hp.
I have never seen a Comp or PS head taper up before the intake manifold and they turn over 10000 rpm.
If you taper up to early the engine will not tolerate an as late closing intake valve as it could with the taper at the right place.

Erland

[Lloyd klem]

Lloyd,
Really appreciate your input and photos etc,you do really nice work.
I have a question for you or anyone else who wants to answer -
My engines are 550 - 600hp 383 sbc stuff I run
Street/ strip car 3600 pounds.
I have done a few single plane intakes
Vic Jr
300 - 25
SV
and I have several others.
When I size a intake and decide on what I think is close I make the CSA of both runners the same only length is the governing factor.
I always open carb pad and have lots of spacers.
The question regards keeping the intake manifold runners the same size.??
I currently run at 6000 - 7500rpm window but one combo will go 8000rpm next year hopefully using the big trickflow intake manifold.
Thanks in advance
20220224_162126.jpg20220224_162138.jpg

I will give you my opinion on where I would be if trying to peak say 7500 and run out to 8000ish.If mine I would have intake valve about 52 percent of bore being used.I would leave my throat 91 to 91.5 of that valve.I measure my runner length from valve seat to say about 3/8" back from radius in plenum opening.So imo for that rpm I would be wanting right at 11" total runner tract.So if head port average is 5.5" then that leave same 5.5" avr of runners in intake manifold.This is my opinion and just something to think about and look at.If you had say 2.55" csa at upper runner area in head I would be looking at about 3.6" on my long runner in plenum for csa and 3.25ish on my short center runners.This can be changed with other variables as cam events etc used .Again this is just where I would be and roughly what I have used in that similar area.I like 2" 4 hole radius into open spacer for general tuning.I like to have carb blades away from floor of manifold etc.

I am going to throw a spanner in the works here -
Lloyd, I don't expect you to give me all the answers here so a yes or no is fine.
Current project engine is out
383 sbc 4.030" bore
11.45 comp hope to bump close to 11.8 ish.
MS 109 fuel.
1.94" intake valve 89% throat
50 degree seats.
2.27 throat with stem taken out.
Going to try to make throat the minimum CSA.
Using big trickflow intake
Looking at 2.4 at head/ intake flange.
Have not measured properly yet but let's say 3.4" approx at runner opening in manifold, plenum will get Work.
266- 272@ 0.050 " comp roller
With the undersized intake valve would you still work on your csa at manifold opening?that you mentioned.
I have never run a throat bigger than 90%.
Considering 52 degree seat on exhaust.
As far as the small valve situation, it is just a personal goal to see what I can/ can't do myself with the learning process.
If I can make 600hp or a shade over that,my aim is to try and run my 3600lb streeter down to 10.0s if at all possible.

I don't Wana get off course here on singled out projects.I didn't do any math but your probably right on number wise.Imo your under valved and under headed to work above 7000 rpm.I find that if I pick one perimeter to try and alter above what engine demand is when under headed it's a battle.I would work hard in the 64-6900 area in your deal.That being said I would look at 11.5" total intake tract and probably 3.4ish on long runners and 3.2" on short.Shape will big of big importance on your whole project.I will look at your whole deal when I get a chance and pm you.

[rfoll]

I'm kind of late to the party but I have been using a different method for port match that only uses a gasket as a spacer. I think the article

port matching.jpg

was from Vizard. There was mention of builing up with epoxy and I may need to do this. Any recommended brands?

[juuhanaa]

There is a good thing with constant taper and that is that it keeps the boundary layer thinner.
But there is a bad thing too.
The reflections för stuffing air into the engine are used before they are needed.
And you will never be able to pull a really deep depression before maximum piston velocity.

Erland

Good morning,

I dont get it. When the the calculated frequency match the given rpm, over scavenging doesnt have to be a problem and when taper is used to increase CSA, it changes the reflections on lower rpm to happen higher rpm.



-juhana

As soon as there is a discontinuity in area in the port the outgoing rarefaction pressure wave will reflect back to the cylinder.
If there is a larger area it will reflect a pressure wave.
So if we taper the head the ports reflections will help with filling the cylinder and on most engines this will prevent the cylinder
to draw a really deep vacuum.
That vacuum is what we need reflected at around BDC and forward to fill the cylinder with a late closing inlet valve.
So 3 things will happen, the vacuum pulled will be less, the returning pressure waves will be spent to early and they will also be weaker.
So where in the port the intake starts to taper up has a lot to do with at what rpm you want maximum hp.
I have never seen a Comp or PS head taper up before the intake manifold and they turn over 10000 rpm.
If you taper up to early the engine will not tolerate an as late closing intake valve as it could with the taper at the right place.

Erland

Yes, an engine tuned to third or fourth order harmonics and running lower piston speeds, we better of maintaining CSA to keep the airspeed up, and waves moving stronger back and forth in the system but.. Do you mean an engine with an induction tuned say at 6500rpm, 4000ft/min piston speed and much taper, that second order cannot arrive at the time of the IVC event?


When..
the "second order" = thing moves back and forth 3 times the tuned length.

Thing has a frequency, and if the system does not take into account the whole lenght, then the following harmonics should occur at much higher RPMs than a calculation using average inputs would show. In other words when we have taper, i don't think wave is reflected back from that area change inside a runner, but rather from the runner entry.

the "third order" = thing moves back and forth 5 times the tuned length

the "fourth order" = thing moves back and forth 7 times the tuned length

Thank you,



-juhana

[ChopperScott]

While I most certainly enjoy the discussions involving the science, I personally don't dive deep into altering the airflow dynamics designed into the manifold. Without a flow bench or dyno mule, it could easily become counter-productive over working the intake. I like to keep it simple...

•clean all casting finish, flash, and burrs
•gasket match with minimal enlargement of the port
•thin and shape divider wall entry
•smooth and blend runner entry from the plenum
•final burr finish in plenum followed by 80 grit in the runners

[Lloyd klem]

I think most of today's manifolds are decent ,just pick one that has area and runner length close to what you need.Get snap guage in above flange about 1" and you will soon see what needs fixed.

[Joe-71]

When I am given a manifold to port for a customer, the first thing I do is flow it on my SF-600 flow bench to see what it flows as cast or as given to me. I have two fixtures that I built back in 1992 or so for flowing each port of an intake manifold separately. I block all the ports except the one being flowed, and I use a radius spacer for the carb pad so that turbulence is at a minimum. No clay, because of the irregularities in shape with clay. I flow each port at 28" and log it in my notebook. I then work the plenum and the ports, flow them again, work the ports again, and bring each port up to the best one. Depending on the cubic inch of the engine, heads capability, and camshaft lift, I port the intake manifold to flow ~115% of the head flow at valve lift for a street engine. For race, I port the intake manifold to flow at least 120% or more again depending on the rpm/gear ratio, tire size, needs of the builder. Been successful with this approach for 50 years of porting heads and intakes. Port finish depends on what fuel, and whether power adder or EFI, etc. Joe-71

[SpeierRacingHeads]

Dorton 300-110 I just finished up today. My favorite manifold.