Inliners International Forums General Discussion Hi Performance Designing a new intake manifold

Now that the 2 piece timing cover is done. My next project will be to make a intake manifold.
Have had experience with a few of the brands available and know their shortcomings and benefits. Will try to address these to get a better design.
The plan is to make one from steel and test and rework as needed. Once the design is ironed out, a casting will then be made.
The intakes available are too expensive and are not the best designs.
I drive a inline and own many of them. My goal has always been to make parts to be driven. Fitment and function are first.

A Cliffenhauser?

First off PLEASE get the 4bbl orientation right... hating Offy's sideways stuff. Have to use a spacer to run a 390!

How about an intake, exhaust manifold combo using exhaust heat to warm the intake whole flowing better and allowing for either a 2 9r 4 bbl?

Sorta like the stock, sorta like Langdon, sorta like Clillford all combines into a nice 2 part package. If you do it right people can upgrade from stock in stages.

Only complaint I have about the clifford manifold is the dumb thing costs $417 for a manifold and adapter. If you can beat that price with a better made manifold That would be neat.

...and that's why many of us go Offy instead. It's a hunk of machined metal, not a priceless piece of artwork.

But, seriously, consider the exhaust heat combo.

Also what about a turbo manifold that isn't made of unobtainium? Might be something to consider as well...

I like a heated intake cast header package idea. No messing with water lines and bolting surfaces matching from the start.

Plus if it matches the location of the stock intake/header one could upgrade the intake or exhaust without doing the other.

Makes things easier on the budget to do it in steps.

An intake/exhaust combo would be like approach GM took with the integrated 1bbl and 2bbl heads. Combining casting, but this would allow a non-integrated head to be used and have access to the intake ports for lumps and port work.

On the intake side; if it had adapters that allowed a 4bbl, 2bbl, or Monojet; so you could swap the intake/exhaust (and head for us integrated head owners) but leave the Monojet on until a 4 barrel or 2 barrel and air intake is available.

To keep the exhaust output the same I guess means a single 2.5" outlet. However there are 3 different exhaust header pipes, which means you have to design it for one of them. The non-integrated pre '75 L6s had and angled outlet with 2". The integrated head Monojet cars, and the later 292 trucks, had a vertical 2.25" or 2.5" outlet. And the integrated Varajet trucks had a dual 2" exhaust outlet. I guess if you were going to choose one exhaust outlet to cast for it would be the integrated/late-292 with 2.5" vertical outlet. But that means older L6s have to update exhaust to use it.

Not really, there isn't a one size fits all type of intake/carb combo. An engine needing a 2 BBL carb is going to have a different plenum requirement than an engine needing a 4 BBL carb. And an engine needing a 1 BBL carb definately can't use a 4 BBL size plenum and be useful. There is more to intake design than just bolting on adapters for different carbs. Edelbrock makes over 50 different intake manifolds for the Small Block Chevy alone, because there's not even 4 or 5 intakes that covers all the needs of those engines or most engines for that matter.

So probably just make it 4bbl intake with dual 2" exhausts is the best option?

It just depends on what his target group is. If he is thinking of a 4 BBL intake, there are already 10 or 11 intakes total on the market for these engines that pretty much covers the needs of 99% of anyone looking to build one of these engines. Most were designed by engineers that brought that knowledge and skill plus scores of experience to the table. Since Tom isn't bringing either of those to the table, by his own admission, its doubtful he is going to be able to offer anything that will bump any of these other intakes out of the way in favor of his.

I didn't make myself clear: the header and exhaust manifolds should be separate like the pre-72 L6. No reason why you can't copy the stock layout but add some volume either vertically or horizontally oposite the engine.

I can probably sketch it out. Heck if I had CAD I could draw it up for you. Not the first casting design I'd have done. I'm an ME.

I took it that this was what you were meaning even though I didn't say anything. I use Solidworks to do all my 3D modeling and have several CAD/CAM software packages I use to create and machine my parts with. I have always liked the factory exhaust/intake setup and how it fit together to heat the intake. This type of design will undoubtedly create the best niche since it can incorporate the stock exhaust and not require a user to have to replace it just because they change intakes.

Exactly. You could either do the headers or intake and not have to do both.

....or like me: do one then about 3 months later do the other.

You got me to thinking now, I may revise several of my intake manifold designs to incorporate the stock exhaust manifold.

Later work on some high flow cast headers with dual outs.

Might want to watch this: https://youtu.be/RWTARjxiqlo

Great series of videos.

That's already on my list. I already have some duals 3D modeled. A turbo exhaust manifold is next.

Whew, there has been a bit of discussion on this one.

Stroker6- I like your name Cliffenhauser. Funny.

I am steering mainly toward aftermarket exhaust. Most people want duals or better performing exh.
My intake will be water heated and be made for a 4bbl.

CNC- Not sure of the 10+ intakes that are available. I can really only name about 5 that are currently available. Most of them have high prices.

I miscounted, there are actually (16) intakes available made by 5 different companies in several different countries. They are all currently still available and as I mentioned previously, can fill the needs of 99% of the enthusiasts desires from mild to wild when used in the correct application. The other 1% build custom sheetmetal intakes for extreme duty apps like Hank and Mighty6, and even Turbo6 and guys like that. I'll list them below:

CLIFFORD:(3)

• 4V
• Twin Weber 38/38 similar to the carbs Langdon sells
• Triple Side Draft Weber

AUSSIESPEED:(2)

• 4V
• Blower Intake

OFFENHAUSER:(2)

• 4V
• 3x2V Rochester, (really 3 intakes in one, 1x2, 2x2 or 3x2)

ENGINE:(7)

• 4V
• 2x4V
• 3x2V (similar to Offy's, has also been configured with 1BBL before in 3 seperate configurations as well, so 6 options in one)
• Single Weber IDF Downdraft
• Dual Weber IDF Downdraft
• Triple Weber IDF Downdraft
• Triple Weber DCOE Sidedraft

JJ INLINES:(1)

• Blower

PES:(1)

• 4V

And this isn't including others that are also in the works by others.

Guess that I should have specified 4BBL intakes. Low cost with good fitment and function.
Back out to the shop I go!

Tom,

I'd suggest doing a dedicated TBI (2 hole BBC size) intake with a mount pad for the MAP/IAT sensor. This way all the connections except for the tach and +12 for the injectors are in 1 place. Makes the wiring easier.

Even the 350 TBI (junkyard) are plenty big to feed a healthy 292.

End users would see a marked increase in fuel economy.

Ok, that does narrow it down a bit then.

I like this idea.

I ran a single barrel Holley Projection on top of a Clifford several years ago but was not very happy with it despite fiddling around for a while. Not sure why. Maybe because it is open loop (no O2 feedback) or maybe the Clifford was too big or too cold, I don't know. I understand that a wet manifold can be more difficult than a dry one but still, I like the TBI concept.

Hmmm

Perhaps a dual TBI 2 x dual ( think of it as a dual 2bbl intake) with the TBI's centered on #2 and #5 using V6 TBI units will help with distribution issues.

The advantage using TBI over a carb is they are not reliant on air speed (signal) through the venturi to properly meter fuel. This avoids the problem when running an overdrive on the highway and when you step on it - if feels like your stepping into a bowl of mush until the revs come up - a TBI meters is fuel based on RPM and manifold pressure (inverse of vacumm).

With Wideband O2 sensors readily available - many of the EFI controls can self learn.

Hey Tom, do you know what would really be good? A turn-key solution! Intake and anything needed to mate with your targeted carburetor. A list of parts, some written directions, an instructional video would do it.

I put on my carb with offy intake because it was the closest thing to bolt-on without modifications. but it still required additional parts and fabrications.