Inliners International Forums General Discussion Bench racing RatRod update (New Manifold)

Hi Inliners,

If you have been a Bulletin Board regular, you know I am collecting parts to build a wild RatRod type Inliner. I wanted to have a multi-carb intake and looked at the GMC 270 with the Howard's 5-carb intake, but decided to go with the tried and true 292 motor. (Hint-I can get one cheap!) The problem is that the only muti-carb intakes available are 3-carb Offy or Clifford set up.
Then I got a call from my Calif. buddy bragging that he has been working for the past 6 months as a Tig welder and working on several Govt spec projects that utilize T-6 6061 aluminum. He even built his own high rise custom aluminum intake for his 1970 buick GSX and it came out fantastic. So he offered if I wanted to have him weld up something for me in aluminum, just send him the parts. Big mistake on his part opening up the flood gates like that.

I have been busy doing some freelance design work for a local Rodshop Fabricator near me, so I got to thinking about the ultimate inline nostalgic intake. During this past summer, I have collected some really nice nostalgic speed parts. A complete 4-71 GMC Blower, a 6-71 GMC Blower Case, and 6-Holley 94's carbs with the 3-bolt base. These carbs are basically look like the Stromberg 97, 94 carbs, but they are much much cheaper! I was thinking about doing the Howards Intake that Patrick's sells with these carbs that I purchased, but I wanted to stay with a "Modern" motor like the 292.
Well, I put mouse to pad and came up with this 6-carb log-type intake. It is all T-6 Aluminum, and my friend now has a whole lot of welding to do. Since the parts are in the cad, I can zip them off to a local Laser cutting die shop and have the parts all laser cut for accuracy. As you can see, the carb plates are set up for the 3-bolt Holleys, but I could have used a 4-bolt Rochester or any other carb pattern. I also included a full length water heated trough with in-out ports. Then I did a little customization with the Bowtie Logo and cooling vanes. I also included the supports for the long rod linkage. I plan to run a straight linkage type set-up with only 3 actual running carbs. The other 2 will look like they are hooked up and will work with the linkage, but the base and fuel intakes will be blocked off with a thin plate.
I'm planning to put 6" tall angle cut velocity stacks on each carb with a trick stainless steel mesh screen and filter on top of each carb(hidden inside the base of the stacks)

Do you think that set up will turn a few heads?

RapRap
1940 ChoppedChevyCoupe

Chopped I don't think it will turn a few heads. It'll turn a Crap Load of them LOL. One thing I see that maybe??? off on the intake is the running to high off the intake floor??? The Fuel I think would puddle at the runner?? But either way It looks pretty Cool:)

Larry,

I thought that might be the case. Any suggestions?
Should I put the intake runners flat to the bottom of the intake log? would that stop puddling? Also, does the 3" ram tubes from the carb plate to the intake log add anything? Also does the volume of the intake box have any relation to the total CFM that I'll be running?

Chopped

G'day RapRap,

The 292 Intake looks great! While you mate is making one, it would probably just as easy to make two or more .

Keep us to date with your progress.

Cheers from Down Under,

Pete

Golly Chitz! Thats outrageous. Better get a bigger gas tank too. Not nitpicking a great design but the only things I might bring up for discussion is the volume of the plenum. Mine started out at 2-1/2" deep and after some research it ended up at only 1".

I'm not sure what you gain with the short runner length between the carb and plenum. Thats a lot of machining and welding. Did you do that for linkage clearance between carb and plenum?

I was also told runner length needs to be as long as practical. In my case something over 12" but I ended up with 8" as thats the length I had to work with. The factory Hyper-Pak 4 bbl runner lengths are close to 18" for manimun velocity.

One thing I will do different on my next plenum intake is make the top plate removable.(screwed down). That way, if I decide to change carbs all I will need is a new top plate machined.

Whats that old saying, "Six in a row make it go"!
And don't forget to go back and "Cad in" some nitrous bungs on your runners....

If you look at stock or other after market intakes The runners are level to the Plenum floors on Carbed intake systems. The ruuner Lenght is ALSO part of the over all Plenum volume.
And I have to agree on the Removable top plate That's the way I am redoing my tunnel Ram.

And Seeing that Your Faking a few of the Carbs is A pretty cool Idea, It will leave Many woundering Why so many carbs to start with,I had the same idea at on time. Hehehe
Now as to another small Question is the Runner and Plenum size, The Bigger they are the easier it will be to Lose signal to the carbs and You would also Lose the street ablility Or low end Power & tork. The Intake should Be in tune with what your going to be running for a cam shaft. A good example is my tunnle Ram The cam i was running was about the smallest that could have Worked with it. anything smaller and I don't think it would have even Idled. Seeing that It was Made for this New Motor of Mine. But I guess you could say I lucked out when it came to driving The car at Local Meets or street cruises.But it sure worked out fine On the track.

I think that Walt, El Plymino, and Twisted 6 are right in it should have a removeable top carb plate. Larry, maybe I could try 3x4's? A nitrous bung may be a little too much for me. I really don't see any reason to run nitrous other than at the drag strip or at Bonnie. I was thinking that the intake plenum was a bit generous as it is 3" high by 25.5" long. That's a lot of swirling gas and air going on. Perhaps the plenum should be as tall as the runners and the plenum should be at least 3" away from the head.
Thanks for all of youe suggestions. I use them in the next design modification. I'll post it when I'm done. Peter, I knew that someone would ask to have more than one fab'd. I plan to make up a jig so my buddy can do all the welding without any hesitations.

RapRap
1940 ChoppedChevyCoupe.

Greetings . . .

The design looks awesome! Especially the second go round with the runners falling downward and closer to the floor of the manifold.

As for the dimensions - I read tech article somewhere that suggested that intake plenum volume should equal the total cubic inches displaced by the engine - for an injected system - and 85% of displacement for carbs (cause that is supposedly the theoretical max volumetric efficiency attainable with carbs which depend on a venturi effect).

A little arithmetic suggests you're right there: 292*.85 = 248 / 25.5 = 9.7 / 3 = 3.24. So a Plenum of 25.5 x 3 x 3.25 seems OK according to that forumula. But when I look at the old Eddie Edmunds plenum designs, he seems to favor width over height.

The question of runner length and cross-section is bit more involved. Here's a tech article on manifolds for the bent eight that has some interesting formulas in it:
Outtakes on Intakes

regards,
Keith

The taller a Intake is the less bottom end you will have.This is part of the reason behind ,When adding a carb spacer plate is to use a closed plate( 2 or 4 port over a Open square hole) to trick the intake(Carb) to thinking it's a low profile to give more bottom end Over the Upper.

As for a 3x4 you can try anything Your mind can come up with Or set it up anyway you want. Example If one wanted 20 carbs 4 bottles of NOS
No one says They all need to be Hooked Up But Just Look like it Hehe:D Heck at One show in Gainsville I seen a Bike with 6 Blowers Stacked On each other starting with a 8-71. But like the guy told me One can do anything they want & besides There empty. Hahahah(but you didn't know that till i told ya)Hahaha My reply was Good Point.

But i see things Like this If it works For you(anyone) and your happy and Makes Heads Turn Go for it. The Only One one has to please Is ones self when it comes to their Ride,s , (Toys)If they don't like it They don't have to Look RIGHT??

With the mention of a 4-71 and 6-71 blower, I was expecting a custom intake, with a blower on it. Oh well. Theres still time.


All joking aside, nice design. Good luck

You guys crack me up!

You should know by now that I do things a little different than most. Yes, I bought the blowers so I could get accurate dimensions. "If I buy it, it may come" I will show a manifold that can place carbs or EFI in a downdraft version and also a Weber side draft version. The neat thing about a fabricated intake like this, I can make it with removeable top and side plate to cover all variations.
I wish this type of technology existed when I was a lad. Just think where it would be today!

Notice: I am not here to self promote myself for any type of monetary advancement, but I am a freelance Industrial Designer, who is doing a lot of side work for many Hotrod and Fab shops.
I am very passionate about this hobby and normally will work with any and all to get things done. If any of you would like to use my services, please contact me off line through my email. My goal is to eventually quit my 8-5 job and be a full time freelance designer in the Hotrod aftermarket. Sooner than later I'm hoping for this to happen.

Bob Malin
RapRap
1940 ChoppedChevyCoupe

since your building from scratch chrysler un the fifties used a long individual runner type manifold on certain bent eights, the carb for the passenger side cyl. ended up on the drivers side valve cover and vica-versa. This was supposed to be a really good torque set-up but the cost was high so they dropped it.Maybe you could do the long skinny runners on yours, it would be unique.

Bob,

I like it. In your first post you mentioned using 5 carbs - I like that idea - real nostalgic. You are going to need an intermediate throttle shaft support in the middle or the shaft will deflect.

Good luck,
Greg

so. not meaning to jack Bob's post at all. but what are the benefits of longer skinnier runners, over wide short ones?

and what hypothetically would be a good dimension for runners on a 3x2 for a 292.

long skinny - low end tq
short fat - high rpm

There are many variables but thats the basic idea.

If you like the look of the Howard's GMC intake, and are looking to keep a "nostalgic" look, why not get the Howard intake and cut off the intake runners and redo them to work with the 292?
It would be alot less work and look more period correct, if that's what you're really after.

Definitely need to make the runners flush with the bottom of the plenum. Just look at all the other intakes out there. Make sure it will clear the exhaust also.

Brian, Sometimes the obvious is staring you right in the freakin' face! I guess I got carried away with all of the Cad design and could definately use the approach you mentioned as the short cut to my problem. I probably will use that scenerio for the short term but I will continue the path of a multi compatible intake system. Who knows, it might just become a marketable piece of inline technology?

If I incorporate enough time and design into the intake, with un-bolt-able top and side plates, then it might become a universal application for many types of engines. Multi carb, Supercharged, EFI, TBI, Multi port, NOS, and in the future, maybe a flux capacitor?

Thanks for of the ideas, suggestions, and comments on this intake. It has helped me far beyond my capabilities and have made you and I a lot more knowlegable on this subject. By all means, let's keep it going or if somone else wants to jump in, please do.

Bob Malin
RapRap
1940 ChoppedChevyCoupe

Chopped something else you need to or think about.
You can not sell the intakes with the Bowtie on it. Because it is a chevy Trade Mark.I got into this issue a few yrs back. which is stil kinda in the works Back to a back burner. But I was told
I could Use it(on my own stuff) as Long as I didn't try to market/Sell it. Because it would/Does have to be approved by GM.

Also your intake would need to be wider for a Blower.

Well, Chevy could be headed for bankruptcy and won't have the money to take you to court for using their trademark logo!! :p Just in case, heres a design I think would be cool to use...

Bob,
If I remember correctly, some time ago I was looking at the Larrowe & Sons site and they offered an open top intake, but I can't remember for what engine. I didn't see it listed when I looked last night. You may want to give them a call before you get too far. No point reinventing the wheel if you don't need to...