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Single 44 idf weber on chevy inline six

General engine tech -- Drag Racing to Circle Track

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chevyfreak
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Re: Single 44 idf weber on chevy inline six

Post by chevyfreak » Sun Dec 01, 2019 12:52 am

modok wrote:
Sat Nov 30, 2019 5:28 pm
What direction the throttles open can have a drastic impact on fuel distribution and wet flow.
I would guess having the LOW hanging end of the throttles toward the outside would be preferable for distribution, but worse for wet flow.
At least.....build it so you can try both ways.

The 38/38 the throttles open toward eachother, maybe you don't think much of it but it makes a difference.
Thats the thing. Over here there were a company that made cast ally intakes for the weber for the inline chevy motors. That was many moons ago, before my time so getting them is like winning the lotto. Carb pad is not parralel to engine. Turned 90deg so that when the weber throttle opens the fuel charge is going towards center of intake . I also experimented on mine and made a small insert to go under carb so when at wot the charge hits it and goes towards plenum and towards the outer runners and not hit the floor and go towards the center runner. Basically like the insert that goes in a essex v6 intake that was in discussion on engine tech about close to 2 months ago. But only on the inner side of intake. Had basically a similar idea for the idf setup.
My mind has been all over on this build intake wise. I made an adapter as to use qjet on this weber intake, just to see how it works out. Then made a intake with bigger plenum for qjet, big plenum made the routing for distribution better but screws up idle signals. Made plenum smaller and smaller and getting idling to be basically perfect. Then went again some more tuning. Need to sort some more needles and jets and weaker springs for piston.
For now the weber intake just so i can at least drive it a bit while building another intake for idf setup. I like your idea of setup on carb to flip it so blades open to other side. Will look into it to do on intake and then see how it works .
Thanks for input.
enigma57 wrote:
Sat Nov 30, 2019 5:20 pm
:D Wish you weren't so far from here (Texas). I've got a few goodies you could play with as far as carbs and intakes for that engine. Also have a new hecho en Mexico cast-iron exhaust manifold for 292 heavy duty truck and bus with single 2-1/2" outlet. In theory, a single 2-1/2" OD exhaust constructed of tubing having 16 gauge wall thickness will support 200 HP without power loss if your muffler will flow 2.2 CFM (or more) per HP generated (measured at flywheel).

More if need be but beyond that point, you will begin to experience back pressure beginning to build incrementally, resulting in diminishing returns as power level and RPMs exceed appreciably beyond that point. Of course, you could always braze or weld a 2nd 2-1/2" outlet to such a manifold. I have done that before using a gutted big block Chevy heat riser having same 3-bolt flange and bevel for donut gasket as this manifold has. These cast-iron manifolds weigh quite a bit, though. Would cost a fortune to ship something that heavy to S. Africa.

FWIW...... If you bring dual 2-1/2" exhaust pipes together and join them 15" - 18" downstream of exhaust head pipe connection...... A single 3" OD system if built to same parameters as discussed with single 2-1/2" will in theory, support 338 HP priour to back pressure beginning to build as discussed earlier.

BTW...... If you are considering a store bought intake for your 44 IDF...... AussieSpeed make a beautiful manifold base for these engines. Its intended to be used with interchangeable tops (either a dual carb top or a supercharger base). However, you could take one of these bases and add a 3/8' thick machined aluminum top plate of your own to fit your IDF carb to this intake......

Image

http://www.aussiespeedshop.com/product/ ... rrency=USD

Just add an engine coolant tube under plenum to warm plenum floor for better atomization and enhanced drivability and you are good to go.

Best regards,

Harry
I made my own headers for this engine. Cost wise to import the clifford shorty headers or the fenton type manifolds is costly, i can almost buy another car for parts or to rebuild.
The exchange rate is bad, the shipping goes up hence the weight and then the import tax works on total of parts and shipping so that stuffs it up even more.
Sadly the aussie speed intake costs more to import that a clifford intake.
I checked all over. For example a offy 2 x 1bbl intake from summit , by the time its gets here and import taxes all there its like paying $880 for it. The 3 x 1bbl is little bit more. Ebay is actually more expensive that the parts houses. And takes longer to get it.

Anyway, over here we had a limited production of the 292 and they used 250 parts mostly.manifold and carbs, So the 292 style exhaust manifold were never used here, i checked.
With the tight space my headers is quite close to the intake , so heats it all over, which helps me sort off. Will take some measure ments later today to see my availible space for intake, maybe i can utilise your idea or something similar in design .
Also modok's idea of trying it both ways regarding blade opening. So will look into that to make it possible on the intake to flip carb over.
Actually looking at some pics on the opala 6cc what they do over there in brazil. As to runner sizes , lengh etc.

Regards.
Adriaan.
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Re: Single 44 idf weber on chevy inline six

Post by chevyfreak » Sun Dec 01, 2019 4:28 am

Found some.
Different designs.
Short. Close to 1bbl design.

Longer center and angled front and rear, most probably done to try even runner lenght and not dump most air charge towards center runner.
And see one with divider for center runner.
Not many designs that run 2 x idf on inline 6. Most single and then some tripple. Majority is single idf.

Discovered a picture of a man-a-fre intake for 3 x 2jets.
Made me think,again,(sadly it never stops, :lol: )
similar setup but 3 weber 32/36dgv progressive carbs. Running all 3 together, with 32 primaries only covering 2 cyl it should be enough for normal driving.
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Re: Single 44 idf weber on chevy inline six

Post by enigma57 » Mon Dec 02, 2019 10:37 am

That gives me a better idea of what you are doing versus what is available, Adriaan. Much appreciated. Yes, I like the Brazilian intakes for Opala as well. ENGINE Co. are very creative there. I began with one of their sidedraught triple DCOE intakes and modified it to accept downdraught DCNF carbs.

If you can locate (or build) a 2 carb intake for 2 Weber 38 DGAS carbs or even the Weber 32/36 2-stage carb...... I believe your 250 engine would like either. FWIW...... In the early 1980s, I built one of the 1600cc Totota 2TC hemi engines for my early '70s Toyota Corolla. Great little engine. This was around 98 cu.in. displacement but rev'd a bit higher than your 250. The 32/36 ran very well on that engine and when I had it topped out on the road, there was still pedal left after it wouldn't go any faster in top gear. So the carb was a bit larger than necessary and 2 of them would probably be all that your 250 would require.

Check out the modified sidedraught intake here. He ran 3 SU clone (Hitachi) carbs from 240 Z Datsun on his 292......

https://www.jalopyjournal.com/forum/thr ... es.708605/

Here is a thread that has quite a few intakes, many hand built. The majority are for V-8 engines, but you will find plenty of them for inline 6's......

https://www.jalopyjournal.com/forum/thr ... d.1042950/

Enjoy,

Harry

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Re: Single 44 idf weber on chevy inline six

Post by chevyfreak » Mon Dec 02, 2019 11:23 am

Hi harry.
Thanks for posting up. Did see that intake for su carbs as i was looking for pics on homebuild intakes. Some very nice ideas and craftmanship out there.
Still pondering on design and then which sort. Sheetmetal, or rectangular tube or round tube, made my templates for the carb base , just waiting for the flanges from laser cutting. Then the build begins.

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Re: Single 44 idf weber on chevy inline six

Post by enigma57 » Mon Dec 02, 2019 5:15 pm

Any of those should be fine for a fabricated manifold, Adriaan. I would lean towards either sheet metal or rectangular tubing due to shape of the 3 siamesed port openings and because it would be easier to form the intake and weld on your carb mounting flanges and the flanges where your intake interfaces with gasket sealing surface of cylinder head.

Found an interesting prototype casting. It is meant for EFI with a single throttle blade at front. Looks heavy as all get out. Would probably serve you well if you needed to beat some sense into someone. :shock:

All kidding aside though...... Imagine if you will, a manifold constructed of welded rectangular tubing and / or thick wall sheet metal similar in layout with open end blanked off. Then you could weld your carb mounting flanges on and use 1, 2, or 3 carbs depending on how you want the final configuration to be.

Or conversely, if you had such a thick casting, you could machine top surface perfectly flat and the drill and tap your carb mounting holes and bore your throttle bores directly into the body of the casting......

Image

Best regards,

Harry

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Re: Single 44 idf weber on chevy inline six

Post by chevyfreak » Tue Dec 03, 2019 12:14 am

Yes. I saw that casting. And like you say is still on the thick side. Can basically machine it for anything.
Did notice it has 6 ports, like for a 12port head. And the shape reminds me of the later brazilian chevrolet omega head, lotus design. But on casting on intake says 292.
Makes one wonder, what they are building.
The brazilians like their turbo and/or efi setups as well. Even coil per cyl setup sometimes.
Hopefully i'm getting my base plates soon and then i can see on building the intake. Sheetmetal or rectangular will make it easier to build, and fitting the base plates.
Getting there slowly for now.

Adriaan.
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Re: Single 44 idf weber on chevy inline six

Post by enigma57 » Tue Dec 03, 2019 12:58 am

Good luck with your build, Adriaan! Please keep us informed of your progress. Very interesting concept. I look forward to seeing your ideas put into action!

Best regards,

Harry

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