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Single 44 idf weber on chevy inline six

General engine tech -- Drag Racing to Circle Track

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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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Re: Single 44 idf weber on chevy inline six

Post by enigma57 » Tue Dec 17, 2019 4:39 am

chevyfreak wrote:
Sun Dec 01, 2019 12:52 am

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.
Adriaan, was revisiting this thread and was curious as to total plenum volume. Most of my Weber experience is with IR intake, so reconfiguring the DCNF carbs for use on open plenum intake has been an interesting undertaking.

Some years ago, I drove over to see Mr. Beck. In those years, he built sheetmetal intakes for high end V-8 engines intended for drag racing, mainly. I asked him about plenum volume but he would not be specific. Only said that there were 2 schools of thought, one being small plenum volume (better throttle response) and the other being large plenum (better top end). I knew that much already, was hoping to quantify open plenum volume under carb(s) versus engine displacement and factor intended RPM range into the equation as well.

For daily driving and/or any application where good throttle response either at low to mid range RPMs or off the corners is necessary...... I tend to lean towards the smallest practical plenum size that will still allow the engine to reach its designed redline RPMs. So was curious as to whether you had cc'd the internal volume of your open plenum intake after decreasing volume and restoring carb signal.

In the available (as cast) intakes for inline Chevy 6, the old Offy designs (small interiour volume overall) generally had good carb signal, but the tradeoff was that with such a long, log type intake positioned close to cylinder head, either 3 carbs or 2 carbs were required for anything resembling equal fuel distribution and with fewer than 3 carbs on straight (non-progressive) throttle linkage...... The air/fuel mixture had to make tight 90 degree directional changes.

The Clifford intakes on the other hand, generally had much larger internal volume, as they were designed for either single or dual 4bbl carb(s) (though 2bbl carbs could be fitted). As such, they tend to run well at higher revs, but are a bit 'soft' coming off the corners if RPMs fall below 2,500 - 3,000 RPMs (depending upon engine displacement and camming).

My 3- carb intake I have been working up has 3 small individual plenums, each fed by an isolated twin throat downdraught carb. So having too large an overall plenum volume isn't such a concern and fuel distribution should be spot on. However...... I may experiment with one of the older Clifford dual carb intakes as well...... Just to see how it will perform with reduced plenum volume. And whilst doing this, I may whittle some hardwood plenum stuffers designed to even out flow to the 3 sets of paired, siamesed intake ports whilst lessening plenum volume, as well.

This is why I was curious as to whether you had cc'd your 250 inline 6 intake after decreasing internal (plenum) volume and restoring carb signal. Am curious as to the relationship of plenum volume versus engine displacement and redline RPMs.

Best regards,

Harry

P.S. >>> FWIW...... Many moons ago, I recall seeing a small Opel car with Chevy inline 6 engine of some sort. I believe this car was built in Germany in the late 1970s or early 1980s. It ran fabricated tubular intake and exhaust and the carburettor was a single triple-throat downdraught Weber of the type used in pairs on the Porsche flat six engines and was topped with tall trumpets. Of course, this tall, upright carb ended up being positioned nearly all above the hoodline and hanging out in the breeze. But the car as I recall was exceedingly quick.

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Re: Single 44 idf weber on chevy inline six

Post by chevyfreak » Tue Dec 17, 2019 10:35 am

enigma57 wrote:
Tue Dec 17, 2019 4:39 am
chevyfreak wrote:
Sun Dec 01, 2019 12:52 am

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.
Adriaan, was revisiting this thread and was curious as to total plenum volume. Most of my Weber experience is with IR intake, so reconfiguring the DCNF carbs for use on open plenum intake has been an interesting undertaking.

Some years ago, I drove over to see Mr. Beck. In those years, he built sheetmetal intakes for high end V-8 engines intended for drag racing, mainly. I asked him about plenum volume but he would not be specific. Only said that there were 2 schools of thought, one being small plenum volume (better throttle response) and the other being large plenum (better top end). I knew that much already, was hoping to quantify open plenum volume under carb(s) versus engine displacement and factor intended RPM range into the equation as well.

For daily driving and/or any application where good throttle response either at low to mid range RPMs or off the corners is necessary...... I tend to lean towards the smallest practical plenum size that will still allow the engine to reach its designed redline RPMs. So was curious as to whether you had cc'd the internal volume of your open plenum intake after decreasing volume and restoring carb signal.

In the available (as cast) intakes for inline Chevy 6, the old Offy designs (small interiour volume overall) generally had good carb signal, but the tradeoff was that with such a long, log type intake positioned close to cylinder head, either 3 carbs or 2 carbs were required for anything resembling equal fuel distribution and with fewer than 3 carbs on straight (non-progressive) throttle linkage...... The air/fuel mixture had to make tight 90 degree directional changes.

The Clifford intakes on the other hand, generally had much larger internal volume, as they were designed for either single or dual 4bbl carb(s) (though 2bbl carbs could be fitted). As such, they tend to run well at higher revs, but are a bit 'soft' coming off the corners if RPMs fall below 2,500 - 3,000 RPMs (depending upon engine displacement and camming).

My 3- carb intake I have been working up has 3 small individual plenums, each fed by an isolated twin throat downdraught carb. So having too large an overall plenum volume isn't such a concern and fuel distribution should be spot on. However...... I may experiment with one of the older Clifford dual carb intakes as well...... Just to see how it will perform with reduced plenum volume. And whilst doing this, I may whittle some hardwood plenum stuffers designed to even out flow to the 3 sets of paired, siamesed intake ports whilst lessening plenum volume, as well.

This is why I was curious as to whether you had cc'd your 250 inline 6 intake after decreasing internal (plenum) volume and restoring carb signal. Am curious as to the relationship of plenum volume versus engine displacement and redline RPMs.

Best regards,

Harry

P.S. >>> FWIW...... Many moons ago, I recall seeing a small Opel car with Chevy inline 6 engine of some sort. I believe this car was built in Germany in the late 1970s or early 1980s. It ran fabricated tubular intake and exhaust and the carburettor was a single triple-throat downdraught Weber of the type used in pairs on the Porsche flat six engines and was topped with tall trumpets. Of course, this tall, upright carb ended up being positioned nearly all above the hoodline and hanging out in the breeze. But the car as I recall was exceedingly quick.

Hi harry.
Didnt measure it sorry. But when it was big it needs more fuel at idle and even then it struggles. I actually put a stock cam back in, had some issues with the hotter cam,

Im trying something else currently, took the weber intake and made a adapter to fit the qjet. Can tell you that with the smaller stock size runners it is crisp. At idle only 1 turn on the mixture screws. Idles at 700rpm cold and at 900 hot. In gear it drops to about 770rpm .
Qjet response is very good .
Still contemplating on the intake, been thinking on that sheetmetal idea, and do a top plate like you mentioned, and then i can try multiple carb setups as its only a lid change away and not building a whole intake. Want to keep runner size similar to the weber intake and plenum just up to size so carbs can still fit. Just havent had time, buzy at work to finish off before the festive season holidays.

Anyways, back to the cam. I did notice i have very low vacuum, like 7.5 in hg, rechecked timing marks just incase, tried another crank gear that advance cam by half a tooth which is about 3.33 degrees, vacuum only jumped 1 higher to 8.5. So the mystery starts and i start checking the cam. I had a stock cam regrind for longer duration, so looked thru the paper work, cam a bit bigger than i asked for, will plot out degrees later when i build the other engine, cam will work with manual trans so can use it still, what i did find in digging the archives, gm stock specs is 172/172 @ 0.050 on a 105Lsa. And i went for a regrind so with the longer duration im suspecting the overlap is whats pulling my vacuum down.
But with the stock cam it runs great so will decide on cam later, for now its the intake and carb setup.

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

Post by chevyfreak » Tue Dec 17, 2019 11:00 am

enigma57 wrote:
Tue Dec 17, 2019 4:39 am
chevyfreak wrote:
Sun Dec 01, 2019 12:52 am

P.S. >>> FWIW...... Many moons ago, I recall seeing a small Opel car with Chevy inline 6 engine of some sort. I believe this car was built in Germany in the late 1970s or early 1980s. It ran fabricated tubular intake and exhaust and the carburettor was a single triple-throat downdraught Weber of the type used in pairs on the Porsche flat six engines and was topped with tall trumpets. Of course, this tall, upright carb ended up being positioned nearly all above the hoodline and hanging out in the breeze. But the car as I recall was exceedingly quick.


Gm did some weird stuff.
Over here they took opel , holden and vauxhall and relabeled them as chevies, so we had a chevy that were a true chevy, a holden which is a chevy , a opel which is a chevy and then a vauxhall which is also a chevy, trust me the confusion is big for many people over here. Even on the ford brand. Had ford models from usa, from uk, from australia and from germany,

holden had some as well, the vb/vc commodores is basically a opel commodore C but some changes were made . Some models there after were closly related to later opel v body platforms and eventually the holdens stood on their own as opel stopped rear drive models.

The opala comodoro 6cc is actually a opel commodore A, also with changes.

The cadillac catera is a opel omega prototype which was labeled as the v8.com. never got production in europe but gm used the setup for the cadillac brand.

If or when you get a chance check on youtube on the lotus carlton. Its actually a opel omega A but came oout in uk as a vauxhall carlton and then lotus did a bit of tweaking.
Will go look for a link to send to you.

Attached is pics of what i have in mind for the sheet metal type intake.

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

Post by chevyfreak » Tue Dec 17, 2019 12:40 pm

Pic of the car. Back when it had a sbc 327 in. Th350 and 2.92 rear.

Now its the 266 with the th350 and 2.92 rear.
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Re: Single 44 idf weber on chevy inline six

Post by enigma57 » Wed Dec 18, 2019 1:00 am

:D Nice car, Adriaan. I bet it was really fast with the 327. Should be a lot of fun with the 266, as well. I found this Opel version in rally trim......



That's a beautifully executed inline 6 intake......

Image

The same concept should work well for your Chevy due to the 3 sets of paired siamesed ports. If I had a true 12-port head such as the intake in the photo was made for...... I'd keep same basic structural architecture, but add dividers in what is now the plenum to isolate each runner and make it a true IR type intake functionally.

Best regards,

Harry

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Re: Single 44 idf weber on chevy inline six

Post by chevyfreak » Wed Dec 18, 2019 2:47 pm

enigma57 wrote:
Wed Dec 18, 2019 1:00 am
:D Nice car, Adriaan. I bet it was really fast with the 327. Should be a lot of fun with the 266, as well.


Best regards,

Harry
Was running quite good but for me i liked the sbc beter with a solid axle rear, can be a bit more of a hooligan when me and my buddy go playing at the track.
With the senator its a irs rear. Sits nice in the corners, drives nice but i liked the 327 beter in my commodore,
As for the inline 6, wont be any faster or slower, as its the same trans and rear, just that with the v8 it gets up to speed a bit quicker.
But the inline has nice low down torque responce so will still be good.
Just playing with induction to get that nice combo and something else to show at carshows.

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Re: Single 44 idf weber on chevy inline six

Post by enigma57 » Wed Dec 18, 2019 5:05 pm

:D Sweet!

HB

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Re: Single 44 idf weber on chevy inline six

Post by chevyfreak » Tue Jun 16, 2020 2:40 am

Been a big while. We had a complete lockdown due to covid19.
Gave me time to finish another project and decided to use the idf setup on this 250 inline six. Head also had bolt boss removed. Bit of a cleanup in the ports. And a bit of a cut to clean up the deck. Had a nasty mark. But cleaned up at .060.
Anyway. Gonna try the idf on here and see how it goes with tuning. Had some steel plates and build an intake so will see how this one goes. Made a short runner for now. Sorting fuel lines, and a couple of other things but should be able to start in a couple of weeks.
Just updating on here a bit.
Took modok's advise and blades opening away from engine. Will try this way first and got some plates to make an adapter to turn it around so it works other way around if need be. I'm just starting somewhere and go from there on further tuning. Some pics added.
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