Calculating effective intake runner length (siamesed intake port)

[enigma57]

Thanks, roc! Yes, I love the Brazilian Opala! And yes, that is the same Brazilian sidedraught intake I began with. Actually, I am joining 2 of them together, each forming 1/2 of a longer runner intake and converting the outboard intake to accept my Weber 42 DCNF downdraught carbs (sidedraught carbs with proper trumpets and either individual air cleaners or an airbox setup will not clear steering column and master cylinder in my engine compartment).

This is the unmodified sidedraught intake that forms the inboard half of my intake setup.....





And this is the modified intake that forms the outboard half of my intake setup (modified to accept DCNF downdraught carbs)......



















I will bolt the intake halves together using their otherwise unused DCOE sidedraught flanges to join them. Note to self...... Need to hand cut a gasket for that.

Thanks to a very understanding wife...... After I figured out what I wanted to do, I hand fitted the pieces at the kitchen counter (AKA 'work bench' for us old retired guys whose garages are full) and then sent the outboard intake half along with the carb flanges and filler pieces to Nick Smithberg and he did the welding and machine work. Outstanding workmanship, as always. Many thanks, Nick!

FWIW...... My '57 Chevy in street trim even with full exhaust and interiour and the heavy front bumper...... Weighs only 150 lbs. more than the Brazilian Opala in street trim. So even though I will not be building a max effort race engine nor stripping down my car to lighten it as with the Opala in the video, my old Chevy should still be a fun ride out on the road. Especially for a 6-banger (souped up 292).

I have the engine build and intake project on the back burner for now as we see to my Mom-in-Law's care (she is 91 and has fallen several times since September, the last fall fracturing a vertebrae).

Still sourcing parts to rebuild and reconfigure the DCNF carburettors. Managed to find a few things here Stateside and Jack Lawrence was kind enough to machine some choke tubes for me, as well. Jack owns Motor Sport Services in Jamestown, New York. He developed an induction system for V-4 Saabs using a single DCNF carb and has quite a few parts for them on hand, though he says he may be retiring before long, as he is well into his 80s now.

A friend in the UK has put me in touch with a fellow in Essex who will be shipping the remainder of DCNF parts I have been unable to locate when weather there permits (he has been snowed in for the past 5 days thus far). Will let you know how the build is coming along when I have more to report.

The 42 DCNF carbs I am rebuilding and reconfiguring for the 292 inline 6 are original to a Maserati Quattroporte. I will rebuild and use 3 of them on the 292 and keep the 4th for spare parts......



To give you a better idea what these carbs look like when cleaned up and rebuilt...... Here are a set of 42 DCNF carbs (not mine) that have been reconditioned......



Best regards,

Harry

[roc]

Hi Harry,
You're determination and accomplishments are impressive! Being someone who has gone through similar endeavours, I certainly tip my hat to you.

I suppose you know, the 'Engine' company (in Brazil) makes intakes for IDF's (but not DCNF's): 'Engine' Intake Manifold for tripple Weber IDF

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I wish your MIL well. Your wife is definitely a keeper! Good luck with your project and keep us posted.

[enigma57]

Many thanks for your kind words and well wishes, roc! Mom-in-Law is doing well for now. Wife took a while to get used to having home furnished in 'early gearhead' after we married. Especially after she got up one morning half asleep and stubbed her toe on a bare 413 MOPAR engine block standing on end and covered with a bath towel which I considered a 'bedside table'. So we both made some adjustments and all has been well now for many years. She has said that she would like her breakfast room (AKA my 'engine parts storage and carburettor rebuilding area') back one day, though.

Yes, I have seen photos of one of the IDF intakes installed on a Brazilian Opala. Very nice setup indeed.

Much like the 400 Pontiac engine I built up and swapped into a '56 Chevy after my GTO convertible was wrecked in the late '70s...... Adapting three Weber DCNF carbs onto the 292 inline 6 is in many ways, a 'marriage of convenience'. You do the best you can with what you have.

I managed to score a couple of new Brazilian made 'Engine' brand sidedraught intakes for a very reasonable price over on the HAMB a while back. Intended on using one and selling the other to recoup a goodly portion of the purchase price and put that towards either a set of Weber DCOE sidedraught carbs...... Or to adapt 3 Mikuni HSR-42 sliding valve motorcycle carbs.

However, after mocking the 292 engine up in my '57 Chevy whilst considering how to fabricate the engine mounts...... I discovered that DCOE sidedraughts with proper trumpets and either individual air cleaners or a hand made airbox fed by trunking...... Would not clear my LHD steering column and master cylinder. Same for Mikunis, though they are more compact and would 'almost' clear. Not wanting to butcher an otherwise original '57 though, I decided to modify one of the Brazilian intakes to fit Weber DCNF downdraught carbs to this engine.

However, due to the tighter center to center spacing of the DCNF throttle bores (46mm versus 90mm for DCOE), positioning the DCNF carbs so as to center the throttle bores on the diverging sidedraught DCOE intake runners resulted in the DCNF carbs being too close to the cylinder head. A bit more measuring indicated that I could 'just' clear the master cylinder and steering column if I were to turn the modified intake 180 degrees and bolt it to the 2nd unmodified intake using the (now former) DCOE mounting flanges to join the halves and thereby form a 2-piece intake having longer runners. And by sheer dumb luck more than anything, it happens that the extended runner length is now spot on for 3rd harmonic. That's how I ended up where I am with the intake at present.

Also...... I enjoy tinkering with Webers and have a set of low mileage Italian made 42 DCNF carburettors original to a Maserati Quattroporte here. Have had them sitting here boxed up for over 20 years now and as this will be my last build, thought I'd put them to good use. I'm 70 now and must get around on 2 canes, as both knees are shot and had back operation for ruptured disc 22 years ago. Hoping I can get the old girl roadworthy over the next several years and enjoy driving her before I get too old and gimped up to do so. Really not into slush boxes and hoping that by adapting some Jeep pieces to make a hydraulic clutch setup, I can retain the stick shift even with my bad knees. An engine such as I am hoping to build deserves nothing less. Should be fun!

Best regards,

Harry