Maybe Dan, but I would take a gasket from a bbd and overlay it with a gasket for the tbi, before I would make that judgment. I would say the flow deflection is about the same as a bbd to bbs adapter.

It's been a while since I had a BBD, but I have been working with a GM TBI at work recently. The pattern is quite similar to the BBD's, although a bit larger. It looks like it would be a small restriction to flow, but I would expect the total restriction to be about the same amount as a BBD.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

This has been done with a one barell intake manifold already....

I'm working on a 1bbl next.

For an 1 11/16" bore GM TBI (the 305-350 V8 size) to a 360/bigblock BBD pattern, there's about .28" of offset at the outer edge of the bore holes. I dont have any CAD drawings on the 1 3/8" 4.3V6 vs the smaller /6-318 BBD.

A person could bolt the adapter onto their intake and take it to a machine shop and get them both hogged out to the same size. There's usually a lot of material around the bores on a factory manifold, at least there is on the 383-2barrel manifolds I have. If you go this route I'd recomment putting 2 locator pins thru the adapter into the manifold to make it easier to align in the future.

Sorry, I'm a bigblock Mopar guy, but I take (and give) EFI info wherever I find it.

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interests include EFI, Megasquirt, turbos and C-bodies (in no particular order!)

Welcome here, and thanks for the info. Just to be clear, it reads like you mean the large (big block) 2bbl flange is smaller than the TBI flange, is that so?

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Too many people who were born on third base actually believe they've hit a triple.

Yes, the bores in the manifold are smaller diameter and closer to each other.

The smaller size in bore has always made me curious about the max capability of the V-8 TBI units.

2-barrel 383s were rated at 270-290hp (gross) depending on year, and the GM engines were rated around 180 (net). I read years ago that multiplying a cat-equipped engine by 1.5 would approximate a gross rating, so 180 *1.5 = 270. But the carb bores are smaller than the TB, and that also includes the restriction that results from the venturis. Seems to me like a TB should feed a mild 360-383 just fine if the injectors are big enough.

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interests include EFI, Megasquirt, turbos and C-bodies (in no particular order!)

To add to this, Even 2.5L TBI bore is BIG. Don't know why. But still is, vs two little holes.

Cheers, Wizard