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Offy 4bbl intake on eBay with odd "fuel dam" on #3-4 cylinders
https://slantsix.org/forum/viewtopic.php?t=68539
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Author:  Jase [ Sat Feb 14, 2026 11:21 am ]
Post subject:  Offy 4bbl intake on eBay with odd "fuel dam" on #3-4 cylinders

Is this necessary on the Offenhauser as a result of #'s 2& 5 running a bit lean. I thought it was cylinders 1 and 6 that were often rich...

See picture #5,

https://www.ebay.com/itm/317847802916?_ ... R4TzstSLZw

Author:  Dart270 [ Sat Feb 14, 2026 12:15 pm ]
Post subject:  Re: Offy 4bbl intake on eBay with odd "fuel dam" on #3-4 cylinders

Absolutely not needed. Probably won't really hurt anything either. Yes, 1 and 6 might run slightly richer, but it is very slight. Unless your carb is really messed up or trying to run right on the edge of lean or detonation, the cylinder-cylinder distribution is very good on all common Slant 6 manifolds.

That said, with a 2bbl mounted with barrels side-side like that, I usually run about 2-3 (holley) jet sizes bigger on the inner barrel and can see a small difference in the plugs if I bother to check.

Lou

Author:  Reed [ Sat Feb 14, 2026 1:05 pm ]
Post subject:  Re: Offy 4bbl intake on eBay with odd "fuel dam" on #3-4 cylinders

The old Mopar Performance racing manual used to recommend a fuel dam like that behid the secondary throttle bores on a normally oriented four barrel intake to combat the tendency of the middle cylinders to run richer than the outer.

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