Inliners International Forums General Discussion Engines Webber DCOE's

While my 292 project incubates, I'm planning another six for a Canadian 55 Pontiac, which is all 55 Chevy underneath. I'm looking at a 250 Mercruiser for sale or another 292 to install and I came across a triple Weber sidedraft carb setup off of a 250. The gentlemen stated it was off of a track car but we didn't get into specifics. His setup does not come with an intake. Can they be run bolted to the block on the street using headers or do you need an intake? Am I asking for trouble going down this road? Asking is $1000, Canadian mind you but still is really really steep regardless, in my opinion. The car will be backed by a 700r4, mods to the 250 Mercruiser will be minimal if at all. Diff looks like 3.08 rear gears or maybe 3.25, and will be summer and long distance driven. Thoughts?

My opinion only. The DCOE does not need or like a plenum intake, they are designed to run with individual short runners to the head. Of course you don't HAVE individual PORTS, so it won't work quite like that. The stock intake is a plenum type. The biggest issue is that the 3x weber setup is likely way too much carb for the application. With individual runners and one choke per cylinder the engine can take a lot more CFM, but still the smallest DCOE is a 40mm (dual). A near stock 250 or 292 would work well with just ONE of them, based on CFM alone. You would be spending a lot of money choking THREE of them down to work with the smallest venturies you can find, and that means all the jets need to be replaced too. Hours of trial and error, and money in parts. And still likely suffer from slow intake velocity not allowing them to work well at low and mid rpms. I have not tried them myself on siamese port engines. Just sounds like a hassle to get them streetable. A hopped up 292 might run well with them.

DCOE's have been used on the 194/292 siamese port head/engines successfully since they were introduced in the early 1960's, so need to suspect otherwise. Hank and several others have also used them on hot street 250's as well. The DCOE's are super tuneable and not bothered by the siamese ports as you might expect. One possible issue is those intakes aren't heated, so it may pose problems in areas where that is needed.

Yes they are extremely tunable, just about everything about them can be adjusted. And like I said, most of it needs to, for this application. Webers are very picky too about everything being just right. Dellortos would be more forgiving and easier to tune.
Everything said and done, I feel that they would work ok in a high performance application where low rpm performance is not important. That is not what the OP was asking for... Very short intake runners, which they are designed to work with, would probably not need heating. They would warm up from the heat conducting from the cylinder head. No plenum for fuel mixture to sit in.

The only intakes for the DCOE's for use on these engines are the IR style short runner intakes that do not have a plenum. Several people make them, I have two myself I make as well as Clifford and one in Brazil is also available. For street use, as I said already, these types of carbs and intakes have been used successfully for decades in many venues from mild to wild. Most every top shelf Chevy 6 engine builder from Sissell to Glen Self has fitted many of their customers with them and had no issues for street use. They aren't all just a race only carb, even though they have set many racing records also.

You also mentioned they are picky and finicky, and they are. It just adds another element of maintenance into the equation that the end user needs to be aware of. But they can also be made to be very reliable and streetable, depending on how much effort someone is willing to devote to them. These carbs may not be for everyone, and his results and experience may vary from others who have used them on the street as he intends too. Since he specified it will be summer driven, he may not need a heated intake. Which the IR intakes are not.

He didn't mention what size DCOE's he was looking at that are for sale. Carb sizing is important for any engine, and if these are larger race size carbs like 45MM or 48MM, or larger, then he may be wanting to rethink using them if his engine is more stock and modified.