Inliners International Forums General Discussion Hi Performance New carb idea!

Bet it could be modded. But they are somewhat hard to find. Also, I think the transition from single primary to dual secondary would be hard to tune to work right.
The standard Holley 600 and 750 are the cheapest, easiest to find and parts are plentiful.

21 mpg out of a 600 Holley is hard to argue with! Even with the one barrel mod.

MBHD: I thought about this before but never actually tried it.
I too thought a spreadbore Holley would be good with it's small primary and big vacuum secondary.
Of course as Tom points out the 600's (and various unidentified 450-ish sized carbs) go cheap at flea markets.
But then I found a cheap 390 and forgot all about it. : )

The spreadbore idea would work fine, just think outside the box about how to make this concept on a smaller scale and still fit the standard Holley bolt pattern. I have it figured out, just seeing if others have their thinking caps on.

Curious, will your idea be cheaper or work as well as the modified Holley's?

Jake and I took the wagon out tonight to a HAMB party about 30 miles away. He again remarked on how the car pulls harder than it ever has. So far the testing has turned out to be positive. I don't consider it a experiment anymore. This is a real, reliable alternative for a carb to give great fuel mileage, easy to get and keeps the initial cost down. Of course you will need to be able to perform a few mods to make it work.

Doubt it would be cheaper, but it will be less unorthodox than your approach. Unless you are replacing the baseplates on these carbs your modifying, which usually have the throttle shafts worn out, its really going to be a hard sell to convince people to buy a modified worn out carb. Its not always about how cheap you can do something, most people don't mind spending more for better quality.

So far the carb's I have been buying are nice ones. They usually bring 100 or less for them.

So what is your idea? Will it be easy to tune and acquire?

Well, I can't take full credit for this idea completely, it and similar concepts have been done for 20-30 years already in different motorsports of racing. If you have ever put a baseplate from an 850 onto the main body of a 750 Holley, then you have already inadvertently performed a similar modification. This was a popular mod 25 years ago or longer that improved performance. In a similar way, in racing classes where you are restricted to a baseplate of a certain butterfly size, usually a 750, then it was common to bolt an 850 main body onto the 750 baseplate to gain an extra edge, and it also was worth some HP to do this. We had a local circle track that required this for a class at one time that we did engines for, and I modded a bunch of these. In the same way, you can create a spreadbore type carb with the standard Holley bolt pattern baseplate by changing the primaries to ones that are smaller just like the ones in a 390 or spreadbore carb. There are several ways you can do this, it's not hard to figure out. But you basically end up doing the same thing you are now, reducing the effective size of the primaries, except now you would be doing it in a way Holley already has done it. You won't have to plug passages here and there and block off one hole barrel completely. And you still have the benefit of a larger secondary with the butterfly size of a 600 like you have now. And it will be as easy to tune as any other Holley, just simple jetting and squirter selection, idle mixtures, etc....

I run a homemade 3 x 2 setup on my Logghe chassied Nostalgia racer that uses three 350 2V main bodies taper-bored out to accept 500 2V base plates. Good throttle response and on a U-flow head they work OK, but my X-flow head needs (3) 540s. Similar principal as what can be done on your 4V.