Jump to content

Dual Intake manifold for v/12


b6vt

Recommended Posts

I have an Edmonds dual intake manifold. I also have the carbs to install. I don't have the linkage. Is this a progressive linkage or is it direct? Where can I get the correct linkage set up? Also, does the dual carb set up present any special problem that I need to be aware of. The intake manifold requires a three bolt carb attachment. Both of my carbs have a 4 bolt base, I need to get two, three bolt bases, does this present any special issues with the carbs? any comments will be appreciated. Thanks in advance. Merry Christmas. Glenn Lorei b6vt

Link to comment
Share on other sites

Guest 65Starfire

It should be a direct with 2 primary carbs. The important thing is to get the carbs jetted correctly and make sure that they are both primary. Swapping the bases may work but I would probably just look for a couple of correct carbs that are correct and sell the pair you have. They will also have to have the Lincoln linkage on the opposite side of the carb from the ford.

Good luck!

Link to comment
Share on other sites

I'm putting on my 'hot rod' hat here as that is my past but not present. Your linkage most likely should be progressive. Most multi-carb setups I've seen are such. An adapter plate to go from 4 bolt carbs to 3 bolt carbs should not be that hard to fab. The carbs need to be synced by using a vacuum gauge. They will also need to be rejeted. As for me they are a PITA and will cost you big bucks with scuffed pistons and such. Don't ask me how I know this.

Now to the questions: Why are you doing it? The v-12 is not a power house by any means. Small intakes, poor outflow, and a host of other problems plague this engine. Over carburation is a very common mistake by hot rodders. Bigger carbs make more power is a myth in most cases. H&H Flatheads with their tricked out & blown V-12 makes 185HP.

I understand the WOW factor of the v-12. I just love all those cylinders. If you just have to have the dual intake you might think about making the second carb a 'dummy'. Many three duces carbs setups I've seen are this way.

Link to comment
Share on other sites

For a dual two-barrel set-up, best results will be obtained using 2 primary carbs and solid linkage. Synchronization of the the two carbs is a must.

Yes, you can get a 3 bolt to 4 bolt adapter, which will add some power to the very high end of the RPM scale (and subtract it from the lower end of the RPM scale). They also will not help your idle smoothness. As the V-12 is not an RPM screamer, I would suggest finding 3 bolt carbs.

Whatever carbs you decide to use, build them absolutely stock for a repeatable baseline. You can always adjust from there.

Jon.

Link to comment
Share on other sites

The design of the Edmunds dual manifold necessitates that the carburetors must be operated in unison. The intake runners are isolated in 4 groups of 3 cylinders making idle adjustments a little tedious. The 3 bolt bases usually do not have the vacuum tap for the distributor so you will need to use the vacuum tap on the manifold. The 4 bolt bases on your carbs can be easily switched and the main jets can be changed to lean up the mixture a tad. I can supply a couple of pre-war Lincoln 3 bolt base reconditioned carbs if needed. These are jetted leaner than the 4 bolt carbs used on post war cars and will work fine. Linkage is available to hook up the accelerator and choke levers so your original linkage will work. If you use and convert your 4 bolt carbs be sure to check the "flatness" of the base of the (center) carb body. These old devils warp causing a loss in vacuum to the power valve making for a rich mixture so those bodys need to be trued up.

Link to comment
Share on other sites

Everyone to their own notion, but I would suggest at least thinking about 2 Carter type WCD carburetors rather than the original Holleys. The Carter WCD's are technologically advanced, infinately more tunable, and virtually all would be less expensive than original Lincoln Holleys; and they don't blow power valves ;). They were used from 1941 to as late as 1970 on various applications.

If you go this route, just be certain that you use 2 identical carburetors.

Jon.

Link to comment
Share on other sites

Guest 65Starfire
Once again, I have learned from the masters. I may change my forum name to 'Grasshopper'.

No worries! When I was looking to upgrade my intake I thought a 3 carb setup would be great and found out fast that given the small displacement the 2 carb setup was better and that the nature of the intake design would necessitate a dual primary setup. I agree with Carbking that the WCD's would be a more tunable option - but they also don't have that cool Zephyr logo on the side...

Link to comment
Share on other sites

No worries! When I was looking to upgrade my intake I thought a 3 carb setup would be great and found out fast that given the small displacement the 2 carb setup was better and that the nature of the intake design would necessitate a dual primary setup. I agree with Carbking that the WCD's would be a more tunable option - but they also don't have that cool Zephyr logo on the side...

For the difference in initial cost, extra power, better drivability, and increased fuel economy; I could print a sticker on my laser printer! ;)

Jon.

Link to comment
Share on other sites

Since you're willing to give up some originality, you should consider the Reds Headers exhaust manifolds with dual exhaust. If you want more mixture into the engine, you've got to get more exhaust out. The headers really do look sharp. I've also heard that the Edmonds setup works better if you add a balance tube between the front and rear.

Abe

Link to comment
Share on other sites

Glen: Been a while since I've seen the Edmonds, Some of the old timers I've talked to claimed the Edelbrock manifold worked better unless you rigged up a tube between the bottom of the carbs, sounds messy. Perhaps someone has a picture. I've been studying how to make a three carb manifold work with either Ford or Chevy two barrel throttle bodies run by a controller in a semi-synchronous injection mode. I do think it is possible.

Abe

Link to comment
Share on other sites

I am not familiar with the Edmonds intake in question; so the following is general information, and may (or may not) be applicable to the Edmonds.

Most of you have probably seen the carburetor sizing equation: CFM = (RPM x CID) / 3456.

What is not generally posted with the equation is that the equation is valid for four-stroke multi-cylinder engines of at least 4 cylinders. If less than 4 cylinders, then the equation must be modified.

Why?

With a "plenum" type intake manifold, the carburetor(s) do not actually feed the cylinders. The carburetor(s) feed the plenum(s), and the plenum(s) feed the cylinders. As the intake valve in a cylinder opens, a low pressure "pulse" draws a portion of the A/F mixture from the plenum; also slightly reducing the pressure in the plenum, thus causing additional mixture to be drawn from the carburetor. With multiple cylinders "pulsing", the carburetor sees the pulse from the plenum for each cylinder, thus maintaining a more constant draw on the carburetor, improving its efficiency.

As I said, not familiar with the Edmonds; however, it could be set up with each barrel of a carburetor feeding a plenum of three cylinders or both barrels of a single carburetor feeding a plenum of six cylinders.

One would think, without additional knowledge, that if the latter were true (both barrels of a single carb feeding a plenum of six cylinders) the pulsing would be sufficient, but possibly not. If the former were true, then our individual plenums would each be feeding less than four cylinders, and the balance tube would make a great improvement.

Adding the "balance tube" (it should be at least the same volume as a runner to a cylinder) between plenums simply adds additional pulsing as in effect the two plenums now become one.

Another intake design is the "IR" or "individual runner" design; where each cylinder is directly fed by one carburetor barrel. VERY efficient for VERY HIGH RPM RACING ENGINES ONLY. With the IR design, total carburetor CFM must be approximately twice what it is for a plenum design.

Jon.

Edited by carbking (see edit history)
Link to comment
Share on other sites

Does anyone have any information on a "balancing tube to run between two carbs on the Edmunds dual intake? Logically I can see how this would help in the balance between the two carbs.

If one would have to manufacture it themselves--What size would the tube need to be and where would it need to be placed--at the base of the carb? b6vt

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...