Carb Conversion "Kits" ETA March-April 2016

[Andrew]

There is nothing magical about the 2100. It is an incredibly simple carburetor, with extremely few parts (replacements for which are readily available from multiple sources), but any suitably sized downdraft carb would work.

I like to use 2100's for my fabricated manifolds because their footprint fits the central plenum block perfectly. It's almost as though they were destined to be mated together (and size of the central plenum block can't be changed because it fits the elbows and runners perfectly). Everything fell right into place when I first started making manifolds in 2008, which is why I still use the same design to this day.

Peugeot 604 manifold is footprinted for Solex carburetors only (two of them -- one 1 barrel and one 2 barrel). Nothing else will bolt up without adapter plates(s). To the best of my knowledge there are no ready made adapter plates for Solex carburetors (I make my adapter plates myself -- they are custom units).

Bill Robertson
#5939

Bill is correct, there are no commercially available adapter plates for the Peugeot manifolds. Furthermore I would say that the 2100 is the anthesis of the Solex setup found on the Peugeot manifolds. Specifically, the 2100s are simple to work on, easy to get parts for and well documented in automotive literature. In contrast, the Solex carbs are very difficult to tune and even more challenging to find parts for. One of the best Solex service manuals that I relied upon (with the help of Dustybarn) was a French shop manual for the Renault Alpine. I used Google to translate it to English.

While I was ultimately able to get my Solex system properly tuned, if I had to do it all over again, I would go with the 2100.

[content22207_2]

Irrespective of merits/demerits of any particular carburetor, when it comes to the Peugeot manifold a 2100 simply fits better.

This is a Solex footprint:

SolexFootprint.jpg

Weber footprint overlaid on Solex (Rochester would be similar):

SolexFootprintVsWeberFootprint.jpg

Venturi's aren't the problem -- it's the rear mounting holes. There's no way to bolt a Solex adapter to the manifold and still have room to mount the rearmost Weber screws.

2100 footprint overlaid on Solex:

SolexFootprintVs2100Footprint.jpg

2100 mounting holes are nowhere near the Solex holes. There is plenty of room for both, which is how I make my adapters:

2100AdaptedPeugeotManifold1.jpg 2100AdaptedPeugeotManifold2.jpg

Bill Robertson
#5939

[Drive Stainless]

2100 mounting holes are nowhere near the Solex holes. There is plenty of room for both, which is how I make my adapters:

2100AdaptedPeugeotManifold1.jpg 2100AdaptedPeugeotManifold2.jpg

Bill Robertson
#5939

When I look at that manifold, it seems like cylinders 1 & 4 are necessarily going to run richer than cylinders 3 & 6.

[content22207_2]

Kind of hard to tell how the adapter works looking straight down from above. Adapter bolts to the manifold using recessed socket head bolts in the original Solex mounting holes. 2100 mounts to the adapter on studs. Venturis are blended together within the thickness of the adapter.

PeugeotAdapter.jpg

Bill Robertson
#5939

[content22207_2]

When I look at that manifold, it seems like cylinders 1 & 4 are necessarily going to run richer than cylinders 3 & 6.

Centralized fuel metering (*VERY* centralized -- there is a common plenum underneath the venturi openings). Carburetor meters fuel via air passing through its venturis. What happens to the mixture after than has no bearing on AFR.

No intake manifold has equal distance runners. Not even K-Jet -- air going into cylinders 3 and 6 travels a shorter distance than air going into cylinders 1 and 4.

Standard V8 manifolds:

ManifoldCompare.jpg

Again, mixture travels shorter distance to cylinders closest to the carburetor than to cylinders farther away (also notice crossover on the upper dual plane manifold -- because the PRV never fires the same side of the engine sequentially that thankfully wasn't a concern I had to worry about on my fabricated manifolds).

I assure you: carburetion works, even on a DeLorean.

Bill Robertson
#5939

[Drive Stainless]

Centralized fuel metering (*VERY* centralized -- there is a common plenum underneath the venturi openings). Carburetor meters fuel via air passing through its venturis. What happens to the mixture after than has no bearing on AFR.

No intake manifold has equal distance runners. Not even K-Jet -- air going into cylinders 3 and 6 travels a shorter distance than air going into cylinders 1 and 4.

Standard V8 manifolds:

ManifoldCompare.jpg

Again, mixture travels shorter distance to cylinders closest to the carburetor than to cylinders farther away (also notice crossover on the upper dual plane manifold -- because the PRV never fires the same side of the engine sequentially that thankfully wasn't a concern I had to worry about on my fabricated manifolds).

I assure you: carburetion works, even on a DeLorean.

Bill Robertson
#5939

With K-Jet, each cylinder gets the same fuel charge by multi-port injection. The distance from injector-->cylinder is the same for all cylinders.

You could test this hypothesis by farting at the next DMA event. Note that the folks sitting next to you will dry heave more forcefully than the folks at the other end of the dinner table. The (flatulent) mixture loses its potency as it travels a greater distance. Same would appear to apply in carburetion?

[content22207_2]

With a carburetor, each cylinder gets the same fuel mixture by virtue of pulling through the same venturi.

When you get right down to it, in terms of AFR, centralized fuel metering is more reliable than multiport injection -- certainly as K-Jet does it. If you have a badly performing injector, that cylinder will suffer AFR discrepancies not experienced by any other cylinders. There is no way for Lambda to tell which cylinder is having problems, so it monkeys with all of them -- 5 good cylinders now perform badly because Lambda is trying to compensate for one bad injector. That's why K-Jetters have to put their injectors in jars and visually inspect what's going on.

People love to Poo Poo carburetion, but I will take certainty of centralized fuel metering over mystery of six individual injectors any day.

Bill Robertson
#5939

[content22207_2]

Drive Stainless seems to misunderstand how carburetors meter fuel. All cylinders connected to a venturi pull air through a common location. Hence all cylinders receive the same fuel charge. You could have a cylinder at the front end of the car, and it would still receive the same fuel charge as a cylinder at the rear (atomized fuel could well fall out of suspension before reaching the front of the car, but the amount of fuel falling out of suspension would still be equal to fuel going into the rear cylinder). That is of course an extreme example -- fuel is not going to fall out of suspension in the short distances of a real world intake manifold.

Bill Robertson
#5939

[content22207_2]

Perhaps it would help to compare centralized fuel metering to the HVAC/Brake booster vacuum barb. HVAC vaccuum canister is at the rear of the car, brake booster vacuum canister is at the front of the car, but they both draw from the same vacuum barb, hence they both have the same vacuum inside.

A carburetor venturi works the same way: the same amount of fuel is metered through it, irrespective of where that fuel goes afterwards.

Bill Robertson
#5939

[content22207_2]

Please note: Peugeot 604/Renault Alpine cylinders pull through *TWO* carburetors at the same time.

Perhaps Andrew can provide more details (for example: is the throttle linkage progressive -- does it open throttle plates on one carburetor before opening them on the other)? I honestly don't know.

Bill Robertson
#5939