weber carb conversion kit - Page 2 - PeachParts Mercedes-Benz Forum

nhdoc · #16 07-24-2009, 12:59 PM

I did a conversion using the JAM kit and was happy overall with it. It was easy to install and it performed very well in my 220Sb. I have heard that people are more satisfied with JAM's adapters and linkage than with Redline's.

mbbuff · #17 07-24-2009, 01:04 PM

My 4A1 works fine, always has, except when the float failed. I think I am the only one that has ever messed with this one. But, then again, I've worked with carburetors off and on for 40+ years. If I were to ever change (which I won't), I would adapt a 390 CFM 4160 Holley (List No. 8007, I believe) to the stock manifold. They offer more flexibility, and reasonably priced parts availability than any other mainstream carb. that I know of. Every system (idle, accelerator pump, main, power, secondary, etc.) can be custom tuned for your application. Linkage would also be easy to adapt using mostly stock components, IMO. Biggest problems would probably be mounting and adjusting the stock MB vacuum governor and making an adapter plate. Hmm, wonder if I should do this as an experiment. Carb. is only about $300-350.

wolf_walker · #18 07-24-2009, 09:04 PM

Quote:

Originally Posted by mbbuff

My 4A1 works fine, always has, except when the float failed. I think I am the only one that has ever messed with this one. But, then again, I've worked with carburetors off and on for 40+ years. If I were to ever change (which I won't), I would adapt a 390 CFM 4160 Holley (List No. 8007, I believe) to the stock manifold. They offer more flexibility, and reasonably priced parts availability than any other mainstream carb. that I know of. Every system (idle, accelerator pump, main, power, secondary, etc.) can be custom tuned for your application. Linkage would also be easy to adapt using mostly stock components, IMO. Biggest problems would probably be mounting and adjusting the stock MB vacuum governor and making an adapter plate. Hmm, wonder if I should do this as an experiment. Carb. is only about $300-350.

I've thought of this one as well, suspect fuel mpg would be icky with the size of the primarys. Who knows though. For the money and effort one could stick 2bbl TBI off a 2.8L GM v6 and it'd probly run alright on the stock maps. And they are quite tune-able these days.

mbbuff · #19 07-24-2009, 11:23 PM

Are those GM TBI's all electronic, or are they mechnical? If electronic, I wonder what kind of adaptation problems, especially wiring to the control unit, would be encountered? Could they easily be re-mapped, if need be? What kind of fuel pump and pressure do they use? Wonder what kind of parts availability they have? I agree though that a good FI unit would definitely be the way to go, if possible.

Years ago I used the 390 CFM Holley on a 250 C.I. Chevy (Nova) six, with a Muncie close ratio 4speed. Granted, the M110 engine is quite a bit smaller, but in the Chevy (as I recall) I got around 24 mpg on the highway....way better than the stock 2 bbl.
I have an old Holley sitting around. I think I'll pull it out and check it out to see how hard this might be. (I do love to tinker.) The good thing about the Holley is the vacuum secondaries. When set correctly they "size" the carb. to engine demand, so you're not likely to ever be over-carbureted, as you would with mechanically controlled secondaries. As far as the Rochester Quadrajet goes, I wouldn't consider it solely because of parts (tuning) availability. You'd have to hunt the junkyards, and know the exact models that had the parts you'd need. IMO, they were pretty good carbs. though, after about 1968.

wolf_walker · #20 07-25-2009, 12:11 AM

Summit or Jeg's should have, or used to, most of what you'd need to tune the q-jet. There are actually a few good books on it around even. It's not as easy as the Holley, for sure.

The GM TBI is electronic, but pretty basic. Electric fuel pump with relativly low pressure, not a lot of wiring really. It's a pretty common swap on a lot of older cars. Other than it's probly run ok out of the box so to speak, MegaSquirt would likely be as cheap. Learning curve on the tuning there though.

mbbuff · #21 07-25-2009, 01:58 PM

Thanks, Wolf, for the info.

wolf_walker · #22 07-25-2009, 05:17 PM

I'd love to hear some more info on actual alternate carb usage. There are bits and pieces out there, but somehow darn little in the way of hard fact or informed opinions with real life use.

mbbuff · #23 07-25-2009, 11:06 PM

Well, I pulled out my old Holley 4bbl. to do some comparisons with the Solex 4A1 on my M110.921 engine. Here are my observations and feasability assessment of installing the Holley in lieu of the Solex.

1. Air cleaner neck size is slightly (1/8 in.) bigger on the Solex. There probably wouldn't be a problem using the stock air cleaner, unless the choke housing of the Holley hits part of the air cleaner.
2. The overall height of the Holley is about 1/2 in. taller than the Solex, most of that being the choke housing. The distance from the carb. base to the air cleaner mount flange is about 3/16 in. higher on the Solex. There would probably be NO problems, based on these dimensions, with adapting the stock air cleaner, at this point.
3. The Holley is about 1 1/4 in. wider from the throttle linkage across to the outside of the choke housing. This would perhaps require a slight repositioning of the power steering pump and maybe the ignition coil, which should not be a problem. Adapting most of the stock throttle and transmission throttle pressure linkage should also not be a problem.
4. Primary and secondary throttle bore sizes (not venturi) are as follows:
Holley: 1 9/16 in. and 1 9/16 in.
Solex: 1 1/4 in. and 2 1/8 in.
This would require a "smaller to larger" type adapter due to the larger secondaries on the Solex.
5. The Solex is about 1/2 in. longer due to the long fuel inlet snout. Fuel inlet for the Holley is on the front outside and would not be a problem....just a slight re-route.
6. The mount bolt spacing is slightly different but would be relatively easy to modify with a custom adapter plate between the manifold and the carb. I have one that's about 3/4 in. thick, and could be easily modified to work. Because the adapter thickness would cause a net increase in height of about 9/16 in. at the air cleaner mount flange, there may now be a hood clearance problem. I did not check hood clearance, but think it would probably be OK.
7. Probably the biggest problem may be the manifold. I didn't remove the carb. but I did look at the Shop Manual and it appears to be a cross H, or two level manifold that feeds half of the cylinders from one side of the carburetor, and the other cylinders from the other side of the carb. If this is the case the adapter has to be partitioned like the manifold for it to work properly.
8. Finally, another potential problem. The M110 engine is 167.6 cu. in., and has a rev. limit around 6000 RPM. The proper carb. size, based on 80% volumetric efficiency, would be one that flowed about 233 cubic feet per minute (cfm) of air. The smallest carb. Holley makes is the 390 cfm, Model 4160. Over carbureting could cause poor throttle response, flat spots, stumbling, etc. because the engine may not be capable of pulling enough air through the carb. to make the main and power systems work properly. Of course this is based on all 4 barrels of the carb. working at the same time, so the only way to be sure is try it. It may work OK on the primaries. Holley also makes a 450 cfm Quadrajet replacement (Model 4360), which may be easier to adapt, but not have tuning parts as readily available as the 4160.

Overall, I think it could be done without a huge amount of work, or breaking the bank, but there would be some problems to work through to get it right. Access to a machine shop would make it a lot easier, as the adapter plate would be the hardest thing to make. I think it could be done for about $500 or a little less. Anyone want to try it?

wolf_walker · #24 07-26-2009, 10:03 PM

Still makes me wonder why they felt the need to put that 4A1 on there, which has GOT to be a 600cfm carb, at least. I guess the tiny primarys were supposed to help make up for the marginal intake vacuum at idle and low speeds. I wonder if that Holley can meter correctly at idle? It's bad enough they put a vacuum pump on the carb'd M110's. Wouldn't be an issue with EFI.
Or Mech FI even. For the money, I say TBI.