Weber 38 conversion

[bill65]

I'm working on an 84 Sunrader 22r with 110000 miles. It has some carburetor problems, I'm considering a Weber 38 conversion thinking this might perform better at higher altitudes. I travel mostly in the inter-mountain west where the roads have long steep grades. Any experiences or opinions concerning this idea or rebuilding the stock carburetor would be greatly appreciated.

thank you

[zero]

I can't comment on the Weber 38 on a Toyota. I had two British sports cars that were converted to 38 mm "progressive" Webers. Note that these cars had pretty awful carburetion to start with (twin SUs on each). With the expensive Weber kits they performed better at higher RPMs, worse at lower RPMs, started a little better in cold weather and got worse gas mileage in any driving. When I installed the kit on my 1972 MGB - it came with many jets and instructions on picking the right ones was by "trial and error." Considering the Toyota has a pretty well designed central and single carb OEM, with a real choke, accelerator pump, primary-secondary system, etc. I'd want to fix it if it had problems other then choosing any generic aftermarket carb. I say "generic" because it's rare that an aftermarket carb is custom designed for one specific engine.

Like I said though, I've know nothing of a Weber 38 on a Toyota. Any carb run at high altitudes needs different jetting then one run at lower - regardless of who made it.

With my two British cars - I did not buy the Weber kits myself. In fact one came with the new Weber 38 mm kit still in the box. I installed it, didn't like it and went back to original carburetion. I put it on Ebay and it sold for over $300 so I was pleased. If you want an all-around driver I think 38 mm is too big for a Toyota 2.2 or 2.4. The Weber 32/36 kit with progressive secondary opening makes more sense to me. A big carb performs well at high RPM but at lower RPMs, due to its large bore - has velocity problems through the air-hole. When you have velocity problems you get a venturi not working as well as it should. Since carbs rely 100% on the venturi principal and fuel atomization, having the air-hole to match your engine size is important.

The OEM Aisan carb is very well designed. In fact it's light-years ahead of what Ford or GM used on many small US built engines. It is a two-bore carburetor with a primary and a secondary - so it acts like a one-barrel carb when that's all that needed. When more power is called for and the RPMs are ready to accept it - it becomes twice the size with the second bore opening. That type of setup gives good gas mileage potential and power potential. The Aisan has a vacuum controlled secondary - or at least my 2.2 Toyota engine does. That means the second barrel of the carb only opens upon demand by vacuum control. Aftermarket Webers come with synchronous or progressive opening. Synchronous is probably the worst thing to have on an all-around driver and underpowered Toyota RV. Both barrels work together and open and close at the same time. No "primary and secondary." The other Weber option is the progressive opening setup. No vacuum control - just mechanical (I think). Once the first barrel is opened beyond a certain point - the second one opens regardless if the engine can use it or not.

If you ever messed with "muscle" cars - the "double-pumper" Holley 4-barrels worked that way. Stomp the pedal to the floor and all barrels open whether needed or not. I say "needed" because even when you put the pedal to the floor, having all barrels wide open is wasteful unless you've got the RPMs and velocity to match. Holley also made carbs with vacuum controlled secondaries similar to how the Aisan OEM carb works on the Toyota.

[zero]

Any experiences or opinions concerning this idea or rebuilding the stock carburetor would be greatly appreciated.

thank you

Due to the age of these Toyotas - many new old-stock parts are being sold off as "obsolete" stock. Carb kits that normally sold for $40-$50 are now selling for $10-$18. If you intend to fix the carb you've got it would behoove you to buy a kit. At Rock Auto the Auto-Tune kit is $10, and the Airtex kit is available for $19 (normally $40).

http://www.rockauto.com/catalog/x,carcode,1277243,parttype,5964

[5Toyota]

I HAVE owned a number of toyotas the stock toyota carbs have been good if it is rebuildable should be ok check for throttle plate slop shaft wear . much better then nissian carbs. BUT AS I HAVE HAD two weBER carbs the weber 32 36 would be my choice electric choke very simple des.many jets available. I HAVE REBUILT THE OLDER 20 R CARBS

[Boots]

Hi

Just remember that the r22 campers have an altitude compensator that makes adjustments to the engine performance. It may be connected to the computer so, if you are planning on replacing the carbs, you might end up with a reduction in power.

Brian

[bill65]

Thanks to all of you for the replies, they are very helpful.