S5 T2 Weber blow through project
04-23-08, 01:35 PM
#27
I've got another idea I'd like to play with, Jeff, maybe I can come over again tomorrow and try it.
I've gotta finish up the engine bay and get the exhaust in there so you can come over whenever.
04-23-08, 08:31 PM
#28
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You read my mind. 
Looks like the studs on the manifold are offset slightly. It could still work if we slotted the holes on the turbo. Indeed, it seems to me like doing that and making an Aaron Cake style spacer would make everything fit really nicely with room for a heat shield or turbo blanket or something. I'll have to figure out which way could be done cheapest/easiest.
Looks like the studs on the manifold are offset slightly. It could still work if we slotted the holes on the turbo. Indeed, it seems to me like doing that and making an Aaron Cake style spacer would make everything fit really nicely with room for a heat shield or turbo blanket or something. I'll have to figure out which way could be done cheapest/easiest.
09-27-11, 07:49 PM
#30
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sorry guys i hope im not making an idiot of my self but i have a similar project and i have no clue on how to boost prep a weber, any help will greatly be appreciated i want to run maybe 10 psi
09-27-11, 09:17 PM
#31
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As long as you know how a carb works, it's really straightforward and mostly the same as a normal rebuild. From memory, some things to watch out for:
The thin paper float bowl cover gasket that comes with most rebuild kits isn't good enough. I ended up cutting my own, but I think there are places that stock neoprene bowl cover gaskets. You'll most likely have to cut your own carb hat gasket, though.
If you have the carb spacers with the o-rings, I don't know whether they'll withstand boost. I have mine hard-mounted and haven't had an issue with it.
If your carb has the brass floats, you need to get some solid ones from a later style Weber. Any place that stocks Weber parts should have them.
If you have a choke, you'll have to make a block-off plate for it.
I enlarged the fuel inlet into the carb slightly, though I don't know how much that actually helps.
It's a good idea to seal the threads of the main and booster venturi holder screws, as they can leak boost. Likewise, make sure any other threads that see positive pressure are either sealed or have an o-ring (aside from the idle mixture screws, obviously).
Also, don't forget to reference your float bowl to the carb hat pressure. Take your FPR reference from the carb hat as well.
Other than that, it's all jetting. Get the biggest needle valve you can; I believe 3.00 is the largest available. You'll need to go up on your main jets and down on your air correctors; 210 main 150 AC is a good starting point, but start with low boost and conservative timing and watch your wideband. You may need to play with emulsion tubes as well to get your mixture right at the transition.
The thin paper float bowl cover gasket that comes with most rebuild kits isn't good enough. I ended up cutting my own, but I think there are places that stock neoprene bowl cover gaskets. You'll most likely have to cut your own carb hat gasket, though.
If you have the carb spacers with the o-rings, I don't know whether they'll withstand boost. I have mine hard-mounted and haven't had an issue with it.
If your carb has the brass floats, you need to get some solid ones from a later style Weber. Any place that stocks Weber parts should have them.
If you have a choke, you'll have to make a block-off plate for it.
I enlarged the fuel inlet into the carb slightly, though I don't know how much that actually helps.
It's a good idea to seal the threads of the main and booster venturi holder screws, as they can leak boost. Likewise, make sure any other threads that see positive pressure are either sealed or have an o-ring (aside from the idle mixture screws, obviously).
Also, don't forget to reference your float bowl to the carb hat pressure. Take your FPR reference from the carb hat as well.
Other than that, it's all jetting. Get the biggest needle valve you can; I believe 3.00 is the largest available. You'll need to go up on your main jets and down on your air correctors; 210 main 150 AC is a good starting point, but start with low boost and conservative timing and watch your wideband. You may need to play with emulsion tubes as well to get your mixture right at the transition.
09-28-11, 12:14 AM
#33
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I ended up with F11 as the best compromise of the tubes I have, but my transition is still really rich at low load. I don't know why, but this carb has always liked unusually lean jetting on the idle circuit. I think I'm currently running 50F9 idle jets to give you an idea. On the other hand, I've got 70 AP jets and a blank bypass jet and it still seems to want more AP shot. I dunno. I've kind of lost interest in trying to figure it out since I'll be pulling this motor shortly and dropping in an REW block with EFI. The carb will probably end up in my REPU until I can afford another MegaSquirt, though, so maybe I'll get back into it then.
09-28-11, 12:45 AM
#35
Originally Posted by PercentSevenC
The carb will probably end up in my REPU until I can afford another MegaSquirt, though, so maybe I'll get back into it then.
This is an informative thread. I had forgotten about it. Now I have a pic to post in the red truck's Nikki blow through thread.
09-28-11, 12:58 AM
#36
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It is informative, and I'm glad I had the excuse to post those boost prepping notes before I completely forgot everything about the process (not that it's particularly difficult to figure out). Always feels a little weird reading your own posts after three and a half years, though.
09-28-11, 08:45 PM
#39
Junior Member
thanks for the help guys my jets arnt to far off from what your running except for my air correction and main jet im runing 175ac and 180main jet but firts thing after work tommorow ill go pick up new ones
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