Hey im doing a blow through setup on an a12 and read on a site that "The trick is to pressurize the fuel bowl by connecting the vent port to boost"

This was done on a Weber 32 DFTA but i was woundering if it could be done on a stocky a12 carby and where is the vent port on the stocky. also what does it mean by "vent port to boost" does it mean to hook it up to the boost inlet so boost is running into the vent port.

Cheers

It can all be found with the search button. I think I am the only one to have explained how to run real boost through the stock hitachi ( un boxed )
I dont wish to explain it again.
All threads like this just bring out Internet Mechanics who know better but never actually tried.

Yeh i no iv been serching for about 3 months now and and cant find much on runing boost through a stock hitachi. phunk could you please give me some key words to help me find adiquite forums about doing so.

Thanks.

i am an internet mechanic in this case (nice term by the way) but there are a couple of tubes that stick out into the oncoming air stream in the stock carb, these are cut off level with the inlet to the carb and provide a pressure reference to the float bowl.

these are therefore the tubes that need to see the boost pressure and by blowing air into the top of the carb with a seal where the factory air filter would seal you are effectively setting it up correctly.

i would think your problems are

1) sealing off the throttle shafts
2) float collapse
3) Upping fuel pressure under boost and
4) setting up jetting to provide the extra fuel

i guess the best person to speak to is someone who has done it before (ie search THESE forums for keywords) and get more info off the fella below

does the secondary throttle get blown open instantly? and is this a problem??

these are thoughts i had but not stuff i have done before (would rather see efi on it)


ben

Ben I think its good to be an Internet Mechanic aslong as you think about what advice you are giving and make a point of showing that its just thoughts, not making it sound like tried and tested, like most do.

Throttle shafts never gave any problems, But I would never put a carbie together without having good bushes regardless of boost or not.

As for secondaries ( for boost they must be mechanically activated )
As to the secondaries blowing open. - Ben think about how the carbie works. Boost is pressure not moving force. The carbie still works the same except filled with pressure.

Chris I dont know where the info is, maybe just try heaps of different key words. Blowthrough, blow through, blow-through, blow-thru etc etc.
Your first questions lead me to believe that you have very little understanding of how a carbie works - if you dont know where the vents are for the bowl. Maybe pull one apart and research how it all works. No way you can make it work with boost - if you cant already make it work without boost.
I am happy to answer PMs if you seem like you have an understanding, but I have no wish to put everyone through a boring topic again especially when some will jump up and say "Yeah i did this" " you cant do that" Why do that" etc etc and believe me they will.

One thing you need to make a hitachi handle real boost it Threebond 1211.

"Ben think about how the carbie works. Boost is pressure not moving force."

i thought that the secondary had a weight that counterbalanced it may damage the interlock between the primary or fully open before the primary was open all the way? the swap to mechanical would fix that obviously

i may be thinking of a different carb, i swapped mine for twin SUs soon after purchasing the car

sorry for not "thinking" and offending u :)

i was only trying to help cos he seemed really lost

ben

Quote:
No need to be sorry Ben. I was under the impression from your post, that you were actually thinking about what would happen.

The hitachi does have a weighted secondaries. It still works like normal and will open under load just like in naturally aspirated form. Boost isnt a flowing force, Its a surrounding pressure.