Hello, can any 1 please tell me what mods i would have to do to my 350 Holley to make it handel Boost running through it? I have been told I will need a plastic float and fuel pressure higher then the boost ill be running, is there anything else i will need to do, any help will be great, Thank-You.

Im sure some 1 out there has put boost through a carby b4, please, i need help fast,

If you do a search over there <------ you will find some good info. Not much on a holley but it is all pretty much the same. there is a certain boost pressure you can get to without having to have it enclosed.

u dont necessarily need different floats, u just need to supply the bowls with the same boost as your putting down the throats, for example on my twin sidedraught turbo setup, theres a breather on the bowls where the throats are , on the airbox ive made i just put a hole in it so the same boost is going in the breather. im not entirely sure but other than that u just have to do the obvious and just seal everything properly.

Holley's come with hollow copper floats, hollow plastic floats and plastic floats which are filled with honey comb plastic foam similar to the datsun hitachi carbs. Your need the filled plastic float so it cannot crush under boost.
You need mechanical secondaries
You need to make sure your throttle shaft bushes are good.
There is a company ( forget who) that sells rubber gaskets for Holley's, but with the way the holleys bolt together, they arent required unless really high pressures are used. All the mating surfaces of these carbies are thick enough to prevent bending and releasing pressure under boost.

EDIT: Stress the solid float is a major requirement. I have seen what was left of a hitachi copper float after it was squashed and popped from boost.

Thanx heaps, there is just 1 more question, with the little breather coming out of the fuel bowel do i need to have that coming out of the boxed (boosted area) or do i just need to get the fuel pressure up higher then the boost im running? thank you

breather needs to go to boosted area

all said and done mine leaks fuel under boost still, im choosing to ignore that at this stage though

Yeah Dato1000 just like 1200rallycar said, the fuel bowl breathers need a boost reference. Basically for a holley 350 you just need to make a hat to cover everything that was originally inside the aircleaner.

1200rallycar its not a good idea to overlook the fuel that is leaking from your carbie.
One important thing to remember is, the fuel isnt leaking because of fuel pressure, it is leaking because boost is leaking and this is causing a vacuum effect and sucking the fuel out.
In other words your engine is working normally trying to draw in fuel but the fuel is being sucked out by the leaking boost. This is making the Air/Fuel ratio leaner. The engine might be going hard because the combustion event is the hottest it can get. But white hot is too hot.

Hey i was woundering with a Hitachi if you had to drill a hole in the fuel bowl and hook it up to boost to equilize the pressure, or is there a hole in the carby to start with to hook the line up to.

i put 6 psi through my standerd 1000 carby and it worked fine. i had a couple of issues where it lean out put that could be fixed wit a bigger fuel pump.