Jas,s 1200s

[jas1200]

The carb greendog was selling had a blowoff valve at the back of the hat too.......How did you get started with yours, did you get everthing in and going right from day one or did you have to fix problems as you went. I,d be happy if I could drive it at low reves and just have a bit of power on wednesday. I am going to have take it all off end of the week so I can get a wof, once I get a new wof i,ll be into it.
How did you get on with the gearboxes, get them going ok? got your 1200 going again, shame it was off the road when I was in chch.......
My cars blowing blue now, think the scores we sore in #1 bore are letting oil past......

[Bartman]

I slapped my drawthrough set up together. It ran, but not too well. A huge backfire blew a giant hole in the hoses I used to join the blower manifold to the intake runners. I replaced them with silicon hoses, and rebuilt the carb, Then it went pretty hard.
My gearbox is still in bits. I got the 4speed for my sunny back together and in.

your 60 series 5 speed should be plenty strong enough to begin with. I gave my old 60 absolute death, and it took it like a trooper.

The carb greendog has was probably used in a turbo set up. If you close the throttle on a turbo set up, and blow off the body of pressure, the turbo stops pumping. BUt as a blower is belt driven, it'll keep on forcing the air in. I think you'd need to run the blower off a throttle switch to make a carb blowthrough work.
Since you're plaanning to go EFI later, it might be easier to start with drawtrhough, and build the efi later. Unless the pump you're running now can supply 9psi fuel pressure, it'l be no good for carb blowtrhough. I think a Low pressure rising rate fuel pressure reg is $125. But that will be no good for an EFI set up. It just seems to me like you're trying to do it the hard way twice. If carb is only temporary, it seems foolish to go to such lengths when it's not a perminant thing.
You could find a 2bl holley and modify it yourself. And a boost hat for a holley isn't too hard to make.

[jas1200]

The reason I decided to go this way was because of a thred I read on 1200.com (think you might have read it also), there are a couple of guys getting 170 hp atw from standard a12s, both were intercoled and injected. It seamed the logical thing if I was going to continue to delevop it was to blow through something........I was going to start looking for and fitting an intercoler next but a mate of mine said "lets run a pipe from here to here and see what happens".
Yep see how a blower will keep blowing after you take your foot off, do you know of any blow through supercharged setups?
Whats a throttle switch?
You might be wright about the draw through, Yep was hoping my 5 speed would do the job.

[Bartman]

You'll have to set up a switch which is triggered once you hit wide open throttle, or perhaps go over 3/4 throttle. Use this to trigger the relay which controls the clutch on your supercharger. That way you're only going to make boost when you've got your foot up it.
TBH, I wouldn't bother trying to blowthrough the standard carb. I really dont think it's suitable.
When you go to efi later, you'll need to either fit the throttle body to the intake of the supercharger, or once again use the throttle switch to disengage the blower when you dont have your boot up it.

[jas1200]

This is a lot of help, thanks. I,m starting to get a better picture of how it all works and practical ways of fixing potenial problems.
I,m going to formulate a new plan soon and hopefully it solves all the probs we have talked about.
One last question.......you said I could buy a two barrel carb and mod it to suit. Did you mean buy a 350 holloy and why are they better for blow through? .....thanks in advance.....jas

[Bartman]

Yeah I was. I think the main attraction for them is you can remove the bowl quite easily to change jets etc. They can be a bit prone to leaking though. (Well mine is lol)

[jas1200]

Sweet, I,ll get back to uou with my new plan in the next couple of days. In the mean time im still going to fit my mod carb piece tomorrow and see what happens ......

[Bartman]

PM me your address if you'd like to borrow a book or two on the subject. I have some on old school performance. Might help you get a more complete understanding of the principles involved?

[jas1200]

PM sent.......

[jas1200]

Surprice surprice, manage to get it to run today and drove it......it ran really bad, felt like it needed more fuel but I think it was a positive day........