[v869tr6]

My blowthru carb works great up to about 18 PSI but after that I think my single 0.150" needle and seats can't keep up. Don't want to send the money for dual needles and seat bowls since I plan to step up to EFI fairly soon. Would adding a 125HP shot of nitrous cause lots of trouble? I already have the nitrous kit. Anybody ever just plumb a fuel line into a carb bowl with a orifice and add fuel only under boost?

[Tom Vaught]

Several people have used just the fuel side of a NOS plate to get by the fuel issue on the single Needle and seat per bowl blow thru carbs.

Plates are cheap at swap meets.

Only issue with NOS fuel plates is making sure the fuel soleniod works

Tom Vaught

[taff2]

V869, I have seen a few setups with fuel lines plumbed through NOS fuel solenoids and restrictors into the float bowls. The solenoids were activated by an adjustable boost pressue switch(Hobbs).

[v869tr6]

Originally Posted by taff2

V869, I have seen a few setups with fuel lines plumbed through NOS fuel solenoids and restrictors into the float bowls. The solenoids were activated by an adjustable boost pressue switch(Hobbs).

Thanks Taff, thats one of the things I was thinking about doing. Do you know where in the bowl they added the line? AN -4 or a steel line?

[taff2]

V869, both setups used -4 braided line, both fed fuel into the bowl opposite to the normal feed inlet, but one fed the fuel into the bowl near the top, the other fed fuel in near the bottom-below the fuel level- I assume to prevent aeration or frothing. TomV would probably know which way is best.
If I remember right ,a .100" restriction was used.

[62fatcat]

i did thid at one time it helped, but it was a bandaid.
if it were me i would use the plate instead, you have a lot more to tune with.
with the bowl injection you run the rick of overflowing the bowls, and that could get ugly real fast.
you may also try to rase your base fuel pressure this can make it richer with the same jet or try small vent tube extensions(about 2-3"long), they will allow you to run smaller jets, therefore decreasing the fuel suply demands.
good luck with your combo,

brad spidel

[Tom Vaught]

Originally Posted by 62fatcat

i did thid at one time it helped, but it was a bandaid.

If it were me i would use the plate instead, you have a lot more to tune with.
With the bowl injection you run the rick of overflowing the bowls, and that could get ugly real fast. Brad Spidel

That is why I recommended the plate also Brad. Too easy to overflow the bowls and have a backfire/ fire with the bowl deal.

He may already be using the vent tubes, I am not sure on that deal. If not presently using them, they will definitely move more fuel through the same jetting.

Tom Vaught

[v869tr6]

What I think is happening to my car is the bowls are getting emptied out at the end of the 1/4 when the boost gets turned up. I have 2950 lbs. going 150 mph with no trouble but turning up the boost to go faster is when the pistons melted. My carb has 0.150" needles.
My a/f is in the 11's and when I spray water/meth it go's into the 10's on a/f, but I don't know what the a/f is down track because I don't want to be looking around.
Timing is at 19 degrees total.

[62fatcat]

you need to be able to log the a/f with the rpm to know for sure.
some guys video the guages as they go down the track.
i learned this from "chicken hawk"

[BruceWilkie]

Has anyone considered adding an extra pair of fuel bowls? (or just one)

Seems you could close off the open sides of a pair of bowls(and floats) with a plate(or just bolt a pair together) and simply plumb each one to the existing bowls with a line to the bottom for fuel and a line at the top for venting. It would be important to mount them at same level as the existing bowls. That would give you 4 needles pretty easy. This gives extra capacity as well. It may look different but should work ok. It also offers the opportunity to add more vent tubes under the bonnet. Sure less expensive than converting to EFI or custom dual needle bowls. Certainly more trustworthy IMO than fuel solenoids.

I would try using long studs with nuts vs bowl screws. Adjust bowl levels at the sight plugs closest to the carb.

IMO draw thru systems or EFI seem far less difficult to dial in. I'm not a big fan of blow-thru. A draw-thru carb setup functions pretty much like a regular carb. Gives great atomization and fuel distribution and can still be intercooled(if properly designed) too. The turbo compressor needs to be properly sealed is the biggest requirement there. Multi-port EFI is great but still costly.

[wrench]

Here is a link to something a Friend of mine came up with. He runs a Local shop and specializes in boost. He is a very smart person.


http://www.sd-concepts.com/documents/Fuel%20Tool.pdf

[turbo69bird]

What are you jetted at?
I am sure you thought of this but you may have maxed out your metering blocks and are now using the blocks as the jets?

a standard metering block is usually all done at a 98 Jet size with out openening it up or switching to a alky metering block.

I ran 1.20 needle and seats in my car up to 145 MPH I was running 98 jets squared.

Thats when I stepped up to the fuel inejction

[BruceWilkie]

Originally Posted by turbo69bird

What are you jetted at?
I am sure you thought of this but you may have maxed out your metering blocks and are now using the blocks as the jets?

a standard metering block is usually all done at a 98 Jet size with out openening it up or switching to a alky metering block.

I ran 1.20 needle and seats in my car up to 145 MPH I was running 98 jets squared.

Thats when I stepped up to the fuel inejction

Excellent point on the metering blocks. I suppose the fuel passage in the boosters could eventually become a restriction at some point as well. He could also opt for dual quads.

[taff2]

Bruce I made up a set of bowls exactly as you've described a while back and posted pics on the turboforums, this is when the fuel solenoid deal was described to me. I never gave it much thought about the possibility of the solenoids sticking and flooding the bowls,as I didn't intend using the idea.
One reason I've gone for dual carbs is because I will have 4 float bowls for fuel supply.