HS4 Question

Hey Folks,

I have been overcoming what I believe is running out of gas in the float bowls (or lean because low fuel level) by running two large inline pumps turned down to 2lbs at the carbs to "refill them fast". I hear there are .125 needle and seats out there, is this the fix/insurance. If I use these on the street will it cause any other ill effects? Yes I drive it pretty hard too.

Am I on the right track here?, I know Prather runs 1.5 inch on his MGA so he must have overcome this or know what the driver of the problem really is....

Many thanks,
Brandon

There are .090" jets, .100" jets and .125" jets. You'll never use .125" jets in an HS4. You should probably be running .090" jets. In an MGA, OA7 to OA8 needles were my racing standard with .090" needles. In a Spridget, Joe Huffaker runs KA needles [check your needle chart to see if that fits a .090" jet or a .100" jet.] It's doubtful that either the jet or the needle is your problem if you're running out of gas. First, check your fuel pressure - 2 pounds may be a bit low - 2.5-3 pounds might be better. Then check your floats and needle/seats in the float bowls. Sometimes they hang up. If you're using the Grose Jet type of needle and seat, replace them with another type - few racers have any luck with them. Best of luck. Basil

Hi Basil, thanks for your response, probably wasn't very clear was addressing the size of the needle and seat not the jet size, hearing rumors that guys are putting larger needle and seat (.125) in the HS4's to correct this problem

also.... have some feedback that you can drill inside the floatbowl so the gas comes in higher up in the bowl that can also help with this issue a bit....

I know what you mean.... the float bowl needle valve.

Yes... go up to viton tipped .125 kits, I think STD is .080 or .090, they are direct replacement.

What I did was grind out the bottom of the bowl to allow the fuel to pick up lower... You will see what I mean if you look, there is a portion of the bowl to collect crap... shouldn't be a issue on a race car.

This is not known to be a problem as HS8's(2") uses the same fuel bowl.

Increase fuel pressure to 3psi...

Well you are at it, i think you can get new floats that allow you to adjust the level of fuel in the bowl.... worth fitting, as there is massive variation.

bullobb Wrote:

Thanks James, will put in an order...

you do not need to have the trick of the week when using those carburetors. Make sure you have the lids oriented properly and the float level set correctly as well as the float drop.

A 5/16" fuel hardline form the cell and one fuel pump will be way more than adaquate and use a good regulator and 2.5 psi at the carburetors.

You might inspect your fuel filter for debris. disconnect the line at the carbs and run the pumps and do a volume test. Convert the numbers into horsepower.

I with Jerry on this one, I had in my hands some of the trickest race carbs form literally most US go fast builder, whether it be Huffaker, Tabor etc. , the float bowls were basicly un-modified usinf the same flaot bowl from the smallish HS2 right up to the HS8s. Jerry talks about flaot lid orientation, that is a good topic, orientate you lids so they don't hinge form sidew to side this could cause problem in high G corners. I was albe to do this on Fred's HS6s palying around with alot of dfferent flaot lids until I got the ones I wanted, but you can orientate what you have many times, byt just turning them and using washers on the top, rather the the bolt eyelets. Hope this helps.

Also On the HS4s on the 1275 engine we used to use .100 jet, and #7 needles to get the fuel we needed for this application, WE used the same set up on Fred's first engien I built him, with HS4, it was little over 11.0 to one, so that might work for you as well, his EGT were right where we wanted them at WOT ( about 12.5-13.0). With the new and improved engine we went for the HS6s, now the learning curve starts over again :)