bmcnitt

I have a holley 4175 spreadbore carb. The fill tube has a hose w/ a pcv valve that goes into the front of the carb. This arrangement is not working out for me for about 3 reasons. I noticed in pics that a lot of you have that hose running around to the side of the carb. Can you tell me which if any of the nozzels I have highlighted would be a place to run the PVC line. I don't know enough about carbs to know the significance of these locations.

al89

hook to the bottom fitting ,it needs constant manifold vacum

66since71

I'd say none of the ones you circled. The correct fitting should be on the throttle plate (like the bottom one you circled) but it should also be for a 3/8 hose. It looks to me like you've routed it correctly. Can you tell us what the three problems are?

Harry

midyearvette

i can't tell from the pic if the one circled under the choke is 3/8" or not. if it is then you could use it. by chance is there a fitting at the rear with a plug over it??....you need direct manifold vacuum for the pcv and they are usually 3/8" fittings...good luck

66since71

Pulled up the 4175 on Summit's site:

http://store.summitracing.com/largei...-0-80555cp.jpg

The PCV tube from the carb faces forward. and it looks from your picture like you've made the connection there.

I don't see a PCV valve at the oil filler in your pic, so I assume the brass hex fitting at the other end of the hose is the valve. I'd be sure its installed in the right direction, and probably route the hose to give it all a little more room to fit. You can get the breather from a 66/67 350 hp car, that accepts a screw on PCV valve. That would make some more room. What are the problems you're having?

Harry

bmcnitt

Thanks everyone. The problem I have is a series of one problem leading to another, to another, etc,..... I want to use my braided radiator to thermostat housing hose. That hose touches my alternator bracket. I want to leave my alternator on the drivers side but move it lower so it is away from the hose. I dont have bolt holes in my heads so I was trying to find brackets that would mount to my water pump and let me get lower (on driver side). No luck w the type I have in mind. Took my grinder and manipulated some pep boys brackets but still didn't get very low. Now I was thinking if I got one of those tall water necks that come out at 45 deg and swivel I could route that radiator hose well above the alternator bracket but my fill tube pcv line would be in the way. Everyone thouroghly confused yet. Sorry, like George Carlin used to say these are the things that keep me from getting ahead in life. Also the braided tube fill line makes to sharp of a turn for braided and is a little unnatural. If I could bring it to one of the other ports on the carb it might solve a couple of problems. There is a port on the back of the carb base but w my new edelbrock intake it is pretty well blocked by my intake vac to booster fitting.

midyearvette

can you tee off of the back fitting for the brake booster at the carb??

bmcnitt

Well thats interesting, you mean I would have a tee threaded into the intake, one side going to the booster and the other to the fill tube pcv valve line? I would have to take the carb off to do it cause the carb is so close to that fitting that it can't be turned. With my GM intake that fitting was several inches from the carb. That could be a real good idea if thats a kosher installation.

jdk971

the lowest or bottom circled is where i would of put the vacuum line from the distributor. jim

midyearvette

yes you can tee off the line there, if you have room for everything to fit. that is direct manifold vacuum, and if you have to remove the carb for a custom installation go for it......it would look nice......

al89

if you tee it there you will loose some vac for the booster if you have a bit of cam in your mtr and your brakes are border line your brakes wont be as good

midyearvette

that thought crossed my mind also but i think the draw from the pcv will have a minimal affect if any on the vacuum signal for the booster, but it could be a consideration. he will know when he drives the car. he can always change it back...it's called "hot roddin"!

JohnZ

Nope. Makes no difference - vacuum is vacuum; doesn't matter what full manifold vacuum source it's connected to - all draw from the same plenum.

JohnZ

I wouldn't do that. A) The port is too small - PCV requires a 3/8" port so it doesn't get plugged up, and B) That baseplate port is probably "ported" vacuum - the 4175's were Q-Jet replacements, and all of those small ports on a Q-Jet are ported sources. You can't just pick one without verifying with a vacuum gauge at idle whether or not they're a ported source.

al89

well i guess we agree to dissagree yes its the same plenum but hook 2 water hoses up to the same tap see what happens, also the diaphram in the booster does not like oil fumes , even with the engine off they migrate up and will destroy it

midyearvette

your water tap analogy is a poor comparison.....youre confusing vacuum with pressure, a tap in the manifold has the same effect no matter the location...... as far a the booster goes, it would have the same port location even without the tee......

al89

the pcv hookup is a leak to an otherwise closed vac pull of the booster . if your booster has a leak it will not perform as well so when you hook up pcv thats pulling vacum out of crankcase in a loop its a leak

midyearvette

please....let's not confuse the issue......a leaky booster is entirely a separate problem. a tapped vacuum port shared by the pcv and booster is ok because in the scheme of things, they share the same vacuum source any way from the intake manifold....

StingU2