Technical holley 600 vac. secondary issue.

If you cant find a double pumper 600 locally I have one that is near new, but I dont know how feasible it is to ship it from Tennessee.

 

Thanks but i have carb guy thats getting one for $825, the rest are $1250ish or more. JW

 

Found the instructions for my quick change spring kit, this might help, note: the spring opening rates are for a 350 c.i.
with a 750 vacuum secondary.
Might be worth trying the short yellow (lightest) spring on your 301 c.i.

 

Thanks for that and i will have a good read soon. As for the lightest spring, that is what i put in awhile back and it had no affect. Got the air cleaner to try next for restrictions. This carb will most likely end up on the Jeep motor in my Belly Tank as a 300 cfm 2 bbl. JW

 

Interesting they state : all tests done with air cleaner removed , using an air cleaner would cause EARLIER opening in all Case's ! So , air cleaner restriction raises venturi velocity ...makes sense !

 

I will still try what i was going to do with the air cleaner and report the findings in few days AND read all that info that Tickety Boo posted. JW

 

Ok..
Reading thru all the replys....

Where the vac cannister bolts to the main body..
( where the cork gasket is )

There is a small brass restrictor pressed into the main body..

Way back when , we would drill the restrictor out a little bit at a time and test drive..
In the end it almost always ended up just removing the entire restrictor..
This was before the quick change kits came out.. we would cut 1 coil off the spring and stretch it out just a bit..
Just enough to hold the diaphragm closed..

It would RIP the secondaries open when you mashed the pedal !

Give it a try.

Dave

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I may try that if all else fails just for shits n giggles, thanks. JW

 

I got to test the car again today with air cleaner on and off with not a lot of difference between the two. I was only able to get up to 90 mph due to gusty cross winds. The paper clip on the rod again only moved about a 1/4'' and a bit less with the air filter open. I measured the opening of the air cleaner and its 6300 sq mm or say 4''x 2 3/8'' for example.
My test road just out back behind my home. JW

 

Air cleaner restriction would cause a drop in pressure (vacuum) and since the diaphragm outer side has atmospheric pressure "pushing" on it, would open more. Venturi velocity would be less with air cleaner restriction. This is why carbs have a balance tube for the bowl. It references bowl pressure to air pressure inside the air cleaner. If referenced to atmosphere, gas would be sucked out of the bowl rather than venturi pressure drop. Science class dismissed.

 

I really like the traditional look of that air cleaner, what is it off of ?
When you tried the lightest (yellow short spring) a while back was the old hard diaphragm still in yet ?
The spring chart opening rates for the 350 c.i. shows fully opens at 5680 r.p.m.
My best S.W.A.G. is the light yellow short spring with 301 c.i. would first fully open around 5900 - 6000 r.p.m. when every thing is working correctly.
A mechanical secondary carburetor might be the best way to get your Butt Dynamometer working correctly
The Vacuum secondary is opening only as much as the engine requires and may be smoother and faster

 

The old diaphragm was still in when i changed the spring. I don,t really have a big desire to be pulling those sort of revs. With the long radius rods in the back there is very little wheel spin, it just goes. Our top speed on roads over here is 60 mph and i am looking for more in the 1/8 mile sprints where it gets to around 80 mph BUT only gains another 10 to full 1/4. Will see what the mechanical secondary does when it gets here. As for the air filter housing, when i got it i was told it was off a Ford flathead 6, is it? as i haven't seen another the same JW

 

Take the spring out and test it,usually to much back pressure keeps the secondaries from opening.

 

May try that soon, before i replace it.
I really get the feeling that there is not a good sized Vac Sec 4 bbl for the smaller cube motors and to flow enough through the primaries to get the secondaries to start to open. JW

 

My 283 in my 67 el caminos has had a 4360 and a 3310 with no problem, how big is you exhaust

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Two inch. My manifolds were two inch so i continued that out the rear. JW

 

In an 1850, if the carb is working good, you never know when the secondary's open. If you can feel it then something is wrong. Feeling them open may actually be recovering from a bog because the secondarys opened too soon. The paper clip thing is good but you really have to load [beat on] the engine; as in race track, wot even if its just an 1/8 with time/mph slips or a data logger.

 

What are the mufflers?

 

How does it run with that air cleaner removed? You may not be getting enough air. I may be looking the wrong way but I helped two customers who converted old oil bath air cleaners and they weren't getting enough air for a 350. just a thought.

 

Mufflers are straight though. It ran the same with the air cleaner off and as for the opening i discussed that in post#69. JW

 

Years ago I had a '62 hipo Vette 327 320bhp with a 4150 carb and after reading an article in the tech section of HRM I did a mod on my Holley vac secondary carb. I removed the spring and also removed the check ball in the bottom of the dia. housing. Worked real well.

 

I may just try that, Dave. JW

 

Remind me not to let you surface my carbs then, I've done it many times with great results..
If you know what you're doing with a flat glass and a sheet of fine wet and dry, you should not have a problem..
I agree, grinders should only be used to make a crap weld job look good, and not used on carburetors..

 

I have a friend whom I regard as good on Holleys who I have seen take the center casting and check it for flatness as it comes as cast and sometimes they aren't flat. Those that need it get mounted on his vertical mill and the surfaces where bowls mount are skim cut to flatness.

 

^^^^^ neither of you are novices ( I hope ) their are more novices than experienced mechanics looking for advice & its impossible to sort who knows what ! I wouldn't knowingly tell someone to do something that could cause irreparable damage to their part .
The " blue" holley non stick gaskets are , at least, .030" thick , if the surface is off so far that they don't seal with new gaskets , I'd get some different ones .. The cost of hiring someone to machine them is not a cost effective operation , unless the part is very rare / irreplaceable.
When you abrade , machine , sand a carburetor surface , you remove the protective zinc-chromate finish also , which leads to early corrosion

 

I have also used the glass and wet n dry method on my Willys carbs in the 70's, 80's and on there Stromberg upgrades. JW

 

.
My new 600 mech. secondary arrives tomorrow so will have a report in a couple days......... if no report back at all it may have gone too well..
One thing i forgot to mention at the start was atmospheric pressure, i live in an area that is only 250 ft above sea level. JW

 

You need to change your sea level. That's the problem. Secondaries like 1-2 00 feet above sea level. If your under sea level, You need an edelbrock carb.

 

^^^^^^^^^^^SAY WHAAAAT??????????