My local speedshop did a great job putting a new set of annular booster venturies into my throttle body.

I just finished putting it all back together:



I'll post back later this week when I put it on and try it out/dial it in....


Here are some pics of the new venturies (top and bottom):

1




and a pic of the original venturi set on top of the new one for comparision






This should create a slight bit of restriction, and boost the signal and get a bit of better throttle response due to increased atomization out of the boosters.


formula I'm starting with is:

Holley 80457 600cfm Vac. Secondary 4160
Quick change Vac. Sec. spring kit, left the black spring in so I can tune the primary and idle better (that sucker is pretty stiff....)
Electric choke.
4150 secondary metering block
#35 non- tube type shooter, hollow screw
Pink #330 pump cam in the #2 position
Primary jets are #62's
Secondary jets are #64's
Requalified the carb settings (choke setting, pump arm tolerance, etc..)


Originally this carb was:
primary jets #62
Secondary metering plate #39 (29 idle circuit and #73 jet equiv.)
Black secondary spring
#31 shooter
and came equipped with a #466 orange pump cam

as the Hpak saga continues....

-D.Idiot

Hey D.I

those primary jets are gonna be alittle big to start with, i'd say a 55 would be a better starting point. i started with 65's and right now i'm at a 52, if i went to a 55 it'd be better, i hazzard to guess that you'll end up around the 57 -60ish mark for a good jet size (but you also have all the little gizmos (aka 02 sensor) to test mixtures with.

Justin

The orifice calc said the I should be looking around 61's to start, then find the happy medium there.... I'm up a couple of jet numbers on the little 390 from stock so I might be close in the 55-58 range.

I'll let you know how it goes.

-D.Idiot

I installed the carb, and primed the bowls, and it fired right up. I warmed it up, and set the low idle and mix.

Don't have to drill holes in the plates to keep this one running.

I drove it around with the secondaries locked out and I found I had a low rpm lean out at 1400-1800 rpm, the shooter needs to be increased in size, and it's mid-line rich at cruise. Throttle response is much better than the 390 was. Tomorrow I'll reset the secondary springs to 'brown' or 'plain' and rejet the primaries to 60 or 61.... I usually leave the line at 2K anyway at stop lights, so I usually mis any off-idle problems...


Oh yeah, and Lou if you're reading this, I did a 5K shift from 1 to 2....
5K in 1st @50 mph dumped to 3k in 2nd and quickly climbed up to 60 mph when the clutch disengaged....
need to get a more 'controlled' test track though...

-D.Idiot

see sometimes alil bigger carb is better for a lil engine glad to hear ya got it running and starting the "diagnosing". i think the pink cam is too small personally (the one in my engine is on the first setting and i have 28 shooters, it likes to rev no problem if in neutral, if in drive and i hammer on it from a start, it'll bog and just plain die i have some 35 shooters to try and maybe try that again for the second time.

anyways, keep us updated, i think you'll be alot happier with the toned down 600 than having to live with using the 390...

Justin

My machinist and I talked this scenario through and he told me about a local racer using a 327 in his Camaro with a Holley 750 on it, my machinist told him to try a 600-650 cfm carb to see 'what changes' with a wink. They guy took it out and swapped carbs to a 650 and his 60' time decreased slightly and 1/8 mile time decreased by .1, but his 1/4 was still the same as before... that really got that guy wondering since he was a 'bigger=better' guy.

I figure this carb allows small changes to occur and is more 'tolerant' to what's going on than the 390 which is smaller and more 'sensitive' to lean outs, signal drops and slight tweaks...

Shooter and jet change coming up, once it's running, then a road trip for mileage will ensue.

If you're running a pink cam in #1 and you're having problems with a stock slant you've got something else that's a problem. I think #31 should be the limit for it, and check your secondary springs if you have anything like a yellow or purple in there it may be opening the secondaries on load too soon and leaning it out and killing it. Don't forget a #35 needs a hollow screw to work properly too.

-D.Idiot

D.I, i know about the bigger = better thing LOL i've been messing around with diff carbs on my stock slant, but i really dont wanna spend the cash on a new 390 saying i cant find a used one anywhere.

i figure for what i'm going to be doing the 600 will suite my slant better than a 390 would once i install all of the stuff i've been gathering in the spring (big cam, big valves, and a whack load more porting than i expected i'd ever do not to mention the .1 and some change decked off the head.) I've got no clue what the problem is with my Bog, i have the silver (no color) spring in there right now, the pink cam and 28 shooters with 52 jets pri and the WHOPPER #39 plate in the back (i kno i kno but the block kit will have to wait till spring). i can definatly tell when the secondaries open (guessing around 3000rpm b/c the motor seems to really pull extremely hard from 3-4500rpm) I tried the pink pumpcam in the #2 position and it really sucked bag off the line (any gas and it'd die ). however i fixed all my vac leaks and pull a good 19" of vac at idle (800rpm) but it goes up to a hight of 21" at 1200 or so. its cool out right now and i'm going to have to jet ritcher for the winter (i think a 55 should do it).

sorry to kinda jack your thread or anything, but i think we're all in this tuning thing together right now anyways keep us updated. i figure you should pull a nice 20+MPG with this carb tuned in (i'm at about 19ish right now but then again, i cant remember a time when i didnt wind it to 4500rpm )

Justin

no color= plain spring it's still pretty light and might flop them open a bit early, I'd try to find a Brown spring to see if you can 'limit' the secondaries a bit. Increase shooter size, leave the cam alone...leave the line @ 2000 rpm, anything less with small cam and a bigger carb is a bog...I've been there, I think even Dennis posted it at one point and time.


more later,

-D.Idiot

Thanks D.I

I'll go out and buy a spring kit for the secondaries. i also have a 2 other 4160 carbs kicking around so i can check them for different parts. i DO have 2.76 gears in the car right now (when the car doesnt want to bog it'll break loose not for long but it'll squeel, and in rain it'll light em up on demand prettymuch ) i'm going to have a pretty big cam in the car, i'm aim'n for something around 250-260 @ 0.050.

cant wait untill spring when the 3.93SG, 8.25 goes in along with all the other performance stuff

If ya dont mind me asking How much were the boosters? the machine shop didnt say how much they'd restrict flow did they? (rough estimate?)

Justin

my quote was primaries only= $50
All 4 cost $94...

Restriction was estimated at about 30 cfm...roughly.

-D.Idiot

Holley 390s show up on ebay all the time. They seem to go for resonnable prices. But Holley 600s are a dime a dozen.

I got all of my 600's for free, so I'm into this carb for $94 venturi change, and $24 rebuild kit... that's still cheaper than a new one.



-D.Idiot