JamesC

iTrader: (5)

The Holley 4160 (600 CFM) was standard equipment on my 350 HO Deluxe.
Out of the crate, the carb was equipped with the following:
65 jets
6.5 power valve
A 31 squirter and orange pump cam (this info is in passing as no change was necessary)
A black secondary spring

After Sofa’s tune:
63 jets (I bought a 67, a 63 and a 61)
10.5 power valve (I bought an 8.5, a 9.5, and a 10.5)
Though he didn’t address secondary springs, I swapped from black (heaviest) to short yellow (next to lightest). BTW, to verify that the secondaries are opening, many recommend a paperclip. I suggest a hairpin.

I followed Sofa’s directions from top to bottom and after a few scratch-my-head moments ended with a tune that eliminated both a burn-your-nose gas smell and a part-throttle stumble. To make life simpler, I installed an allen set screw in place of the secondary throttle stop screw, which allows idle adjustment without removing the carb. You’ll have to lift the linkage a bit to access the allen screw and use the long arm of the allen wrench at an angle to make adjustments. Pic below. Recommended. A few further words from Sofa concerning the allen set screw:

"Usually I just set the idle right w the pri, then flip it over and re-adjust; and however far the pri moves from where it was to get to "ideal", I just adjust the sec the same amount. Usually only takes acoupla shots to get it right. With the screw accessible from above though, you can take it off once and set the pri to the right spot and approximate the sec once, then start it up and see where the idle is and shut it off and re-tweek the sec, repeatedly if necessary, until you get the idle speed where you want it. It might even change so much that you have to re-adjust the mixture screws, which you can do with vacuum if you have a gauge; find max vac, then lean the idle 1/8 to 1/4 turn." I actually enriched by a 1/4.

So how much of the primary transition slot is showing? No idea. I closed the primaries and opened the secondaries (along with idle mixture tuning) until the burn-your-nose smell was eliminated and the idle was right. I assume it’s in the .020 to .040 range but that’s a guess. One day when I’ve yanked the carb, I’ll take a peek.

That day has come: With the same set-up as above, but with a new 600 VS Holley Street Warrior (P/N 0-80457S), I adjusted the primary transition slot to .20 and turned the idle stop screw 1/8 past the factory setting. After adjusting the idle mixture screws (which jumped the vacuum from 15 to 17), the car idled smoothly at 750. Very nice.

Performance results? After completing a roundabout on my favorite tune road, I got on the car in second. Immediate burning rubber and sideways movement. This old man nearly soiled his tidy whities. Sofa mentioned something about the car running like a bat out of hell after the tune—yep.

After a few fill-ups, I’ll report on gas mileage. According to my gas cubby, before the tune the car was averaging 13.1 mpg.

On Aug. 4, 2017 the mpg was 19.5. Mostly highway.
On Aug. 20, 2017 the mpg was 19.8. Mostly highway.
On Aug. 26, 2017 the mpg was 19.8. Mostly highway.
On Nov. 7, 2017 the mpg was 18.6. I was pleased with the result after a needle/seat issue, repeated tuning, and some spirited driving city/highway.

I fully expect to crack 20+ at some point. We'll see.

On April 12, 2018 with the carb functioning without issue the mpg was 20.4. Mostly highway.
On May 12, 2018 the mpg was 16. Mostly city.
On June 16, 2018 the mpg was 16. Mostly city.
On July 22, 2018 the mpg was 16.9. Mostly city.
On September 17, 2018 the mpg was 18.7 mixed.

Helpful parts:
Allen set screw, M5-.80 (with purple Loctite 24024)

Holley’s quick change (20-59) and spring kit (20-13) is a nice addition if you have vac secondary carb. I used the above because the two kits were already in place. From what I’ve read on TGO, a better choice would be Quick Fuel’s kit (63-1).

A vacuum gauge.

A carb stand is useful considering the number of times the carb may be removed and tinkered with. I used a Moroso 67020.

Mess saving:
I set the stand/carb in a cheap alum turkey basting pan and used a rattle can top to catch the fuel after removing one of the lower bowl screws.

A note: Holley’s reusable nylon bowl screw washers (98-10) gave me fits, though I confess I suspect the bowl casting itself was the issue. At any rate, achieving a leak-proof seal was difficult. I finally purchased the standard paper replacements (2-20) and the problem disappeared immediately.

A second note: My 4160 didn’t come with a carb filter. The screen/mesh type is available as 26-141.

A third note: Before you begin your tune, make certain that the accelerator pump arm is adjusted correctly.

How much did I spend on the tune? I’d guess around $50 to $60 on jets and power valves—and less than a buck on the set screw. All in all pretty cheap for the performance increase and eventual savings in fuel mileage.

Sooo, for those who simply swap a Holley into place without tuning and are content, well, you might reconsider. Is the above tune rocket science? No. Does it require some time and fiddling? Yes. In the end, however, you’ll learn a great deal about carburetors (I sure did) and your car will run better for your efforts. Highly advised.

If others have general advice or tips, please post.

JamesC

Damon

I had no idea that carb came with the Black spring in the secondary vacuum chamber. That's the heaviest spring there is. You'd have to suck a whole Kansas twister through that carb before the secondaries would open fully with that spring in there!

BTW- Yellow is my go-to spring for performance applications. The standard (plain) spring for stock/fuel economy applications. Can't remember EVER using anything heavier than that.

Enjoy the improved performance!

sofakingdom

iTrader: (1)

Thanks for the word James, glad to see it's performing as expected!!

The burn-your-eyes stinky idle and the bog/stumble are the 2 most common Holley tuning complaints, along with gas mileage in the gallons per mile. It amazes me that Holley hasn't figured out how to help their customers dial their product in, to fix all of that, and get em to work optimally on their cars. Seems to me they'd create a significant competitive advantage over other designs if they'd just EDUCATE their customers on how to get the most out of the product. Oh well.

skinny z

You may want to consider a wide band 02 sensor as well. If fuel economy is your objective, being able to dial in 15-16 :1 AFRs on the highway will also return smiles. Combine that with a properly dialed in advance curve (with vacuum advance) and you're golden.

skinny z

I don't think that's possible.
Consider the massive range of possible installations and the thousands of individual iterations and the task becomes just about impossible for one primer to satisfy all.
Even your excellent and well read tuning sticky doesn't cover all of the elements of every installation. An example would be the "burn your eyes stinky idle". Holley can't control how much timing the engine has at idle and that has as much impact on the "stink" as the mixtures screws. It does however provide most of the ground work for taking these carbs out of the box and making it your own. This is why many of the parts are replaceable and why the more expensive versions have even greater replace-ability built in.

JamesC

iTrader: (5)

Performance is the real goal. That said, I believe I'll see an increase in MPG as is. We'll see anyway. May even try a 28 shooter in place of the 31. Going to enjoy the tune for a bit though.

JamesC

bestracing

I'm surprised as well that the black was installed. My street avenger came with the silver and I swapped it out for the yellow. They come with the quick change kit already installed and the two extra springs (black, yellow).

Damon

Bestracing- yeah, it's kinda crazy isn't it? All those springs and only the bottom 3 of the range make a damned bit of difference.

Part of the reason I can womp any Holley-style vac sec carb with a QJet. I can give you whatever "spring" you want on the secondary side by turning a screw!

Ozz1967

iTrader: (4)

Awesome, my neighbor is going to love this! Too bad there isn't a step-by-step like this for Qjets. hehe

Damon

Oh, there is a step-by-step process. You shoot me a PM with your phone number and I call you. That's step 1.

If you're close, I stop by and do the first one for you while I show you how it's done and then help you tune it on the car. Utah is not "close", unfortunately. .

85_ZED28

Great post! I need to do this as well.

weaz4200

iTrader: (2)

Good to know it worked for ya. I just threw a 4160 on my Lt1 cammed 305. Having some issues trying to figure out the overall tune timing and carb wise. I will be taking a look at SOFA'S sticky.

five7kid

iTrader: (14)

Any fuel economy results to report? Or, have you had too much fun threatening your tidy-whities?

Some tips from my Holley days:

Rather than the quick change secondary housing, consider the Proform or Quick Fuel adjustable secondary housing. About $44 on summitracing.com. The whole point of the vacuum secondary system is to open the secondary butterflies slow enough that the main metering circuit can fill up with fuel and not bog the engine (that's what an accelerator pump does, in case you didn't realize it - give a shot of fuel as the throttle opens so there's enough there until the main circuit can supply sufficient fuel). When you control that opening by increasing the spring force, you're also limiting how far the secondaries will open - which is fine if the carb is too big for the engine. But, if properly sized, you really want all four barrels open as soon as possible. With the adjustable housing, the vacuum signal is what is varied, rather than spring force (the lightest spring should work just fine). Works extremely well, and is also easier to tune.

Check the passages in your carb. I had an idle issue with a 650 DP that I just couldn't adjust away. Turns out one of the secondary idle circuits wasn't properly machined in the throttle body. When I cleaned that up, the car would finally idle. Holly QC wasn't always the best, especially back in the 80's and early 90's.

If you remove the fuel bowls often enough, you're likely to eventually strip out the screw threads in the main body. Helicoil to the rescue - doesn't take long to do all 8 screw holes, and you'll never have to worry about them after that.

I took a bowl screw to the hardware store and got nylon washers. I haven't tried Holley's version, but I never had to go back and get more of them (and those bowls came off many, many times).

If you have a 4160 style dual inlet carb, consider a conversion to a 4150 with secondary idle adjustment. Very simple to do, the worst that could happen is you might have to get a different fuel inlet tube (I cut mine in the middle and spliced it back together with a piece of rubber hose & clamps from an old in-line fuel filter - made removing the bowls much easier, as I didn't have to remove the inlet from the bowls that way). You'll be able to change secondary jets and adjust the idle mixture for an even better tune.

91 camaro racer

iTrader: (2)

i need to do this to my 4160 600 cfm on my 350.

calebad

I started following Sofas sticky, but when I started upgrading the power valve (to an 85), my engine got real rough, so I swapped the 65 back in and now she won't start.

sofakingdom

iTrader: (1)

When something like that happens, it's the result of a failure elsewhere besides the exact thing you changed. Either a gasket has got damaged, foreign material has got lodged in a passage, an O-ring is torn, a part got left out or put in wrong; something like that.

"Rebuild" the carb completely. Inspect the gaskets carefully, replace them all if there's any damage to any. Spray them liberally with silicone spray to make them easier to take apart as you tune the carb. Blow every passage out with spray carb cleaner followed by compressed air. Check the float level setting carefully. Put the higher-# PV back in (I wouldn't consider that an "upgrade" BTW, just, a tuning adjustment) and see where you are then.

JamesC

iTrader: (5)

I finally got around to it—kind of. See my first post.

JamesC

JamesC

iTrader: (5)

Edit for some further info.

Purple Loctite (to avoid the allen set screw from working out of place) and gas mileage.

JamesC

iTrader: (5)

I updated mileage in my initial post and I may do so from time to time as I tinker. I'd think 19.8 mpg is pretty decent for a carbed 350, but I wonder how close that number is to, say, a stock LG4 in good operating condition. Anyone have numbers?

JamesC

86LG4Bird

iTrader: (1)

I assume you're looking for Holley /non-feedback carb numbers?
19.8 is decent, but nowhere near what a stock LG4 will do with a functioning E4ME

JamesC

iTrader: (5)

What are those numbers?

JamesC

86LG4Bird

iTrader: (1)

27-28 highway with the stock gearing VERY careful driving. 23-24 mixed.
With the L31 in the car now and the 3.73 gears, I've squeaked out 26mpg driving 2-lane roads at 60 mph and under.

naf

iTrader: (7)

I average 23-24 on a stock LG4 w/2.73 rear for a few years, mixed driving in my 35 mile commute. Regularly got better than 27 on the highway.

The upgrade to LO5 with 062 heads (still ccc-qjet) averages around 21ish for the same commute. (Seems like I've been working here for a long time.)

skinny z

My large cammed 355 (TH700 w/lockup converter and 3.73 gears) will manage 20+ (US) MPG steady state highway driving at about 80 MPH. (Tested last year on a 350 mile round trip, all highway).
I'd say you have room for improvement. Perhaps a wide band O2 sensor and vacuum gauge will allow you to tinker further. I've managed to achieve an ultra lean cruise AFR at 15.5-16:1 (+). With the carb tuned the way I have it, any need for acceleration will bring in the power valve and fatten the mixture.
Highly recommended for an avid carb tuner.

JamesC

iTrader: (5)

I attended a car show today and suddenly wondered if those running Holley carbs had tuned them or whether they'd simply swapped the carb on and done nothing else to speak of. Only one in three had tuned. There's no real way, of course, of guessing, but give it a try. Without reading further, which one of the cars below had been tuned?

Well, if you guessed the Falcon, you're correct. The other two owners had simply bolted on and let be. Shoot, the guy in the Mustang (and perhaps the Chevy too, I didn't inquire) hadn't even verified what secondary spring was in place. Only the Mustang owner was using a DP.

JamesC

skinny z

Back in the day, way back like three decades, I had the privilege of being in a shop where carburetors were routinely disassembled and restored to as new condition. Still, we didn't have the technology available to us as we do today. In particular the wide band O2 sensor. Tuning was difficult but we still managed. At least at idle, via the mixture screws with a vacuum gauge, and WOT, by reading spark plugs. Cruise AFRs was something we didn't think about.
From the results of this impromptu poll, it would seem that the tuning aspect is still in the hands of a select few.

PS. How was your Camaro received as a participant in the show|? I'm finding more and more acceptance among "car people" regarding my 3rd gen.

JamesC

iTrader: (5)

I'm still amazed that a car guy can spend a boatload of money on his ride and yet fail to tune it for the best performance and gas mileage. Why wouldn't you, is the question.

Car shows? 99.9% of the time I'm the sole thirdgen attendee. Old farts my age don't give the IROC a second glance. A younger group, those who grew up with the cars, are always complimentary and quite willing to share their I-wish-I'd-never-sold-that-car stories.

JamesC

Reid Fleming

iTrader: (2)

I've found that it's retired people and young kids who were too young when these cars were around are the ones that give us the most attention. Age 40-60 being the least enthusiastic.

skinny z

Interesting observation. I'm at the upper end (way up) of that demographic and I constantly downplay my enthusiasm for what I own. It's the guys (here at work) in their thirties who thinks it's a cool car to own.

JamesC

iTrader: (5)

I updated the mpg on the Holly tune. I may post others from time to time.

JamesC

skinny z

Well sir, there's your 20 MPG target.
And again, by most assessments, there's more too. I can't see how 25 MPG isn't attainable. Doing that, as you might expect, involves greater expense and effort with fewer returns.
As mentioned, an AFR gauge may prove to be real eye opener and I have no doubts that there would be a reasonable ROI with it's implementation.
Then there's the ignition timing. Vacuum advance is your friend here. You may find considerable improvements addressing the spark curve at highway cruise RPMs however the work involved can be tedious and time consuming although the tools and modifications involved are not expensive (an adjustable distributor vacuum canister along with an advance limiting plate and a hand held vacuum pump).

Congratulations on achieving your goal.
Here's to carburetors!

JamesC

iTrader: (5)

JamesC

JamesC

iTrader: (5)

With the final two mpg entries in my first post, I think I'll come to an end. New tires, new ball joints, a four-wheel thrust alignment, along with the car's running better than ever, have contributed to revived driving enjoyment. I'm content (for the moment).


JamesC

LT1/TA

That is great info James,I am glad to hear your car is running great.

I read Sofa's tuning sticky a while back and I thought it was perfect.It made me want to go out and try it on a carb,I have tried my hand at some idle tuning with a vaccum gauge, changing jets,and spark plug inspections,but I just got by.If I had the information from Sofa back then I think I would have had a better experience with carbs.

sofakingdom

iTrader: (1)

Thanks everybody, a vote of confidence is a great thing to receive from fellow hobbyists.

Apeiron collected bits and pieces of several posts to create that, I do believe. Someday maybe I'll write it up in a more coherent fashion. Probably sometime after Holley has quit making carbs.

I agree, with an AFR gauge improvements are potentially available; but as always, simply knowing numerically what the car is doing now, doesn't necessarily point the way to what it wants in order to do better. I've never tried carb tuning with one though, so I'll reserve judgment until I do. I would definitely agree that it would point out gross misadjustments and allow spotting trends; unfortunately its indication would have to be very fast to catch some of the problems that a poorly set-up carb can create.