OLDS 84 Hurst/Olds and 85 442 Quadrajet Carburetor secondary rod information

69hurstolds

69hurstolds

Royal Smart Person
Jan 2, 2006
1,547
2,049
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#1
There was a discussion about potential "EL" secondary rods found in Hurst/Olds and 85 442 carburetors. Reference post below.

https://gbodyforum.com/threads/84-hurst-olds-techg8.61032/post-677806

Rather than muck that thread up any further, I dug out an original, never been apart, 85 442 carburetor I had sitting on the shelf in the shop. Those that know, know that the 85 442 carburetor is an EXACT clone of the 84 Hurst/Olds carburetor. All they did for the 85 model year is stamp a 5 over the 4 for the year in the carb number and give it some other BS coding on the side of the carb. Just stamped right over that ****. But they put a new sticker on the back of it to show it is a 5554 carb. The 84 H/O carb is 17084554. The 85 442 carb is 17085554. Wow. So close. Much air flow...Doge.

Anyway, the secondary hanger is an "N". Further down the alphabet you go, the sooner the rods raise. I think this one is .580" (edit-corrected value) if the tech info is right.
n-hanger-jpg.105516


carb-number-factory-restamped-jpg.105518


Unmolested, never been apart. Has all the little cover plates and factory metering solenoid with the numbers inked on top- nobody's jacked with it.

unmolested-original-85-442-carb-jpg.105519


number-tag-jpg.105520


Look close- You can see the little baby bump in the body casting....

baby-bump-jpg.105521


No stops on the secondary flaps. They can go FULL OPEN, unlike the Y. You can fix that on the Y engine, though. :)

full-travel-secondary-flap-jpg.105522



They were not EL rods. They turned out to be "DA" rods. GM/Delco p/n 7046010. Supposedly they interchange with CY rods, p/n 7046004.

da-secondary-rods-85-442-carb-jpg.105523


You can see the "DA" stamping a little better here.
da-secondary-rod-stamping-jpg.105524
 
Last edited:
spidereyes455

spidereyes455

Master Mechanic
Mar 6, 2013
280
231
43
Northeastern PA
#2
Good info to know. Any idea if the 86-87 carbs have the same rods and hanger? I changed them out for richer ones in my 87 442 a bunch of years ago and never made a note of what came out of it.
 
69hurstolds

69hurstolds

Royal Smart Person
Jan 2, 2006
1,547
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#3
I don't know. I've never had the 87's carb apart. And honestly, I've never looked at the hanger letter.

Next time I'm fiddling around with the 87 I'll check. It's a Torx 8 head screw. Little bitty thing that holds it in.
 
69hurstolds

69hurstolds

Royal Smart Person
Jan 2, 2006
1,547
2,049
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#4
More weird stuff about the 85 442 carb pictured above.

It was manufactured on Tuesday, June 5, 1984. (12,663 days ago). Date code says 1574, 157th day of 1984. I actually never gave any thought to the production dates before.

84 Hurst Olds production was over by then. However, 1984 model year cars were still in production on that date.

MY theory is that they decided at some point they would use the 84 Hurst/Olds carburetor specifications for the 85 442. They would use the carbs that were being manufactured as replacement carbs for the 84's so perhaps they wouldn't have to make so many up front to keep costs down on the project? I have no idea. Someone came up with the idea of stamping a 5 over the 4 for the year and putting the customer code of JCY overstamped on there as well to make it an 85 Carb. Interestingly, replacement 85 442 carbs sold over the counter at GM dealers had the regular 17085554 stampings as new carbs made after the production run were correctly stamped from the get-go. Perhaps they used the 84 carbs because they were already California compliant and wouldn't have to certify another??? (6th digit being a 5 for meeting California emission standards)

Every 85 442 I've ever seen with the factory carb has the overstamp. My 85 was built near the end of the 442 run in February 85, and it has an overstamp, although I don't know what the date code was, not that it matters much.
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
4,051
1,885
113
Melville,Saskatchewan
#5
Very cool info. Yah, the DA rods are much richer throughout with 440 at 90 degrees, much richer than the vin Y's 1047 and are not supposed to be used past 70 degree opening being extra long. The N hanger is typical, I have seen from J through O on 70's through 80's carbs.
 
84 W40

84 W40

Greasemonkey
Dec 9, 2009
234
270
43
#6
All 80's into 1990 ccc 4 barrel oldsmobile carbs are 800 cfm if its a Y or a 9 engine not sure about the chevy carb its been awhile had put my hands on one, but i do have a few at my other garage. I did take a look at the hanger and rods on my 84 hurst, this carb has never been rebuilt or replaced and still has the original Tamper proof plugs. Hanger has a L on it and the rods have DA . DA rods were used in alot of oldsmobiles back in the mid 60's to early 70's. I did look at few other carbs on my shelf, one was from a 84 olds station wagon Y engine hanger was a R and the rods are DD original carb never taken apart. The other carbs are older , one from a 69 W30 hanger K rods AU. The other from a 69 toronado hanger K rods DS, very rich rods.
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
4,051
1,885
113
Melville,Saskatchewan
#7
This is good info and makes sense. I know my 85 non CCC 307 Qjet, came off a Buick wagon is 800 cfm. It actually had 75 primary jets, I believe 44K rods and a N? hanger and had CV secondary rods.
 
69hurstolds

69hurstolds

Royal Smart Person
Jan 2, 2006
1,547
2,049
113
#8
All 80's into 1990 ccc 4 barrel oldsmobile carbs are 800 cfm if its a Y or a 9 engine not sure about the chevy carb its been awhile had put my hands on one, but i do have a few at my other garage. I did take a look at the hanger and rods on my 84 hurst, this carb has never been rebuilt or replaced and still has the original Tamper proof plugs. Hanger has a L on it and the rods have DA . DA rods were used in alot of oldsmobiles back in the mid 60's to early 70's. I did look at few other carbs on my shelf, one was from a 84 olds station wagon Y engine hanger was a R and the rods are DD original carb never taken apart. The other carbs are older , one from a 69 W30 hanger K rods AU. The other from a 69 toronado hanger K rods DS, very rich rods.
Noticed a lot of AU rod applications were used in 69, like all the 442 variations including the H/O. The machine must've been broke and made way too many AU rods that year.

Keeping with the 84 and 85 VIN 9 carbs, I know it's only a couple of samples here, and I could be wrong, but I'm betting they all came with DA rods.

As far as the hangers, in reality, L isn't that far from N. The L is .0570" which is only .010" of an inch different than the N at .0580". Each letter down the alphabet starting with B (.520") and ending with V (.0615") represents a .005" difference in rod hole to support bar height. I need to check the 84 and the 87 ones out in the shop for giggles. Based on some research, hangers don't really mean squat except for the resting height of the rods sitting in the secondary jets. According to an old employee who used to work at Rochester, the engineers designed rod hangers with different heights to precisely position the rods in the holes. Had nothing to to with opening rates or any of that jazz. The size of the rod makes the biggest difference. You can bend a hanger if you really had to. Makes sense.

Lars Grimsrud is considered one of the most, or probably THE most knowledgeable dude on the planet as far as tuning Q-jets go. Especially older ones. I've actually never read much on his findings only due to the fact I thought he was just a Corvette racer. Comes to find out he's actually got a tuning paper on Q-jets that pertains to mainly older ones yes, but has a lot of info applicable to all Q-jets.

Here's what he has to say about secondary rods/hangers.

What has a greater effect on performance: primary or secondary jetting? I constantly see people swapping around secondary rods,
trying to get the best performance out of their cars. The secondary rods are very easy to change, and since the secondaries are so BIG,
the secondary metering has to be the most important, right?

Wrong.

Most Q-Jets are 750 cfm carbs. This is more airflow than most small block engines can ever handle. Yet, GM used Q-Jets on
everything from Overhead Cam 6-cylinder Pontiacs and Corvair 6-cylinders, to 500 cube Caddys. How?

The secondary airvalve on the Q-Jet effectively makes the Q-Jet a variable-cfm carb. The spring windup of the airvalve combined
with the bleed-off of the choke pulloff diaphragm allow the secondaries to open only as much as the engine can handle. Thus, if the
engine can’t handle all of the cfm, the secondaries simply don’t open all the way.

The primary side, however, is used throughout the rpm range. It is always in use, and provides the metering for the majority of the
power produced by the engine. Let’s look at the scenario:

You’re at the stoplight. You bring the rpm up slightly against the torque converter – 1500 rpm. You’re on the primary side of the
carb only, and this is what is producing all of your torque right now. The light changes, and you put the pedal to the metal. All of
your torque at launch is being produced by the primaries only, as the secondaries don’t see enough airflow to open. The rpm comes
up quickly: 2000, 2500, and now the secondaries might be starting to crack. Almost all of the air is still passing through the
primaries, and the secondaries are now starting to compliment it just a tad. 3000, 4000 rpm, and the secondaries might be half-way
open. The primaries are still providing most of the airflow and metering. 5000, 5500 and you hit redline just as the secondaries hit
about ¾ open. Second gear, your rpm drops, partially closing the secondaries back up, and you’re back to sucking the majority of the
air through the primaries once again.

So we see, the secondaries provide only a compliment to the primaries. The primaries provide the vast majority of the fuel metering,
and primary jetting is absolutely the most critical to proper performance. You cannot compensate for poor primary jetting by rejetting
the secondaries. So we are going to concentrate on jetting the primary side for peak performance, and then we will set up the
secondary side to provide a proper compliment to the correct primary jetting.
He goes on to say once you get your secondary air flap spring set up, do your secondary rods:

Now, you need to adjust the secondary rod hanger height. You’ve read all about the different letter numbers for the secondary
hangers, and how a “Y” hanger will make your car faster than an “M” hanger or whatever. Fact is, you can bend and adjust any
hanger to any hanger height you want, so it doesn’t make a heck of a lot of difference what hanger you choose to use. Just get it set up
right:

With the secondary airvalve held wide open and the secondary rods pulled all the way up, measure the distance from the top of the
rear wall of the choke horn to the secondary rod hanger hole in the hanger. This distance should be 41/64”. Bend the hanger to adjust
– you have to adjust each of the two sides independently. You now have a “performance” rod hanger.

With this set, you can now play with secondary metering rods. A common speed trick mistake is to always install thinner (richer)
secondary rods. Some engines and carbs will produce a secondary “lag” if the rods are too thin. On about half of the engines I work
on, I obtain better performance by installing fatter “non-performance” rods. Again, a quick road test is the only way to set this up, so
go back to your 300-foot stretch and make a few runs with rods both richer and leaner. Once you have found the rods producing the
smoothest secondary transition and the best numbers, you can start unwinding the secondary airvalve spring. Relax the spring tension
in 1/8 turn increments until the car stumbles on acceleration, then tighten up 1/8 turn again. You have now determined the quickest
secondary opening rate that your engine can handle, and your secondary mixture is set.

Note that secondary metering rods come in three different tapers: long tip, short tip, and medium tip (see Figure 3). Most of the
available after-market metering rods have the long tips, and these will produce a full-rich mixture upon the slightest opening of the
secondaries. Many street engines will produce better performance by using the short tipped rods. A short tipped rod does not allow a
full-rich mixture until the secondaries are opened quite a ways, keeping the mixture a little lean initially. This can produce smoother
and crisper performance in many applications. Next time you see a junk Q-Jet laying around, make sure you yank the rods and jets
out of it: many old truck carbs have some really good short-tipped secondary rods in them.
 
84 W40

84 W40

Greasemonkey
Dec 9, 2009
234
270
43
#9
Noticed a lot of AU rod applications were used in 69, like all the 442 variations including the H/O. The machine must've been broke and made way too many AU rods that year.
Yes, they made many of those AU rods and are very hard to find in good condition.

Keeping with the 84 and 85 VIN 9 carbs, I know it's only a couple of samples here, and I could be wrong, but I'm betting they all came with DA rods.
I know they did as long the carburetor is original and not been f**ck with. I do have a spare 83 and 84 hurst carb at my other garage need to look at those.

I do know that theirs not much of a difference between L or N hangers but that's whats on my carb.

Yes you can bend the hangers I have done it but its just as easy to have an assortment of hangers then trying to bend both sides of the hanger equally. There is a reason why GM used different hangers, if they felt that using one type of hanger would of worked they would of done it.

when it comes to rods lean or rich it depends on your application. I do agree going with a richer rod on 250 HP motor you gain nothing but with a motor pushing out between 500 to lets say 800HP it wants a lot of air and fuel.
 

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