Author Topic: Q-Jet for 305?  (Read 784 times)

Offline Ronno6

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Q-Jet for 305?
« on: September 26, 2018, 09:19:20 AM »
Now that my '84 C10 is back on 4 wheels, it is time to address the way it runs.

As purchased, the 305 has a well-worn Edelbrock 1496 750cfm (WAY overkill) sitting on top.
The throttle shaft bore is worn to a point where, when running, the throttle plates will not return to idle without significant spring  tension.
Extremely difficult to drive w/stick shift.

What carb do y'all recommend?
Motor is currently stock, but I have headers and new exhaust for ti, and plan on someday getting better heads,cam and intake.
Maybe upgrade to a 350.
Those mads are a ways down the road a bit,
The Original Q-Jet is rated at 650cfm ??
Seems it was stock on 305 and 350.

I need to be able to drive the critter now.
 
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline Henry

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Re: Q-Jet for 305?
« Reply #1 on: September 26, 2018, 11:58:33 AM »
Hi Ronno6:
If your engine was originally a 305, then in 1984 it came with one of the following Q-jets: E4ME, M4ME, or M4MC. These were probably rated at 650cfm or less...I dont know for sure. As you have stated, a stock 305 that isnt going to need to produce power for you above 5000rpm does not need a 750cfm carb and it probably will not run right anyway. At 5000rpm a stock 305 only needs 425cfm and a 350 engine only needs about 475cfm.

Do you have the oem intake manifold? Do you have the oem electric choke?If you have the oem manifold which has the opening for a 4-barrel, you probably should stick with a 4-barrel to keep life simple but just look for a smaller one than you have. If you are an experienced carb tuner and rebuilder, and you can get a good deal on a Q-jet, go for the M4ME (electric choke) as it is probably the simplest of the 3 for your model year. If you can find an aftermarket 650 cfm (or smaller) by Holley or Edelbrock, I would consider these as they are simpler than the Q-jet and you can probably get one new for the same price as a refurbished M4ME.

The simplest and most economical solution may be to just rebuild your Edelbrock 1496 and just tune it as best you can for your situation...then when you decide to get a bigger engine(or however you decide to get more power) you can still use the 1496. You would have to check and see if throttle shaft sleeve kits are available.

Generally from my experience, the Q-jets have best all around performance (fuel economy, driveability, power), but the problem is that they are all old now and you dont want to buy someone else's problems on a used one....you wouldnt want one that has the APT mechanism. Edelbrock and Holleys have good power but poor fuel economy and are simple to tune and rebuild...parts are much more available and you can get a new one at a good price.

My best recommendation for a specific carb: I used to have a 67 Chevy truck that had a 307 and it had a Rochester 2G carb which was a 2-barrel and was a great carb...but they are all gone now...I think...and you would need a different intake manifold.

Regards,
Henry

Offline Ronno6

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Re: Q-Jet for 305?
« Reply #2 on: September 26, 2018, 12:15:31 PM »
As always, thanks, Henry.

I have seen good deals on refurbed Q-jets.
I have also e=seen good deals on Holley Street Warrior carbs.
Holley reman for $229.00.

I do have the stock intake, with an adapter plate for the Edelbrock.

Door is still open.....

btw: I called Edelbrock to inquire about a sleeve kit.
I was told there is none; they said I should scrap the carb!!!
FINE TECHNICAL ASSISTANCE !!!
« Last Edit: September 26, 2018, 05:22:58 PM by Ronno6 »
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline 75gmck25

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Re: Q-Jet for 305?
« Reply #3 on: September 27, 2018, 07:21:32 AM »
Max CFM on Quadrajets is somewhat misleading, since GM sometimes used the same carburetor body for multiple cars, and made small tweaks and mods to change its performance potential.  Most of the newer Quadrajets can flow up to 750 CFM, and some are closer to 850 CFM maximum, but GM put limiters on flap opening, smaller jets, etc. so they would flow more like 600-650 CFM max.  Since all the mods work together to get a good running engine, tuning and getting it all working effectively can be frustrating.

I like Quadrajets, and I'm currently using one on my 350, but for a new purchase there are probably simpler options.   The Edelbrock 1406 is a favorite because its simple, and usually only needs idle mixture and step-up spring tuning to get it running smoothly.  And that tuning can be done with it still mounted on the engine and the top still on the carburetor.  Another favorite is the Holley 4160/4150, and there seems to be many folks out there who know how to tune them.  Holley also has several good high performance carburetors, but prices go up quickly when you go to the Dominator series or the Ultra XP.

Bruce

Offline Ronno6

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Re: Q-Jet for 305?
« Reply #4 on: September 27, 2018, 08:55:10 AM »
The 4160 seems to be marketed currently as the Street Warrior

So, I am looking at Holley Street Warrior carbs on ebay.
I find a "barely used" one for $220.00 + $9.90 shipping.
That adds up to $229.90. (Not all people understand that...)

Then, I find Holley factory refurbs for $229.99 SHIPPED.
That adds up to $229.99)
This includes a 1 year warranty and new installation kit.
I consider that to be a better deal.

The owner of the used one does not agree............
He says that the Holley Factory refurbs are "old,worn out units" (The Holley auction clearly states that these are NOT old,worn out units,
and they have been tested, calibrated, and, again, come with the SAME warranty as new..........
The seller of the used one disregards this statement.......

In fact, this is an exerp from the actual listing:

This is an official Holley Performance Factory Refurbished Carburetor listing.

Factory Refurbished carbs are NOT old worn-out carbs that have been rebuilt. They are carbs that were returned under warranty. When these carbs are returned, we check them out and most of the time there is nothing wrong with them. Generally, they were simply adjusted out of working range by the installer.

Since these carbs may show signs of a previous installation, our policy is not to sell them as new. Rather than scrapping them, we are making them directly available to the public. Not only does this help us control the costs of our new carbs, it allows you to get a great deal on a like-new carburetor!

Factory Refurbished carbs have undergone a thorough inspection. Any damaged parts that would effect performance have been replaced and the carbs are solvent cleaned before being wet-flow-tested on Holley’s state-of-the-art flow benches allowing them to be recalibrated to new carb specs. Factory Refurbished carbs may have scratches, blemishes, and other visual flaws from previous installation.

I again point out the Holley Warranty Statement:

Warranty & Return Policy

Holley Factory Refurbished Street Warrior Carburetors are warranted for a period of 1 Year from date of sale for defects in material and workmanship. Any defective items will be repaired or replaced at Holley’s discretion.

So, I inquire as to the warranty that would accompany HIS carb..........(no reply as of yet...)



Then, he points out that $230.00 (NOT $229.99) for the refurb is a good price, but @ $220.00 HIS is better (gee, what happened to the $9.90 shipping??)

So, I have undertaken to argue with a fool. This often ends badly.........
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline Ronno6

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Re: Q-Jet for 305?
« Reply #5 on: September 27, 2018, 09:26:19 AM »
Max CFM on Quadrajets is somewhat misleading, since GM sometimes used the same carburetor body for multiple cars, and made small tweaks and mods to change its performance potential.  Most of the newer Quadrajets can flow up to 750 CFM, and some are closer to 850 CFM maximum, but GM put limiters on flap opening, smaller jets, etc. so they would flow more like 600-650 CFM max.  Since all the mods work together to get a good running engine, tuning and getting it all working effectively can be frustrating.

I like Quadrajets, and I'm currently using one on my 350, but for a new purchase there are probably simpler options.   The Edelbrock 1406 is a favorite because its simple, and usually only needs idle mixture and step-up spring tuning to get it running smoothly.  And that tuning can be done with it still mounted on the engine and the top still on the carburetor.  Another favorite is the Holley 4160/4150, and there seems to be many folks out there who know how to tune them.  Holley also has several good high performance carburetors, but prices go up quickly when you go to the Dominator series or the Ultra XP.

Bruce

My dinky 305 doesn't need too much flow,currently.
It has a 1406 or 1407 (can't 'member) and it is way too big.
And, I am very dissatisfied and disheartened at EB's tech and customer service.
When I discussed with them the worn shaft,body situation, their suggestion was "send it to the parts bin..."

I didn't like that......
You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline Henry

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Re: Q-Jet for 305?
« Reply #6 on: September 27, 2018, 02:30:11 PM »
Hi Ronno6:
Can you find out exactly what model Edelbrock you do have? I have an old Edelbrock catalog from 2000 where they have the following info:

#1405 is manual choke 600cfm carb caibrated for performance
#1406 is electric choke 600 cfm carb calibrated for max economy
#1407 is manual choke 750 cfm carb calibrated for performance

On all of these carbs(they used to be called the Performer Series) they advertised you could buy a remanufactured replacement main body or top...maybe they dont do that anymore.

If you have the #1406, I would think this should be OK for your engine if you can rebuild it...my old catalog has #9922 for the remanufactured main body.

Give those guys at Ebrock a call again...maybe you can get someone else on the line who is more customer oriented.

In the decision making process between Holley and Edelbrock, it seems that just as far as ease of tuning, reliability, and simplistic design, Edelbrock may have an edge over the comparable Holley. I bought a marine version of the Ebrock Performer Series for my boat a long time ago based on the above factors.

Regards,
Henry


Offline Ronno6

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Re: Q-Jet for 305?
« Reply #7 on: September 27, 2018, 05:26:11 PM »
I'm pretty sure it is a 1407.
Way too big...I remember that.

I have addressed this issue with EB twice and received the same answer both times.
I have found bushings,tho:  https://www.carburetor-parts.com/Throttle-Shaft-Bushings_p_4596.html#

Now I need to choose the correct reamer....

You can lead a man to water, but yoiu can't keep him from pissing in it.

Offline 75gmck25

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Re: Q-Jet for 305?
« Reply #8 on: September 28, 2018, 07:37:00 AM »
You can download the Edelbrock manual online, and it provides the specs for each model of carburetor (jets, rods, springs).    Don't get confused by the numbers they list in the diagram for each jet/rod combination, because the diagram is unique for each carburetor (1405/1406/1407).    In other words, the #18 combination for a 1406 is different than the #18 combination for a 1407.

Edelbrock also has tuning kits for each model, and most include 3 other jet sizes, 3 other rod sets, and a set of step-up springs.  For example, if you want to make a 1407 leaner, you can probably look at the stock 1406 combination, and just swap rods and jets to get the same results.  However, if that combo is not included in your tuning kit, you will have to buy rods and jets individually, which can get relatively expensive.

One of the most common adjustments to the Edelbrocks, which should be done before any jet or rod changes, is to experiment with using a higher rated step-up spring.    Once you get the idle adjusted right, those springs are what determine your part throttle transition from cruise to power.  If the spring is too light (e.g. 4") it will delay the power transition until the engine drops to that vacuum and you might get a bog.  Swapping to a 7" spring will bring the power mode in sooner, and it often cures a bog.

Bruce