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Holley 715 Install

Started by GeotechDuck, February 10, 2024, 08:41:43 PM

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GeotechDuck

Hi Everyone:
I am reinstalling a Holley 715 after a carb rebuild and I have a couple of quick questions.

1) I have a small 1/4 drive torque wrench (in/lbs).  I looked in the Holley specifications for their typical carbs and it indicated to torque the hold down nuts to 60-80 in-lbs.  Is this correct?  I am running a stock Shelby intake manifold and two gaskets with and a 1/4" heat dissipator.  Right now they are just finger tight. 

2)  Trying to figure out a return spring set up.  I have a generic bracket and a single spring setup.  Anyone have a different setup they would recommend? 

66 Shelby GT350H.
1966 Shelby GT 350H / 2008 Shelby GT

Bob Gaines

#1
Quote from: GeotechDuck on February 10, 2024, 08:41:43 PM
Hi Everyone:
I am reinstalling a Holley 715 after a carb rebuild and I have a couple of quick questions.

1) I have a small 1/4 drive torque wrench (in/lbs).  I looked in the Holley specifications for their typical carbs and it indicated to torque the hold down nuts to 60-80 in-lbs.  Is this correct?  I am running a stock Shelby intake manifold and two gaskets with and a 1/4" heat dissipator.  Right now they are just finger tight. 

2)  Trying to figure out a return spring set up.  I have a generic bracket and a single spring setup.  Anyone have a different setup they would recommend? 

66 Shelby GT350H.
I have done it so long that I use 1/4 drive with extension and 7/16 socket and with one hand tighten until it is a little more then snug which I am guessing is about 15 pounds. But that is just me. Look at this link for what is typical as far as return spring bracket and spring.
https://www.virginiaclassicmustang.com/65-66-V8-4V-ACCELERATOR-RETRACTING-SPRING-BRACKET-ORIGINAL-ZINC-FINISH-P1057.aspx
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

s2ms

Quote from: GeotechDuck on February 10, 2024, 08:41:43 PM
Hi Everyone:
I am reinstalling a Holley 715 after a carb rebuild and I have a couple of quick questions.

1) I have a small 1/4 drive torque wrench (in/lbs).  I looked in the Holley specifications for their typical carbs and it indicated to torque the hold down nuts to 60-80 in-lbs.  Is this correct?  I am running a stock Shelby intake manifold and two gaskets with and a 1/4" heat dissipator.  Right now they are just finger tight. 

2)  Trying to figure out a return spring set up.  I have a generic bracket and a single spring setup.  Anyone have a different setup they would recommend? 

66 Shelby GT350H.

I typically use 8 ft-lbs which I've read as a Holley spec. Your 60-80 in-lbs reference is ~5-7 ft-lbs so in the same ball park.
Dave - 6S1757

GeotechDuck

Thank you everyone for the quick replies.

Here is a picture of my current set up.  My spring is stretched out a little further.  Do I need to adjust?. 
1966 Shelby GT 350H / 2008 Shelby GT

Brant

#4
Another example:

-Brant

www.VirginiaClassicMustang.com

Subscribe to our Blog for the latest updates restoration projects and new parts information for 64 1/2-73 Mustangs!  http://blog.virginiaclassicmustang.com/

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67350#1242

Early shot of the throttle setup with more stretch:
67 GT350  SJ 02/01/67  Gray 4spd A/C
67 Coupe  SJ 11/16/66  White Auto A/C PDB

GeotechDuck

Thank you everyone for the input.  I got everything hooked up yesterday.  I tightened with a hand wrench to snug.  I then used my torque wrench to go to 60 in-lbs, which actually was not very much pressure.  I could turn the torque wrench with 1 finger and went about 1/4 turn before it clicked. 

Started the car up and it runs, but it is running very rough.  Idle mixture screws were out 1.5 turns when I first turned it over.  I played with those for a while, but was not able to clean it up.  I finally turned the mixture screws all the way in and the car continued to barely idle.  I am guessing I still have a vacuum leak and need to tighten more?

Any advice is appreciated.     

1966 Shelby GT 350H / 2008 Shelby GT

FL SAAC

we had a similar situation with our recently acquired 66 GTH, we rebuilt the carb and it did not perform as expected.

lucked out as another saac member had a n.o.s. carb

we replaced it with the n.o.s. car performs like it's a new fuel injected model even better after a recent installation of a petronix module
Home of the "Amazing Hertz 3 + 1 Musketeers"
I have all UNGOLD cars
I am certainly not a Shelby Expert

Drew Pojedinec

If most carbs idle with mixture screws all the way in it points toward finding fuel elsewhere not a vac leak.

I always retorque everything after a few hot/cold cycles.

If you have a stock unchanged 3259-1 it can idle with mix screws in due to massive idle feed. But it shouldn't run well.

FL SAAC

#9
Hi Drew
can you say or pm me the cost of rebuilding one of these
Thanks in advance

Also great advice on retorquing after it has warmed up several times going through its cycles
Home of the "Amazing Hertz 3 + 1 Musketeers"
I have all UNGOLD cars
I am certainly not a Shelby Expert

GeotechDuck

Quote from: Drew Pojedinec on February 17, 2024, 10:43:08 AM
If most carbs idle with mixture screws all the way in it points toward finding fuel elsewhere not a vac leak.

I always retorque everything after a few hot/cold cycles.

If you have a stock unchanged 3259-1 it can idle with mix screws in due to massive idle feed. But it shouldn't run well.

I do have a stock / unchanged 3259-1.  With the screws all they way in, it was barley running and running very rough.  But it was not dying. There is not a ton of difference in how it runs with the screws in or 1.5 turns out.  RPMs are low and jumping around in park.   
1966 Shelby GT 350H / 2008 Shelby GT

GeotechDuck

Quote from: FL SAAC on February 17, 2024, 10:42:01 AM
we had a similar situation with our recently acquired 66 GTH, we rebuilt the carb and it did not perform as expected.

lucked out as another saac member had a n.o.s. carb

we replaced it with the n.o.s. car performs like it's a new fuel injected model even better after a recent installation of a petronix module

Thanks!  I think most Hertz cars had an Autolite 4100 C6ZF-F?  My father purchased this car in 1969 and the carb was already switch out and had a Holley 715 from a manual Shelby.   

A couple of month ago, it started to leak gas, so I had it rebuilt.  I am very confident that the rebuild is solid, as the person that did it has a lot of experience with rare carbs and they ran it on their tester in the shop and measured fuel, gas, etc. before I took delivery. 

I am hoping i just have a vacuum issue between the carb and the intake manifold.  I am going to remove the 1/4" aluminum dissipater and mount it back up with a single gasket to see if I can get it to seal.
1966 Shelby GT 350H / 2008 Shelby GT

Bob Gaines

Quote from: GeotechDuck on February 17, 2024, 01:31:13 PM
Quote from: FL SAAC on February 17, 2024, 10:42:01 AM
we had a similar situation with our recently acquired 66 GTH, we rebuilt the carb and it did not perform as expected.

lucked out as another saac member had a n.o.s. carb

we replaced it with the n.o.s. car performs like it's a new fuel injected model even better after a recent installation of a petronix module

Thanks!  I think most Hertz cars had an Autolite 4100 C6ZF-F?  My father purchased this car in 1969 and the carb was already switch out and had a Holley 715 from a manual Shelby.   

A couple of month ago, it started to leak gas, so I had it rebuilt.  I am very confident that the rebuild is solid, as the person that did it has a lot of experience with rare carbs and they ran it on their tester in the shop and measured fuel, gas, etc. before I took delivery. 

I am hoping i just have a vacuum issue between the carb and the intake manifold.  I am going to remove the 1/4" aluminum dissipater and mount it back up with a single gasket to see if I can get it to seal.
Yes up to approximately # 900 the automatic cars used a Holley, after that the 4100 was used. The Hertz cars running a 4100 carb used a 1/4 thick spacer designed to seal the mismatch between the 4100 base plate and the Cobra intake. 
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

Drew Pojedinec

Quote from: GeotechDuck on February 17, 2024, 11:59:12 AM
I do have a stock / unchanged 3259-1.  With the screws all they way in, it was barley running and running very rough.  But it was not dying. There is not a ton of difference in how it runs with the screws in or 1.5 turns out.  RPMs are low and jumping around in park.   

An explanation of why is in order.

A typical generic carb has a very "normal" idle circuit. This is why they often run fantastically on a myriad of engines.
The two common performance carbs that show a difference with this are the Cobrajet and 3259-1.
The reasons for this:
The CJ carb is designed to idle on the transfer slot. Yes it does in fact have mixture screws, but enough t slot is showing that is provides enough fuel to idle on many engines even if the mix screws are closed. Yes it will run rough.

The 3259 from 1965 has a fairly small and reasonable idle feed at .033, this works great on most engines.
The 3259-1 has an idle feed of .040 which is massive. The carb is designed to provide sufficient idle fuel for radical camshafts like the Lemans Cam.
In modern days we would just use a four corner idle carb and reduce the idle feed jets considerably. In 1966+ this was not an option, so the only way to provide more fuel was with a drastic enlargement of the idle jet.
So what happens when you pit this carb on an engine making more than 12inches of vacuum?  It tends to idle very rich and the mixture screws are often weak with adjustments. You can often close them entirely and the engine will still idle (tho badly as noted).

Typically when rebuilding a 3259-1 I do ask the customer about cam specs as I can make changes easily.

FL saac:
I am not into pushing my business on the main forum. Visit my webpage afscarbs.com and all info you want is there. Feel free to contact me via the page. Thanks

GeotechDuck

Quote from: Drew Pojedinec on February 17, 2024, 03:00:47 PM
Quote from: GeotechDuck on February 17, 2024, 11:59:12 AM
I do have a stock / unchanged 3259-1.  With the screws all they way in, it was barley running and running very rough.  But it was not dying. There is not a ton of difference in how it runs with the screws in or 1.5 turns out.  RPMs are low and jumping around in park.   

An explanation of why is in order.

A typical generic carb has a very "normal" idle circuit. This is why they often run fantastically on a myriad of engines.
The two common performance carbs that show a difference with this are the Cobrajet and 3259-1.
The reasons for this:
The CJ carb is designed to idle on the transfer slot. Yes it does in fact have mixture screws, but enough t slot is showing that is provides enough fuel to idle on many engines even if the mix screws are closed. Yes it will run rough.

The 3259 from 1965 has a fairly small and reasonable idle feed at .033, this works great on most engines.
The 3259-1 has an idle feed of .040 which is massive. The carb is designed to provide sufficient idle fuel for radical camshafts like the Lemans Cam.
In modern days we would just use a four corner idle carb and reduce the idle feed jets considerably. In 1966+ this was not an option, so the only way to provide more fuel was with a drastic enlargement of the idle jet.
So what happens when you pit this carb on an engine making more than 12inches of vacuum?  It tends to idle very rich and the mixture screws are often weak with adjustments. You can often close them entirely and the engine will still idle (tho badly as noted).

Typically when rebuilding a 3259-1 I do ask the customer about cam specs as I can make changes easily.

FL saac:
I am not into pushing my business on the main forum. Visit my webpage afscarbs.com and all info you want is there. Feel free to contact me via the page. Thanks

Thank you for the information.  I don't have much experience with this car, as it is my Dads.  I am learning as I go here.  Is there an easy way for me to check and see how much vacuum I have? 

Ran perfect with this carb for 50 years, so imagine I will eventually find a way to get it dialed in.
1966 Shelby GT 350H / 2008 Shelby GT