I have a 1968 GT350 4 speed with the Holley carburetor. I am reinstalling my freshly rebuilt motor and rebuilt carburetor. This is the first time I have had the correct carb on the car sense I have owned her. Everything is running really well but I felt the idle was high. I can manually depress the dashpot and the idle settles right where it should be and stays there. But when I come off the dash pot it returns to a high idle. I removed the dash pot and it runs great and idles perfectly. What is the point of the dashpot and is mine just too stiff?
Thank you for any help/suggestions.
Corey
Quote from: Corey Bowcutt on February 21, 2022, 01:26:46 PM
I have a 1968 GT350 4 speed with the Holley carburetor. I am reinstalling my freshly rebuilt motor and rebuilt carburetor. This is the first time I have had the correct carb on the car sense I have owned her. Everything is running really well but I felt the idle was high. I can manually depress the dashpot and the idle settles right where it should be and stays there. But when I come off the dash pot it returns to a high idle. I removed the dash pot and it runs great and idles perfectly. What is the point of the dashpot and is mine just too stiff?
Thank you for any help/suggestions.
Corey
The purpose of the dashpot is to prevent the engine from decelerating too quickly. There is adjustment .You screw it in or out. Sometimes the dashpot goes bad. too stiff or too soft .
Quoteis mine just too stiff?
QuoteYou screw it in or out... too stiff or too soft .
:o
It is screwed in as far as it will go. I guess mine is just too stiff.
Quote from: Corey Bowcutt on February 21, 2022, 02:29:16 PM
It is screwed in as far as it will go. I guess mine is just too stiff.
Assuming that your bracket is not bent and assuming that you have the correct dashpot the logical next step would be to try another dashpot.
Quote from: Corey Bowcutt on February 21, 2022, 02:29:16 PM
It is screwed in as far as it will go. I guess mine is just too stiff.
You mean all the way out ?? It should screw back away from the throttle, or forward towards it. Make sure the little pin is not sticking . Good luck.
Several Cobra Jet cars that I have restored have that same dash pot. It works great when it is working right. A new one from Holley (Jegs or Summit) might be the answer. So far the new ones I have bought looked exactly the same as original ones but they tend to be much smoother. The jam nut position might be off on yours - it needs to be forward of the bracket.
The dash pot is screwed all the way into the bracket and the jam nut is on the other side of the bracket. This pushes the dash pot as far away from the throttle as possible. The bracket I actually purchased from Bob about a year ago. It appears to be very correct. I think my dash pot part is just no good. I will try one of the new varieties.
Never too old to learn something new, I believed, cars with automatics only, had carbs with dash pots.
Texas Swede
Quote from: texas swede on February 21, 2022, 09:48:57 PM
Never too old to learn something new, I believed, cars with automatics only, had carbs with dash pots.
Texas Swede
You believed correctly as it relates to 66 and 67 GT350 715 Holley carbs.
The throttle return spring is also part of the equation. If it is not installed correctly you won't have enough tension to overcome the dash pot. You also need the correct return spring and throttle rod of course. The return spring bracket also needs to be the right one.
Quote from: Royce Peterson on February 22, 2022, 10:38:50 AM
The throttle return spring is also part of the equation. If it is not installed correctly you won't have enough tension to overcome the dash pot. You also need the correct return spring and throttle rod of course. The return spring bracket also needs to be the right one.
Is anyone making the correct 68 return spring now?
I am trying to post a picture of my setup but keep getting an error message so I guess I can not post pictures at this time. But to the best of my knowledge my setup is all correct. I really think my dashpot is just too stiff.
I tried looking for a new dashpot on Summit and Jeggs and the ones they show do not look correct to me.
Corey
NPD lists a dashpot for 428 CJ w/ 735 cfm and automatic. I trust it is different or they would have listed for GT 350 also. Might work in a pinch?
Don
gt350bp
Does anyone have a picture of what the correct dashpot should look like?
Well that looks very different from my setup. I wish I could post a picture
Quote from: Corey Bowcutt on February 22, 2022, 01:57:55 PM
Does anyone have a picture of what the correct dashpot should look like?
not the greatest pic but Charles car. https://www.flickr.com/photos/shelbymann1970/51897829288/in/dateposted-public/
Hard to tell for sure but that looks a whole lot more like what I have.
Corey
Quote from: Corey Bowcutt on February 22, 2022, 02:44:29 PM
Hard to tell for sure but that looks a whole lot more like what I have.
Corey
I wish I had a better pic. All I could find so far. I'm sure I got some at home for ref but they are at home and I am not. Gary
Thank you Gary.
The dash pot is the same. The bracket for the dash pot is different.
This is a 735 CFM carb but the dash pot mount is similar to yours.
(https://www.supermotors.net/getfile/1168788/original/c9afu-carb-a.jpg)
Quote from: gt350bp on February 22, 2022, 01:49:48 PM
NPD lists a dashpot for 428 CJ w/ 735 cfm and automatic. I trust it is different or they would have listed for GT 350 also. Might work in a pinch?
Don
gt350bp
The picture of the car shows an Autolite dash pot. My picture shows a Holley.
Quote from: Royce Peterson on February 22, 2022, 04:11:28 PM
The picture of the car shows an Autolite dash pot. My picture shows a Holley.
Thanks Royce. I posted a Holley originally and he said it didn't look like his Royce so I posted the other photo. This is my first photo. Can't upload. Full... https://www.flickr.com/photos/shelbymann1970/51896737332/in/dateposted-public/
The 68 Holley dashpot bracket is different then the 69 version.
So is the one shown in the photo a 69?
This is a typical Autolite dash pot and bracket. I don't think any new ones are available.
(https://www.supermotors.net/getfile/1168789/original/autolite-dash-pot-a.jpg)
(https://www.supermotors.net/getfile/1168790/original/autolite-dash-pot-b.jpg)
Quote from: Corey Bowcutt on February 22, 2022, 06:26:02 PM
So is the one shown in the photo a 69?
The one in reply #22 is of a 69 Holley. Of course 69/70 GT350 didn't come with a Holley from the factory . The GT500's did and that is what a automatic carb would look like.
The 69 dashpot bracket sticks out too far on a 68 Holley throttle linkage and it has a eyelet for a kick down lever spring . 68's do not. If your dashpot lines up with the throttle linkage then you have the correct one. The NPD sells the 69 type dashpot which will work but it should look like the one Royce posted.
I thought the '68 GT350/500 with Holley's shared the same dash pot?
https://www.saacforum.com/index.php?topic=15634.msg127819#msg127819
My findings also agree with Royce on the Autolite dashpot. They are clearly not the same as the Holley version. Holley has the plunger shaft going through the threaded portion. Autolite has it opposite of the threads.
Trying to add photos. Upload Folder is full?
Try spraying a small amount of silicon lubricant on the plunger and see if it frees it up and it starts working again correctly.
Roy
Quote from: Bob Gaines on February 22, 2022, 06:22:32 PM
The 68 Holley dashpot bracket is different then the 69 version.
Do you have a side by side comparison Bob of the brackets? My pic was to show Corey the Dash pot and placement for a Holley. That Holley on my 70 is a U service replacement and bolted on at a show to replace a problematic 67 390 Holley carb and I haven't taken it back off yet years later because it runs too good. My 4300 is shelved and has been for a while.
Bob, my friend is contemplating putting a Holley on his engine(currently had AL intake and 4100) and wants to make sure it has the correct dashpot bracket. Gary
I sure wish I could post a picture of my setup. It agrees with others that have sent me pictures for a 68 GT350 Holley setup. But it is very different from the pictures shown of the dashpots mounted to the Holley carb specifically reply #20.
BTW I have lubricated my dashpot with no luck. It slides in and out full travel pretty smoothly but clearly takes more force than my return spring provides.
Corey
(https://www.saac.com/forum/gallery/483-230222081540.jpeg)
https://www.saac.com/forum/gallery/483-230222081540.jpeg
With a little experimentation I was able to post a picture. Not easy but at least it worked.
Corey
Quote from: Corey Bowcutt on February 23, 2022, 08:12:51 AM
I sure wish I could post a picture of my setup. It agrees with others that have sent me pictures for a 68 GT350 Holley setup. But it is very different from the pictures shown of the dashpots mounted to the Holley carb specifically reply #20.
BTW I have lubricated my dashpot with no luck. It slides in and out full travel pretty smoothly but clearly takes more force than my return spring provides.
Corey
Being that is an original spring Corey, perhaps finding a new (stiffer) one and finishing it so that it at least "looks the part" might be an option.
Terry
https://www.ebay.com/itm/255057297047
https://autopartsobsolete.com/1967-68-69-70-ford-mustang-cougar-carburetor-dashpot-c80z-9b549-a-NOS.html
Roy
Looks like your application uses a C8 Autolite dash pot with the 600 CFM Holley carb.
The one in post #20 is the Holley dash pot you can buy right now from Holley. Not correct for your application.
The return spring and bracket should look like this if they are properly installed.
(https://www.supermotors.net/getfile/400855/original/2005throttl.jpg)
Quote from: Royce Peterson on February 23, 2022, 09:53:34 AM
Looks like your application uses a C8 Autolite dash pot with the 600 CFM Holley carb.
The one in post #20 is the Holley dash pot you can buy right now from Holley. Not correct for your application.
The return spring and bracket should look like this if they are properly installed.
(https://www.supermotors.net/getfile/400855/original/2005throttl.jpg)
Reading your post Royce "not right for your application" is that a ref to your pic(Holley)or his(autolite)? Is the throttle return spring available anywhere? Royce, is that return spring bracket at the base supposed to be "curved" up like that?
Corey's photo shows a Holley carburetor with an Autolite dash pot. The return spring bracket is available from Mansfield Mustang. Not sure which return spring Corey needs - it may be Shelby specific.
The 302 return springs are reproduced, however they are not correct. The GT 350 spring is not unique.
I am not sure which dashpot would be correct.
Quote from: Royce Peterson on February 23, 2022, 10:15:34 AM
Corey's photo shows a Holley carburetor with an Autolite dash pot. The return spring bracket is available from Mansfield Mustang. Not sure which return spring Corey needs - it may be Shelby specific.
My friend's car has the original spring return bracket. It was bent like a rounded open "C". I straightened it out with some pliers Charles mentioned that worked great but that pic in Royce's post shows the bottom part of the bracket being curved. Should it be straight like the pic below that was sent to me by another member a few months ago? Thanks.
(http://www.saacforum.com/gallery/152-230222104600.jpeg)
The return spring and return spring bracket on Corey's car are both original and correct for his application. The items were removed from an unmolested 1968 J-Code 302.
Terry
By the way that sketch is from me.
Corey
Quote from: Corey Bowcutt on February 23, 2022, 12:14:54 PM
By the way that sketch is from me.
Corey
Yes, and thanks again. I actually printed up the pic and bent it to the pic. It is done now. I saw the pic of the one above mounted with the spring and the base is bent/curved. I see your pic(huge on my screen) shows the spring with the clip(had to scroll over to see. Nice shot. I saved that pic
The one in my picture is bent - don't recall how that happened but it should be similar to the drawing.
Quote from: Royce Peterson on February 22, 2022, 06:29:53 PM
This is a typical Autolite dash pot and bracket. I don't think any new ones are available.
(https://www.supermotors.net/getfile/1168789/original/autolite-dash-pot-a.jpg)
(https://www.supermotors.net/getfile/1168790/original/autolite-dash-pot-b.jpg)
That is an amazing photo. I have no words to express.
QSS
Found this pic on my IPhone downloading pics.
(http://www.saacforum.com/gallery/152-020322180259.jpeg)