Topic: C8OF-9510-C 390 carb wrong date?

[Benstang]

Hello!

What can be the reason that a 68 390 gt 4 speed carb has got a date code from 1969??:

C8OF-9510-c
List-3795-1
9A4

[Bob Gaines]

Hello!

What can be the reason that a 68 390 gt 4 speed carb has got a date code from 1969??:

C8OF-9510-c
List-3795-1
9A4

It may be service replacement is one reason there may be others.

[Benstang]

Ok thanks for the answer.

So It can be a legit 390 gt 68 manual carb.. but I will never be date correct

[J_Speegle]

Ok thanks for the answer.

So It can be a legit 390 gt 68 manual carb.. but I will never be date correct

May not apply in this specific case but service replacements (any of them) car be different from the originals. Could be plating, parts shaped differently, different hardware used and so on. Just wanted to remind others of this possibility and to compare and check for the details

[Bob Gaines]

Ok thanks for the answer.

So It can be a legit 390 gt 68 manual carb.. but I will never be date correct

The only reason to be concerned about a date code is if you are concerned about originality. With that said the most important thing is that it is the correct carb for the car with correct components. The date code is not considered in concours Trailered Competition and is only a issue in Thoroughbred where the battery ,belts ,tires etc. have to be date code correct too. Nice to have for your own satisfaction however it is secondary to most things as it relates to the cars. For example if you have a car that has been messed with over the years like most have been and many things are not assemblyline correct like non assemblyline workmanship details ,no orange peel slick paint job , replacement tires ,battery, exhaust  etc. then the date code on one item wether it is assemblyline correct or not doesn't mean much in the big picture of the cars originality.

[Benstang]

Is it normal that the old holleys had some kind of ball blocking the idle passage or did someone mess with my carb there?

Looks like on one side it is 100% sealed.



Ben

[J_Speegle]

Is it normal that the old holleys had some kind of ball blocking the idle passage or did someone mess with my carb there?

Looks like on one side it is 100% sealed.

Not something I ever recall seeing. Don't have a similar carb handy at the moment

[Benstang]

Hmmm seems like someone messed with it..

But I don?t get why you want to restrict or even fully close the idle circuit.

Makes no sense for me.

Ben

[Benstang]

These are some sort of idle mix screws...

I have never seen them before.

Does anyone know how to adjust them?

I had problems with my idle mix screws don?t respond proper.

I assume these?base plate idle screws? had been to far in.


Ben

[ruppstang]

Our early 68 S code carb has those screws and I could not get it to run correctly so I sent it to a friend in Seattle who is pretty good with carbs and he said the early 68 carbs had those extra mixture screws and that most that
have them run poorly. He said that they are really difficult to get out. When I got my carb back it ran great. 

[Benstang]

My first thought would be to let the screws out complete and just plug the hole and adjust the idle only with the normal metering block idle screws.

[PacificaXR7GT]

I also had this problem with my 68 S code manual carb. I sent it to Rob Campbell and it came back running like a champ.

[Benstang]

Long story short answer:

I did open the screws about 4 rotations and closed the hole from outside so that there is no vacuum leak and almost no restriction.

Runs like a champ now..

700 rpm idle 16,5 hg  air fuel ratio around 11  (68 390 gt 4speed)

Carb pulls very strong. Deacceleration popping is gone!

 Thanks guys for your help!