Topic: 68 S code dashpot?

[WT8095]

I think I know the answer to this, but it would help if the experts could confirm or deny. It looks like for 1968, the S code 390 Holley 4150 C8OF-D (A/T) carburetor did NOT have a dashpot. I have not seen one on the few cars I have witnessed firsthand, and the carbs I've acquired as well as numerous online photos have not shown signs of a dashpot either. The May '75 MPC does not include a dashpot or mounting hardware for this application, which is about the best I can find for documentation.

I've seen a good number of dashpots for sale that include "1968 390" or "390GT" in their descriptions, but I believe they are simply casting as wide a net as possible to try to sell their item.

[J_Speegle]

Can't figure out the 68 MPC - Carb section is a puzzle

Have you checked the assembly manuals for additional clues?

Other 68 FE applications use a dash pot - Shelby's  as well as 69's

Only picture I could find with an air cleaner off is below - it has one.

8T02S1187xx - Non AC car



Hope this helps a little

[WT8095]

My initial post was partly incorrect, it appears that the MPC does list a dashpot after all. But no mounting hardware!

The carb section of the MPC can be a bit tricky, but it makes sense once you get used to it. First you look up a carb in the list at the begining of section 95 (first image). For each carb there is an associated code. For a C8OF-D carb, the code is 20J. That means, got to section 95.20 (Holley 4V carbs). Within that section (second image), look for parts in column "J". There is a dashpot listed in column J in this case (which I missed previously - oops!!  ), but none of the mounting hardware is called out in column J. Does that mean it's considered part of the carb and not serviced? Guess I'll need to do more research.

In the meantime, thank you for the photo. That poor engine sure looks rough - hopefully someone can give it a new home! Do you know if it was an A/T car? It looks like there might be a transmission vacuum line at the far left (in the photo) corner of the carb.

I haven't seen anything in the assembly manuals yet, but I'll go through them again. I'm including the '69 engine manual, since there isn't one for '68 and '69 seems to be very similar for the 390GT. Service manual has general references to dashpot but doesn't outright state if one was used on the Holleys. Plus the books sometimes are out of sync with what actually came off the line, as everyone here knows.

[J_Speegle]

The carb section of the MPC can be a bit tricky, but it makes sense once you get used to it. First you look up a carb in the list at the beginning of section 95 (first image). For each carb there is an associated code. For a C8OF-D carb, the code is 20J. That means, got to section 95.20 (Holley 4V carbs). Within that section (second image), look for parts in column "J". There is a dashpot listed in column J in this case (which I missed previously - oops!!  ), but none of the mounting hardware is called out in column J. Does that mean it's considered part of the carb and not serviced? Guess I'll need to do more research.

The 68 MPC is laid out very different from the 75 version.
Dash pot brackets and mounting machine screw are mentioned - its figuring the application that's a pain. The 390 engine is also covered under three different carburetor sections to cover the X as well as the Holley and non-Holley applications.

In the meantime, thank you for the photo.............. Do you know if it was an A/T car? ...........

4 speed.

I haven't seen anything in the assembly manuals yet, but I'll go through them again. I'm including the '69 engine manual, since there isn't one for '68 and '69 seems to be very similar for the 390GT. ..........

Unfortunately the 69 didn't use a Holley, no thermactor, the engine internals were slightly different also I believe as well as other details 

Don't think I would use the 69 as any sort of guide or for help. Think the 68 CJ might be a better guide and help in a pinch

[preaction]

Was 68 the first use for a dash pot on a mustang ?

[J_Speegle]

Was 68 the first use for a dash pot on a mustang ?

Either 65 or 66 was

[WT8095]

The 68 MPC is laid out very different from the 75 version.
Dash pot brackets and mounting machine screw are mentioned - its figuring the application that's a pain. The 390 engine is also covered under three different carburetor sections to cover the X as well as the Holley and non-Holley applications.

Could you post the relevant pages from the '68 MPC? I've been trying to find a '68 MPC in any format, but no luck. If anyone knows where I can get ahold of one, please let me know!

Unfortunately the 69 didn't use a Holley, no thermactor, the engine internals were slightly different also I believe as well as other details

Don't think I would use the 69 as any sort of guide or for help. Think the 68 CJ might be a better guide and help in a pinch

The '69 engine AM has some helpful information regarding brackets and fasteners for the alternator and smog pump setup. In particular the page for 428 smog system. What I've been able to find from other sources matches pretty well, pulleys etc. Fasteners don't seem to be documented very well for the 390s. A lot of the CJ stuff matches, but not all of it. I'm going through all the books and photos I can find, and I'm working with Jim C. to corroborate my findings on the fasteners. Plus I'm going to run everything past the forum users for confirmation as to what's been seen "in the field" (unless it's already been covered in other threads).

[WT8095]

I've been doing a bit of digging, a bit of consulting, and a bit of shopping  and I believe I have a decent handle on the dashpot for S-code motors for '68.

The May '75 MPC lists three possible dashpots for carbs in the "20" group (shown in earlier post):

• C1AZ-A
• C8OZ-A
• C8OZ-B

My specific application, 1968 S code, uses column "J", but column J is blank for which dashpot to use.

The three dashpots look like this:

C1AZ-A


C8OZ-A


C8OZ-B (could not find a photo with a marked package for confirmation)



Searching online revealed a small number of photos of carbs with dashpots in place:








If I have correctly kept track of my sources, that last photo is from Tim Lea. In email conversations, Tim indicated that he has removed this style of dashpot from multiple S-code carburetors. Note that of the three examples, only the second one has the bellows around the piston rod. I believe all three are the same dashpot, but the bellows has disintegrated and is no longer present on two of them. The photo Jeff posted looks like it MIGHT have the same dashpot with the white plastic front, but it's very hard to say for sure.

Based on what I have found so far, it appears to me that the C8OF-A dashpot is correct for this application. I will follow up in a separate reply with my findings on the bracket and the locknut. As always, i present this as a hypothesis based on my limited amount of data. I do not claim this is conclusive.