Builds Helga: 1966 FJ40 FST

[tucker74]

For as simple as they seem, carbs are just black-magic to get right. I did the same on my ‘73 Pig, ended up mailing it to @65swb45 after I mucked it all up … and it turned out I was missing parts! He got it sorted out, but I’ve never done more than simple adjustments to any carb since. You’ll love the Sniper, I’d throw the SD40 on the shelf … that truck is original enough you might want it some day

 

[KennyBob]

You aren’t wrong. I’ve definitely thought about keeping it for that reason. Although the chunk of money those sell for is very tempting…

 

[locklaw]

You aren’t wrong. I’ve definitely thought about keeping it for that reason. Although the chunk of money those sell for is very tempting…

What is so troublesome on your carb? Why mess up hard to find parts?

I rebuilt my 64's SD40 last week (only found the metering rod spring fiddly and the throttle connector link clip fiddly) with great results. Found it actually had a piece of the metering rod was missing, yet it still idled beautifully just very rich and flooded, hence had starts after sitting for a few days.

For a fraction of the cost send the carb to a good rebuilder and be done with it. It worked for almost 60 years, no reason it cannot continue to do so.

 

[KennyBob]

What is so troublesome on your carb? Why mess up hard to find parts?

I rebuilt my 64's SD40 last week (only found the metering rod spring fiddly and the throttle connector link clip fiddly) with great results. Found it actually had a piece of the metering rod was missing, yet it still idled beautifully just very rich and flooded, hence had starts after sitting for a few days.

For a fraction of the cost send the carb to a good rebuilder and be done with it. It worked for almost 60 years, no reason it cannot continue to do so.

That’s a fair question. I’ve rebuilt it three times myself already and it still won’t run right off of idle or idle without the choke partially closed. I reached out to Mark at one point and the price he quoted was about half the cost of a sniper. I figured the benefits of fuel injection made up for the extra cost.

I’d be willing to give it another go to see if I can get it. I’m just not sure what else to do. I’ve been thinking of putting the stuff I took out back in but I’m not sure it would make a difference.

 

[locklaw]

That’s a fair question. I’ve rebuilt it three times myself already and it still won’t run right off of idle or idle without the choke partially closed. I reached out to Mark at one point and the price he quoted was about half the cost of a sniper. I figured the benefits of fuel injection made up for the extra cost.

I’d be willing to give it another go to see if I can get it. I’m just not sure what else to do. I’ve been thinking of putting the stuff I took out back in but I’m not sure it would make a difference.

Ok, did not think a rebuild would be so spendy stateside. Well, barring vacuum leaks and the like, here are the basic elements related to idling and off idle per the FSM -

As such, your likely culprit is a plugged idle circuit, low speed jet or metering rod adjustment. This is the latter's spec and the like per the FSM -

 

[locklaw]

More -

 

[KennyBob]

It appears that my metering rod is non-adjustable.

 

[locklaw]

It appears that my metering rod is non-adjustable.

View attachment 3032401

Ok, but I would not sweat the installed height of the metering rod too much since you can play with the position also with the u shaped clip that goes into the rod and throttle plate.

If you need choke at idle, you have a lean situation it seems so what you must do is get more fuel to it. A metering rod would more likely enrichen the mix).

There are only 8 components at play. From earlier posts I see you used all the new Keyster bits. I have seen from 3 kits now that they tend to have smaller spec than original, which may be the cause (unless the bypasses are partially plugged).

Swop out the low speed jet (#4) for the older one which is likely larger (it's easily accessible) and see if this does not help.

If not, swop out the metering rod and jet for the old ones. You are just about there.

Obviously ensure the idle screw is at least 2 turns out for baseline

 

[locklaw]

It appears that my metering rod is non-adjustable.

View attachment 3032401

Ok, but I would not sweat the installed height of the metering rod too much since you can play with the position also with the u shaped clip that goes into the rod and throttle plate.

If you need choke at idle, you have a lean situation it seems so what you must do is get more fuel to it. A metering rod would more likely enrichen the mix).

There are only 8 components at play. From earlier posts I see you used all the new Keyster bits. I have seen from 3 kits now that they tend to have smaller spec than original, which may be the cause (unless the bypasses are partially plugged).

Swop out the low speed jet (#4) for the older one which is likely larger (it's easily accessible) and see if this does not help.

If not, swop out the metering rod and jet for the old ones. You are just about there.

Obviously ensure the idle screw is at least 2 turns out for baseline

 

[KennyBob]

Ok, but I would not sweat the installed height of the metering rod too much since you can play with the position also with the u shaped clip that goes into the rod and throttle plate.

If you need choke at idle, you have a lean situation it seems so what you must do is get more fuel to it. A metering rod would more likely enrichen the mix).

There are only 8 components at play. From earlier posts I see you used all the new Keyster bits. I have seen from 3 kits now that they tend to have smaller spec than original, which may be the cause (unless the bypasses are partially plugged).

Swop out the low speed jet (#4) for the older one which is likely larger (it's easily accessible) and see if this does not help.

If not, swop out the metering rod and jet for the old ones. You are just about there.

Obviously ensure the idle screw is at least 2 turns out for baseline

Thanks for the advice! I had just swapped the metering rod in that picture actually. It seemed to be a bit better. Still bogging and backfiring just off of idle though. I’ll give the low speed jet a try next. Thanks again.

 

[locklaw]

Thanks for the advice! I had just swapped the metering rod in that picture actually. It seemed to be a bit better. Still bogging and backfiring just off of idle though. I’ll give the low speed jet a try next. Thanks again.

Happy to help! Please let me know if the slow jet works. Also, check and check again for vacuum leaks to cure bogging if it's not related to fuel starvation from the jet.

Backfire is generall timing/valve lash/vacuum advance related. Is your advance mechanism working correctly?

The advantage of going through all this is that you will know your carb afterwards and likely have gone through less issues than you would face with EFI. Just look at the issues prominent and seasoned posters are going through with EFI conversions on multiple threads (wngrog purely as an example)

 

[KennyBob]

Happy to help! Please let me know if the slow jet works. Also, check and check again for vacuum leaks to cure bogging if it's not related to fuel starvation from the jet.

Backfire is generall timing/valve lash/vacuum advance related. Is your advance mechanism working correctly?

The advantage of going through all this is that you will know your carb afterwards and likely have gone through less issues than you would face with EFI. Just look at the issues prominent and seasoned posters are going through with EFI conversions on multiple threads (wngrog purely as an example)

To be honest, I’m not 100% sure the advance is working. I know I’m getting vacuum to it, but I’ll have to see if it’s doing anything on the dizzy side. If memory serves, the timing mark should move with throttle if it’s working correctly? And valve lash should be set after it’s warm?

 

[locklaw]

To be honest, I’m not 100% sure the advance is working. I know I’m getting vacuum to it, but I’ll have to see if it’s doing anything on the dizzy side. If memory serves, the timing mark should move with throttle if it’s working correctly? And valve lash should be set after it’s warm?

Put a 3mm ID hose on the diaphragm and with the cap off, suck on it. You should clearly see movement. Setting lash warm is best but rather err on the side of too loose than too tight.

 

[KennyBob]

Verified the vacuum advance is working and I swapped the slow jet back to what was in there. Looks like a gnats ass of difference between the two if anything. Still idled pretty rough until it got warmer. Still bogs and stumbles with throttle. Had to leave the choke partially closed for it to stay running. Didn’t have time to adjust the valve lash unfortunately.

 

[77mustard40]

Kenny have you confirmed you don't have a vacuum leak?

 

[KennyBob]

Kenny have you confirmed you don't have a vacuum leak?

I think as best as I can but maybe I’m missing something. I’ve sprayed carb cleaner/starting fluid all over that thing and I can’t find anything. Up for suggestions on specific places to check though of course.

 

[77mustard40]

I can lend you a vacuum gauge if you dont have one so you can get a reading at idle. I live the 2F world so I may not be the best source of info on your machine, but it really has helped me in the past in tuning my carb and setting optimal timing.

 

[locklaw]

I think as best as I can but maybe I’m missing something. I’ve sprayed carb cleaner/starting fluid all over that thing and I can’t find anything. Up for suggestions on specific places to check though of course.

Bummer, but don't give up. Have you eliminated the carb isolator base vacuum line and FD hose as potential vacuum leaks? In post 217 I believe the hoses look very much old and potentially brittle

 

[KennyBob]

I can lend you a vacuum gauge if you dont have one so you can get a reading at idle. I live the 2F world so I may not be the best source of info on your machine, but it really has helped me in the past in tuning my carb and setting optimal timing.

Thanks Kelly. I’ve got one and used it recently to check the vacuum to the distributor. It was steady and increased with throttle. I don’t remember what it was reading though.

Bummer, but don't give up. Have you eliminated the carb isolator base vacuum line and FD hose as potential vacuum leaks? In post 217 I believe the hoses look very much old and potentially brittle

I have sprayed all around the insulator plate as well as focusing on the joint of the connection to the pcv. I hadn’t even thought about the FD hose… it’s connected straight to the manifold right? Do you happen to know what size those tubes are offhand?

 

[middlecalf]

It was steady and increased with throttle. I don’t remember what it was reading though.

It should actually drop when you first throttle up, then when holding throttle the vacuum will return. Did this occur?