Starting Carb Conversion: Flat Tops to Paltechs

[Dadsun 17]

I'm in Louisiana. I would think if I were in Canada the coolant (heating) lines going through the manifold would be more important.  This other topic has several folks voting to keep the lines flowing, however, due to keeping temps from getting too uneven in spots.

 

[siteunseen 3,420 5 Vehicles]

23 hours ago, Patcon said:

Maybe somebody else will confirm. I wouldn't think twice about deleting manifold heating

I can't tell if your pro or con on this. Doesn't matter but being a southerner that phrase could go either way.

 

Edited December 13, 2020 by siteunseen

[Dadsun 17]

I bought this replacement gasket from Z Car Depot. Is it recommended to use a gasket sealant on this?

[DatsunZGuy 127]

2 hours ago, Dadsun said:

I bought this replacement gasket from Z Car Depot. Is it recommended to use a gasket sealant on this?

I recently installed a new manifold gasket and did not use sealant.  No issues experienced here.

 

[7tooZ 187 1 Vehicles]

45 minutes ago, DatsunZGuy said:

 

I agree

[Dadsun 17]

Getting very close to the finish line. 

I sometimes, on projects like these, wake up and think about things I've forgotten... Like whether the throttle linkage arm is the same length on both flat tops and round tops setups. Alas, they are not. :-(. Looks like my flat tops arm is an inch or two short for this project.

My options seem to be to (a) make an extension, or (b) keep looking for one. 

 

In the meantime, here are some pics....

 

Edited January 3 by Dadsun

[Captain Obvious 2,364]

Right. When you switch to the 240 style balance tube, you'll find that your old shepherds hook is too short.

Not the most beautiful thing in the world, but you can cut your original in the middle-ish and weld on a piece of tubing to take up the gap. Here's one from a 74 260 as an example. I believe they changed the pivot mechanism that mounts to the firewall and the shepherds hook design between 73 and 74, so yours won't look like this. But the concept is the same:

Extendo mod used on a 74 that switched to a 240 balance tube:

And here's a pic after the welding is done and cleaned up a little and installed. Note the newer design throttle linkage pivot on the firewall. Seen on the right side of this pic:

So I don't know if the newer design pivot will bolt right up to your firewall, but if it does, you could switch to that and a longer shepherds hook from a 280 or ZX.

[Dadsun 17]

Hmmm. Thanks. I was just assuming the way to go for a non-welder like myself would be to affix an extension of the eyes that receive the shepherds hook. 

[Captain Obvious 2,364]

Many different ways to lengthen the linkage, so whatever works easiest for you.

If you take a good pic of the piece that mounts to the firewall, I'll snap one of the later version. If it looks like the new one will swap over as a bolt-up, I've got one here and a longer shepherds hook that I could part with. You could just bolt that in and go. I'll snap a pic of that if I get a chance and you're interested.

[Dadsun 17]

Yes, interested. Thanks. Here are a couple of pics. It looks to me like the shaft is about 2" to 2.25" short on the new setup.

[Dadsun 17]

Actually, the old flat top setup's receiving rod adds back the two inches. So, I'll insert that and should be stable enough to do the job. See pic:

 

[Captain Obvious 2,364]

That old flat-top part should get you out of the woods for now. It really wants a bearing support closer to the end, but I think it should be OK for now.

So here's what I have. Question is... Will the pivoting mechanism mount to your firewall? Are the mounting holes in the same location(s)?

 

[Dadsun 17]

Wow,.that's nice. And yes, I'm wondering about the support on the carb side with that longer arm. Here is a picture of the underside. Looks like the middle hole is flipped, but the two outer holes line up. 

[Captain Obvious 2,364]

If I get a chance, I'll take another pic today with a tape measure up against the bolt holes so you can see if it's the same as what you currently have.

[Dadsun 17]

Center to center distance on those two mount holes is 1 9/16". 

[Captain Obvious 2,364]

It looks like the newer design will bolt up. I'm kinda surprised.

Here's a pic of the dimensions on what I have:

Send me a PM and we'll see if we can reach an agreeable agreement.   

[Dadsun 17]

Well, the carbs are on, no leaks, and it starts every time. Progress!

Now I need to tune them. I have a Uni-Syn tool that came with the car. I'm getting no air draw on the front carb, just the back. Is that normal?

I have a service manual and saw some old threads here on tuning/balancing, but if y'all have a go-to reference please pass along. 

[siteunseen 3,420 5 Vehicles]

Edit: That looks damn good!

That front one has a nipple on the backside for distributor vacuum advance. Is it open?

Here's what I used to begin a basic tune. Thank you! @240260280

 

 

Edited Wednesday at 11:22 PM by siteunseen

[Dadsun 17]

I have a line from that nipple to the distributor, so I think that's the correct setup. See pic.