Starting Carb Conversion: Flat Tops to Paltechs

[SteveJ]

To go with @Racer X's comments, hardware kits: https://www.thezstore.com/page/TZS/CTGY/classic19o

And header gaskets: https://www.thezstore.com/page/TZS/CTGY/classic19a

Edited January 25, 2021 by SteveJ

[Racer X]

I forgot to mention, check the header and manifold mating surfaces for flatness. Using a straightedge with a ground flat edge check that all surfaces are flat, and square. Anything more than .002” or .003” off will be difficult to get sealed and kept tight.

[dutchzcarguy]

10 hours ago, Racer X said:

Get good hardware and a better quality header and you should be able to get the leaks fixed.

Totally agree, But.. would it be possible to weld some extra on that exhaust header and (let it) shave flat?  So that the "ring" becomes a bit wider for a better fit.

He could do that?

(I'm also interested because in the near furure i have to take a head apart.. 😉  ) 

[Racer X]

3 hours ago, dutchzcarguy said:

Totally agree, But.. would it be possible to weld some extra on that exhaust header and (let it) shave flat?  So that the "ring" becomes a bit wider for a better fit.

He could do that?

(I'm also interested because in the near furure i have to take a head apart.. 😉  ) 

Sure, a competent fabricator might be able to modify it.

But.

It would be more work and expense than simply getting a header with flanges of the proper thickness. After welding then the header would need to be set up in a jig, and the flanges cut and ground true and straight.

[Dadsun]

I'm going to disagree, even from my novice position here, that a new header is required.  This header is original and has worked with no leaks, I'm assuming, for years.  The only things that changed since I bought it were:

1. I removed it and got it ceramic coated at Jet-Hot.  If anything, this smoothed the mounting surfaces that meet up with the head.

2. Someone noted the pitted holes in one of the header pipes. I took that pic to send to a welder friend. Had him braze weld the holes.

3. He went a little overboard around those holes and messed up the pre-made mount point for the washers that clamp down on exhaust manifold at the same time it clamps down on the intake maniful.  Note: Those thick flange side plates are made to be the same thickness as the intake manifold flange -- meaning that where you saw one of the nut/washers clamping down it was a mismatch because of the weld work. (I.e., the OEM flanges of the exhaust manifold weren't designed to be same thickness of the intake manifold flanges.)  Instead of taking off the header at that point and grinding it down to the appropriate, I used a smaller washer and tried to make due.  Obviously, that needs fixing. Here is the spot I'm talking about:

And here is what a normal one looks like:

4. I did not try to tighten the bolts/studs a ton because I did not want to break off a stud -- which I'd just done when removing the thermostat housing.  This is also why I'd opted not to replace the whole set of studs/washers/bolts with a kit from MSA.  I did not want to deal with another drill-out into the head.  But, alas, I may have to take that chance.

For now I'm going to take off the intake manifold, take off exhaust manifold and grind down that spot to receive the washer, triple check that I've got the new manifold gasket facing the right way, and try to tighten down.  In the meantime, I'll look into the h/w kit.  

[Racer X]

49 minutes ago, Dadsun said:

 

4. I did not try to tighten the bolts/studs a ton because I did not want to break off a stud -- which I'd just done when removing the thermostat housing.  This is also why I'd opted not to replace the whole set of studs/washers/bolts with a kit from MSA.  I did not want to deal with another drill-out into the head.  But, alas, I may have to take that chance.

 

 

 

49 minutes ago, Dadsun said:

For now I'm going to take off the intake manifold, take off exhaust manifold and grind down that spot to receive the washer, triple check that I've got the new manifold gasket facing the right way, and try to tighten down.  In the meantime, I'll look into the h/w kit.  

Sounds like a good plan. Be sure and check the flanges for straightness, and check the head surface too.

I highly recommend the hardware pictured earlier. At the time I put it together the cost wasn't anymore than he kit from MSA, the quality is better, and I got it all locally. The hardware has been used on two cylinder heads, on four engines in my race car with no leaks.

Use PB Blaster and some heat from a propane torch, the studs should come out without drama. It also helps to set a brass drift punch on the end of the studs and give a sharp rap with a 3lb drill hammer to break the corrosion on the threads.

Don't forget the high temp antisieze on asembly.

[Dadsun]

4 minutes ago, Racer X said:

I highly recommend the hardware pictured earlier.

I just went ahead and ordered it from MSA. Those big thick washers are going to be important, I think.

4 minutes ago, Racer X said:

Use PB Blaster and some heat from a propane torch, the studs should come out without drama. It also helps to set a brass drift punch on the end of the studs and give a sharp rap with a 3lb drill hammer to break the corrosion on the threads.

Don't forget the high temp antisieze on asembly.

Sounds good.  Yes, I've been putting the anti-seize stuff on liberally after dealing with two broken off bolts, both involved with the thermostat housing. 

[siteunseen]

Both of mine have MSAs ceramic coated 6to1 headers. I love the fit and finish plus the sound is music to my ears. They have their flange thickness down pat. too. I bought Nissan manifold studs and out of round clamp nuts.

I'd read a lot of bad fitment issues with all the others. Rebello sales pacesetters but then I read they rusted out too quick.

You'll be happy. But going along with the "while I'm at it" mantra you should get the 2.5" performance exhaust. Beautiful sound.

 

Edited January 25, 2021 by siteunseen

[Dadsun]

1 hour ago, siteunseen said:

But going along with the "while I'm at it" mantra you should get the 2.5" performance exhaust. Beautiful sound

I'll put that on my longer range to do list, along with finding a 5-speed transmission. 🙂

[siteunseen]

A+ plan! Those two are the best money spent.

Edited January 26, 2021 by siteunseen

[w3wilkes]

Just one comment on the header gasket and not sure it applies in your case. The MSA headers come with a gasket that MSA says should be used rather than the OEM gasket. Here's the gasket for headers.

Motorsport! Performance Header Gasket, 70-74 240Z-260Z - The Z Store! Nissan-Datsun 240Z 260Z 280Z 280ZX 300ZX ( Z31 Z32 ) 350Z 370Z Parts

[siteunseen]

36 minutes ago, w3wilkes said:

Just one comment on the header gasket and not sure it applies in your case. The MSA headers come with a gasket that MSA says should be used rather than the OEM gasket. Here's the gasket for headers.

Motorsport! Performance Header Gasket, 70-74 240Z-260Z - The Z Store! Nissan-Datsun 240Z 260Z 280Z 280ZX 300ZX ( Z31 Z32 ) 350Z 370Z Parts

They also say use their stud kit. I can't find a sarcasm font.