Wanted: L20B Square port Exhaust Manifold.

[Dawgz83948]

I need a L20B exhaust manifold that will work for this head:

 

 

 

It needs to fit a 74 620. I've already spent WAY too much oney on this truck, so I'm kind of begging for a good deal if possible. Whatever collector pipes are needed would be great too, I don't care if it's 4-2-1 or 4-1, as long as it fits on the 620. I have a large exhaust leak on the current manifold but I'm pretty sure it's because I have a round port header. (which is what I think I currently have)

[datzenmike]

There is no square port L20B manifold that will give you what you want, but an earlier L16/18 will work nicely and are basically a cast iron header.

 

 

It's smog free, four into two with the down pipe having the two into one and back to the muffler. The L20B square port exhaust manifolds have to be bolted to the intake and use a heat riser valve to use hot exhaust to warm the intake instead of water from the head. Here one I got off a '75 L20B. You can see where they bolt together.

 

This little plate is sandwiched between them so both have a huge hole in them. That's the holes for the carb looking up from under.

 

 

 

 

Yours must be a U-67 head.

[Dawgz83948]

There is no square port L20B manifold that will give you what you want, but an earlier L16/18 will work nicely and are basically a cast iron header.

 

 

It's smog free, four into two with the down pipe having the two into one and back to the muffler. The L20B square port exhaust manifolds have to be bolted to the intake and use a heat riser valve to use hot exhaust to warm the intake instead of water from the head. Here one I got off a '75 L20B. You can see where they bolt together.

 

This little plate is sandwiched between them so both have a huge hole in them. That's the holes for the carb looking up from under.

 

 

 

 

Yours must be a U-67 head.

 

Thanks for the response.

 

I have a non smog intake so I'm guessing a L20B manifold will not work correctly. If anyone has a manifold for sale (or free) that I could use I'd appreciate it.

[banzai510(hainz)]

Key is the Y pipe also as you have a truck and needs to clear the torsion bar

Mklotz sells flanges for the old style manifolds so to make a new y pipe

 

 

PS !!!!!!!

Whats the deal with the hose going from crankcase to the valvecover??? You want to destroy this motor????

[Dawgz83948]

Key is the Y pipe also as you have a truck and needs to clear the torsion bar

Mklotz sells flanges for the old style manifolds so to make a new y pipe

 

 

PS !!!!!!!

Whats the deal with the hose going from crankcase to the valvecover??? You want to destroy this motor????

 

That was just for the install since I cant get to the PCV valve after the manifold was bolted to it. The hose goes from the pcv hole to the pcv valve in the intake and a hose goes from the valve cover tot he air cleaner. I'm pretty sure that's how it's supposed to go.

[Chris#51EPGraham]

That was just for the install since I cant get to the PCV valve after the manifold was bolted to it. The hose goes from the pcv hole to the pcv valve in the intake and a hose goes from the valve cover tot he air cleaner. I'm pretty sure that's how it's supposed to go.

 

Yeah, at least vent the crankcase into a vented catch tank. Venting it into itself will probably

blow crankshaft seals or other gaskets. That setup will pressurize the crankcase.

 

If the original PCV valve design/location is a problem, you can probably use one from a different

vehicle app.

[Dawgz83948]

Yeah, at least vent the crankcase into a vented catch tank. Venting it into itself will probably

blow crankshaft seals or other gaskets. That setup will pressurize the crankcase.

 

If the original PCV valve design/location is a problem, you can probably use one from a different

vehicle app.

 

 

I used a Chevy grommet (trimmed a bit) and a chevy LT1 Inlet PCV opening. Used those on the block routed it into the PCV Valve on the intake. Connected a tube from the upper pcv nipple (inlet) to the Air cleaner. That "should" be the stock routing.

[Datsun Parts]

I sell new headers for those....