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L20b exhaust and intake manifold


Nate.a.v

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Hi everybody I have a question that I'm having a hard time finding the answer for. Sorry if its answered already. So I just recently picked a up l20b from a 1976 610 wagon and I'm in the process of removing both manifolds. My question is, is it ok to use a l16 exhaust manifold but keep the stock l20b intake manifold. I know that stock on 76 l20bs both manifolds are sandwiched together. The reason I want to take out the l20b exhaust manifold is because of all the smog stuff on it. So should I be looking for a new intake manifold or will I be ok with the one i have? This is going into my 72 510 wagon btw. Thanks for the help everyone! 

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7 hours ago, Nate.a.v said:

Hi everybody I have a question that I'm having a hard time finding the answer for. Sorry if its answered already. So I just recently picked a up l20b from a 1976 610 wagon and I'm in the process of removing both manifolds. My question is, is it ok to use a l16 exhaust manifold but keep the stock l20b intake manifold. I know that stock on 76 l20bs both manifolds are sandwiched together. The reason I want to take out the l20b exhaust manifold is because of all the smog stuff on it. So should I be looking for a new intake manifold or will I be ok with the one i have? This is going into my 72 510 wagon btw. Thanks for the help everyone! 

 

 

SN1MtW7.jpg

 

The '75-'77 L20B used a co-joined intake and exhaust manifold that are bolted together. Removing the exhaust will leave a big hole in the bottom of the intake. There is a plate sandwiched between them that could maybe be bolted on to seal but it's pretty thin. A steel plate could be made for it. Why not just unbolt the 4 air injection tubes and plug the holes? The EGR pipe can be removed and plugged also or cut leaving 2" and crush flat with vice grips and roll the end to seal.... emissions 'stuff' gone, no plate to make or any chance of a vacuum leak and no need for custom down pipe to fit the L16 exhaust manifold..

 

xVkEyEu.jpg

 

 

I have replaced the stock L20B exhaust manifold on my '76 710 with an L16. I replaced the intake with one from a '79 (a '78 will also work) that is not joined to the exhaust. An L16 intake will also work but the L20B has larger runners.

 

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53 minutes ago, datzenmike said:

 

 

SN1MtW7.jpg

 

The '75-'77 L20B used a co-joined intake and exhaust manifold that are bolted together. Removing the exhaust will leave a big hole in the bottom of the intake. There is a plate sandwiched between them that could maybe be bolted on to seal but it's pretty thin. A steel plate could be made for it. Why not just unbolt the 4 air injection tubes and plug the holes? The EGR pipe can be removed and plugged also or cut leaving 2" and crush flat with vice grips and roll the end to seal.... emissions 'stuff' gone, no plate to make or any chance of a vacuum leak and no need for custom down pipe to fit the L16 exhaust manifold..

 

xVkEyEu.jpg

 

 

I have replaced the stock L20B exhaust manifold on my '76 710 with an L16. I replaced the intake with one from a '79 (a '78 will also work) that is not joined to the exhaust. An L16 intake will also work but the L20B has larger runners.

 

Ok cool thanks mike, looks like I'll be in the market for a 78 or 79 l20b intake manifold.

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L16/18 will also work and might be all you can find.

 

The '75-'77 L20B with the U67 head used exhaust heat to warm the intake and speed up evaporation of gas. I think it a poor idea and while it has a mechanical coil that closes off the exhaust when warmed up, they almost always rust out and fail over time, baking the intake. All other engines before and after have two holes in the head that pipe coolant through the intake runners to do the same thing but they also draw away excessive heat in the summer that is radiated from the hot exhaust manifold. So it does two things. You don't have to but you could drill these holes out and connect the outlet pipe on the intake to the thermostat bypass hose. I did this on my '76 710. You're in California so warming not necessary.

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17 minutes ago, datzenmike said:

L16/18 will also work and might be all you can find.

 

The '75-'77 L20B with the U67 head used exhaust heat to warm the intake and speed up evaporation of gas. I think it a poor idea and while it has a mechanical coil that closes off the exhaust when warmed up, they almost always rust out and fail over time, baking the intake. All other engines before and after have two holes in the head that pipe coolant through the intake runners to do the same thing but they also draw away excessive heat in the summer that is radiated from the hot exhaust manifold. So it does two things. You don't have to but you could drill these holes out and connect the outlet pipe on the intake to the thermostat bypass hose. I did this on my '76 710. You're in California so warming not necessary.

I have l16 intake manifold with su's on it so if I  cant find a good 78 or 79 l20 manifold I'll use the l16 one.

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You could, but an SU setup has it's own pros and cons. SUs are totally different from a single  downdraft carb. From a performance standpoint I think the SUs have more potential.

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4 hours ago, datzenmike said:

 

 

SN1MtW7.jpg

 

The '75-'77 L20B used a co-joined intake and exhaust manifold that are bolted together. Removing the exhaust will leave a big hole in the bottom of the intake. There is a plate sandwiched between them that could maybe be bolted on to seal but it's pretty thin. A steel plate could be made for it. Why not just unbolt the 4 air injection tubes and plug the holes? The EGR pipe can be removed and plugged also or cut leaving 2" and crush flat with vice grips and roll the end to seal.... emissions 'stuff' gone, no plate to make or any chance of a vacuum leak and no need for custom down pipe to fit the L16 exhaust manifold..

 

xVkEyEu.jpg

 

 

I have replaced the stock L20B exhaust manifold on my '76 710 with an L16. I replaced the intake with one from a '79 (a '78 will also work) that is not joined to the exhaust. An L16 intake will also work but the L20B has larger runners.

 

Where did you get the plug from, I had to tap the tube hole and run an Allen screw in it with some jb weld .

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Local hardware store. I just took one of those air tubes in and matched the thread. I thought metric but 5/16 X 16 X 1/4" long screwed into the manifold. If you have a welder you can weld them up.

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On 4/30/2020 at 3:22 PM, datzenmike said:

Local hardware store. I just took one of those air tubes in and matched the thread. I thought metric but 5/16 X 16 X 1/4" long screwed into the manifold. If you have a welder you can weld them up.

Why thank you Mike, I have another or two I need to fix up.

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The L20B should have a big port cylinder head, so be sure to buy a big port intake manifold to match.  I think the L20B intake that you want is a casting #W58.  I have a freshly glassbeaded L20B intake listed on eBay if interested!  I also have a couple different choices of the stamped steel heatshields for the carb & intake manifold, both dirty raw & re-plated in yellow zinc.  And yes, the 510 L16 exhaust manifold will bolt right up!

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W58 sounds right, it would be on the '78-'80 L20Bs. It has a large bolt on EGR manifold but you can remove it and with some material removed with die grinder and some good old JB weld

 

 

 

 

Here's the one I did from a '79 L20B with a little sculpting and taping a hole for the PCV. Looks like the earlier L16 intake with working PCV and no chance o'fs a block off gasket leak.

 

CFOY8X4.jpg

 

After

wPXiRYX.jpg

 

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