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77 Cali 620 smog delete


Radiant-Designer

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I got a 77 620 from Cali a few years ago. I put a Weber carb on it, and did what I could to desmog it. I was wonderign how hard it was to find an intake that would eliminate a lot of the ports and maybe the EGR. i see some for other engines (I have a L20B) but not sure what the interchangeability may be.

 

Any insights?

 

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The '75-'77 L20Bs had the intake and exhaust bolted together. It used exhaust heat directed up against the bottom of the intake to warm it. You can't easily replace one witout addressing the other. Definitely get the L16'18 exhaust manifold. Other than weight it is a cast header. For the intake you can retain the 4 bolt cober on the bottom where the exhaust clamped to it. I've seen this done. It keeps the larger runner intake.

 

Only the early L16 and some L18s had the intake without the EGR valve but the ports are smaller than the L20B intake. You can remove the small EGR manifold that bolts to the side of the L20B intake and block it off but the problem is that the PCV is also located on it and this should be kept.

 

 

Have to say that disabling the 'smog' is as easy as pulling a small hose of the carb. Disabling it or removing it will do nothing for performance. I don't see the sense in messing with it at all. Seen enough vacuum leak problems caused buy this.

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Definitely get the L16'18 exhaust manifold. Other than weight it is a cast header. For the intake you can retain the 4 bolt cober on the bottom where the exhaust clamped to it. I've seen this done. It keeps the larger runner intake.

 

Only the early L16 and some L18s had the intake without the EGR valve but the ports are smaller than the L20B intake. You can remove the small EGR manifold that bolts to the side of the L20B intake and block it off but the problem is that the PCV is also located on it and this should be kept.

 

Im not that familure with these, what vehicles would normally have the L16 or L18 manifolds?  would it be possible to get the intake and the exhaust together? Apparently my exhaust manifold is cracked, I just got a call from the guy who did the cat delete and the rest of the exhaust work.

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hmmm so after i took the heat sheild off there is a hole in my exhaust manifold... it looks like it is a factoy thing.... its below the carb and almost lines up where the fuel inlet is on the Weber... I tried using high temp Quick Steel (like JB weld) which worked for a little while, but seems to have burned off. I may try stove cement.

 

 

Wonder what this hole is for...????

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Probably the heat riser. There should be a rod running through the manifold. Look on the other side there should be a rod with a coil spring and a bob weight on it.

 

 

Upu are absolutely right! Is it supposed to be a souce for an exhaust leak? I have noticed it runs a lot better when it has been warmed up

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now that its not raining, the counter weight moves pretty easily on the back, its hard to see if the spring is broken or anything. Was ther supposed to be a cap or something on there, or some way so there wasnt an exhaust leak?

 

 

I may go with my original thought and go with a L16/l18 intake/exaust

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There should be a rod passing through the exhaust manifold from front to back. On the inside is a door that directs hot exhaust against the bottom of the attached intake to warm it and help evaporate the fuel on cold days. On the very rear is a coiled bi-metal spring that expands and un-coils as it warms and closes the 'door'. There is a small weight to help keep the door closed but heavy throttle exhaust can push it open for more performance. The problem is they can stick open (slow to warm and cold opperation is sluggish) or stick closed... intake runs too hot when warmed and performance is impared.

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It seems like the rod isnt going all the way through, becuase it looks like a hole from the front tha goes in a little bit then I can see the end of the rod. it does cause an exhaust leak,and if I put my finger over it it sounds  alot better (When the truck first gets started and it isnt too hot to do)  Its ard for me to see if the bimetal spring is still intact or if it is stuck one way or the other.

 

 

I do know that on very cold days it is hard to start and sometimes takes a little. Like i said before it is a Weber now, so not sure if that matters.

 

Ill see if i can get some pics to help explain what is there and get some tips how to make it work better.

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