devilsbullet Posted June 3, 2013 Report Share Posted June 3, 2013 you need to smog a 78 in Beaverton? damn i'm glad i'm just across the river. 25 years and its good to go 1 Quote Link to comment
crackerjack69 Posted June 3, 2013 Report Share Posted June 3, 2013 Oregon DEQ is pre 75. We don't have the rolling DEQ which sucks. Pretty sure you can get a 620 to pass deq without the smog equipment. All else fails, you can get a waiver if you spend $200 at a legit shop trying to fix the problem. Quote Link to comment
DattoChinook Posted June 15, 2013 Author Report Share Posted June 15, 2013 So I pinpointed the leak. It seems to be coming from the flange with two bolts midway under the truck where the exhaust meets the the cat. Not from the manifold thank goodness. Any advice on how to put a new seal in there? Is this seal a something specific to a 1978 620? If pb blast those bolts and manage to get them off without breaking the studs, will I have room to squeeze a new gasket in there or will I have to disconnect other things that hold the back part of the exhaust on? Quote Link to comment
datzenmike Posted June 15, 2013 Report Share Posted June 15, 2013 What's a 620 Chinook???? California 620s had cats. The gasket between the down pipe and the front of the cat is part # 20692-M3060 about $7 if still available. Maybe use this number to find an after market one. The stock ones don't use studs but nuts and bolts so break them off and just replace them. Quote Link to comment
DattoChinook Posted June 15, 2013 Author Report Share Posted June 15, 2013 What's a 620 Chinook???? California 620s had cats. The gasket between the down pipe and the front of the cat is part # 20692-M3060 about $7 if still available. Maybe use this number to find an after market one. The stock ones don't use studs but nuts and bolts so break them off and just replace them. 620 Recreational vehicle LOL Quote Link to comment
DattoChinook Posted June 15, 2013 Author Report Share Posted June 15, 2013 620 Recreational vehicle LOL 1 Quote Link to comment
datzenmike Posted June 15, 2013 Report Share Posted June 15, 2013 Ahhhhh seen them. The Jan '78 to the end of the '78 model year and all of the '79 model year had a Cab/Chassis option. These were sold without a bed and could be fitted with specialized commercial work boxes or campers. Later the 720s had dual rear tires. 1 Quote Link to comment
DattoChinook Posted June 15, 2013 Author Report Share Posted June 15, 2013 What's a 620 Chinook???? California 620s had cats. The gasket between the down pipe and the front of the cat is part # 20692-M3060 about $7 if still available. Maybe use this number to find an after market one. The stock ones don't use studs but nuts and bolts so break them off and just replace them. Thanks man! My local autozone has a felpro one in stock for 1.99. So If I get the nuts and bolts off will I have enough play to squeeze the gasket in there? Quote Link to comment
datzenmike Posted June 15, 2013 Report Share Posted June 15, 2013 I think so. The pipes aren't bolted solid to the body... they're on hangers. 1 Quote Link to comment
DattoChinook Posted June 15, 2013 Author Report Share Posted June 15, 2013 So I got the nutz and bolts off the cat today, cleaned the flanges up, and put the new gasket in. I re-tightened the bolts and noticed that everything meets on the sides and the top, but not on the bottom. There is a gap on the bottom. I definitely think the flange is rusted/warped to the point that it doesnt meet on the bottom. It is now a way worse leak than before. I guess I am wondering what I should do about this? Should I try doubling up the gasket and adding some high temp rtv for a temporary fix lol? Quote Link to comment
datzenmike Posted June 15, 2013 Report Share Posted June 15, 2013 RTV is barely good to 500F. Double or triple the gaskets. Quote Link to comment
Z-train Posted June 15, 2013 Report Share Posted June 15, 2013 RTV is barely good to 500F. Double or triple the gaskets.Ultra Copper is good for exhaust temps. Quote Link to comment
its_karl Posted June 16, 2013 Report Share Posted June 16, 2013 is it a flat mutlilayered gasket or a donut? if its a donut - just have to hold it in a better position and tighten it down. Any chance you can take a picture or is it too tight in there? Quote Link to comment
DattoChinook Posted June 16, 2013 Author Report Share Posted June 16, 2013 is it a flat mutlilayered gasket or a donut? if its a donut - just have to hold it in a better position and tighten it down. Any chance you can take a picture or is it too tight in there? It is a donut type with holes where the bolts go through. Cant really move it around once the bolts go through the holes. I bought "Versa Chem Exhaust system Joint and crack sealer" and smeared it all over the gasket on both sides. I then tightened it up, and this stuff was squeezing all through the joint. I then smeared it all around the outside joint with my finger. I hope this stuff does the job. It says to let it dry for 2 to 4 hours. Ill will test it later tonight... If this doesnt work or last, I am gonna have to scrape all this stuff off and then buy 2 or three gaskets and double or triple them up and see if that works like DatzenMike suggested. Quote Link to comment
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