351W Thermactor pipe
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Cross-Country
Joined: Nov 2022
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From: Near Jonesbourogh, TN
Thank you, Dave. I don't know if the PO removed it, as I haven't looked. I have what sounds like a large exhaust leak coming from the passenger side, in the back. It may be that pipe is broke or a plug has come out.
Chuck
Chuck
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From: Virginia
I think that is a good place too look. They do rust out. Sometimes you can take the assembly out, and get it welded shut and put it back on without the piping. There is usually one bolt in each side.
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Cross-Country
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From: Near Jonesbourogh, TN
I've seen threaded 3/8 x 11 threaded plugs to block the head passages if they are threaded. The leak is definitely on the passenger side as opposed to the middle or drivers side.
I'm hoping it's not a cracked header.
Tomorrow is supposed to be warmer, I'll check it out.
Chuck
I'm hoping it's not a cracked header.
Tomorrow is supposed to be warmer, I'll check it out.
Chuck
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On each head at the front, I think you’ll see a plugged 5/8” hole and a smaller open hole (5/16”?) for the mount bolt. A bracket may use that same smaller threaded hole, so it may not be obvious at first glance.
Not home right now but can look later to be sure. Might be a few days.
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Cross-Country
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From: Near Jonesbourogh, TN
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That was easy...glad I could help.
The other guys can advise you on what other things you'll need to do to delete that system. Maybe one of them can link us to the steps...? For those of us that live in states where these trucks no long have to be tested for emissions.
The other guys can advise you on what other things you'll need to do to delete that system. Maybe one of them can link us to the steps...? For those of us that live in states where these trucks no long have to be tested for emissions.
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Those plugs would probably be very tricky to install in the tight confines against the firewall. Looks like they are designed for a large flat blade screwdriver. Perfect for the front of the engine, but not so much at the back.
I think you’d be much better off with a short 5/8”-11 bolt with a copper crush washer under the head. You could turn the head with a socket or ratcheting dogbone. Use lots of high temp anti seize.
Are you positive you want to delete the system? I know it’s always popular to join the “Rip out the pollution crap” club. However, the thermactor heads are designed to blow relatively cool air (from the dreaded smog pump) directly on the back of the exhaust valves. A contentious subject around here, but this feature supposedly helps the valves live longer.
I think you’d be much better off with a short 5/8”-11 bolt with a copper crush washer under the head. You could turn the head with a socket or ratcheting dogbone. Use lots of high temp anti seize.
Are you positive you want to delete the system? I know it’s always popular to join the “Rip out the pollution crap” club. However, the thermactor heads are designed to blow relatively cool air (from the dreaded smog pump) directly on the back of the exhaust valves. A contentious subject around here, but this feature supposedly helps the valves live longer.
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Cross-Country
Joined: Nov 2022
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From: Near Jonesbourogh, TN
Yes, I'm sure. As the pump and EGR were already removed by the PO, and I can hear what sounds like an exhaust leak from the passenger side rear of the engine, it is serving no purpose except a possible leak source.
I will go with the short bolt and copper crush washer.
Chuck
I will go with the short bolt and copper crush washer.
Chuck
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From: Atlantic Canada
I used short 5/8 bolts to plug the back of my factory heads. I forget the length, but they're either 1" or 3/4" long. I started out using a pair of 5/8" set-screws from work (Allen socket drive), but I was worried they weren't going to stay put so I used bolts and lock washers with high temp sealant. Time will tell if they last or not.
I installed a set of GT40 heads from an Explorer on my other 302, but they did not have thermactor holes at all....I'm not sure what system was used on those engines after 1996.
I installed a set of GT40 heads from an Explorer on my other 302, but they did not have thermactor holes at all....I'm not sure what system was used on those engines after 1996.
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