'67 AIM questions
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From: Purcellville, Virginia
'67 AIM questions - ehaust manifold - heat riser
I have what sounds like an exhaust leak from the pass. side manifold area. I had a missing nut where the exhaust bolts on, but replacing it didn't solve the problem. There is a big spacer on that side -heard people say its a 'heat riser' and should have a spring and a counterweight and it might not be operating. I am not mechanicaly inclined and dont have a lift - but in comparing it to my 1959, its not freely moving and if when working properly the counter-weight should rasie up to the same level as the one on my '59 then the '67 one appears to be stuck in the half position.
Where do I find a picture of what the heck we are talking about here and how can I tell if its operational and causing my exhaust leak noise?
Where do I find a picture of what the heck we are talking about here and how can I tell if its operational and causing my exhaust leak noise?
Last edited by lemish; Nov 6, 2004 at 02:23 PM.
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From: Ontario
Here is the heat riser. When the engine is cold the weight on the side will be in the up position and the butterfly valve shut. The thermo spring will pull that weight down and open the butterfly valve as the engine warms up. Grab that weight and move/rotate it to see if things move freely. They do tend to freeze up and that apparently is the case with yours. Mine is mig-welded open as I do not drive in cold weather. Or you can replace it with a true spacer. A third option is to gut the one you have (remove weight, spring, shaft, butterfly), seal shaft holes and re-install. But watch the exhaust manifold studs. If they snap you have a nasty job on your hands. Not sure what you mean by a "bolt." The studs are threaded at each end and the exhaust pipe held on by brass nuts.
http://www.ecklers.com/product.asp?d...RPXA597MR9BV21
Here is a 1979 manifold without the heat riser.
http://www.ecklers.com/product.asp?d...RPXA597MR9BV21
Here is a 1979 manifold without the heat riser.
Last edited by Paul L; Nov 6, 2004 at 02:19 PM.
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[QUOTE=paul67] Not sure what you mean by a "bolt." The studs are threaded at each end and the exhaust pipe held on by brass nuts.
QUOTE]
I edited my post and changed "bolt" to "nut" - I told you I wansn't mechanicaly inclined. BTW, what do these brass nuts look like - the ones I have are brass, but I was told they were wrong?
If the 'up' position should be equivilent to and look like what I see on my '59 Vette - then from what I can tell the counterweight is frozen about 1/2 way and when I try to move the counterweight it has about 1/4 inch of play is all. Sound like I'm describing one that has frozen up?
Can these be rebuilt, fixed? This is a low-mileage all original car and I understand I don't want to replace anything, I want to fix it if I can.
I appoligize for my stupidity - but could this have anything to do with hearing the exhaust leak sound over on that side?
QUOTE]
I edited my post and changed "bolt" to "nut" - I told you I wansn't mechanicaly inclined. BTW, what do these brass nuts look like - the ones I have are brass, but I was told they were wrong?
If the 'up' position should be equivilent to and look like what I see on my '59 Vette - then from what I can tell the counterweight is frozen about 1/2 way and when I try to move the counterweight it has about 1/4 inch of play is all. Sound like I'm describing one that has frozen up?
Can these be rebuilt, fixed? This is a low-mileage all original car and I understand I don't want to replace anything, I want to fix it if I can.
I appoligize for my stupidity - but could this have anything to do with hearing the exhaust leak sound over on that side?
Last edited by lemish; Nov 6, 2004 at 02:47 PM.
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From: Ontario
Like most exhaust parts they simply burn out with time. I suppose you could try to find an NOS replacement but I would just visit a local muffler shop. It is just a "Chevrolet" part.
You can see the brass nuts in my pic of the 1979 manifold. I don't have any in basement inventory at the moment to take any more pics. The brass is correct to avoid a "welding" of steel to steel (nut to stud) over time with heat and corrosion leading to a non-removeable situation. Some use stainless nuts as a replacement.
There is generally no gasket/doughnut used with the heat riser. So they either fit or do not. I suspect your studs have deteriorated to the point where a proper fit is not possible. A muffler shop can get them out with a torch and put new ones in, along with a new heat riser. As to movement, mine was (now welded as noted) pretty close to 60 degrees; quite substantial.
You can see the brass nuts in my pic of the 1979 manifold. I don't have any in basement inventory at the moment to take any more pics. The brass is correct to avoid a "welding" of steel to steel (nut to stud) over time with heat and corrosion leading to a non-removeable situation. Some use stainless nuts as a replacement.
There is generally no gasket/doughnut used with the heat riser. So they either fit or do not. I suspect your studs have deteriorated to the point where a proper fit is not possible. A muffler shop can get them out with a torch and put new ones in, along with a new heat riser. As to movement, mine was (now welded as noted) pretty close to 60 degrees; quite substantial.
Last edited by Paul L; Nov 6, 2004 at 04:24 PM.
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From: Purcellville, Virginia
Paul, Thanks for the help. I learned a lot today - especially once I saw photos.
However, I think I will have to see if someone can get it loosened up.
In my last post, replace "all original car" with "original car that I want to take for NCRS Bowtie" - and you will understand why I dont want to have to replace the part if I dont have to.
However, I think I will have to see if someone can get it loosened up.
In my last post, replace "all original car" with "original car that I want to take for NCRS Bowtie" - and you will understand why I dont want to have to replace the part if I dont have to.
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From: Ontario
That's a completely different matter: Bowtie Judging. I thought you were trying to get proper exhaust and intake manifold cross-passage flow to avoid leaks and carb boil. If that butterfly is closed it will direct exhaust across to the driver's side even when the engine is hot. Not a good idea as the passage runs under the carb. Things can warp under those conditions.
As to NCRS, you can remove the heat riser and try to free it up with a strong penetrating oil. I am not familiar with Bowtie Judging but surely a replacement heat riser is not a major concern?? BTW, your advisor was correct on the nuts. I checked my NCRS judging manual for 1967 and they..."are steel self locking, not brass." My apologies for the bad info.
I enjoy and admire the work of NCRS but as you can see from the pic of my engine, I tend to function rather than absolute originality.
As to NCRS, you can remove the heat riser and try to free it up with a strong penetrating oil. I am not familiar with Bowtie Judging but surely a replacement heat riser is not a major concern?? BTW, your advisor was correct on the nuts. I checked my NCRS judging manual for 1967 and they..."are steel self locking, not brass." My apologies for the bad info.
I enjoy and admire the work of NCRS but as you can see from the pic of my engine, I tend to function rather than absolute originality.
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"Bowtie" is the NCRS category for unrestored untouched original cars. Replacement ANYTHING is definitely a problem. In fact, removing something and putting it back on can be a problem because if a part shows evidence of being removed it then becomes questionable if that part is indeed the original, from the factory part. It is a very difficult and often controversial area of judging.
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From: Ontario
Thanks PRND21,
That kind of judging is not for me. In fact it does not make sense if a vehicle cannot be operated without harm as I alluded to earlier. Taking the concept to an extreme you could have a Bowtie winner completely non-functional. In other words not in operating but correct appearance condition. It was my understanding that most NCRS cars must go through an Operations Check. That is why I suggested a "correct" heat riser replacement, along with new studs. Am I wrong on Bowtie? Surely there is allowance for the wear and tear of time.
That kind of judging is not for me. In fact it does not make sense if a vehicle cannot be operated without harm as I alluded to earlier. Taking the concept to an extreme you could have a Bowtie winner completely non-functional. In other words not in operating but correct appearance condition. It was my understanding that most NCRS cars must go through an Operations Check. That is why I suggested a "correct" heat riser replacement, along with new studs. Am I wrong on Bowtie? Surely there is allowance for the wear and tear of time.
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From: Beverly Hills/Pine Ridge Florida
The original exhaust nuts were "toploc" nuts. Sort of look like rocker arm adjustment nuts with one flat and one rounded surface. They're steel, not brass.
Bowtie judging (NCRS) and Survivor judging (Bloomington Gold) are areas for untouched original cars. Anything replaced is a deduction, anything obviously "messed with" is/can be a deduction. There is an allowance for maintenance items. Chuck
Bowtie judging (NCRS) and Survivor judging (Bloomington Gold) are areas for untouched original cars. Anything replaced is a deduction, anything obviously "messed with" is/can be a deduction. There is an allowance for maintenance items. Chuck
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From: Ontario
Thanks Chuck. Perhaps the valve can be freed up on the car with penetrating oil and some patient wiggling.
In the 1967 NCRS Technical...Judging Guide there is an operations check. Does that apply to Bowtie?
In the 1967 NCRS Technical...Judging Guide there is an operations check. Does that apply to Bowtie?
