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I have a 66 Toronado I've owned for a few years now and am working to get it put back into factory configuration. It's been "touched" by previous owners and I just want to put things back the way they belong. My Toro is not the CA emissions one, and I have the correct 7026250 carburetor. I also own the service manual. I see from research that there is a heat riser on the driver side exhaust manual. My car does not have it. Is that a CA emission feature for that year, or has someone replaced the exhaust manifold on the car with one from a different year? I'm having trouble finding that out. Also, I'm seeing something called a carburetor throttle return valve (GM #392902) and a filter (GM #6420962). Is this something these cars came with also? I ask because people advertise things on E-Bay and other places and sometimes get application year wrong. If the 66 has one, can someone tell me where it attaches and its purpose? I couldn't find either this or the heat riser in the service manual, but perhaps I missed it. Thanks.
All '66 Toros had same left exhaust manifold #392851, with heat riser valve.
Except for AIR, '66 Toros had that Throttle Return Check Valve and its filter (and holding bracket and spring on the intake manifold). Highly unlikely to find new, but might try John Dorcey for used. Somewhere, possibly this forum, I saw that maybe you can get by without the check valve.
There were some earlier posts on this subject. I thought (and posted) that valve's function was to slow the sudden drop in RPM when taking foot of accelerator and prevent stalling, hesitation, etc. Someone else posted another answer which was possibly more plausible than mine. Earlier discussion was perhaps less than 6 months ago, so you might try scrolling back through old posts.
There were some earlier posts on this subject. I thought (and posted) that valve's function was to slow the sudden drop in RPM when taking foot of accelerator and prevent stalling, hesitation, etc. Someone else posted another answer which was possibly more plausible than mine. Earlier discussion was perhaps less than 6 months ago, so you might try scrolling back through old posts.
All '66 Toros had same left exhaust manifold #392851, with heat riser valve.
Except for AIR, '66 Toros had that Throttle Return Check Valve and its filter (and holding bracket and spring on the intake manifold). Highly unlikely to find new, but might try John Dorcey for used. Somewhere, possibly this forum, I saw that maybe you can get by without the check valve.
Interesting,
My manifolds just happen to be on my bench here. Unless someone swapped them out between 1966 and 1973, these would be the original ones to my car and most likely have never been off. The LH manifold has the PN 387393 (or it may be 387993.....the casting isn't clear anymore) GM LH stamped on it. The RH has 387992 RH stamped in it. I wonder why my left hand one doesn't match the parts catalog? My 1970 parts catalog lists the PN's for the LH as 399425 (Supp 392851)
387992 and 387993 are correct castings for the 1966 Toro. The '993 LH manifold came from the factory with a heat riser flapper. The later parts book only lists parts that were in the network at the time of printing, which is why it is not a reliable source of part number data for older cars. Also, the parts book lists PART numbers, which may or may not be the casting number. In the case of 387993, that casting went through an assembly process to add the heat riser flapper, so the PART number for that assembly was 392851.
Last edited by joe_padavano; Feb 11, 2026 at 06:18 AM.
387992 and 387993 are correct castings for the 1966 Toro. The '993 LH manifold came from the factory with a heat riser flapper. The later parts book only lists parts that were in the network at the time of printing, which is why it is not a reliable source of part number data for older cars. Also, the parts book lists PART numbers, which may or may not be the casting number. In the case of 387993, that casting went through an assembly process to add the heat riser flapper, so the PART number for that assembly was 392851.
Ahh.....I get it. They must have gotten that idea from Rochester then? Perhaps the other way around?? I kid, I kid.
Ahh.....I get it. They must have gotten that idea from Rochester then? Perhaps the other way around?? I kid, I kid.
Which idea? Standard engineering drawing practice is to assign unique drawing (part) numbers to each subsequent operation or assembly, so while there is a drawing for the bare 387993 casting, there are also drawings for the heat riser flapper door, the shaft, and the spring. There may or may not be a separate drawing that machines the bare casting and drills the holes for the heat riser shaft, or those activities may be detailed on the assembly drawing. 392851 is the assembly drawing that puts them all together, and this is the assembly part number.
Which idea? Standard engineering drawing practice is to assign unique drawing (part) numbers to each subsequent operation or assembly, so while there is a drawing for the bare 387993 casting, there are also drawings for the heat riser flapper door, the shaft, and the spring. There may or may not be a separate drawing that machines the bare casting and drills the holes for the heat riser shaft, or those activities may be detailed on the assembly drawing. 392851 is the assembly drawing that puts them all together, and this is the assembly part number.
I'm just kiddin' around.......I'm referring to the casting numbers stamped on Qjets that don't match the PN's in the parts catalog. Just something that throws people off if they're not familiar with the casting vs. PN issue when they're looking for parts (like I was for a good period before I was enlightened).
Thanks everyone for all the great information. It's been very helpful. I'll get a look at that manifold part number and verify that the heat riser is / is not there. I also reached out to Mr. Dorcey. Hope he still has one available.
Thanks everyone for all the great information. It's been very helpful. I'll get a look at that manifold part number and verify that the heat riser is / is not there. I also reached out to Mr. Dorcey. Hope he still has one available.
MajD
Just to clarify, the only number you will see on the manifold is the CASTING number, not the part number.
Thanks for the clarification. I am interested to see if the manifold was replaced at some point, as I'm almost positive there isn't a heat riser. The car is stored in another location for the winter, so it's not like I can go out in the garage and look. I will be going there this month though and will be sure to check. I thought the driver side exhaust manifold was unique to the Toronado because the exhaust pipe had to go up and over the transmission. So if the heat riser isn't there, maybe the manifold is from a later model. I'll post what I find out. Thanks.
Thanks for the clarification. I am interested to see if the manifold was replaced at some point, as I'm almost positive there isn't a heat riser. The car is stored in another location for the winter, so it's not like I can go out in the garage and look. I will be going there this month though and will be sure to check. I thought the driver side exhaust manifold was unique to the Toronado because the exhaust pipe had to go up and over the transmission. So if the heat riser isn't there, maybe the manifold is from a later model. I'll post what I find out. Thanks.
MajD
Replacement manifolds would have come with the heat riser. Unlike later cars, here was no version of 387993 that didn't have a heat riser installed. When the heat riser seized up, it was common to remove it and plug the holes.
Ignore the incorrect "68" marking on this manifold. 387993 was only used on 66-67 cars. Note the shaft for the heat riser, though the spring appears to be missing.
Here are both 387992 and 387993. Note the coil spring and counterweight on '993 for the heat riser valve.
Thanks again for all the helpful information on getting my Toronado sorted out. I was at my garage this weekend and managed to get some pictures of the LH casting. The first number was badly corroded but I'm almost positive it's a 3. The only other option would be an 8. Since the remaining numbers are clearly 87993, it seems I have the correct manifold. It is missing the heat riser pieces on the outside except for a corroded stub sticking out of the manifold on the inner side facing the transmission...probably the remains of the heat riser. Now I have to see if it's a "repair", or if the original heat riser is stuck.
