1965 Gran Sport exhaust

[RivNut]

I think it’s pretty common knowledge that the Gran Sport exhaust pipes were a larger diameter and had a smoother radius in the bends.  All that to supposedly allow the exhaust to exit more freely.  My question is this. Did the Gran Sport exhaust manifolds have larger diameter holes where they joined the exhaust pipes?  If not, what was the point of the larger pipes if the exhaust had to be choked through the same sized manifold as the standard 401/425 engines?  

[RodA67Riv]

Great question. Taking a quick look at the parts book, I don't see a separate manifold for the GS. All other exhaust components have a separate GS part #, but not the manifolds. Holy restrictive manifold Batman! Hope I'm wrong.

 

[RivNut]

21 minutes ago, RodA67Riv said:

Great question. Taking a quick look at the parts book, I don't see a separate manifold for the GS. All other exhaust components have a separate GS part #, but not the manifolds. Holy restrictive manifold Batman! Hope I'm wrong.

 

I don’t think you are. I’ve checked casting numbers for nailhead engines 1964 - 1966.  There are a couple of different right side manifolds based on whether the heat riser is built in or bolt on.  There may be hope if all exhaust manifolds have the larger hole where they bolt to the exhaust pipe but I doubt it. A number of years ago I bought some reproduction Gran Sport exhaust pipes.  They were 2-1/4” pipes but the was a smaller pipe welded to the larger pipes so the flange would fit over the pipe. Another blockage. The company basically told me to pound sand. 🤬

Edited August 3, 2021 by RivNut (see edit history)

[BulldogDriver]

Just finished installing a full GS stainless steel system from Classic Exhaust that was 2 1/4” end to end. Had to tweak one long pipe’s bend and shorted the resonator eliminators by 1 1/2”. Also had to make new exhaust studs that were longer to get the header flanges to fit. Couldn’t  find 1/2” exhaust studs that worked.  My guess on the manifolds is Buick knew the Nailhead was short for this world and just left things as they were. Probably thought the larger diameter of the exhaust pipes would be enough for the few years left for that block.

 

Ray

[telriv]

The exhaust manifolds, for stock manifolds, flow pretty well as they are.  IF you increase the size of the outlets it helps. ALSO, when bolting them to the engine, NO GASKETS,  start the bolts finger tight then lift them until they will go no more & tighten the bolts. If you look at the bottom outlet on the floor exit you will see a raised little bump. This is to help the exhaust gases go up which is whats desired.  Thats one reaon that putting Sanderson block huggers, Shorty headers etc. lose HP because you normally can't get ALL the pipes to go up. Space constraits won't normally allow it.

 

Tom T.

Edited August 3, 2021 by telriv (see edit history)

[1965rivgs]

12 hours ago, RodA67Riv said:

Great question. Taking a quick look at the parts book, I don't see a separate manifold for the GS. All other exhaust components have a separate GS part #, but not the manifolds. Holy restrictive manifold Batman! Hope I'm wrong.

 

Rod,

  Check the part numbers for the "over the axle" pipes.

Tom

[1965rivgs]

11 hours ago, BulldogDriver said:

Just finished installing a full GS stainless steel system from Classic Exhaust that was 2 1/4” end to end. Had to tweak one long pipe’s bend and shorted the resonator eliminators by 1 1/2”. Also had to make new exhaust studs that were longer to get the header flanges to fit. Couldn’t  find 1/2” exhaust studs that worked.  My guess on the manifolds is Buick knew the Nailhead was short for this world and just left things as they were. Probably thought the larger diameter of the exhaust pipes would be enough for the few years left for that block.

 

Ray

Ray,

  Gran Sport tail pipes were originally 2 inches in diameter

Tom

[RivNut]

12 hours ago, RodA67Riv said:

Great question. Taking a quick look at the parts book, I don't see a separate manifold for the GS. All other exhaust components have a separate GS part #, but not the manifolds. Holy restrictive manifold Batman! Hope I'm wrong.

 

I took a closer look at all the part numbers and see separate part numbers for everything GS except for the over the axle pipe. ?????  Is that just an error of omission?

Edited August 3, 2021 by RivNut (see edit history)

[RodA67Riv]

10 minutes ago, 1965rivgs said:

Rod,

  Check the part numbers for the "over the axle" pipes.

Tom

You're right Tom. Another no-GS part #. I'm not really sure what GM was thinking here. If the restrictions end in little to no gain, then why not just have separate resonators/muffler for sound effect and larger diameter tailpipes for the visual?

[RivNut]

Could someone with a parts number book check to see if the illustration is correct or whether there is an omission on the illustration.  I don't see how a smaller pipe could be fitted to the larger GS pipe unless the GS pipe has been reduced at the end of the resonator pipe then enlarged again to fit the GS muffler.  If the over the axle pipe has been stretched to fit the GS pipe, then it wouldn't fit the stock application. 

[BulldogDriver]

Tom, I did read that the tail pipes were 2” on a GS somewhere here on the forum.
 

The over axle pipe being 2” could be true being the resonators and the muffler are different for GS. They could have sized those parts for the axle pipe. I’ll look in the parts book next time I hobble up to the study. Stress fractured a leg and stairs are a once a day thing for the next month or so. Glad I got the exhaust system done before this happened.

 

Ray

[MikeJS]

2 hours ago, RivNut said:

Could someone with a parts number book check to see if the illustration is correct or whether there is an omission on the illustration.

Ed, good day.

 

In the Canadian edition I have, the illustration is different, but only one part number for each side is listed for the over axle (in group 3609), and all other part numbers I’m the other groups appear to match the illustration posted above.

 

The edition is effective December 1964.

 

Sorry I can’t explain it, I just had the books handy and I’m hoping this is the info you were looking for.

 

Take care.

 

Later,

 

[RivNut]

As I read this, 1372850 and 1372861 are specific over the axle pipes for the 1965 Gran Sport. Just not listed on the illustration.

[MikeJS]

Ed, maybe I’m missing something but 1372850 and 1372851 are pipes 9 and 10 on the diagram, the front pipes, while pipes 6 and 12 are over the axles and are the last two listed in group 3.609 - 1353876 and 1353877, and they’re not specifically listed as Gran Sport...

[RivNut]

@MikeJS

 

in @RodA67Riv's illustration, the over the axle pipes are listed as Group 3.609, #1353876 for the R and #1353877 for the L.  

 

You posted a parts list (Canadian.) The entire page consists of Group 3.609 over the axle pipes for a bunch of years and a bunch of models.

 

The last two part numbers on bottom are parts #1353876 - right-rear and #1383877 right-left; same as in the illustration.. 

They are shown for 1965/490. (1965 for the year /490 - being the designator - style 44947 for Riviera. The 1965 Buick Service manual refers to the Riviera as 49000.)

 

The 5th and 6th numbers from the bottom are "#1372850 - 1965/490 - with gran sport - right,  and #1372851 1965/490 with grand sport - left. 

 

Two distinct and separate part numbers for the standard Riviera, and two distinct and separate part number for the Gran Sport. 

The illustration has omitted the "G.S" number for the 3.609 pipe. 

 

Betcha that caused some confusion for the mechanic; hopefully the parts dept mgr caught it before it was ordered.

 

Ed

[RodA67Riv]

Combining the illustration with the part #s, here's the way that I read it:

 

#9 - Pipe, exhaust-front-right

        1372850 with Grand Sport Front Right

        1355762 Exc Grand Sport Front Right

 

#10 - Pipe, exhaust-front-left

        1372851 with Grand Sport Front Left

        1368069 Exc Grand Sport Front Left

 

#12 - Pipe, exhaust-rear-right

        1353876 Rear Right

 

#6 - Pipe, exhaust-rear-left

        1353877 Rear Left

 

No separate over the axle pipes (exhaust-rear) for the GS vs. non-GS.

[RivNut]

I admit that I have confused some numbers, but If you look at the illustration that RodA67Riv posted, you will see part numbers for a muffler and tail pipes for the Gran Sport that do no appear on the the list that you posted.  So now I believe there are omissions on both.  You cannot convince me that both the basic Riviera and the Gran Sport shared a common pipe. They could but only if the flanges on the ends of the resonators and the inlets on the muffler were reduced would this work. But why would Buick have choked down the entire length of the system with this one pipe when everything else had been opened up?  Still more investigation is needed in my humble opinion.

[MikeJS]

Ed, the page I posted was only group 3.609, the tailpipes are in group 3.705., mufflers in group 3.701 and they list the same numbers as the original image for both GS and non.

 

 

 

[MikeJS]

For what it’s worth, to finish the main components, the manifolds are in group 3.601 and the resonators are in group 3.702... same same...

[RivNut]

137298 shows the description as "with gran sport - arvin", the other resonator for 490 "except gran sport" describes it as includes center exhaust pipe. Any ideas on what that includes?

[RivNut]

I have two sets of unmounted exhaust manifolds so I took a set of calipers and measured the outlets on each of the four. Each of the four has an inner diameter of 2". 

[RodA67Riv]

On 8/3/2021 at 6:13 PM, BulldogDriver said:

Tom, I did read that the tail pipes were 2” on a GS somewhere here on the forum.
 

The over axle pipe being 2” could be true being the resonators and the muffler are different for GS. They could have sized those parts for the axle pipe. I’ll look in the parts book next time I hobble up to the study. Stress fractured a leg and stairs are a once a day thing for the next month or so. Glad I got the exhaust system done before this happened.

 

Ray

Maybe Ray has it right. Perhaps the over the axel pipes are already sized to match the GS and 'oversized' for the non-GS. The only way to know for sure is to get out a tape measure on original pipes (if they're still around).  Thinking about it a bit more, it probably makes sense that the over-the-axel pipes were larger diameter (for the non-GS) given the bends that they have and the added restriction that this would cause. 

Edited August 5, 2021 by RodA67Riv (see edit history)

[KRmanr]

Was the "advertised" HP & Torque ratings different between (any year) GS and non-GS Riv's?

Honestly, I would not be surprised if all Riv pipes were identical, except for possibly 2x4 barrel carb engines. Mufflers and Resonators seem a more likely difference. 

Also, the over the axle pipes sizing is limited because of the inherited tight clearance between frame rails and tires/wheels. Larger diameter pipes must be flattened out (even more to some extent) for clearance. I thought the factory over the axle pipes were flattened to some extent already?   That's my recollection of tailpipe issues.

Edited August 5, 2021 by KRmanr (see edit history)

[BulldogDriver]

My previous post was not to be  construed  to say that the factory had sized the axle pipe for a GS engine. Why as it appears, Buick elected to use various pipe sizes throughout the entire system one can only guess at this point in time. 
 

My car is not a GS model and has a 401 that is bored 0.060” over. So I’m around a 412 now. Whether good or bad, I elected to put a GS exhaust system in it and as previously stated is 2 1/4” end to end. I had no problem getting the clearances noted in the shop manual after the adjustments noted in my previous post. Tom T. noted to the same adjustments in one of his posts in another exhaust thread. 
 

Can’t imagine any of this really matters much with these cars. It looks as if the output numbers for the GS were done with the smaller axle pipes and until now, that I’ve noticed, no one has brought the smaller pipes up in a thread before. 
 

Maybe Tom T. could elaborate  on his exhaust system. 
 

Ray

Edited August 5, 2021 by BulldogDriver (see edit history)

[1965rivgs]

1 hour ago, BulldogDriver said:

My previous post was not to be  construed  to say that the factory had sized the axle pipe for a GS engine. Why as it appears, Buick elected to use various pipe sizes throughout the entire system one can only guess at this point in time. 
 

My car is not a GS model and has a 401 that is bored 0.060” over. So I’m around a 412 now. Whether good or bad, I elected to put a GS exhaust system in it and as previously stated is 2 1/4” end to end. I had no problem getting the clearances noted in the shop manual after the adjustments noted in my previous post. Tom T. noted to the same adjustments in one of his posts in another exhaust thread. 
 

Can’t imagine any of this really matters much with these cars. It looks as if the output numbers for the GS were done with the smaller axle pipes and until now, that I’ve noticed, no one has brought the smaller pipes up in a thread before. 
 

Maybe Tom T. could elaborate  on his exhaust system. 
 

Ray

Ray,

  How did you put 2 1/4 inch tailpipes on a GS muffler which has 2 inch tailpipe stubs? Or did you use a muffler other than the factory GS muffler?

Tom

[1965rivgs]

3 hours ago, KRmanr said:

Was the "advertised" HP & Torque ratings different between (any year) GS and non-GS Riv's?

Honestly, I would not be surprised if all Riv pipes were identical, except for possibly 2x4 barrel carb engines. Mufflers and Resonators seem a more likely difference. 

Also, the over the axle pipes sizing is limited because of the inherited tight clearance between frame rails and tires/wheels. Larger diameter pipes must be flattened out (even more to some extent) for clearance. I thought the factory over the axle pipes were flattened to some extent already?   That's my recollection of tailpipe issues.

KRmanr,

  The Gran Sport cars came standard with dual quads and they were rated at 20 extra HP. You are right on regarding your statements about the over axle pipes.

Tom

[BulldogDriver]

14 minutes ago, 1965rivgs said:

Ray,

  How did you put 2 1/4 inch tailpipes on a GS muffler which has 2 inch tailpipe stubs? Or did you use a muffler other than the factory GS muffler?

Tom

Tom,

 

The system I used is from Classic Exhaust. They make the entire system so I guess they can size the outlets to their specs. All clamps were 2 1/4” and the hangers purchased from Walden Exhaust had to be opened for the clamps going to the muffler. It was the only pair that attached to the clamps at the base. 
 

From my reading, original mufflers are very rare. My car is a driver and I went with what would look original at a glance but would keep me from climbing under it for a very long time.

 

Ray

[1965rivgs]

2 hours ago, BulldogDriver said:

Tom,

 

The system I used is from Classic Exhaust. They make the entire system so I guess they can size the outlets to their specs. All clamps were 2 1/4” and the hangers purchased from Walden Exhaust had to be opened for the clamps going to the muffler. It was the only pair that attached to the clamps at the base. 
 

From my reading, original mufflers are very rare. My car is a driver and I went with what would look original at a glance but would keep me from climbing under it for a very long time.

 

Ray

Hi Ray,

  Thanks...yes, I`m sure they fabbed the muffler so they may have built it with larger tailpipe stubs. Do you have a pic of the finished product? I`m curious how the larger than stock tailpipes look...

Tom

[BulldogDriver]

Looks pretty much stock. It’s a stainless steel system with a two piece long pipe coming off the headers. Easier to ship and gave some wiggly room for installation but you install two more clamps. What I removed was not stock and the hangers were cobbled together so I had nothing to compare to. Bought a new set of Waldon hangers for GS. Once I had the parts assembled and aligned, it looks stock other than all pipes being 2 14” and muffler is not oval but round. Price was good especially  for a 316 SS system. Should never rust. Went with resonator eliminators as I have a fuel filter in that area, was going with EFI originally but decided carb was a better fit for me and didn’t want to re-plumb fuel lines. Exhaust that was on the car didn’t have resonators either.  

My plan was/is to have an updated gen 1 Riviera that when you look at the exterior and interior it looks mostly stock. Open up the hood and the upgrades show. Performance and handling is as good as possible using original suspension design with updates. 4l60E transmission, Vintage Air A/C, Rostra cruise control, hidden oil pressure/volts/temp gauge and usb power connector, disc brakes, sway bar front and back, springs, Bilstein shocks and variable ratio steering box. If you remember, I drove this piece back to Raleigh NC from Anaheim CA after it sat on a Buick dealership’s showroom for almost 20 years. I don’t normally talk about the upgrades as I don’t want to offend the purists on the forum unless someone is looking for advice on what I’ve done. I had two original one owner 65’s that were lost in a fire back in 1980. Would’ve kept at least one of them.
 

Would like to get photos but can’t get down on the ground for a couple months. Stress fracture to my left femur and on crutches. Can’t bend my leg and NO weight on it so I can’t do anything on the car at this point. Was hoping to finish the interior enough to drive it by end of this month but if I’m lucky, maybe by spring at this point. 
 

Getting old sucks!

 

Ray

[BulldogDriver]

5 hours ago, 1965rivgs said:

KRmanr,

  The Gran Sport cars came standard with dual quads and they were rated at 20 extra HP. You are right on regarding your statements about the over axle pipes.

Tom

The axle pipes that came with my installation  weren’t  flattened just bent to conform to the area. Looked like the ones removed.

 

Ray

[1965rivgs]

36 minutes ago, BulldogDriver said:

Looks pretty much stock. It’s a stainless steel system with a two piece long pipe coming off the headers. Easier to ship and gave some wiggly room for installation but you install two more clamps. What I removed was not stock and the hangers were cobbled together so I had nothing to compare to. Bought a new set of Waldon hangers for GS. Once I had the parts assembled and aligned, it looks stock other than all pipes being 2 14” and muffler is not oval but round. Price was good especially  for a 316 SS system. Should never rust. Went with resonator eliminators as I have a fuel filter in that area, was going with EFI originally but decided carb was a better fit for me and didn’t want to re-plumb fuel lines. Exhaust that was on the car didn’t have resonators either.  

My plan was/is to have an updated gen 1 Riviera that when you look at the exterior and interior it looks mostly stock. Open up the hood and the upgrades show. Performance and handling is as good as possible using original suspension design with updates. 4l60E transmission, Vintage Air A/C, Rostra cruise control, hidden oil pressure/volts/temp gauge and usb power connector, disc brakes, sway bar front and back, springs, Bilstein shocks and variable ratio steering box. If you remember, I drove this piece back to Raleigh NC from Anaheim CA after it sat on a Buick dealership’s showroom for almost 20 years. I don’t normally talk about the upgrades as I don’t want to offend the purists on the forum unless someone is looking for advice on what I’ve done. I had two original one owner 65’s that were lost in a fire back in 1980. Would’ve kept at least one of them.
 

Would like to get photos but can’t get down on the ground for a couple months. Stress fracture to my left femur and on crutches. Can’t bend my leg and NO weight on it so I can’t do anything on the car at this point. Was hoping to finish the interior enough to drive it by end of this month but if I’m lucky, maybe by spring at this point. 
 

Getting old sucks!

 

Ray

  Am interested to see what the larger tails look like to the average viewer when looking at the rear of the car from a standing position...if you ever get pics would like to see them

Tom

[1965rivgs]

29 minutes ago, BulldogDriver said:

The axle pipes that came with my installation  weren’t  flattened just bent to conform to the area. Looked like the ones removed.

 

Ray

  The originals are flattened in the area adjacent to wheel/tire

Tom

[BulldogDriver]

Tom, 

 

As I haven’t driven is yet, I don’t know if not being flattened will be an issue. Others have installed this vendor’s system and they haven’t mentioned it being a problem. Hope it’s not.
 

I wonder if the tooling cost to make that piece might have been a factor in leaving the size of the pipe the same as a non GS car. Buick might have thought it didn’t justify a retooling for the number they projected to make.
 

Photo from the back is not an issue. Will have it posted tomorrow.

 

Ray

[telriv]

All,

 

    The only thing I can think off as since the Riv. is supposed to be a personnal, luxury, preformance vehicle IF the pipes are too large the exhaust tone gets louder.  With smaller tail & over axle pipes will have a tendensy to be queiter with 2". When you put your foot to the floor that is when the proper noise level is louder.

    This is one of the things. If we are comparing don't forget the 2" long exhaust pipes had a big restrictive loop in them under the seat area. So not only restrictive but when the left motor mount breaks, AND it will, it restricts the amount of lift to try & save the radiator, shroud, fan blade & other parts from  breakage.

    My thoughts on the matter.

 

Tom T.

Edited August 6, 2021 by telriv (see edit history)

[1965rivgs]

10 hours ago, telriv said:

All,

 

    The only thing I can think off as since the Riv. is supposed to be a personnal, luxury, preformance vehicle IF the pipes are to large the exhaust tone gets louder.  With smaller tail & over axle pipes will have a tendensy to be queiter with 2". When you put your foot to the floor that is when the proper noise level is louder.

    This is one of the things. If we are comparing don't forget the 2" long exhaust pipes had a big restrictive loop in them under the seat area. So not only restrictive but when the left motor mount breaks, AND it will, it restricts the amount of lift to try & save the radiator, shroud, fan blade & other parts from  breakage.

    My thoughts on the matter.

 

Tom T.

Hi Tom,

  The Gran Sport exhaust has larger tail pipes than the standard system.

Tom M

[BulldogDriver]

Couple photos of the tailpipes and muffler. 
 

Ray

[telriv]

Tom,

   After I thought the standard exhause tail pipes IF I remember correctly are 1 3/4".

    So to rehash:

    GS exhaust pipes are 2/14" & follow the X frame.   Non GS  is 2" with a big loop under the seats.

    GS resonators are 2 1/4" inlet & 2" outlet.   Non GS are 2" inlet & 2" outlet.

    GS over axle pipes are 2" inlet & 2" outlet.  Same for non GS.

    GS mufflers are 2 1/4 " inlet & 2" outlet. Non GS is 2" inlet & 1 3/4" outlet.

    GS tailpipes are 2". Non GS is 1 3/4".

 

Thank you for bringing this up.  I totally forgot about this.

 

Tom T.

[RivNut]

So, the over the axle pipe is choking down the Gran Sport system?  Except for the smoother radius bends, there is no real advantage to the Gran Sport system? Especially since it's choked back coming from the manifolds. 

[telriv]

Since GS & non GS have the same manifolds one could enlage the openings from 2" outlet up t 2 1/4" along as what I've posted previously.  Anything you can do to improve this flow is all good.

And installing the GS system on any 1st. gen Riv. will only enhance performance especially IF you made other mods.

 

Tom T.

[RivNut]

The one mod that seems to be needed, besides opening up the manifold, would be the installation of the unoptainium over the axle pipe, if you're going with OE parts.  Sounds like exhaust exiting ahead of the rear tires might be a performance upgrade but not much for aesthetics.