Startup condensation.

[Mad4slalom]

Morning all. I have alwsys noticed on starting the 72, after it has sat in the garage for 2-3 minutes warming up that i get a 2-3” pool of water under the drivers side rear box. It comes from the joint between the muffler and the front exhaust pipe. I loosened and re positioned the exhaust clamp but made no difference and puddle still there on next start up. Anyone else had this? I presume if it didnt leak out it would come out the tailpipe as steam. I had heard from a corvette owner back in the day how he drilled the low point of his mufflers to allow condensation tho drip out rather than rust out his mufflers. If the car is driven and got up to temp then any water would evaporate anyway. Maybe a bit of assembly paste and re fit again?

 

[Roscobbc]

Morning all. I have alwsys noticed on starting the 72, after it has sat in the garage for 2-3 minutes warming up that i get a 2-3” pool of water under the drivers side rear box. It comes from the joint between the muffler and the front exhaust pipe. I loosened and re positioned the exhaust clamp but made no difference and puddle still there on next start up. Anyone else had this? I presume if it didnt leak out it would come out the tailpipe as steam. I had heard from a corvette owner back in the day how he drilled the low point of his mufflers to allow condensation tho drip out rather than rust out his mufflers. If the car is driven and got up to temp then any water would evaporate anyway. Maybe a bit of assembly paste and re fit again?

Presumably a stock system with exhaust to carb heat stove would explain the issue?

 

[Mad4slalom]

Presumably a stock system with exhaust to carb heat stove would explain the issue?

Hest stove? Remember something like that on an air cooled beetle motor, did the corvettes use that system? Mine has a holley 650dp with no choke. I am talking about a bit of condensation dripping out of the back muffler.

 

[Chuffer]

Morning all. I have alwsys noticed on starting the 72, after it has sat in the garage for 2-3 minutes warming up that i get a 2-3” pool of water under the drivers side rear box. It comes from the joint between the muffler and the front exhaust pipe. I loosened and re positioned the exhaust clamp but made no difference and puddle still there on next start up. Anyone else had this? I presume if it didnt leak out it would come out the tailpipe as steam. I had heard from a corvette owner back in the day how he drilled the low point of his mufflers to allow condensation tho drip out rather than rust out his mufflers. If the car is driven and got up to temp then any water would evaporate anyway. Maybe a bit of assembly paste and re fit again?

If the exhaust us not actually blowing once warmed up I would be tempted to leave it . Better to have the water drain out rather than collect and rust away exhaust , especially if you don`t drive it very often and only short journeys .

 

[Roscobbc]

I am talking about a bit of condensation dripping out of the back muffler.

Yes, but......if condensation is noticable out of drivers side exhaust AND you still have the oem exhaust manifolds and front downpipes in place (not headers) even if the heat stove components are missing there could still be the heat riser valve sitting between the passenger side manifold exit and the exhaust pipe flange. This was controlled by exhaust heat (and bi-metal spring?).
The idea being that when cold it would partly close the passenger side exhaust manifold outlet.....effectively forcing the passenger side exhaust gases partly back up through the inlet manifold cross-over in to the drivers side exhaust manifold to aid quick warm-ups.
If the flap is still present AND you have the stock or aftermarket inlet manifold with exhaust heat cross-over it might explain the reason why the drivers side exhaust shows more condensation and moisture whilst engine is warming-up.

https://www.corvettekingdom.co.uk/part/75-79-exhaust-heat-riser-valve-2/40

 

[Mad4slalom]

Yes, but......if condensation is noticable out of drivers side exhaust AND you still have the oem exhaust manifolds and front downpipes in place (not headers) even if the heat stove components are missing there could still be the heat riser valve sitting between the passenger side manifold exit and the exhaust pipe flange. This was controlled by exhaust heat (and bi-metal spring?).
The idea being that when cold it would partly close the passenger side exhaust manifold outlet.....effectively forcing the passenger side exhaust gases partly back up through the inlet manifold cross-over in to the drivers side exhaust manifold to aid quick warm-ups.
If the flap is still present AND you have the stock or aftermarket inlet manifold with exhaust heat cross-over it might explain the reason why the drivers side exhaust shows more condensation and moisture whilst engine is warming-up.

https://www.corvettekingdom.co.uk/part/75-79-exhaust-heat-riser-valve-2/40

Thanks rosscob for that detailed explanation, I have the stock rams horns , I will have a good look around , I think I would have noticed anything attached to them. I will look in the assembly manual. I guess the po in the states who fitted the manifold and holley carb may have removed it all when he ditched the choke mechanism.

 

[Mad4slalom]

If the exhaust us not actually blowing once warmed up I would be tempted to leave it . Better to have the water drain out rather than collect and rust away exhaust , especially if you don`t drive it very often and only short journeys .

Yes There is a tiny bit of soot on the joint but cant say I notice it blowing. It still leaked water after re tightening so like u say better out than in.

 

[Mad4slalom]

Thanks rosscob for that detailed explanation, I have the stock rams horns , I will have a good look around , I think I would have noticed anything attached to them. I will look in the assembly manual. I guess the po in the states who fitted the manifold and holley carb may have removed it all when he ditched the choke mechanism.

Had a Look around the manifolds and cant see anything that looks like the system parts you describe. I guess he was going for the clean , uncluttered engine bay look.

 

[Roscobbc]

It seems to me that even current model cars with multiple exhaust outlets often seem to emit differing levels of visible exhaust......certainly on cold start-ups or before fully heated through.