85 Chevy 350 Conversion Van Overheats):
Hello! So I'm new to this forum and rving in general. I bought my dream car so I could drag my sorry arse out the bay area and find where I belong. Everything about this beast was perfect. A li...
Forum Discussion
Okay, let's trouble shoot this puppy and see what comes up. Being an '85, it should be carbureted. This can make a big difference as FI has different tendencies. On the other hand, 1985-86 is when GM was switching over.
When I saw it overheated quickly, my first thougght was plugged exhaust from sitting and mice building a condo in the pipes. However, did it still do it when the exhaust was unhooked? If the pipes weren't unhooked, it may be a bad catalytic converter or muffler. A vacuum gauge will tell the tale here. If the pipes were unhooked, check your heat bypass on the passenger side exhaust manifold. It diverts exhaust gasses through the manifold to keep the carburetor from icing up during warm up. I've seen manifolds glow cherry red from a blocked exhaust.
Now, some other things I've seen in no particular order are,
A bad lower hose where the spring has rusted away can collapse and close off water flow.
Water pump impellers can corrode when the antifreeze isn't replaced every few years. I've also seen (only once thank goodness) pieces of gasket material but with no water holes at the pump block meeting.
Timing off.
What was supposed to be a 350 was actually an SB400 with 350 heads. (No steam holes).
The timing chain was installed off time.
Lack of air flow, although this usually doesn't over heat that fast.
Burnt valves. (Have you done a compression test?)
When you fixed the blown head gasket, did you use the right gasket? 350 and 400 are different. Like other posters have mentioned, belt routing does make a difference. When you had the intake off to replace the gasket, did you clean the cross over tube in the intake? It gets blocked with carbon.
When I saw it overheated quickly, my first thougght was plugged exhaust from sitting and mice building a condo in the pipes. However, did it still do it when the exhaust was unhooked? If the pipes weren't unhooked, it may be a bad catalytic converter or muffler. A vacuum gauge will tell the tale here. If the pipes were unhooked, check your heat bypass on the passenger side exhaust manifold. It diverts exhaust gasses through the manifold to keep the carburetor from icing up during warm up. I've seen manifolds glow cherry red from a blocked exhaust.
Now, some other things I've seen in no particular order are,
A bad lower hose where the spring has rusted away can collapse and close off water flow.
Water pump impellers can corrode when the antifreeze isn't replaced every few years. I've also seen (only once thank goodness) pieces of gasket material but with no water holes at the pump block meeting.
Timing off.
What was supposed to be a 350 was actually an SB400 with 350 heads. (No steam holes).
The timing chain was installed off time.
Lack of air flow, although this usually doesn't over heat that fast.
Burnt valves. (Have you done a compression test?)
When you fixed the blown head gasket, did you use the right gasket? 350 and 400 are different. Like other posters have mentioned, belt routing does make a difference. When you had the intake off to replace the gasket, did you clean the cross over tube in the intake? It gets blocked with carbon.
