1973 eldo 500 intake manifold

[J Kinley]

This is a picture of the left side of my intake manifold .  The blue paint is turning white on the 4-6 intake port.  There was a post earlier about the heat tube rusting out on a 472 manifold.  Do I have the same thing going on and how do I fix it?

[TJ Hopland]

I didn't think any of the 472/500's had the internal choke tubes but I could be wrong about the first few years.  The ones with the tubes had the choke coil on the side of the carb and the warm air came from the tube that was internal to the manifold.  The early 70's Cads had a recessed well in the intake and the choke coil mounted in that well and then a rod that ran to the carb.   

The area that is burnt is the exhaust crossover and it is normal for that to get hotter than the rest of the intake.  Does your car have a 'heat riser' valve at the end of the right exhaust manifold?  If so make sure its not staying closed and forcing the exhaust through the crossover when it shouldn't.  If you don't have one I would be inspecting the exhaust system for anything that could cause a restriction on one side over the other.  The original stock system had some areas that were double walled pipe so you could have an internal failure and still look Ok on the outside.  If you have an aftermarket dual system then maybe a muffler internal failure?         

[35-709]

Yes, that discoloration is normal --- the heat riser valve should be something you check regularly to ensure it is free, it will cause other problems if neglected/ignored.   

[V63]

Those passages route exhaust into the intake manifold for cold start situations and EGR. If your fuel mixture is too lean they would get Significantly hotter than Designed, as the whitish appearance might indicate.

I have started blocking that port with stainless steel due to alcohol blended fuel issues and the desert climate I reside. i also block the EGR. So far,  I'm remain very pleased with the intended results. Top image is open second is 'blocked' with sheet stainless

Well, I posted the same blocked image twice 🤦🏻‍♂️

[J Kinley]

I don't have a heat riser valve on the right side.  The exhaust doesn't look original and the muffler is new enough to still have a silver  color to it.  It can sit in the garage for a week and start right up.  but if we drive 6 miles to supper, and come out to go home ,  it might start and run for 5 seconds and then quit.   I can keep trying it and it will start just when I think the optima battery is going to give up.  I can drive home,  shut it off in the garage and it will start right back up.  I open  the hood and it just seems like there is a lot of heat coming off the engine.