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76’ 400ci overheating bad

Just got it out for 25 miles. Floor still gets hot as hell. Just parked it and took some temp readings. Trans is only 165 degrees. Exhaust is insanely hot at 450 at the end of the manifolds on both sides. That normal?

The good news is the intake manifold is only 145 compared to the 230 it was prior.
 
I could probably have fried eggs on the bare floor of my '72 K5,and it only had a bone stock 350,didn't change any when I ditched the ailing TH350 in favor of an SM465 either..

It's probably not unusual for the exhaust manifolds to get that hot--after all they have 4 cylinders pumping combustion gases that reach much higher temps..the 400 SB I had in a '77 GMC K2500 used to turn the exhaust manifolds a dull red at night after a highway cruise or when I had been pushing heavy wet snow with it for a half hour..engine didn't peuke coolant out and the temp gauge read normal too..the manifolds were thin due to rust making them flake away and that probably made it easier to see just how hot it is in those cast iron logs..
 
Ok. So it’s normal.

Now I noticed something else. Ugh. It looks like a TINY leak at the front of the intake smack center right above the timing cover. I ntoiced it because the gasket for the cover was wet at the top. Then I noticed a little trail. I mean tiny amount. Please tell me there’s a trick for this without pulling the intake again?

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Yeah, I don't think that your temperatures are a concern. But most of us leave the rubber end seals out and only use silicone on the intake.
 
CraigFulton said:
I put silicone on both sides like the Chilton called for
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Yes, but what I mean is to not use the rubber pieces, just silicone.
With the rubber in there, it is a hit or miss scenario, from my experience. An old guy told me to throw the rubber parts away. I have had a better success rate since then.
 
Per the leak, like a couple others have already said; just pull the manifold, toss the rubber ends in the trash and reseal using a 1/2” bead of good RTV. You’re more likely to experience a leak with the rubber seals than without them.
 
1975Jimmy said:
Per the leak, like a couple others have already said; just pull the manifold, toss the rubber ends in the trash and reseal using a 1/2” bead of good RTV. You’re more likely to experience a leak with the rubber seals than without them.
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Dude. Hahaha. That’s like another 3 hours of work on top of the 12 I spent on this conversion.
 
X2 on ditching those rubber seals,they suck..

You "might" be able to seal the leak up by using a trick I saw on YouTube that worked for me on a oil pan on my truck that rotted thru and had pinholes oozing oil.

I put my shop vac's hose on the oil filler spout on the engine using duct tape to make a good seal,blocked off the breather on the other valve cover,and turned the vac on,and I could see the oil drops oozing out of the oil pan,get drawn back into the crankcase,the vacuum creates a suction in the crank case..--then I was able to wash the oil pan down good with brake cleaner after wire brushing the heaviest gook off,and apply some RTV,I used the black stuff,but "Right Stuff" was reportedly better for this purpose..
I let the vacuum run about 10 minutes until the RTV had hardened some,and the leaks were stopped..

Seeing there is supposed to be a vacuum in the valley created by the PCV valve and no real "pressure",this might seal up your minor weeping in that spot,which is easy to get at --your lucky,every time I had a intake leak I used those stupid rubber seals on,it leaked like a seive out of the rear,onto the bell housing,and it didn't always leak right away,instead it made me feel confident I did it right and could trust it,and the first long ride I took,I almost had to get towed home,so much oil was leaking and getting onto the exhaust pipes..
 
That’s a great trick! I might give that a shot.

I may have gotten lucky. I cleaned it off last night and then drove it to work today...25 miles. I just checked. No oil there. All dry.
 
end gaskets rubbers get tossed in the trash when you open the box .

then good thick bead of black rtv or even better THE RIGHT STUFF sealer . then set it down and bolt it down .

and toss that blue rtv in the trash can . thats so 1970's and against the clean blazer you got and nice orange painted engine it looks like crap .
 
Supposedly the "Ultra Blue" was supposed to be the best choice for oil exposure like on valve covers,etc,but I agree the stuff was invented 40 years ago and though its still around,the other choices like "Ultra Black" seems to have taken over in most shops ,and the "Right Stuff" ,though expensive,seems to be the best of all..

The Hi-Temp Orange silicone RTV I liked a lot,and it matches Chevy Orange paint pretty good too..I also like the Ultra Copper RTV,but I hate the cost of ALL the different RTV choices,especially the "Right Stuff"..at $10 a tube or nearly $30 for a caulking gun cartridge of it,I think they are gouging charging that much...you could buy RTV for $2.99 a tube when it just started becoming popular..

I have bought some "Versa-Chem" brand for much less,like $3 a tube, that seems to work equally well,and I think its actually an offshoot of the Loctite/Permatex company that makes it..probably the same thing in a different packaging..
 
Ok. Point taken :D

I did the blue because I remember all those times using that with my dad and that unique smell. It took me back. The last builder used the black. I plan to trim the blue away and if I redo it I will get the right stuff.
 
FWIW, I actually got lucky with the NP241 leak (straight RTV) by using brake clean on it, letting it dry thoroughly, then spreading a new coat of RTV over it. Leaked everywhere else, but THAT spot didn't.

Just in case you see it again, I think it would be worth a shot. I like the variation Diesel gave above. The only alternative would be to pull it and do it over. Pretty much standard on the SBC to not use those gaskets. I think some of the instructions even state to toss them. Why they are still in the kits, I have no clue. I've never heard anyone recommend them.
 
I just ordered a T-shirt that has a photo of those gaskets and on the back it says “yeah I’m the guy that actually used them”. Hahahaha

I just drove it again and no leaks. Who knows. Maybe it didn’t even leak from the seal. If it comes back I will redo it. For now I’m going to move on with a new radio install. I got one of those retro stereos. Some new window and door seals. And I have some old wiring to remove from the original owner for trailering and spare fuel tanks. I plan to get it repainted next year and have the tanks removed entirely.
 
Drive home from work in death heat FL rush hour

I won’t lie. I was nervous as shit sitting at lights waiting for it to die. I made it home! However. The floor was 128 degrees! The AC can’t even keep up so I shut it off. Got home and checked the fuel tank is 120-140 degrees. Hopefully this vapor lock is solved.
 
CraigFulton said:
Drive home from work in death heat FL rush hour

I won’t lie. I was nervous as shit sitting at lights waiting for it to die. I made it home! However. The floor was 128 degrees! The AC can’t even keep up so I shut it off. Got home and checked the fuel tank is 120-140 degrees. Hopefully this vapor lock is solved.
Click to expand...
Put an aluminum shield between the floor and the exhaust.
 
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