CK5
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76’ 400ci overheating bad
- Thread starter CraigFulton
- Start date
CraigFulton
1/2 ton status
I will add that the temp gauge gets to half pretty quick. My other cars it takes 4 times as long but they are modern.
What is the coolant mixture? @K5wrench asked that a few posts back, and maybe I missed your answer. If this thing is running straight water, we have an issue
Also, how close is the new exhaust to the fuel lines? They may have created a problem there
CraigFulton
1/2 ton status
This area gets so hot that touching it will burn your hand.
CraigFulton
1/2 ton status
Coolant is almost 50/50. Definitely more the green stuff than water.
You can see the exhaust. Seems to be stock location. The fuel lines are stock too. They are installed inside the C frame and wrapped in thermal barrier
So the engine has not boiled over?
Just the floor gets hot?
If that is true; check for an exhaust leak, or maybe just pipe run too close to floor.
You mentioned the "tube" in quadrajet missing.
Those main jet air bleeds fall out all the time.
Can also cause poor driveability that seems like vapor lock.
Check that you have the right gasket at top of quadrajet.
There were some that look alike except the main jet air bleed area of gasket is square or round.
Mixing them will cause big lean running issues.
Also, loose carb top screws or broken gasket can cause vapor lock type symptoms.
Usually runs okay at idle but stumbles when secondarys open.
Confusing the issue with a broken or misadjusted secondary air valve spring.
CraigFulton
1/2 ton status
The mufflers are directly under where the floor is getting hot first. Must be spreading from there. So the exhaust might be the part that is getting hot as Fu&$
CraigFulton
1/2 ton status
Engine has never boiled over. The engine has never overheated. It vapor locks only. 100% confirmed vapor lock.
The manifold vacuum tube was gone from the carb. I installed a new tube and put the vacuum advance on it.
The vapor lock I’m getting is a complete shut down. I fan the engine area with a flat cardboard box for about 30-45 minutes. Put a little fuel directly into carb and it starts again.
The carb was rebuilt before I rebuilt it. The reason I had to rebuilt was because when I was adding the mr gasket heat risers I somehow caused the primary to leak. It was dumping gas into driver venturi. After I rebuilt it that seems to have gone away. Any idea on torque spec for carb bolts to manifold? (The ported vacuum is plugged at the end). Pointing to tube I replaced.
What and where are the mufflers?
They didn't run the inlet as the outlet did they?
Going to injection may help some of the issues due to an electric fuel pump. But if you are heating the fuel, it will possibly remain an issue even then
They didn't run the inlet as the outlet did they?
Going to injection may help some of the issues due to an electric fuel pump. But if you are heating the fuel, it will possibly remain an issue even then
CraigFulton
1/2 ton status
Adding more pics.
And oh man the transmission pan is very very hot tot he touch. Blazer has been sitting for 2 hours. Thoughts?
And oh man the transmission pan is very very hot tot he touch. Blazer has been sitting for 2 hours. Thoughts?
CraigFulton
1/2 ton status
Another pic of exhaust near fuel lines
And the mufflers. Inlet?! I have to imagine there are two inlets on these mufflers?
And the mufflers. Inlet?! I have to imagine there are two inlets on these mufflers?
CraigFulton
1/2 ton status
Mufflers are cool as a cucumber but the transmission is super hot
CraigFulton
1/2 ton status
It’s one below the N. Under the impression thisnis all time 4WD. No locks on hubs to turn.
I would guess that the head gaskets possibly are not opened for the stream holes. But again at least one head needs to come off to check
If it runs well wouldn’t think retarded timing is the cause.
Definitely don’t keep overheating a 400 block.
Vapor lock is a common problem with today’s fuel. Overheating only exasperates the problem obviously.
I had to run a return from just before the carb back to the tank to help the vapor lock issue although my 74 350 although it never quit and shut off completely.
If it runs well wouldn’t think retarded timing is the cause.
Definitely don’t keep overheating a 400 block.
Vapor lock is a common problem with today’s fuel. Overheating only exasperates the problem obviously.
I had to run a return from just before the carb back to the tank to help the vapor lock issue although my 74 350 although it never quit and shut off completely.
CraigFulton
1/2 ton status
So I completely forgot something my son just reminded me. The last guy told me during the re-assembly he thought the trans fluid fill tube seal was leaking. I put a quart of ATF and the next day about a 1/4 of it was now on the ground. No more has leaked in a couple of months. I figured whatever made it leak must’ve been overflow. Haha. I can’t believe I forgot that and haven’t gone back to check.
CraigFulton
1/2 ton status
So it sounds like the main thing I need to do is pull the intake and a head and see what the gasket looks like?
Still waiting to hear from last guy who he had rebuild this in San Diego.
Still waiting to hear from last guy who he had rebuild this in San Diego.
CraigFulton
1/2 ton status
Checked again. Engine is warm and can be touched. Transmission pan is so hot you can’t touch it for long.
I just recalled an epsisode of vapor lock my 76 k5 with the 400 had.
Could have happened to and sbc but i so happened to have that same k5.
It was outside Ely Nevada and 100 degree day.
Kept stalling on those passes.
For whatever reason, I pulled the gas cap and a blast of pressurised vapor came out.
My vent line thru thr canister was plugged by prev. Owner.
Fixed it.
Still had issues.
Replaced fuel pump.
Still had issues.
Tightened top of carb.
Problem solved.
But any one of those things could have been the issue.
The plugged fuel tank vent was bad but wasn't the cause of the stall.
Sometimes it just takes a steadfast approach of following each problem and correcting them.
I would start by actually verifying the coolant is getting too hot.
Use a seperate thermometer.
If it is, check that the thermostat is opening, or not in backwards.
If the coolant is only reaching 180 at the top hose and perhaps 150 at the bottom hose, you don't have an engine over heat problem.
Could have happened to and sbc but i so happened to have that same k5.
It was outside Ely Nevada and 100 degree day.
Kept stalling on those passes.
For whatever reason, I pulled the gas cap and a blast of pressurised vapor came out.
My vent line thru thr canister was plugged by prev. Owner.
Fixed it.
Still had issues.
Replaced fuel pump.
Still had issues.
Tightened top of carb.
Problem solved.
But any one of those things could have been the issue.
The plugged fuel tank vent was bad but wasn't the cause of the stall.
Sometimes it just takes a steadfast approach of following each problem and correcting them.
I would start by actually verifying the coolant is getting too hot.
Use a seperate thermometer.
If it is, check that the thermostat is opening, or not in backwards.
If the coolant is only reaching 180 at the top hose and perhaps 150 at the bottom hose, you don't have an engine over heat problem.
CraigFulton
1/2 ton status
Block is never overheating. I think the fuel is getting hot from exhaust/transmission before it gets to the pump
