Engine will not maintain temps

[bp71k5]

I looked back at the OP sensor adapter. I am pretty sure you can get an adapter that will allow that sensor to mount flush with the intake. Pretty sure Ace hardware or Homeless Depot has a brass adapter that goes flush. This would eliminate any air pocket and put the sensor right into the coolant flow to get an accurate reading. I still think that moving the sensor to the front of the intake near the T stat housing would be best, combined with the flush mount adapter. That 383 should be putting out plenty of heat otherwise.

X2 on all of that.

 

[The_Tomato]

OP I think we need some action here before we all drive ourselves up a wall figuring this out

 

[dyeager535]

Sorry, but it will make a difference. If the coolant can't flow past it, how will it tell when the system gets hot?
Coolant must flow to do it's job, and monitoring stagnant coolant isn't going to work. Same as if the bushing holds it out too far, but more pronounced.
Yes, location will make a difference in how much flow goes past the sensor.

What I'm saying is being exposed to flow isn't as important as being in coolant. Stagnant coolant will be hotter than non-stagnant coolant. Is that what his temperature sensor is telling him?

 

[Joel Wilson]

What I'm saying is being exposed to flow isn't as important as being in coolant. Stagnant coolant will be hotter than non-stagnant coolant. Is that what his temperature sensor is telling him?

Why and how would the coolant be stagnant? If it's stagnant and still exposed to heat, that coolant will boil. and I would think that the temps would be higher. A 400 has somewhat stagnant pockets which is why the steam holes are drilled.

The sensor location from the back of the intake to the front of the intake is roughly half the engine heat with the coolant getting hotter the closer it gets to the thermostat.

I'm still trying to figure out what kind of intake that is that actually has a coolant port in the rear of the intake. I know there are ports back there for vacuum, but do not remember ports for coolant.

Hopefully the OP is okay and not underwater from Ida. Maybe he could send some of that water out west. Lord knows we need it.

 

[az_762_nato]

Just dropped a GMPP vortec tbi intake onto a Blueprint 383 for the k30 crewcab that has the coolant port (heater hose) back there

 

[dyeager535]

Why and how would the coolant be stagnant? If it's stagnant and still exposed to heat, that coolant will boil. and I would think that the temps would be higher. A 400 has somewhat stagnant pockets which is why the steam holes are drilled.

I'm still trying to figure out what kind of intake that is that actually has a coolant port in the rear of the intake. I know there are ports back there for vacuum, but do not remember ports for coolant.

It's not likely to be stagnant. The point was, non-moving coolant is going to get hot, fast. If the sensor is in a running engine, reading head temperature, in coolant, whether or not the coolant is moving is irrelevant. Fluid temp will not be 150* except for a short period before the engine actually warms up. Especially given that in this case, the coolant temperature is warmer elsewhere apparently.

Maybe you know this, not to be condescending. SBC heads are one casting ...there is no left and right, therefore the coolant ports are identical at the "back" of the heads as to the front. In almost all setups the coolant passages that end up being at the rear of the heads are just "dead ends" because the intake has no crossover. But the passages in the heads are still there, so by drilling down through the intake, you will hit those passages, and thus coolant.

In any case, at least some later rigs with the SBC were setup to feed the heater core off one of those passages, so the intakes had to be drilled. It's not super uncommon. I'm not sure what drove some to use that rear coolant pipe setup, but from my limited experience with them, maybe it's TBI-era only? I know my buddies TBI suburban had it.

 

[Joel Wilson]

It's not likely to be stagnant. The point was, non-moving coolant is going to get hot, fast. If the sensor is in a running engine, reading head temperature, in coolant, whether or not the coolant is moving is irrelevant. Fluid temp will not be 150* except for a short period before the engine actually warms up. Especially given that in this case, the coolant temperature is warmer elsewhere apparently.

Maybe you know this, not to be condescending. SBC heads are one casting ...there is no left and right, therefore the coolant ports are identical at the "back" of the heads as to the front. In almost all setups the coolant passages that end up being at the rear of the heads are just "dead ends" because the intake has no crossover. But the passages in the heads are still there, so by drilling down through the intake, you will hit those passages, and thus coolant.

In any case, at least some later rigs with the SBC were setup to feed the heater core off one of those passages, so the intakes had to be drilled. It's not super uncommon. I'm not sure what drove some to use that rear coolant pipe setup, but from my limited experience with them, maybe it's TBI-era only? I know my buddies TBI suburban had it.

Right. I am aware that SBC heads are one casting, otherwise it would be a huge PITA getting the right size replacement head, for the right side...

When I got the heads for my 400, I spent a good amount of time just comparing the new to the old. I figured it's going to be awhile before I get to play with a set of brand new heads so I made it count.

I only mentioned the drilling of the heads for a 400 because of the hotspots that were created with the increased bore size. Not an apples to apples comparison, but more of an orange to mandarin comparison.

Never had a chance to play with a TBI, that was pretty much the time I was in the Navy so didn't have a whole lot of time or space to play with engines. Everything else has been 76 to 85. Maybe that TBI intake flows better? I looked on Summit to try and find it to possibly come up with a more educated guess but ran out of time yesterday.

And whoever sent rain to Norcal, many many thanks. .26 of an inch of rain in Sept is way better than nothing. Hopefully it will clean some of this smoke out of the air for a little bit.

 

[TJ1978]

Get a heat gun and make sure your temp gauge is accurate.

 

[PJ Walters]

Well boys WE DID IT!!! The smoking gun was the sensor location. As noted I am running a sniper EFI and the sensor was in the back of the manifold. So you boys that called that, you're on it! I moved the sensor to by the thermostat housing and it works great. maintains and holds temps as it should. I really appreciate the help and now I can go chase down other gremlins! Thanks again guys.