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GMPP 12496820 Carb to TBI

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Old 04-20-2022, 09:27 PM
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GMPP 12496820 Carb to TBI

Well, after reading THIS thread and watching the linked video, it got me thinking about my latest intake purchase. Based on some of the discussion of what the intake may or may not have, and to help me understand what will need to be done to make this work on my L03 with L30 Vortec heads, I thought this image might help. Please feel free to tell me if I have something labeled incorrectly, or if you can fill in the ??? items. I skipped labeling the 8 intake bolts, and the carb flange.



Old 04-20-2022, 09:45 PM
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Re: GMPP 12496820 Carb to TBI

I think the one on drivers side center is for the old a/c support bracket
Old 04-20-2022, 09:46 PM
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Re: GMPP 12496820 Carb to TBI

1&2 coil bracket
Old 04-20-2022, 11:41 PM
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Re: GMPP 12496820 Carb to TBI

What you have labeled "??? Linkage Bracket ???": Front hole is for brace to alternator on my K1500. Rear hole I don't know. Potentially the two threaded bosses could be used for an A/C compressor bracket or somesuch.

"Temp sensor / TVS??? Forward Facing" is for the Vortec coolant bypass to the Vortec water pump.

"??? A/C Compressor or belt tensioner" I haven't seen used on pickups. My stock TBI manifold has the boss, but it's not drilled and tapped. I think it's used on vans; and perhaps cars.

"??? To or From Heater Core ???" is the outlet TO the heater core, it cannot be "from" the heater core. The heater core return hose would connect to the radiator "cool" tank, or to the water pump. Be sure to use a restricted fitting in that port, so the heater core does not get full water pump pressure. Makes a difference at higher RPM.

You've got no place to mount the EST module, EGR solenoid, or MAP sensor, which are all on one bracket on my K1500, just ahead of the EGR valve.
Old 04-21-2022, 04:55 PM
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Re: GMPP 12496820 Carb to TBI

Thanks guys. While I've owned this car for many years, I have had to do nothing under the hood except clean. I really don't know my way around under there as well as I should.

Originally Posted by Tuned Performance
1&2 coil bracket
Got it. Very hard to see anything under the hood with everything in place. But I can see a few anchor points for the coil in these photos, one shared with the cable bracket. Looks like I should be able to modify the cable bracket to work with the corner bolts on the Vortec intake.





Originally Posted by Schurkey
What you have labeled "??? Linkage Bracket ???": Front hole is for brace to alternator on my K1500. Rear hole I don't know. Potentially the two threaded bosses could be used for an A/C compressor bracket or somesuch.
Looks like those are unused on the factory TBI intake. I love the extra loose nut laying in the intake...had not seen that before. Looks just like the one on the stud in the foreground. I'm guessing they dropped one while driving the one on to the stud.




Originally Posted by Schurkey
"Temp sensor / TVS??? Forward Facing" is for the Vortec coolant bypass to the Vortec water pump.
Good to know. As sold to me, it has a sensor in it, so mine was just a guess, hence the ???. Now, with Vortec heads, do I need to use that as the factory did on a Vortec engine, or can I just cap it off? There's nothing like that on the current TBI intake or pump.




Originally Posted by Schurkey
"??? A/C Compressor or belt tensioner" I haven't seen used on pickups. My stock TBI manifold has the boss, but it's not drilled and tapped. I think it's used on vans; and perhaps cars.
Looks to be the same on my TBI intake as well.



Originally Posted by Schurkey
"??? To or From Heater Core ???" is the outlet TO the heater core, it cannot be "from" the heater core. The heater core return hose would connect to the radiator "cool" tank, or to the water pump. Be sure to use a restricted fitting in that port, so the heater core does not get full water pump pressure. Makes a difference at higher RPM.
Out of the engine TO the heater core. Got it. Thank you. Looking under the hood, I can see the Rube Goldberg-like heater hoses running here and there to the control valve. What a mess....something I already planned to attack. The only one I can't trace is the one coming out of the core, and it turns straight down. I'm assuming it's attached to the water pump somewhere/somehow, but I sure can't see it with everything in place.

Heater hose restriction...did not know about that. Thanks for sharing that info. In the "auction" picture of the intake posted above (the one with the intake sunning itself by the pool), you can see a fitting for that heater core hose. The fitting is smaller in diameter inside by far than the hole in the intake. Is that the sort of restriction you are speaking of? Let me go get a picture of that.




Originally Posted by Schurkey
You've got no place to mount the EST module, EGR solenoid, or MAP sensor, which are all on one bracket on my K1500, just ahead of the EGR valve.
Yes, that was mentioned in the video, and I think you mentioned it above. Too congested back there for me to SEE what you are talking about at the moment, but I'll take your word for it. Something will have to be fabricated for sure.

I can also see how the TBI EGR is mounted now. Never paid much attention to it before. But I can clearly see that will have a new home (location) on the new intake. And I can see how that adapter might help. We'll see.




It also appears that the GMPP intake does not have a provision for the stud/nut that anchor the end of that alternator pencil brace. (Yes, mine came with a cross-threaded nut muscled into the now non-useable stud, leaving a gap to the pencil brace. Thank you Mr. Goodwrench.)



Last edited by DynoDave43; 04-21-2022 at 05:03 PM.
Old 04-21-2022, 05:28 PM
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Re: GMPP 12496820 Carb to TBI

Originally Posted by DynoDave43
Looks like I should be able to modify the cable bracket to work with the corner bolts on the Vortec intake.
That bracket is different than the one on my K1500; yes, it does appear easier than mine to modify to adapt to the Vortec bolt pattern.

Originally Posted by DynoDave43
Now, with Vortec heads, do I need to use that as the factory did on a Vortec engine, or can I just cap it off? There's nothing like that on the current TBI intake or pump.
If you use a Vortec water pump, you'll need to use the Vortec coolant bypass pipe that connects to that port. With a TBI water pump, cap it off.

Originally Posted by DynoDave43
Out of the engine TO the heater core...

...Heater hose restriction...did not know about that. Thanks for sharing that info. In the "auction" picture of the intake posted above (the one with the intake sunning itself by the pool), you can see a fitting for that heater core hose. The fitting is smaller in diameter inside by far than the hole in the intake. Is that the sort of restriction you are speaking of? Let me go get a picture of that.

Yes, that's the sort of restriction I'm talking about. The quick-coupler on my K1500 is even more restricted. The restriction is intentional, it prevents gurgling noises in the heater core, it also prevents the heater core from exploding at high RPM due to water pump pressure. That's also why heater core outlet connections/hoses are usually (not always) larger than the inlet hoses.

Photo of the quick-coupler, note how the coolant passage is restricted to about 1/4 inch, with a plastic divider cutting flow even more.
(Lower left corner of photo.)


Originally Posted by DynoDave43
It also appears that the GMPP intake does not have a provision for the stud/nut that anchor the end of that alternator pencil brace. (Yes, mine came with a cross-threaded nut muscled into the now non-useable stud, leaving a gap to the pencil brace. Thank you Mr. Goodwrench.)
Isn't that just the front left corner of the intake manifold? To fix that, you'd just need a replacement studded bolt (or repair the threads on the one you have.) The studded bolt should be available from GM, or from any Treasure Yard. On my K1500, that "pencil brace" goes to the forward one of those two bosses on the side of the manifold below the throttle body.

However, since the angle the bolt goes into the manifold/cylinder head is different on the Vortec than the TBI, your "pencil brace" will need modification or you'll have to fabricate a different one.

Last edited by Schurkey; 04-21-2022 at 05:34 PM.
Old 04-21-2022, 06:59 PM
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Re: GMPP 12496820 Carb to TBI

Originally Posted by Schurkey
Isn't that just the front left corner of the intake manifold?

However, since the angle the bolt goes into the manifold/cylinder head is different on the Vortec than the TBI, your "pencil brace" will need modification or you'll have to fabricate a different one.
Yes, it is the intake bolt. Also has an engine lift hook stacked up under it. It's a busy corner.


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