350 tbi to 350 vortec

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monk

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I have a good used 350 tbi motor. I want to remove the heads and install vortec heads with a carb. I am planning on installing a comp cams 12-300-4 cam. My questions are which intake to use, and headers or manifolds with out smog? This will replace the 305 in my 1983 k10. Thanks for the help.
 

1987 GMC Jimmy

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I have a good used 350 tbi motor. I want to remove the heads and install vortec heads with a carb. I am planning on installing a comp cams 12-300-4 cam. My questions are which intake to use, and headers or manifolds with out smog? This will replace the 305 in my 1983 k10. Thanks for the help.

Use Chevrolet Performance 12496820. It's the cheapest one I know of, but you'll still be running the EGR on this one. I'd plop a nice Quadrajet on there or get an adapter if you're not a fan. If you're doing this much, you might as well get a set of headers. Personally, I don't care about brand so I'd shop online for the cheapest set of Action Line/Square Body long headers you can find. It shouldn't be much more over a hundred.
 

Camar068

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I read some decent reviews of some of the ones on ebay for about $150. Swear I read some of the reviews here.
 

HotRodPC

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Just a bit of warning here, HOW USED is this TBI 350? Remember, Vortec heads are going to raise the compression significantly. If those older used rings are a bit tired, they'll be in the oil pan in no time with the vortec head compression bump. Now I don't mean literally in the oil pan. Just saying, them rings might give up, and adding a mild or RV cam too, I'd say you can likely expect it to happen if it's a 100,000 mile or so engine.

Maybe a total rebuild isn't necessary, but I think I'd at least Re-Ring and Rod Bearing that used TBI 350 before I put Vortec heads on it with a bigger cam and headers.

Edelbrok also make that conversion intake. Check Summit and Jeggs.
 

monk

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The motor has well under 100,000. If I were guessing I would say somewhere in the 30-40 range. I did pick up a set of vortec heads today the 906.
 

HotRodPC

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The motor has well under 100,000. If I were guessing I would say somewhere in the 30-40 range. I did pick up a set of vortec heads today the 906.

30-40,000 mile range, you should be good to go without any issues. Dr that bitch up and let it eat !!!
 

77 K20

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How cold is it there where you are in NC? I ask because my 383 came with that GM performance manifold (12496820). I live in Montana where it can get very cold in winter and even in the summer can get cold at night.
I spent a year fighting with 2 carbs and then fuel injection trying to figure out why when it was less than 45 degrees it would run like crap.
It was the intake manifold. Vortec heads do not have the exhaust crossover that puts exhaust under the carb in the intake manifold. Plus the design of that manifold is perfectly smooth under the carb. Most manifolds have a waffle pattern or "speed bumps" on the manifold there. When atomized fuel hits cold metal and has to change direction by 90 degrees the fuel can drop out of suspension. This makes a puddle of fuel form. By having raised ridges then the fuel can lift off and be carried away by the air.
After finally figuring that out I bought an Edelbrock 7116 manifold that you can plumb either exhaust or coolant thru a heat passage under the carb.
Unfortunately I bought a defective one. Somehow after driving it and the engine would cool down it would leak coolant up into the intake plenum and would then burn off a very small bit of coolant next time I would start it up. Edelbrock said they had never heard of that before. I bypassed the heat plenum and the coolant loss problem went away. So- I bought a second @#$^$# Edelbrock 7116 and installed it. All is good now. The manifold heats up pretty fast with having coolant go thru it.

And speaking of coolant... when using Vortec heads there is supposed to be a coolant bypass:
Any small block engine, regardless of year, that uses Vortec heads, will require an external coolant bypass line from the intake
manifold to the 5/8" hose nipple on the water pump (passenger’s side). Suggested routing is from the 3/8 NPSF boss on
intake manifold to the water pump.

With the 7116 manifold I'm running the bypass from the front fitting near the thermostat to the heat plenum under the carb then to the return on the water pump. This allows circulation before the thermostat opens.
I also have a loop from the intake manifold thru the heater core back to the top of the radiator. At first I tried just the heater loop- but had wild coolant temperature fluctuations. The other loop stopped all of this.

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1987 GMC Jimmy

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This is a good testimonial. I was thinking about building a Vortec motor in mine and modifying the TBI to handle it and a bunch of other upgrades including the Chevy Perdormance intake. I'll probably end up getting a good set older cast iron heads and using Holley 300-49. I'm still figuring it out, though.
 

RangRayy

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I am currently in the middle of a carb swap on my TBI '87. I opted to keep the swirl port heads that came on the motor for budget reasons and I will upgrade heads when I fully rebuild the motor. I am sitting at 129k miles and I too was thinking of the 12-300-4 cam and from what I have read and the testaments from members here it is a good cam for low power up to the 4500rpm range.

I went with edlebrock 2104 intake for the canted 2 center bolts to match the heads and the non egr. as far as vortec heads go im sure you can find a decent intake online, I found my on CL and had the guy ship it to me. He was in Springfield MO and I am in Kansas City MO so it only took about a day to get to me.

I used Hooker Headers p/n2452 for 2wd and 2451 for 4wd??:shrug:cannot remember sorry. They were about $200 on Jegs but were on sale. Flowtech is the other brand Holley makes and they might be cheaper. I also used Hookers 2 1/4 exhaust pipe kit to complete the exhaust.
 

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