New Crate Vortec L31 into 94' Sierra 4X4. Any tips for the newbie???

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Old Gasser

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Hi everyone. I know this has been done thousands of times, but I would like some input before I forge ahead and have to start reinventing the wheel!
My 94' Sierra has @ 207K miles on it and is tired. It runs fine, but is weak. And the trans is definitely going south! But I will fix that later.

My question is: What is required to run my stock(or probably upgraded some) TBI, and all my stock accessories,i.e. air conditioning, power steering...etc. on a Vortec 350? I have read some info, but I would really hope some of you guys that have done this could give an idea what I would need to do to make the swap.

Before suggestions of 383's and LS swaps start rolling in, I'll just say I can get a deal on a Chevy replacement engine in a crate, and even the budget 383 motors I have put together, after machine work and parts will surpass the cost of the crate motor. It's purely a matter of economics. I have two hot rods already, don't need a pickup that will be a pain in the ass too! lol I do all my work myself.

I bought a beautiful 1994 Z-71 in 1996, only had 20K miles on it. Traded it in on a new 1998 K2500HD with a 454, and drove it until we bought a new 2015 Z-71! I had to do a cam swap on that 7.4, if anybody has a cam go bad I could tell you about that experience.

I know most of you guys on this board know these trucks very well. I hope somebody can give me a laundry list of stuff I i will need to do , and watch for.

Thanks in advance, I'm looking forward to hearing from you!
 

letitsnow

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What do you plan to use as an intake manifold? Do you have to worry about the distributor working correctly on the vortec motor??

I haven't done the swap that you are talking about, but did just install a new gm 5.7 in my '99.
 

Gramps

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All your accessories and brackets will bolt up fine.
You will need a new intake manifold and a tbi to 4bbl adaptor OR a manifold with the tbi boss on it(fairly expensive)

The distributor will work but you need a melonized drive gear on it otherwise it will eat the cam.

If you stay with the stock cam then the stock tbi will handle the fueling requirements maybe with a slight bump in fuel pressure.
 

Old Gasser

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All your accessories and brackets will bolt up fine.
You will need a new intake manifold and a tbi to 4bbl adaptor OR a manifold with the tbi boss on it(fairly expensive)

The distributor will work but you need a melonized drive gear on it otherwise it will eat the cam.

If you stay with the stock cam then the stock tbi will handle the fueling requirements maybe with a slight bump in fuel pressure.

Thank you Gramps. I do plan to experiment a bit with the TBI, after its running and broken in. I have read some on what that requires. I may put a new Vortec fuel pump in while I'm doing the rest, then tweaking on the TBI as I go. Bottom end torque and economy are my goals. From my observations so far, if I have good torque from @ 1500 or 1800rpm thru 4000, I'll feel this was a success. So far I've just driven highway/freeway, and cruise rpm is around 1800. But pulling my 4 wheeler and all my gear to hunting camp this year seemed to be a chore for the poor thing.

I'm familiar with the dist gear/steel roller cam situation. I would change the gear.
Thanks for the input!
 

JayMB

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What Gramps mentioned above is that you could also run any carb-style intake manifold that works with vortec heads (potentially cheap if found used), and then use a carb-to-tbi adapter - unless you need full emissions compliance, in which case I don't know anything about that ;). It is my understanding that there exists a factory application with a carb-to-tbi adapter (early tbi 454?) And I'm sure there's someone in the aftermarket that makes them too.
 

NightRunner

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Summit has TBI adapters so you can place it on a carb'd Vortec intake. Just look up throttle body adapters on Summit and you'll find it.
 

Elroy

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the GM performance intake in that summit link is the way to go, i put vortec heads on the original motor , had it on the 90 suburban in my pic, and a bored TB , intake bell, and bigger injectors from Turbo City in Anaheim
 

Schurkey

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1. Vortec block is not machined to mate with a TBI water pump. You will need to drill one hole (3/8" diameter) in the front face of the block to allow coolant to pass back into the water pump inlet. Use a water pump gasket as a template to locate the hole on the right side of the block just below the existing coolant inlet hole. I drilled a 1/8 pilot hole, then went through with the 3/8 bit. SOME vortec blocks have this hole partially-drilled, some have no trace of the hole. If you use the Vortec water pump, you don't need to drill the block, but you'll need to add the Vortec hose and fittings for coolant bypass from the intake manifold.

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2. Vortec blocks are not machined for all the bolts needed to attach a TBI sheetmetal front cover. You will need to drill and tap two holes. Use timing cover gasket as a template. Drill straight and true, and tap straight and true. IIRC, it's 1/4-20 threads, but you'd want to confirm that. The Vortec damper is different from the TBI damper. The Vortec front cover has the timing marks in a different place compared to the TBI front cover. Therefore, the Vortec damper and cover are a "matched set", and the TBI damper and cover are matched.

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3. If you buy the suggested intake manifold, you'll still have some fun getting the throttle cable/cruise cable/TV cable bracket to bolt up--the intake bolts are at a different angle on the Vortec heads.

4. EGR will be a problem--you'll need to route exhaust gas from the driver's side manifold/header to the EGR inlet of the manifold. Do-able, not fun. GM has a parts list of OEM items, short story would be "special" driver's exhaust manifold, "special" nipples, "special" high-temperature hose. Dorman offers these parts (made in China) for less money than Genuine GM, and I think the Genuine GM stuff is discontinued. The last time I bought a Dorman exhaust manifold, it looked like it had been planed by a twelve-year-old, and then the casting "relaxed" after machining so that it needed to be planed AGAIN after I bought it. The gasket surface was .006 out-of-true. (Trailblazer 6-popper manifold) You've been warned to double-check EVERYTING Dorman sells. Their QA sucks.

5. Similar to the damper/timing cover, the front accessory drives may/may not be different. The Vortec water pump I have has different belt spacing to the front of the engine compared to the TBI water pump. Therefore belt alignment could be a problem unless you get all the accessories from the same engine as the water pump.

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6. My contact at Pace Performance told me that ALL the small-diameter HEI distributors (TBI-onward) have a Melonized gear as standard equipment. The Melonized gear can still wear excessively, if the gear is worn it needs to be replaced and the camshaft gear checked. If it's not worn...it's fine as-is.
 
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