How to Put a Vortec Motor in a TBI Truck

aledfelt said:

Was the EGR system on the vortec engines external routed to the intake? Is that why you should switch manifolds with the vortec heads?

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The intake ports are taller on Vortec heads. The TBI intake won't cover the top of the port. In the pic below you can see the top of the port peeking out past the manifold. That's a TBI head on the left, Vortec on the right, and a TBI intake. Supposedly you can weld the intake taller and port it out to match, but that's a crapload of work. Buy a spreadbore Vortec manifold and put a TBI adapter on it. Also note how far off the mounting holes are.

Erik the Awful said:

The intake ports are taller on Vortec heads. The TBI intake won't cover the top of the port. In the pic below you can see the top of the port peeking out past the manifold. That's a TBI head on the left, Vortec on the right, and a TBI intake. Supposedly you can weld the intake taller and port it out to match, but that's a crapload of work. Buy a spreadbore Vortec manifold and put a TBI adapter on it. Also note how far off the mounting holes are.

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Thanks, I was actually referring to the exhaust manifolds that came with the TBI engine. I ended up pulling the trigger on a used GMPP vortec to TBI intake.

First thanks for reply. I probably should have started off with what I have, and what I want to do. 1995, K2500 truck, 350 TBI, NV4500 transmission. Has spril port heads on it and switching out to vortec heads. Swirl port had a broken bolt in the passenger side rear and didn't want to try to drill it out. Note I used passive voice. I did not actively brake the bolt. The factory exhaust is almost completely rusted out (behind the cat), and I was taking stock of what I needed to replace (and how big of a project I wanted to get into) when I noticed the broke bolt. I have never seen anything like that before. Has anyone else? I don't mind fabricating some exhaust, but I don't want this project to take too long. Actually to be more exact, I do not want this project to take too much of my time. This is not my daily driver. I was hoping to reuse the prebent tubes from the cat. (y-pipe) and factory manifolds. But if I need to switch manifolds, I can fabricate some of the exhaust myself.

Why the vortecs? Simply because I have them already. I rebuilt a set for the salvage yard and was going to use on a 400. But I decided to go another direction on that project. Decided if I was going to pull the heads off the truck, I would either rebuild the swirl ports or use the vortecs. The intake has been leaking oil from the front and back for a while, and I have been wanting to fixt that for some time.

I just need a running truck that can pull a car from time to time, get a load of rock, make runs to the hardward store, etc. I probably only put 2-3k miles on it a year. Might do an LS swap ten years from now. When the kids get older and I have more time than I know what to do with.

I purchased a used GMPP TPI to Vortec intake manifold (previous post).

Schurkey said:

Debateable, depending on the quality of the headers. Specifically, the thickness of the flange at the cylinder head.


Is the rest of the exhaust worth saving?

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Post cat, the rest of the exhaust is pretty much needs to get completely replaced.

Schurkey said:

There's also an extended pattern, needed when the rearmost runner sweeps back over the top of what would have been the rear bolt. The actual rear bolt is farther to the rear.

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I guess you are saying vortecs have the extended bolt pattern? I have read several articles on vortec vs swirl port heads, and I guess I am simply missed that as being one of the differences. I guess that is why I assumed I could bolt my old exhaust manifolds on. I have a set of LT1 (mid 90's) manifolds from a firebird and a cheap set of long headers given to me free, purchased for a square body truck. The LT1 manifolds should have the extended bolt pattern on the last bolt as well as EGR/O2 provision on both sides if I remember correctly. Anyone reading this do not hold me to that. I am going off memory. I can check tonight.

Get those Vortecs magnafluxed and inspected before you do anything. They're really bad about cracking between the valves, and between the valves and spark plug.

If you need a whole new exhaust, is there anything keeping you from jumping to long-tube headers? I built the exhaust in WCJr with headers, cats, mufflers, flanges, hangers, straight pipe, and x-pipe, and a single mandrel-bent u-pipe that I cut in half. It took me a solid afternoon of fitting



The downside is that the crossmember was in the way, and I ended up having to build a dropped crossmember to fit it, and that took a few evenings.

Erik the Awful said:

Get those Vortecs magnafluxed and inspected before you do anything. They're really bad about cracking between the valves, and between the valves and spark plug.

If you need a whole new exhaust, is there anything keeping you from jumping to long-tube headers? I built the exhaust in WCJr with headers, cats, mufflers, flanges, hangers, straight pipe, and x-pipe, and a single mandrel-bent u-pipe that I cut in half. It took me a solid afternoon of fitting

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The downside is that the crossmember was in the way, and I ended up having to build a dropped crossmember to fit it, and that took a few evenings.

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The exhaust on my L31 powered 87 G20 is similar, except I used an inexpensive dual in/dual out Magnaflow made muffler. On the van the crossmember luckily had plenty of space for the exhaust to pass through.



The initial component layout before anything was cut to length.

375+ hp of clean burning, sequentially injected 350 power.

L31MaxExpress said:

375+ hp of clean burning, sequentially injected 350 power.

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"regular" TBI distributor in the Vortec block? I just started looking at the differences between the TBI and Vortec distributors tonight. I was shocked to see that the vortec dist. is mainly plastic.

Firewood truck said:

"regular" TBI distributor in the Vortec block? I just started looking at the differences between the TBI and Vortec distributors tonight. I was shocked to see that the vortec dist. is mainly plastic.

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Edelbrock dual sync distributor.

Erik the Awful said:

As I understand it, the TBIs are all flat tappet, but some of the blocks have roller provisions. The original engine in my '89 did not have roller provisions. Vortecs are all rollers. When it comes to main bearings, the 1500s almost always have 2-bolt mains, and the 2500/3500s almost always have 4-bolt mains. In my humble opinion, the Holy Grail blocks are 4-bolt main TBI blocks with roller provisions. Fortunately my '89 has one, now.

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And what may your Engine code be? Is it 14093638 TBI

19971997 said:

And what may your Engine code be? Is it 14093638 TBI

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That's not an "Engine code". That's a casting number.

Casting numbers are not part numbers. One casting can potentially be machined into multiple part numbers, by varying the machining done to the raw casting.

Examples: A single block casting may be machined for roller lifters, including drilling/tapping for the cam thrust plate and the lifter-dogbone spider hold-down bolt holes, or for flat-tappet lifters. It can be machined for 2-bolt mains or 4-bolt mains. It may or may not get engine-driven fuel pump provisions. It may or may not get the double-drilled coolant bypass provisions--a hole bored at an angle down from the block deck, intersecting a hole bored horizontally from the water pump gasket area.



A buddy of mine--an automotive machinist by trade--got caught with casting number/part number problems on his "shop truck", an S10 "powered" by the hateful 151 "Iron Duke" four-popper. He replaced the original, cracked cylinder head with another of the same casting number, and then spent a year where every time he drove the truck out-of-town, the head gasket popped.

Turns out, the replacement head had a coolant hole drilled out-of-place for his S-10 application, and it didn't line-up properly with the hole in the head gasket. (The coolant hole location would have been correct for some other application.) I don't remember if he changed heads, or more-likely re-drilled the head to match the head gasket coolant opening. Either way, the head gasket problems were solved by correcting the coolant opening.