Head Swap Options For 5.7L 350 TBI Engine

[Erik the Awful]

#1, ditch that open air cleaner and put the stock box back in. It draws cool air from the fender. There's a necked-down restriction in it, but you can cut a slit in it and pull it out.

 

[Majoraslayer]

#1, ditch that open air cleaner and put the stock box back in. It draws cool air from the fender. There's a necked-down restriction in it, but you can cut a slit in it and pull it out.

I mostly installed it as a preventative measure. No one seems to agree on how much of a difference it really makes and I've never noticed anything significant. My understanding is that the stock air cleaner has a wax-actuated flap inside that acts somewhat like a choke; the wax holds the flap closed until a small duct from the factory manifold transfers enough heat to melt the wax and release the flap. These are known to fail over time, and really only exists to smooth out idle a tiny bit on a cold start. The easiest solution to prevent ending up with a stuck flap is to just block off the heat duct hole and remove the flap. Since no one could seem to agree on how much difference the air temperature actually made in practice anyway, I just skipped modifying my factory cleaner and threw the open style one on. The ECM probably sees a difference and adjusts timing for it, but seat-of-the-pants I've never noticed a performance difference besides aesthetics under the hood. I'll consider swapping it back though, especially if other performance mods might benefit from it.

 

[Moleman]

Here's what I did for a tbi vortec head combo.

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I picked up this 880 block they already have the windage tray and roller cam and all that stuff.

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I got me one of these vortec QJET square bore intakes for 130 and then bought a transdapt adapter for 40 and came up with this.

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Here's what it should look like.

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As for you accessories that's easy. They all line up. The 880 blocks harmonics balancer will work with the 87-95 water pump but you need one with a hole in the back or you can drill 2 holes in your thermostat ive done both and they work. That block and heads do not have the internal coolant bypass. If you don't do the bypass.your thermostat will just open and close and you'll get all sorts of weird overheating problems.

Now when you're first starting out after finishing the conversion of you don't have the computer tuned,it will run lean and backfire through the tbi due to the tbi not getting enough AE enrichment.

Now this is the part I never made it too because I went Edelbrock carb.

From what I read elsewhere you have to put an adjustable fuel pressure reg,maybe The ultimate tbi mods kit, Caprice 9c1 cop car injectors,hypertech stage 1 or 2 chip. Then it should run pretty decent,I'm sure there's more tuning with fuel tables and spark and timing tables. But I don't know anything about that.

 

[Schurkey]

Your manifold isn't compatible with EGR. That's gonna be another tuning issue.

We used different parts, but accomplished about the same thing. I used a ZZ4 intake manifold with the TBI adapter plate. All the OEM items bolted-up or screwed-in (although with some changes in location or thread size) except for the brace from the A/C compressor. There was a fair amount of fabrication to get everything in place and functional.

The A/C brace could be re-made to work with that manifold, all I need is the gumption to bother.

 

[L31MaxExpress]

I mostly installed it as a preventative measure. No one seems to agree on how much of a difference it really makes and I've never noticed anything significant. My understanding is that the stock air cleaner has a wax-actuated flap inside that acts somewhat like a choke; the wax holds the flap closed until a small duct from the factory manifold transfers enough heat to melt the wax and release the flap. These are known to fail over time, and really only exists to smooth out idle a tiny bit on a cold start. The easiest solution to prevent ending up with a stuck flap is to just block off the heat duct hole and remove the flap. Since no one could seem to agree on how much difference the air temperature actually made in practice anyway, I just skipped modifying my factory cleaner and threw the open style one on. The ECM probably sees a difference and adjusts timing for it, but seat-of-the-pants I've never noticed a performance difference besides aesthetics under the hood. I'll consider swapping it back though, especially if other performance mods might benefit from it.

The air cleaner is heated to keep the fueling consistent. Without it the fueling is all over the place.

 

[Schurkey]

...and it makes a MAJOR difference when the humidity is high and the weather is not much above freezing.

Raining and 40-degrees is a perfect time for throttle-blade icing. The danger zone is from about 35 degees to about 45 degrees, and high humidity.

Heating the air so the moisture in it doesn't freeze on the throttle plates started in the later 1960s. My first car--'66 Biscayne 283 2bbl--did not have a heated-air intake, and would stall in the above conditions until the residual engine heat melted the ice off the throttles.

 

[Moleman]

Oh yeah I forgot about those brackets that bolt to the intake. get the 92-94 accessories bracket that way you don't have to worry about that.

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[tayto]

just remove your heads, get them repaired/plained and put it back together.

 

[Sean Buick 76]

I vote for re using the stock heads as well. In my opinion the strength of the TBI is reliability in stock form. Yes there are some modifications that can increase the Performance however the mail order tune chips are not ideal.

I would look at one of the following two options:

1. Find another Chevy 350 to build, just ensure it’s a roller cam version and do a complete rebuild on it and swap it in with a carb or a self tuning EFI kit.

2. Find a 99-06 LM-7 5.3 and regasket it and drop it in with a modified wiring and computer package. The LS engine is light years ahead of the TBI for performance and fuel economy.

 

[International47]

I vote for re using the stock heads as well. In my opinion the strength of the TBI is reliability in stock form. Yes there are some modifications that can increase the Performance however the mail order tune chips are not ideal.

I would look at one of the following two options:

1. Find another Chevy 350 to build, just ensure it’s a roller cam version and do a complete rebuild on it and swap it in with a carb or a self tuning EFI kit.

2. Find a 99-06 LM-7 5.3 and regasket it and drop it in with a modified wiring and computer package. The LS engine is light years ahead of the TBI for performance and fuel economy.

The LS swap isint that easy,
if your not using the trans that came with the LS then what are you using to control the old 4l60E? unless its a 5sp trans.
new trans usually involves cutting a new driveshaft.
you need to update the fuel pump- possible lines.
exhaust needs a bit of work to bolt up.
adaptor motor mounts.. not sure if the oil pan will clear,
cooling/new rad
All these things add up real quick.