1999 406, TH350 swap

[99Silverado]

Well I'm planning on taking a 406 Small block and a TH350 and replacing my 5.7 4L60E in my 1999 C1500. I'm working with a shop on the swap, I want to make sure I have as many parts purchased for it ahead of time as possible.

I understand how many of you may consider this an enormous step backwards, consider my position. I have a brand new 406 that's built pretty stout. 230cc iron heads, roller rockers, big valves, 525 lift, 244/248 @050 (thinking about a cam swap), can't remember the compression exactly but it needs 93, and mix in the summer or timing pulled. The TH350 was built to suit the engine, 9" stall. The engine was a driver out of my previous project, a 1978 Vette that my dad and I worked on. Ended up keeping the motor and trans, sold the shell (Dads least favorite vette, didn't feel bad selling it.) But I wanted to keep the drivetrain to keep Dad with me project to project, if you know what I mean. We'll my grandfather passed and I was blessed with a pristine 1999 C1500 ECSB White, tan interior, never smoked in, 103,000 miles and a hypertuner sticker in the door.

Well the truck is shifting hard 1-2, and I have this drive train just sitting there begging to run in something. So I'm going to marry the two, and maybe make it into a show truck with a story one day. I've purchased several parts already listed below.

RC 2/4 Drop kit w/shocks
18x8 Rocket Racing Booster Hypershots
245/50r18 of some flavor
10" Punch p2 under seat
400w Fosgate amp
UTE-73BT Alpine headunit
1 5/8" mid length headers Jegs brand I picked up at a swap meet. Probably going to wrap them.


So my plan is to work with a shop to retain as many creature comforts as possible, cruise, ac, gauges etc. while they handle the swap as I just don't have time. I'm not thinking there will be many mounting issues since it's a small block coming out and a small block going in, the 4l60e getting replaced by the TH350 I think should be as simple as elongating some holes and maybe a new driveshaft. But as far as gauges and wiring go I have no idea and will be relying mostly on their knowledge and wiring diagrams. Any and all input is appreciated!

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Last pic for inspiration, I know he's lower than 2/4

 

[Erik the Awful]

Honestly? I'd find something more race-oriented for the engine, because that's on the ragged edge of being streetable. Gas mileage is going to suck, and the truck's weight will sap a lot of that performance. You need a dang-ol' Camaro.

That's a very nice looking truck, and it needs to be driven and enjoyed. Having put a barely-streetable motor into a street car before, it was a disaster and I really couldn't drive the car that often any more.

the truck is shifting hard 1-2, and I have this drive train just sitting there begging to run in something.

Very likely the 1-2 accumulator is hanging up. There's a Sonnax kit to eliminate it, and I believe you can install it with the transmission in the truck.

 

[DerekTheGreat]

Oh wow, that truck is a cream puff as it is, amazing it made it that far in life with the factory paint and drivetrain. Before you cut that up, I'd seriously consider selling it and buying a project in need of a heart transplant. You'll probably save money that route and make a purist really happy.

 

[99Silverado]

Oh wow, that truck is a cream puff as it is, amazing it made it that far in life with the factory paint and drivetrain. Before you cut that up, I'd seriously consider selling it and buying a project in need of a heart transplant. You'll probably save money that route and make a purist really happy.

Grandpas Truck + Dad's Engine = Never Getting sold lol! Thanks for the compliments man, its a very pretty truck.

 

[99Silverado]

Honestly? I'd find something more race-oriented for the engine, because that's on the ragged edge of being streetable. Gas mileage is going to suck, and the truck's weight will sap a lot of that performance. You need a dang-ol' Camaro.

That's a very nice looking truck, and it needs to be driven and enjoyed. Having put a barely-streetable motor into a street car before, it was a disaster and I really couldn't drive the car that often any more.


Very likely the 1-2 accumulator is hanging up. There's a Sonnax kit to eliminate it, and I believe you can install it with the transmission in the truck.

Im considering swapping the cam to something more streetable, and if necessary the converter too. If anyone has recommendations Im all ears!

Looked for a clean shell and they are absolutely sky high right now. I considered another project, but why when I have such a pristine truck that could be a 400SS Tribute truck, I mean the 454SS had a TH400 in it right?

 

[PlayingWithTBI]

I mean the 454SS had a TH400 in it right?

IIRC in 90 & 91 it did but, in 92 it got the 4L80E.

 

[DerekTheGreat]

IIRC in 90 & 91 it did but, in 92 it got the 4L80E.

Yep, and thems be the ones I'd want. Low production numbers compared to the earlier years make them hard to find.

I vote to do the shell. Worse case scenario the engine can continue to sit. Time is your friend. I wish I'd never modified dad's Firebird. Who knew some twenty years later unmolested third gens would be practically non-existent? Not I.

 

[99Silverado]

Yep, and thems be the ones I'd want. Low production numbers compared to the earlier years make them hard to find.

I vote to do the shell. Worse case scenario the engine can continue to sit. Time is your friend. I wish I'd never modified dad's Firebird. Who knew some twenty years later unmolested third gens would be practically non-existent? Not I.

I absolutely understand your point of view, but the work is scheduled and parts are purchased, I'm going to go through with the build. It may involve different transmissions along the way but the powerplant is going to be the 406cu with a milder cam if nothing else, maybe aftermarket fuel injection? Who knows!

 

[Sean Buick 76]

Any update? I think it’s a cool build it will be a lot of fun! If it were me I would add thicker head gaskets to lower the compression and run a milder cam.

 

[99Silverado]

You must be registered for see images attach