Rebuilding the 350 finally

[rich weyand]

Thank you, I've never had any of this explained before in a way I could grasp it,
Now say I want 500ftlb of torque, I would need to bore the engine or stroke to have more displacement to run a better cam to get that number correct?
This won't be my daily driver, that said it will be driven when it's being driven, I tend to have a heavy foot, with a budget of 1000$ what would you say is the best "bang for buck"

Basically, yes. 420 lbft is sort of the end of the line for a driveable 350. Not sure there isn't some marine cam totally unsuited to road use that goes higher, but the 12-300-4 is about the end of the line for torque in a roadable 350 (without changing heads or pistons or a bunch of other stuff not in your budget). More torque needs more cubes. Swapping out the crank and piston rods for a 400 crank and piston rods will get you a 383, which can go up to 450 lbft. Lotta work for a bit more torque. You can also go to a big block, also a lot of work, but a bunch more potential torque. That Buick GSX was a 455.

How many miles does the engine have on it? Assuming the engine's OK:

To get the 415-420 lbft, you can go with one of the first four cams in the list. You need to replace lifters whenever you do a cam, because they bed into each other in the first few minutes. Run a new cam on old lifters, and you'll wipe the cam very quickly. You also need new stock springs for the stock lift cam, and new heavier Comp Cams springs for the higher lift cams. You should do new valve seals while you're in there. The oil and filter need to be changed several times while you break it in. You also need the dual-plane intake (e.g. Edelbrock 2101 or 2701 depending on the carb) and headers (e.g. Hooker 2453 on a K truck), and 2.25" duals with a 2" H-pipe. Oh, and do the timing sprockets and chain; you're going to have to take most of that off anyway, might as well put back new. Add gaskets and such, and...

That's your thousand bucks right there, assuming you do all the labor. Add another 1000-1500 if you shop it.

If the engine's not OK, buy a new crate engine and swap the cam before you even put it in the truck. Now you're looking at $2000 in parts, easy, and another $1500 in labor if you shop it.

 

[rich weyand]

BTW, "the General" = General Motors.

 

[silverscottsk10]

Basically, yes. 420 lbft is sort of the end of the line for a driveable 350. Not sure there isn't some marine cam totally unsuited to road use that goes higher, but the 12-300-4 is about the end of the line for torque in a roadable 350 (without changing heads or pistons or a bunch of other stuff not in your budget). More torque needs more cubes. Swapping out the crank and piston rods for a 400 crank and piston rods will get you a 383, which can go up to 450 lbft. Lotta work for a bit more torque. You can also go to a big block, also a lot of work, but a bunch more potential torque. That Buick GSX was a 455.

How many miles does the engine have on it? Assuming the engine's OK:

To get the 415-420 lbft, you can go with one of the first four cams in the list. You need to replace lifters whenever you do a cam, because they bed into each other in the first few minutes. Run a new cam on old lifters, and you'll wipe the cam very quickly. You also need new stock springs for the stock lift cam, and new heavier Comp Cams springs for the higher lift cams. You should do new valve seals while you're in there. The oil and filter need to be changed several times while you break it in. You also need the dual-plane intake (e.g. Edelbrock 2101 or 2701 depending on the carb) and headers (e.g. Hooker 2453 on a K truck), and 2.25" duals with a 2" H-pipe. Oh, and do the timing sprockets and chain; you're going to have to take most of that off anyway, might as well put back new. Add gaskets and such, and...

That's your thousand bucks right there, assuming you do all the labor. Add another 1000-1500 if you shop it.

If the engine's not OK, buy a new crate engine and swap the cam before you even put it in the truck. Now you're looking at $2000 in parts, easy, and another $1500 in labor if you shop it.

Miles are unknown but I put 20k on it and it was put in the truck in 2010
I could get a set of correct heads for cheap from junkyard to build so they could be a viable option for me as well to up the torque, I say 1000$ but that's what I could spend today, as time progresses I'll be able to up the budget
I want everything new in this engine, only want to re use block and crank and heads if needed


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[Johnnyz453]

Thinking about going with a 12-235-2 for my k10 truck but dont know if that would be ok with the 2800 stall converter thats on it. 350 with aturbo 350 trans and 373 gears. Going to be around 9.5:1 compression when done with the build. Heads will have 2.020 and 1.600 valves with 185cc and 62cc runners.

 

[rich weyand]

It'll be OK with a 2800 stall, but you don't need it. That cam will run just fine with a stock torque converter.

Changing torque converters on a K truck is a PITA. But, since you're going to do the cam anyway, it might be easier to pull the engine and do both at once. Easier to do the cam swap out of the truck, and you can change the TC while it's out.

 

[silverscottsk10]

It'll be OK with a 2800 stall, but you don't need it. That cam will run just fine with a stock torque converter.

Changing torque converters on a K truck is a PITA. But, since you're going to do the cam anyway, it might be easier to pull the engine and do both at once. Easier to do the cam swap out of the truck, and you can change the TC while it's out.

I can agree on the changing torque converters in the k series, I did the last one while it was -8 outside, never again



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[rich weyand]

Thinking about it, I would really worry about a 2800 rpm stall torque converter if there's a G80 in the diff. That's a lot of torque on hand when the clutches grab....

 

[silverscottsk10]

Thinking about it, I would really worry about a 2800 rpm stall torque converter if there's a G80 in the diff. That's a lot of torque on hand when the clutches grab....

My understanding of a stall converter is the Rpm needed to hit to successfully gain enough centrifugal force to engage the transmission, correct?
Like his 2800 needs to hit 2800 rpm to start moving?


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[rich weyand]

My understanding of a stall converter is the Rpm needed to hit to successfully gain enough centrifugal force to engage the transmission, correct?
Like his 2800 needs to hit 2800 rpm to start moving?

Basically, yeah. http://hughesperformance.com/tc-stall/

 

[Johnnyz453]

It'll be OK with a 2800 stall, but you don't need it. That cam will run just fine with a stock torque converter.

Changing torque converters on a K truck is a PITA. But, since you're going to do the cam anyway, it might be easier to pull the engine and do both at once. Easier to do the cam swap out of the truck, and you can change the TC while it's out.

It already has the 2800 in it thats why i was wondering how much of a difference it would make.

 

[rich weyand]

For all the work you're going to do, pull the engine, and leave the transmission and transfer case in place. You don't want to do all that work over the fenders and through the front. You can thank me later.

And once the engine's out, changing the torque converter is easy.

Look, you're at the edge of what the TH350 can take, maybe a touch over. Same thing with the G80 you probably have in the back. Horsepower is torque times RPMs. When the torque converter kicks in at 2800 rpm, with all that rotational inertia and RPMs, and the engine well up into the beefy part of the torque curve, a whole lot of horsepower is going to surge through that powertrain at once. With a built TH350, or a TH400, and a 14-bolt or Ford nine-inch in the rear, that would be way cool, but unless you are going to replace a bunch of stuff all at once from the start, you may be replacing it one piece at a time later, after sweeping the drivetrain off the street and having the truck towed home.

The cams we are talking about here have a ton of torque in the bottom. Use it, and give the tranny and diff a break.