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Discussion Starter · #1 ·
Hey everyone, need some input here.
1977 Chevrolet K10 LWB, TH350, 4.11 Gears, 35x12.50r15 tires.

350, .30 over
XE274 Cam
Aluminum Flotek Heads 64cc chambers 180cc intake runners
Scorpion 1.5 full roller rockers
Flat top pistons
Tooley chromoly rods
Air gap RPM intake
Holley 750 Classic
Heddman mid length headers
Full true dual exhaust
* and running 93 octane fuel

Granted, this is a full-size 4x4 with 35 inch mud tires, but I feel as if it lacks power. My power goal was 350-400 horse and maybe 400 torque. Any issues with my combination?Or is it just too heavy of a truck. The truck is kind of torquey, but lacks any mojo when taking off. I wanted more low end power which is why I stuck with 180 runners, but if I’m honest it’s kind of a dog.
 

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4.11 gear and 35" tire gives the same engine to ground contact ratio as 3.42 gears and 30" tires like the truck came stock with...
You need a lot more gear....or a whole lot more torque(Nitrous, turbo, bigger cubes)

If you want the truck to have the kind of jump it would have had with 4.11 gear and 30" tires, with those big 35" tires you'd need at least a 4.79 rear gears....the math don't lie.

'77, that's 12-bolt truck rear, Dana 44 front IIRC? Or do you have one of the first year for the 8.5" 10-bolt ?
4.88 is probably the closest available ratio for both of those.
 

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Discussion Starter · #5 ·
4.11 gear and 35" tire gives the same engine to ground contact ratio as 3.42 gears and 30" tires like the truck came stock with...
You need a lot more gear....or a whole lot more torque(Nitrous, turbo, bigger cubes)

If you want the truck to have the kind of jump it would have had with 4.11 gear and 30" tires, with those big 35" tires you'd need at least a 4.79 rear gears....the math don't lie.

'77, that's 12-bolt truck rear, Dana 44 front IIRC? Or do you have one of the first year for the 8.5" 10-bolt ?
4.88 is probably the closest available ratio for both of those.
Understood. When I was mounting the 35s, the truck was on 31s for a little while. Even then, it seemed like the truck was lacking power. Leaving the 35s out of the equation, do you see any issues with my combination?
 

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That truck is heavy too.
Run it across the scales at your local scrapyard, or landfill. Guaranteed to be well over 4000.
Like others have said, you need more gear.
4.88 would make a difference, and not kill you too bad on the highway.
Are you running an automatic? A custom converter would probably help too.
 

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Discussion Starter · #7 ·
That truck is heavy too.
Run it across the scales at your local scrapyard, or landfill. Guaranteed to be well over 4000.
Like others have said, you need more gear.
4.88 would make a difference, and not kill you too bad on the highway.
Are you running an automatic? A custom converter would probably help too.
Currently running a 2200ish stall. Like I said earlier, even on 31s and 4.11s the truck seemed sluggish. I just want to be sure I’m not mismatched in the engine department. TH350 will soon be replaced with a 4 speed SM465.
 

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Currently running a 2200ish stall. Like I said earlier, even on 31s and 4.11s the truck seemed sluggish. I just want to be sure I’m not mismatched in the engine department. TH350 will soon be replaced with a 4 speed SM465.
If you are running the cheap converter, that will soak up around 50hp. Plus the losses in the tranny.
When I switched to a good converter, it was a difference you could feel in the seat. They behaved exactly the same, just one went half second quicker in the 1/4.

Start looking to put the truck on a diet. Mine weighed over 4200 and is only 2wd. I am currently down to 3920 with me in it, and no fiberglass panels.
Chevys like timing too.
Also your compression might be a little low.

You said flat tops, but there are a few other factors to calculate static compression.

What is your initial timing? How about at 3000?
 

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Discussion Starter · #9 ·
If you are running the cheap converter, that will soak up around 50hp. Plus the losses in the tranny.
When I switched to a good converter, it was a difference you could feel in the seat. They behaved exactly the same, just one went half second quicker in the 1/4.

Start looking to put the truck on a diet. Mine weighed over 4200 and is only 2wd. I am currently down to 3920 with me in it, and no fiberglass panels.
Chevys like timing too.
Also your compression might be a little low.

You said flat tops, but there are a few other factors to calculate static compression.

What is your initial timing? How about at 3000?
Initial timing I believe was around 14.I’ll have to check at 3K. What factors would help bump up compression besides some pop tops?
 

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First thing we need to do is find out a part number on your Pistons, and did you have your block deck machined? Also what cc are the chambers of the cylinder heads you bought? This is just a start, but will get you a ballpark figure.
 

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Discussion Starter · #13 ·
First thing we need to do is find out a part number on your Pistons, and did you have your block deck machined? Also what cc are the chambers of the cylinder heads you bought? This is just a start, but will get you a ballpark figure.
Block was decked just enough to give a new working surface. 64cc chambers, and I’ll have to look for the part number, but they were just a run of the mill flat top. Nothing too entirely fancy. Head gasket was just a basic gasket that is aluminum safe.
 

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Discussion Starter · #16 ·
Cam is not going to produce much off idle torque unless the compression is 11:1.
Big cam, big intake runners, big carb all make for lazy flow at high load and low RPM.
What would you recommend the replacement be? I had a 600 eddy prior to the 750 Holley and it seemed as if it wasn’t enough.
 

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As I said earlier forget all the nonsense and build it as a 383. Too bad you pee‘d away so much money on the fancy rods. Not that I’m opposed to super rods where needed but a decent set of lowest cost 4340 SCATs would have been just fine. Assuming these are 5.7 or even 6 inchers all you need is the striker crank and the piston set for your rod length. You‘lol need to check for pan rail, upper crankcase clearance and trim accordingly for about .050 inch clearance and the same activity for rod to cam lobe and ease enough material off the rod and it’s fastener for the same mysterious .050 inch of miss. This is usually just two rods.

Use all your other existing parts except for the gaskets. Be sure to keep the lifters organized so they go back to the same cam lobe they broke-in with. For a few days of work and about 500 bucks, problem solved; or at the least greatly improved.

Your 350 is already, at least on paper, those parts should be making 400 ft lbs of torque and about the same power. If that ain’t enough the only solutions which do not include under sizing the carb or intake or cam for that matter are changes that chase more top end power at higher RPM. Those same changes will do the same to torque but will lower it under the peak where for most operation is where you need it. More displacement begets more torque without having to chase it up the RPM band. Them’s the physics, everything else is just grabbing your privates and playing around. Obviously the big fix is a 454. Any Texan can tell you that bigger is better.

Torque is mostly related to size, horsepower to speed, yes for any size there is space to play the numbers but nothing comes for free. Without changing the size getting bigger numbers is about getting the engine to act like it’s bigger, the only choice since the displacement is fixed is to turn it faster, just in case you never found yourself in a bar room brawl with a short guy now you know what to expect.

Bogie
 

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You're probably at about 9:1 compression. That cam really needs 10:1 or better. It's also (IMO) too big for your application. If you want bigger power in a big vehicle, you MUST do big cubes (or forced induction which is kinda the same thing)

As I'm sure you know, when you make more power from the same cubes, you have to use a cam that shifts the torque peak higher which is exactly what you don't want in a heavy vehicle. I think the engine you built is perfect for a street engine in a Camaro or Nova, but not for a big truck with big tires.

383, or better yet, 454. If everything else stays the same, adding cubes gives more torque at a lower RPM peak but keeps the same general hp.

I built a 468 for a 73 Impala station wagon with an XE268 cam. It was just right. You have 100 fewer cubes, more cam, and about the same compression in a heavier vehicle with much larger tires. It's not going to feel peppy.
 

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Discussion Starter · #19 · (Edited)
As I said earlier forget all the nonsense and build it as a 383. Too bad you pee‘d away so much money on the fancy rods. Not that I’m opposed to super rods where needed but a decent set of lowest cost 4340 SCATs would have been just fine. Assuming these are 5.7 or even 6 inchers all you need is the striker crank and the piston set for your rod length. You‘lol need to check for pan rail, upper crankcase clearance and trim accordingly for about .050 inch clearance and the same activity for rod to cam lobe and ease enough material off the rod and it’s fastener for the same mysterious .050 inch of miss. This is usually just two rods.

Use all your other existing parts except for the gaskets. Be sure to keep the lifters organized so they go back to the same cam lobe they broke-in with. For a few days of work and about 500 bucks, problem solved; or at the least greatly improved.

Your 350 is already, at least on paper, those parts should be making 400 ft lbs of torque and about the same power. If that ain’t enough the only solutions which do not include under sizing the carb or intake or cam for that matter are changes that chase more top end power at higher RPM. Those same changes will do the same to torque but will lower it under the peak where for most operation is where you need it. More displacement begets more torque without having to chase it up the RPM band. Them’s the physics, everything else is just grabbing your privates and playing around. Obviously the big fix is a 454. Any Texan can tell you that bigger is better.

Torque is mostly related to size, horsepower to speed, yes for any size there is space to play the numbers but nothing comes for free. Without changing the size getting bigger numbers is about getting the engine to act like it’s bigger, the only choice since the displacement is fixed is to turn it faster, just in case you never found yourself in a bar room brawl with a short guy now you know what to expect.

Bogie
Tooley chromoly pushrods not connecting rods.. To go 383 would I not need a 400 crank? I guess I should just buy a rotating assembly?
 

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Start looking at your truck. What is on it, or in it, that can go away? Tool boxes, grille guards, running boards. Stuff like that. One thing I did was battery relocation to where the saddle tank used to be. Removed the metal splash shields along with all that battery support crap, and installed plastic liners from a 2012 Ram Pickup. They weigh a whopping pound each!

Each hundred pounds you lose you will feel. Also I sold my built 350 for $2500 and built a 406. But a 383 Like Bogie said, will be about the same for wayyyy less.

Like you I ended up wishing I knew these guys sooner. But my truck runs mid 12s now and I am happy every time I drive it!
615857
Wheel Tire Vehicle Car Window
 
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