Jmantx's Square Body Build

[Jmantx]

I've been a long time lurker who hardly posts on this forum, but I figured I'd start a build thread. I'm a 19 year old guy with a pretty good job, but if rather build something than buy something, so I do all my own work on my cars. Several months ago I purchased a 1985 C10 Silverado in pretty nice shape. It's an original 305 sbc long bed fleetside truck. The goal is to make it fast in a budget minded manner. To kick things off, I picked up an lq4 for a steal. They original plan was to start with heads and a cam, then go fi later. I started tear down, and guess what I found:
Apparently piston 8 decided to quit. It's ok though, as my cost to build the short block will be less than most stock short blocks in my area. I'm going to be building this all myself, with the exception of machine work. Suspension wise, I'll be starting with an axle flip, c notch, drop spindles and springs, shocks, and sway bars. Eventually I would like to change to a 4 link rear end and a front end with better geometry, but I figured this is a start that will get me moving. I will be converting it to a short bed.

Build requirements:
This truck has to stay street legal. It also needs to be able to do truck things, as I'm planning to build a house in a few years. AC is also a requirement, as I live in south Texas, and average summer temperatures are around 100f. I don't expect it to be faster than modern performance cars, but I do want it to be decently fast.

[egoman]

Looks like a good candidate for a Crown Vic crossmember and a 8.8 diff. Modernize and lighten at the same time for a reasonable price.

[SkinnyG]

+1 on spindles and flip kit. Get Moog 6454 or used 1-ton coils and just trim them to get the "rake" you want. I think I trimmed one coil to work with my 3" spindles. You'll want the 1-ton sway bars as well, and a rear sway bar can be good, but I have Big 10 long leafs in the back of my shortened '77, and it can get a little tail-happy without a rear bar at all.

[Vimes]

Old Chevy/GMC square bodies, probably the best truck ever made by anyone. I only wish that my purposes would be suited by one. But, they have their flaws. I'm going to suggest reinforcing the frame if you plan to use the stock frame. GM lightened the crap out of the 81-87 truck frames compared to the 73-80 models in the interest of fuel economy, and part of that was lightening the frame. I drove several from both eras over the years, and always thought the 81-87 had too much frame flex compared to the 73-80 models.

Also, pay close attention to where the steering box attaches to the frame. The frame on those trucks is known to crack at this point.

[Jmantx]

Looks like a good candidate for a Crown Vic crossmember and a 8.8 diff. Modernize and lighten at the same time for a reasonable price.

I was told the crown Vic cross member was too wide. Is that accurate? Would I need to cut down the Vic member?

[Jmantx]

Old Chevy/GMC square bodies, probably the best truck ever made by anyone. I only wish that my purposes would be suited by one. But, they have their flaws. I'm going to suggest reinforcing the frame if you plan to use the stock frame. GM lightened the crap out of the 81-87 truck frames compared to the 73-80 models in the interest of fuel economy, and part of that was lightening the frame. I drove several from both eras over the years, and always thought the 81-87 had too much frame flex compared to the 73-80 models.

Also, pay close attention to where the steering box attaches to the frame. The frame on those trucks is known to crack at this point.

Definitely planning some frame reinforcements. I can't justify a $30k frame when I'll be using it mainly as a weekend type driver.

[Jmantx]

Any thoughts on drivetrain? I'm thinking of building this lq4 as a forged 370ci with a twin turbo setup, probably through a 4l80e. I'm looking for 600ish whp. I know I will need a decent sized transmission cooler to keep it alive.

[egoman]

There are people cutting them down but a square body is a fairly wide truck to begin with.

[SkinnyG]

The drivetrain sounds cool. You definitely want the 4L80E, though a stick would be nice (but way more money than a 4L80E).

[Jmantx]

The drivetrain sounds cool. You definitely want the 4L80E, though a stick would be nice (but way more money than a 4L80E).

Yup, I looked at a t56 or a tr6060, even a cd009 and adapters. It was all rather pricey. I've heard too many stories to even consider a 60e. I briefly looked at 6l80s and 90s, but the lack of controllers on the market is kind of restrictive.

[SkinnyG]

I have an LQ4/7875/4L80E in my '61 Apache, and will be controlling it all with a factory ECU tuned with HPT. If you want to get a LOT more options (like boost control, traction contol, etc), you should go with one of the Holley ECUs. If you're cheap, "Megashift" is a stand-alone controller based on the Megasquirt (DIY) ECUs. There are many other controllers; the controller is not your limitation.

I would SO rather row gears, but the cost for a transmission/clutch/bellhousing/etc. that could handle 900hp at the crank is a fair bit of coin. And my LQ4/4L80E fell into my lap for cheap.

[Jmantx]

I have an LQ4/7875/4L80E in my '61 Apache, and will be controlling it all with a factory ECU tuned with HPT. If you want to get a LOT more options (like boost control, traction contol, etc), you should go with one of the Holley ECUs. If you're cheap, "Megashift" is a stand-alone controller based on the Megasquirt (DIY) ECUs. There are many other controllers; the controller is not your limitation.

I would SO rather row gears, but the cost for a transmission/clutch/bellhousing/etc. that could handle 900hp at the crank is a fair bit of coin. And my LQ4/4L80E fell into my lap for cheap.

Yeah, I've looked at megasquirt/microsquirt/megashift. My dad was one of the early users of the original megasquirt in his Kias. I'll probably start na with a factory computer, then upgrade to MS3X and one of their transmission controllers.

[Vimes]

No worries, boxing the frame should be fine. On the problem with the frame breaking at the steering box, it's a common enough problem that several companies offer a fix.

There are many other controllers; the controller is not your limitation.

Actually it is, if you want more than 4 gears in an auto. You'd think a company like Holley at least would be supporting 10 speeds by now, or at the very least 8 speeds as they've been out for years now. The lack of trans support is the only reason I'm not going to run a Holley on my project. My knee won't take a clutch anymore, and I don't want a 4 speed after having had a couple of 8 speeds. If Holley would put out a GM 8 speed trans support, I'd be one of their first customers for it provided I don't already have one working.

[Jmantx]

No worries, boxing the frame should be fine. On the problem with the frame breaking at the steering box, it's a common enough problem that several companies offer a fix.



Actually it is, if you want more than 4 gears in an auto. You'd think a company like Holley at least would be supporting 10 speeds by now, or at the very least 8 speeds as they've been out for years now. The lack of trans support is the only reason I'm not going to run a Holley on my project. My knee won't take a clutch anymore, and I don't want a 4 speed after having had a couple of 8 speeds. If Holley would put out a GM 8 speed trans support, I'd be one of their first customers for it provided I don't already have one working.

I was trying to see if there was a way to use a cut down harness from a factory 6 or 8 speed, but I haven't found diagrams for those. I read about how great the 10 speed is, but then you have to use an Lt transmission with a gen3 based engine (more complicated imo).

[SkinnyG]

I'm sure there are factory wiring diagrams available.

Then just study them, and see how to integrate them. Depends how good you are with electrical (or, at least: reading a schematic).

[Jmantx]

I completely forgot about this thread, but I guess there was no real progress in it anyways. Unfortunately, I no longer own the truck. I decided I was going to college, so something had to go. I ended up selling it and making a nice chunk of cash that helped with my first semester of school. Part of me wants to buy another C10 as a daily now (read: the BMW is rather unreliable).