1984 GMC K2500 Sierra Classic

[BBamm]

I might have been convinced to throw the twin T25's on here. It would make the exhaust a lot simpler, though I'd run low boost without an intercooler at first. Then I could save the Northstar for the T Type. Argh! Can't decide!.....

I don't think you will have enough room in there, it's looking pretty cramped already.

Cramped? That truck came with an optional big-block! I can't imagine there not being enough room under the hood for a twin-turbo 6 with accessories. I say go for it!

[Wes]

I might have been convinced to throw the twin T25's on here. It would make the exhaust a lot simpler, though I'd run low boost without an intercooler at first. Then I could save the Northstar for the T Type. Argh! Can't decide!.....

I don't think you will have enough room in there, it's looking pretty cramped already.

Cramped? That truck came with an optional big-block! I can't imagine there not being enough room under the hood for a twin-turbo 6 with accessories. I say go for it!

I was hoping my sarcasm would come through in text.

[BBamm]

I don't think you will have enough room in there, it's looking pretty cramped already.

Cramped? That truck came with an optional big-block! I can't imagine there not being enough room under the hood for a twin-turbo 6 with accessories. I say go for it!

I was hoping my sarcasm would come through in text.

My bad, I'm usually the sarcastic one so I can't believe I missed it.

[Wes]

Haha, no problem! It can be hard to tell sometimes.

[MattStrike]

Motor mount update! Had some fun with this, the engine block is a lot shorter than the V8/I6 engines you would have normally found in this frame.

The drivers side mount is done:


Passenger side mount getting fabricated. I ended up having to remove and plug the holes for the knock sensor and the oil pressure sensor to make room for the mount.


Clearance to the oil filter bracket, engine looks crooked as I have all the weight pulled off the mount-in-progress.


And the main structure of the mount it tacked together, needs a few more small pieces for bracing.

[Jrs3800]

Moving right along with things. Got the engine all cleaned up and working on the belt drive. I'm planning a dual alternator setup now, started mocking that up today:


I've been thinking about converting this to OBD-2, so I can tune it. The first thing that comes to mind as a roadblock is the crank/cam trigger. Aside from the adjustable mount for the crank sensor, does anybody know if the timing on the crank and cam interrupts is the same between the L27 and a series 2? I think I found a good spot on the block to add the dual knock sensors. Anything else I might be forgetting about?

I think the crank and cam interrupts are the same, They use the same ignition module.. The 93 and up used a non adjustable crank sensor and it was used till the end of production.. The cam sensor is only used for a #1 TDC reference for SFI.. I believe the timing difference/s are in the tune..

Sandrock ran his Series 1 L67 with an OBD2 PCM.. I know he dorked with a couple of Series II files trying to get things to work.. Car actually ran really well..

[MattStrike]

The internet has rewarded me some new surprises for this build. Should be fun!

[Jrs3800]

Do tell...

[MattStrike]

This weekend saw the front end re-assembled and the truck back on all 4 wheels, which gets a lot of stuff out of the way and back on the truck. However I'll need to find a different replacement spindle lock washer. This is the one I replaced already, but typical of cheap aftermarket parts it's not a direct re-make of the originals. The washer has a tab on the ID that locks into the spindle, and there are holes around the face of the washer where a pin on the inner lock nut will fit into. The aftermarket part, these holes are symmetrically opposite to the tab, meaning you can't flip the lock washer when the pin in the nut is between holes to get it to line up. This results in either an over-tightened bearing or under-tightened bearing. With the OE washer, they holes are offset from the tab. Effectively that offset creates 2x's the resolution compared to the aftermarket part, so you can get the bearing closer to where it should be.

I also got the electric power steering unit. So I started mocking up what needs to happen there too. It did not come with the steering universal joint though, I'll need to grab one because the shaft is splined and not the standard D shape. The upside is that I can replace the rubber coupler for a proper universal. I may also have to pull a steering wheel that mates up to the other end to use to make an adapter to connect the steering shaft from the truck to the unit. I'll be bolting it directly to the frame.

I'm still working on the plumbing for the engine, water lines and oil lines, sensors, etc..

[MattStrike]

Time to let the cat out of the bag, you probably suspected this from the beginning, but the turbo bug has bit hard. I'll be putting the twin T25 Saab turbos on here. Rebuilding the T25 turbos now, the first one is apart. Needs new bearings, seals, but good news is no excessive heat. It was stored indoors with oil in it but the oil must have leaked out and wasn't spinning freely. The turbine side was coked up really bad in addition to the oxidation on the shaft; so the jury is out on whether or not it can be re-used. The second turbo won't need a full rebuild, no shaft play, no signs of oil in the turbine housing. It will need to be re-clocked, cleaned up, etc.

As much room as it seems like there is, there are some areas that are a little tight to fit. In an effort to keep things simple, the starter motor has a close fit to where i want to mount the left turbo. I've changed out the starter for the gear reduction unit, but still will need to wrap the turbine housing and downpipe so I don't cook the starter. I might even need to wrap the starter.

Headers, like the SSEi, are going to be drainpipe headers. They will be able to handle the weight of a turbo, but I will also be making a bracket similar to what I did on the SSEi to take the majority of the weight off the header so that I never have to worry about cracking the header or mount.

[Wes]

And that engine looks so tiny in there.

[BonnieBoy08]

Turbo all the things!!!

You can never just keep things simple can you? Hopefully it’s all done in time for the meet. Definitely going to get some looks pulling this thing in the parking lot Saturday. Either way this is shaping up to be a one of a kind truck. Eventually you want to put a Northstar in this one right? And then keep the turbos for that I’d assume. Can’t wait to see all the madness in person.

[crash93ssei]

I am really curious to see how the L27 holds up to boost.

[Jfridge92]

Didn't sandrock also top swap an L27 that ended up dying within the first few thousand miles of seeing boost? Not saying it won't work, and you'd definitely be able to build the motor for boost I'm sure, just something to check into for the build.

Other than that, this thing is coming together nicely!!!

[00Beast]

From what I remember, Don said that that engine had been on the way out, they just didn't know it until they did an autopsy. It will be interesting though to see the final outcome. Keep at it Matt!

[Jfridge92]

Hopefully that's the case, and this works well! I can't really recall many high hp series 1 builds.

[MattStrike]

I'll be starting out at 5psi or so, should be safe as long as it's tuned right. From what I can tell, the key is to not run too much timing due to piston dwell time with the longer connecting rod engine, the connecting rods won't handle the stress of getting peak pressure right after TDC because they need a few extra degrees of rotation to get moving.

I don't expect this to add too much time to the overall build, though having it done for the meet will be pushing it. I have a three day weekend coming up so I should be able to make some decent progress. The list of things to do is getting really small:
-Headers/turbos/downpipes
-Engine plumbing/brackets
-Wire harness and PCM
-Fenders and grill
-Steering
-Brakes

Might need to squeeze in a junkyard run for a few misc things, but otherwise I should have everything I need to get done.

[MattStrike]

Got a few more small things done tonight, including installing the L67 fuel injectors:

[Jrs3800]

The good thing is you are already starting off with lower compression.. But just for giggles....
Ford Mustang Split Port 3.8 Piston/Rod assembly on the left..... L27 3800 In the Middle...... L36 On the right

[Jrs3800]

From what I remember, Don said that that engine had been on the way out, they just didn't know it until they did an autopsy. It will be interesting though to see the final outcome. Keep at it Matt!

Yes, from what I learned later this engine suffered a lack of lubrication due to fuel fouled oil, damage was done before we ever put the engine into service.. The pistons were still in top shape even after beating the car for a few thousand miles during tuning.. It was running a 2.2 pulley, with nothing for KR.. I swear to this day it had more off the line grunt than an LS4..

Gen 3 M62 with a 2.2 pulley, running an OBD2 PCM... On a 94 L27 with 9.0:1 compression, with the roller pivot rockers( 93-95 )... And the L27 rod in the picture is from that very engine..