'98 Vortec into a '88 K2500, retaining the TBI

Firewood truck said:

Here's a few update pics. I was hoping to get more done then I did over the holiday weekend, but at least there's still some progress. The heat has been brutal in the Mid-Atlantic region, I've had heat exhaustion for the past few days, so it's slowing me down. Today I will study the wiring schematics to figure out how to adapt the 2 separate oil pressure sensor and OP switch to work with the later 3 wire multi sensor. I wouldn't think it should be too difficult.

This has been a small PIA to work around. I'm not 100% satisfied with my solution, but it should work. The "regular" hex reducer bushings sat way too high, the sensor was touching the EGR valve, no way to install the plug. The next attempt was to use a face bushing ( basically a hex bushing with the hex removed), it was an improvement but the sensor still sat too high, the plug was touching the EGR valve body. I ran a tap into the 1/2 NPT port in the manifold, so that I could deepen the taper, in effect moving the taper farther down towards the water jacket. This got the face bushing a lot deeper, to the point of almost being flush. I then did the same thing with the 3/8 NPT internal thread, which allowed the sensor to sit deeper into the bushing. I used thread sealant on the outer threads of the bushing and the threads on the sensor. I have a tiny bit of clearance between the top of the plug and the body of the EGR valve. What a crappy design by GM, The Eldebrock version of this intake has the EGR in a relatively stock position. Just food for thought.

The sensor looks really crooked in the pics for some reason, but it isn't.

The next item to figure out was the throttle cable bracket The original one on my TBI engine was a 2 piece design. I made an attempt to re-bend that one but it wasn't working out very well, so while I was getting a few wiring harness pigtails from a junkyard on Saturday morning, I saw a throttle cable bracket on a '93 C1500 that only used one manifold bolt and the bolt on the coil mount bracket. I snagged that and got home and made a second attempt, this time just using the cutoff wheel and the MIG welder. It was kind of fun, I don't get to do much fabricating anymore just the mechanical design work with 3D design software.

They aren't the prettiest welds, but they aren't coming apart.

I got the exhaust all hooked back up. The relocated O2 bung will work well, the harness had enough slack to reach to the top of the Y pipe. One thing that was an eye opener for me was when I ordered the exhaust manifold doughnuts. The 1st ones from NAPA were way too big in diameter even though they were "Supposed" to be for the correct application from the donor truck
( '97 K2500 8500# GVW ). I took one of the old ones with me, the store manager looked at it and said " oh, those doughnuts. I stock them, we sell the hell out of those things to the repair shops". It turns out that the application for the matching doughnuts were for a 5.7 Vortec Suburban. The inner diameter must have been a 1/2" larger between the ones for the truck VS. the ones that matched the one that I got off of the manifold. There' a lot of airflow waiting to be unleashed, but I'm guessing that I'd need the truck exhaust manifolds and down pipe(s). That's more then I'm willing to do right now.

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Firewood truck said:

The progress has been slow, the high heat and humidity have been making it hard to get anything done after work during the week. I hit the junkyard on Saturday morning to get the wiring harness plugs for the AC compressor and some loom covering. While I was walking around the yard, I came across a early 90's Caprice. I remembered someone in here mentioning that the T-stat housing worked for their conversion, so I snagged it and gave it a try today. It's the closest that I've found to a GM part that could work, it still isn't ideal. The hose will touch the heat wrapping on the EGR tube cover. I know that the EGR cover gets pretty toasty, so unless I wrap the radiator hose with some type of heat resistant tape this housing isn't going to work for the long term.

I'm back to either getting a 90° t-stat housing ( outlet points straight up) and use the TBI hose, or I have to fabricate an outlet. I had grabbed a steel tube upper outlet off of a 2000 4.3 silverado, the same problem exists with the mounting holes on the flange, they are clocked differently because of the way it mounts on the Vortec intake.

All of this makes me wonder what GM or Eldebrock suggested to use for a housing. I'm guessing that they intended for people to reuse the TBI accessory drive which would make things a bit easier. I will get something figured out and share.

The pinion seal and yoke got replaced tonight, so the rear driveshaft is back in.

There wasn't much difference in the length of the rear driveshafts between the original from my truck and the one from the donor of the NV4500. The u-joints were the same, so I used the flared driveshaft from the NV4500 donor.

The front driveshafts are really different in length, I need to measure to be sure but I'm feeling like the original one from my SM465 will be the one to use.

It's interesting how the drive flange is on the slip yoke end of the driveshaft from the NV4500 donor.

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