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

[Firewood truck]

A tiny update. The AN fittings for the vac port weren't going to work without modifying the return fuel line (which is still an option that is dancing around in the back of my head). The lines on my truck are braided steel, I saw a '93 in the bone yard that was regular steel hard lines. I wonder when the change occurred. Today I got a straight nipple, the whole thing is about 2" tall. It BARELY fit next to the fuel line, getting the rubber vac hose on it will be tight. Overall I'm pretty disappointed in the GMPP intake, they dropped the ball on too many design features. I know it's way past too late past the party to ***** about things, but as a mechanical designer I just cringe at how poorly thought out some of the design features are with this manifold.

I got all of the small EVAP plumbing done, battery cables were made and installed last night. I will do a full power up tomorrow, just to do a function check of headlights and things like that. If I can get the brake booster hose routed tomorrow, I should be able to fire it up once I prime the oil system and get the dizzy dropped back in place.

I'm still not 100% sure about how the ground wire on the headlamp harness gets routed through the core support, if anyone has a pic with their grill/bumper off it would be a big help to me. TIA

 

[PlayingWithTBI]

I'm still not 100% sure about how the ground wire on the headlamp harness gets routed through the core support, if anyone has a pic with their grill/bumper off it would be a big help to me

Here's what my 88 looks like with the wiring harness along the bottom of the core support but, you can always ground each side to any place there or on the fenders.

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[Firewood truck]

Thanks for that pic, it helped. I got it to fire up tonight. I ran the priming tool with the cordless drill, the gauge showed 30 PSI so it looked good and it seemed that I got the 3 wire sending unit wired correctly. The 1st few attempts to start kept sounding like the timing was off. I was positive that it was at TDC when I was checking the timing chain marks and installing the balancer (with the VC's off) and I never bumped it afterwards, so I set the dizzy where I wanted #1 to be and had no luck when cranking it. I swapped the plug wires 180° on the cap and it fired right up. Hell if I know.. this isn't my 1st rodeo yet I still got it wrong. Simple enough to fix, pop out the dizzy and spin the rotor. It fired up again but I never saw the OP gauge go past 30 PSI, it never went up or down- only at 30 PSI unless I shut it off. The bigger concern is a loud metallic sound that is steady and increases with RPM. I will start tomorrow with pulling off the metal inspection cover/dust cover and hope that it is just hitting the flywheel. I will also change out the OP sender. I tied the tan wire from the '88 harness to the top terminal of the 3 prong plug (#31 tan), lower left terminal ( #440 orange) from the harness to the orange wire on the plug and the pink/blk from the harness to the (#120 grey) on the plug. The alt was just 1 wire ( tan, I think) single wire from the '88 harness to the single wire on the plug for the Vortec alternator. I feel like I got those correct, if anyone sees a mistake with the wiring, please let me know. The alternator got pretty warm to the touch after just a few minutes of running.

My grounds are- battery to the front of the block, braided cable from the front of the block to the frame. I ran a ground cable from the alt housing to the chassis. There's a ground cable from the cab ( under the heater hoses on the firewall) to the chassis. I added a ground from the battery cable to the pass side fender where the headlight harness grounds to

 

[Tim W]

Great Job with the swap progress. I put a 97 vortec motor in my 94. My intake manifold is an Edelbrock RPM airgap. Custom brackets were for my A/C though. Mine was a little less complex since im running a Sniper and the only thing my ECM is controlling are my gauges and knock sensor. I'm also not running an EGR. My Heads are GM vortec center bolt heads that have been ported and polished.

At the time the swap was done, I did not realize the heads had to be drilled for the coolant bypass. I actually plugged the hole in the TBI h20 pump. I've learned a lot from these fine folks on this forum

I did however plumb a coolant hose into the front of the intake. The intake has numerous passages that lead to the heads. Iv been running this setup since 2019 (TBI accessory drive and fan).

I live in south Texas where its triple digits nearly every day in the summer. I can sit in traffic while running my A/C and I do not have any weird temp spikes. My temp hangs in the 180s and might see 190 if im sitting still for a long time while running my A/C during the hottest part of the day.

Anyway, good luck with the rest of the swap and keep us up to date.

 

[PlayingWithTBI]

I was positive that it was at TDC when I was checking the timing chain marks and installing the balancer (with the VC's off) and I never bumped it afterwards, so I set the dizzy where I wanted #1 to be and had no luck when cranking it. I swapped the plug wires 180° on the cap and it fired right up. Hell if I know.

If you had the timing gears dots pointing at each other (12 O'clock on the crank and 6 O'clock on the cam) you're at TDC on the Exhaust stroke. The cam gear has to be at 12 O'clock too. A lot of folks make that mistake too.

 

[Firewood truck]

If you had the timing gears dots pointing at each other (12 O'clock on the crank and 6 O'clock on the cam) you're at TDC on the Exhaust stroke. The cam gear has to be at 12 O'clock too. A lot of folks make that mistake too.

That must be where it went wrong for me, even though I saw that both rocker arms were flat when I was at that point. I guess that they were completely bled down by that point. It's been a while since I've been this deep into an engine. Old fart making a rookie mistake!

 

[Firewood truck]

For now, this is how I was able to route the vacuum booster. I used a 1" nipple, the kind that has a screw drive slot in the very top. A short piece of vac hose, the 90° elbow then routed the hose around the backside of the engine. I need to trim it up and make a hose holder from the bracket off of the TBI engine. I reused the wire set that was on the TBI engine, none of them are close to being the right length so eventually I will have to find a better set, they work for right now but the routing is horrible and it looks like hack work.

The 11 blade fan from the Vortec engine fits pretty good inside of the TBI fan shroud.

Now for the major disappointment of the day. I found where the loud 'bang bang bang' is coming from. I located it as I was looking for the source of an oil leak. The oil is coming out of the bottom of the Holly timing cover. *sigh*. As I was looking closer, I put my hand on the oil pan because the noise sounded like it was coming from the front of the engine. I thought that maybe the fan was hitting the shroud. Nope, I can't get that lucky.. As soon as I touched the front of the pan, I could feel a rod or counter weight hitting it on the other side. I shut it down and got a closer look. The front of the oil pan is dented pretty badly, I never noticed it. I was relieved to figure out the problem, I'm beyond disgusted at all of the work that I will have to re-do to drop the oil pan. I need to find out if the tBI pan is the same one that the Vortec uses. I don't want to try to beat it back into shape.

 

[PlayingWithTBI]

this is how I was able to route the vacuum booster. I used a 1" nipple, the kind that has a screw drive slot in the very top. A short piece of vac hose, the 90° elbow then routed the hose around the backside of the engine.

Are you talking about the brake booster? It looks like its hose it connected to the Throttle Body spacer ring. There's almost no vacuum there, you won't have power brakes that way. You need to hook that hose to somewhere under the TB so, you get full manifold vacuum.

 

[Firewood truck]

Are you talking about the brake booster? It looks like its hose it connected to the Throttle Body spacer ring. There's almost no vacuum there, you won't have power brakes that way. You need to hook that hose to somewhere under the TB so, you get full manifold vacuum.

its just the angle of the pic, the brake booster is getting direct manifold vacuum from the port behind the throttle body. I added a pic that shows it better.

 

[Firewood truck]

Not much got done during the week except trying to get the ignition timing figured out. When I used a light to set the dizzy to the 'zero' mark', the engine idled horribly and would back fire through the TB when I blipped the throttle. ( The tan/brown-ish timing plug was disconnected) so I started to turn the dizzy until it was at a smooth idle and would give a quick rev when the throttle was blipped. I put the light back on the balancer, just curious to see where the TDC mark ended up. I would have to guess that it's somewhere in the 20° BTDC ( advanced) area.. I borrowed an adjustable timing light today but I got rained out, so tomorrow I will fire it up and advance the timing on the light until I get it to the TDC mark on the cover. I'm surprised to see it that far off, its making me wonder if something strange is going on. The engine was a factory warranty L31 crate motor, so it would have came with a new balancer on it. I can't imagine that the Holly TC has the pointer that far out of whack.