1992 GMC Sierra ZZ4 Engine Swap Question

[Chad Goll]

Working on a 1992 GMC Sierra Regular Cab Shortbox. Pulling the original motor and replacing with a GM ZZ4 crate motor I removed from a 1969 Camaro a while back.

My question is? Can I make the engine swap and remove and reinstall the factory throttle body on the ZZ4? I intend to use all the factory accesory drive brackets, pulleys, AC, etc. Also use the factory ignition coil, etc.

The ZZ4 has a Holley Sniper EFI that I was going to use but I am thinking the TBI may be a better route as it will retian the cruise control and likely would be a lot less modifications.

I cant see why this would not work and be a better route...but woudl appreciate any input.

 

[dannyboy0225]

If was doing the swap I would stick with the sniper efi. Have you checked for an adapter for the cruise control?


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[Schurkey]

I used a "ZZ4" intake manifold on my aftermarket-cylinder-head 1988 K1500 TBI. It seemed approximately impossible to use the stock TBI intake manifold on heads that DON'T have the screwy-angled center bolt holes. The TBI manifold is just a hint shorter than the ZZ4 manifold. They're very close. I used a center-mount TBI-to-Q-Jet plate (Trans-Dapt 2211) With the adapter plate the ZZ4 manifold is a little taller, so BE SURE TO READJUST your TV cable. I also had to pull some extra length of fuel hose through the clamps to get enough to attach to the raised throttle body.

Getting the EGR to work properly is a pain. The manifold has the wrong-style EGR flange, and it's positioned right in the way of the IAC motor. Edelbrock makes an EGR repositioning flange that moves the EGR rearward enough to clear the IAC. I had to invent an adapter to use the TBI EGR valve.

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There's a boss on the manifold for the alternator brace. I can't remember if the brace from the tensioner and the brace from the A/C compressor have bosses on that manifold. The EGR solenoid and the...electronic thing...next to it need to be hung off the choke hot-air flange mounting bolt. Not a great solution, but it works.

The coil bracket will have to be adapted to the manifold, the bosses on the manifold aren't spaced quite right.

The vacuum supply for the booster relocates to the rear of the throttle body with the aid of a reducer bushing. I cut the tube, it needs to make a ~90 degree bend--I just spliced the tube back together with 3/8 vacuum hose. Some brutalizing required.

The heater quick-connect needs rework (cut new pipe threads on the INSIDE) and a 45 degree 1/4 pipe thread brass street elbow and a short nipple.

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DO NOT use the standard TBI intake gaskets. You want gaskets with the full opening at the rear coolant hole on the cylinder head.

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[Chad Goll]

Thanks! That is great information.

No emissions testing and installing headers so I will just delete the EGR system. I dont think the Camaro headers will fit...but going to try.

Other than the alternator boss, How about the accesory drive, water pump and pulleys on the front end?

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[Schurkey]

You'll re-use the same style of accessory drive as was on the truck to begin with. Same water pump, and same brackets, same pulleys, same damper, etc. Make sure the timing indicator on the timing cover matches the damper you're using. I don't think you can see the older-style timing marks; you need the sort that you see between the legs of the water pump ("straight down", not 13 degrees to the left side.)

The alternator brace bolt-hole is on the manifold, drilled, tapped, ready for use. The issue is with the brace for the A/C compressor. There's no place on the manifold to bolt the brace for the A/C. I'll be forming and welding-up a new brace that attaches with a longer intake manifold bolt sometime this spring/summer.
[Edit] The brace for the tensioner goes to a thermostat-housing bolt. No problem. [/Edit]

You'll need a custom PROM to eliminate the EGR. Not my first choice. Whoever programs the PROM will have to dick with fueling and ignition timing to cover-up the detonation that the EGR suppresses.

You'll want the original engine oil dipstick and tube, otherwise the air cleaner snorkel/duct will be in the way.

 

[Chad Goll]

I convinced myself to go with the Holley sniper I have on the shelf. Should be easier for me to tune myself and ran great prior on the engine.

Only question now is will the stock gages work with the existing harness sensors? Not sure how they get their signals? Direct or through the ECM.

I intend to just remove all the un-used wiring for the TBI harness.

 

[L31MaxExpress]

I convinced myself to go with the Holley sniper I have on the shelf. Should be easier for me to tune myself and ran great prior on the engine.

Only question now is will the stock gages work with the existing harness sensors? Not sure how they get their signals? Direct or through the ECM.

I intend to just remove all the un-used wiring for the TBI harness.

All get the signal direct. Cruise also gets its signal direct from the VSSB or Drac.

Factory TBI would have been easier.

I used a TBI adapter on a performer rpm intake years ago with a 454 TBI on top of a 350 TBI with ZZ4 heads and cam. I tapped the adapter for the necessary vacuum fittings. Used a brake vacuum steel hard line off a Q-Jet for the brake booster.

 

[Erik the Awful]

I think the factory TBI is easier if you're experienced with it. I wasn't, and the Holley Sniper was far easier to install and set up. If you don't already have the TBI programming tools, the Sniper isn't much more expensive. The TBI's selling point nowadays is that it's been reverse-engineered to the point where you can have ultimate control over it - if you're willing to invest the time. I was willing to give up some control to let Holley do the heavy lifting for me.