The Official Vortec 454 Info thread

[stutaeng]

Correct, top driver side A/C mount just like a 7.4 Vortec. Wild guess? Probably their own unique accessory drive brackets for a GMT455 w/8.1. The 3500HD was mostly a "parts bin" design pulling things off the shelf that already existed for other models, but that doesn't necessarily rule out a few special-made parts, IMO. I mean - they had to come up with engine harness, stuff like that for these trucks. Also keep in mind while the U.S. only got them for 2 years, they continued producing them for the Mexico market for several more years with the 8.1 (and 6.5td) - through at least 2006 or so.

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Richard

Interesante! I'd like to find one of these on the wrecking yard so I can swap a 8.1 into my GMT400 K3500...

 

[someotherguy]

Interesante! I'd like to find one of these on the wrecking yard so I can swap a 8.1 into my GMT400 K3500...

IMO that's the best donor for a GMT400 8.1 swap - a 3500HD with same. Engine, accessory drive, engine harness, PCM, air cleaner assembly, etc. you have -all of it- right there for the picking. Just don't bother with the transmission as it'll be the super long tail version with the parking brake on the back of it. Get you a 4L80E from a regular late model 400.. Oh, and don't bother with the radiator either, as it's the one with the taller filler neck that only fits the HD core support (see it poking up in the 2nd pic), won't even fit a regular 3500.

One of these days..

Richard

 

[454cid]

What was the question again? Regarding accessories?

How did the C3500HD and the Kodiak with the factory 8.1 accessories work? I thought those mounted the AC compressor high similar to the position of SBC/BBC?

I googled las night for pictures, and I found what you mentioned.... it looked like at least two layouts for the accessory drive, for the 8.1L.

 

[Piratehunter]

In final stages of rebuilding my ‘97 454, prechecking the dizzy reinstallation for alignment of new United Motors billet dizzy. when bottomed out on the oil pump shaft, this new one sets about .050 above the surface of the bottom plenum without a gasket. My 120k mile factory dizzy sets flush without a gasket, but I can see that it has about .060 of up/down travel.

anyone seen this before? I can stack some gaskets to fill the gap and a bit of clearance, but concerned about pressure on the oil pump drive to dizzy structure and hold down strength.
what would you do?

 

[Schurkey]

I would put the original distributor against the United Motor Products distributor, and see where the extra length or other difference(s) are.

Specifically, the 7.4L Vortec uses a different distributor from the Small-Block Vortecs. Do you have the correct distributor?

Does the distributor gear have a burr or improper machining so that it won't slide all the way into the oil pump drive shaft?

 

[Supercharged111]

I would put the original distributor against the United Motor Products distributor, and see where the extra length or other difference(s) are.

Specifically, the 7.4L Vortec uses a different distributor from the Small-Block Vortecs. Do you have the correct distributor?

Does the distributor gear have a burr or improper machining so that it won't slide all the way into the oil pump drive shaft?

Wasn't the difference between them something so piddly that a distributor could be made to fit both?

 

[Schurkey]

The 7.4L distributor has a "Thermal Washer" above the drive gear. I guess the drive gear has been shortened to accommodate the thickness of the "Thermal Washer". The small-block distributors don't have that "Thermal Washer".

Wild guess: The aluminum housing doesn't need protection from heat like the OEM plastic housing.

Note that I've never held a 7.4L Vortec distributor in my hand, although I did touch one enough to get the sensor alignment within spec.

 

[Piratehunter]

The United Motors part numbers are different for the 7.4 and the 5.7, as are the ACDelco part numbers for each. The significant difference I can see between the two is the thickness of the “thermal washers” above the gear.
this new one came with a .060 gasket that looks to fill the gap at the plenum, just seems very tight. My fel-pro complete gasket kit included a .030 gasket. Will take some pictures in a bit.

 

[Dropped88]

Appreciate the input so looks like I'll have to find a 8.1 from gmt400hd or at least the accessory setup before I start the swap

 

[Piratehunter]

attached some pics. The main difference is the original one has about .050 of up/down play that is allowing it to set flush on the plenum, without a gasket. the new one has about .005 up/down play. When laid flipped end to end, they are within.010 of each other, when I pull the slack out on the old one. I’ll use two gaskets to get to .065 and allow some compression to fill the gap of the new one.