The Stupid Engine Questions Thread

Frank Enstein said:

Don't agree. The Rotella T hasn't had the higher zinc since 2007 or 2008 from my sources.

Use whatever brand and viscosity you deem appropriate.

I recommend contacting the oil manufacturer and asking them "What oil is o.k. for my PERFORMANCE FLAT TAPPET CAM".

A factory 91 cam with 91 springs is probably fine with the new oils but it's a horrible mess if it eats the cam.

Oil is cheap.

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I'll look into that oil thing. I wasn't aware they changed the diesel oils. Thanks for the heads up.

I use Mobil1 FS 0w-40 European spec oil. It's higher in Phosphorus and Zinc (1000/1100 respectively) Keep in mind, too high of ZDDP will kill your Cat(s).

PlayingWithTBI said:

I use Mobil1 FS 0w-40 European spec oil. It's higher in Phosphorus and Zinc (1000/1100 respectively) Keep in mind, too high of ZDDP will kill your Cat(s).

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The cam manufacturers recommend 1200 to 1400 ppm depending on who you ask.

It's not even that simple. Valvoline VR1 race oil has last I checked had 900 ppm or less (SM requires no more than 900 ppm but I see it's now an SN oil which requires even less ZDDP) but it doesn't eat cams because they lower the detergent (calcium) content.

The calcium scrubs the engine keeping it clean inside so low detergent=sludge and gunk buildup.

It also scrubs the zinc from the metal to metal contact areas. So normal detergent level needs more ZDDP in the oil.

No big deal for a race engine that gets torn down and freshened up every year.

It'll do in a pinch but you don't really want it in a 200,000 mile engine.

Oh and trivia for the day:

It's not the Zinc that kills cats and O2 sensors, it's the Phosphorous.

steveed said:

I think the only option for that wiring harness is your local pick and pull. The wiring digram manual for my 92 says it is C102 the connector itself is #12020100. https://www.connectorpeople.com/Connector/DELPHI-PACKARD/1/12020100

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Much appreciated! Thank you!

Idle Issue. Every fifth or sixth cold crank truck will not idle until driven a mile or so. Idles after crank fine after that. Never starts hard, busts right off, runs great.

1997 K1500, 328,000 miles, 5.7, 5 speed, Lex 0411 swap (Issue has been there since before computer swap), no CEL, Spider upgraded to multi port.

I have the opportunity tomorrow to buy two different trucks, one is the TBI 350 the other is the TBI 454. Both have a turbo 4L80E. I won't be towing anything, it'll just be for hauling scrap or getting through nasty weather. Which engine is better for longevity? Neither truck was used for towing and are in pretty good condition. They're both in a 3500 srw 4x4, ones in 88 and the other is a 94. Both have about 140,000 MI.

Krash said:

I have the opportunity tomorrow to buy two different trucks, one is the TBI 350 the other is the TBI 454. Both have a turbo 4L80E. I won't be towing anything, it'll just be for hauling scrap or getting through nasty weather. Which engine is better for longevity? Neither truck was used for towing and are in pretty good condition. They're both in a 3500 srw 4x4, ones in 88 and the other is a 94. Both have about 140,000 MI.

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All other things being equal, the 350 will be better on fuel, that's for sure. Double check that 88. 4L80E wasn't available in the trucks until '93, I think. Chances are the 88 has a TH400 3 speed (no OD) or someone has done some kind of swap. Assuming it's the 88 that has the 350, if it only has the 3-speed, fuel economy will be much closer between the two.

andy396 said:

All other things being equal, the 350 will be better on fuel, that's for sure. Double check that 88. 4L80E wasn't available in the trucks until '93, I think. Chances are the 88 has a TH400 3 speed (no OD) or someone has done some kind of swap. Assuming it's the 88 that has the 350, if it only has the 3-speed, fuel economy will be much closer between the two.

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Id almost bet that 350 truck has a 700r4 if its an 88 because 1) i bet a th350 or th400 wasnt the go-to pick for a 88 gmt 400. A "4 speed" would be more likely in my opinion, so 4 speed would be a 4l60 as it would be renamed in 1990, 4l60e when it was made electronic.

Check to see if there is a TV cable somewhere on the truck and also check the shifter. I bet it has PRND321 not PRND21 (I could be wrong?)

The 454 id say is more likely to have the th400 but of course it depends all on how it was made and who had it since then. I would verify the 4l80e claims
pLus, the 88 ECM wouldnt be able to control a 4l80e

edit: didnt see one is a 94. that makes it more complex an answer. carry on

Krash said:

I have the opportunity tomorrow to buy two different trucks, one is the TBI 350 the other is the TBI 454. Both have a turbo 4L80E. I won't be towing anything, it'll just be for hauling scrap or getting through nasty weather. Which engine is better for longevity? Neither truck was used for towing and are in pretty good condition. They're both in a 3500 srw 4x4, ones in 88 and the other is a 94. Both have about 140,000 MI.

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whats the rear end gearing, does both of them have a trans aux cooler in front of the radiator, can you see a TV cable under the hood anywhere for either, and what do the shifters have for a pattern

AuroraGirl said:

Id almost bet that 350 truck has a 700r4 if its an 88

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I don't think GM put a 700R4 in any heavy duty applications, like a K3500 or behind a 454 - too weak. It probably was a TH400.