91 350 TBI Engine maintenance.

[Erik the Awful]

I'm about to put NGKs in my Mustang as well. I went autocrossing this weekend and on my last good run the engine fell on its face as I crossed the finish. The check engine light came on, and the code reader said "Cyl #4 misfire". It's only doing it under a load, and last time I had this the welded-on ground strap on the spark plug broke off! Autolite had one job...

 

[DerekTheGreat]

Autolites have been made from Chinesium for awhile now, if anything, use Motorcraft branded plugs. Also Chinesium but not as crappy? What I've got in my Town Car and I haven't had to touch them in over six years.. A/C Smelco isn't GM either, least not for the old stuff like we've got. It's just outsourced junk in a box with pretty blue & red accents along with an inflated price tag.

I was conditioned to do everything A/C Delco for my GM's and Motorcraft on my Fords, I'm slowly learning to undo that.

 

[Erik the Awful]

Last I heard, Autolite and Motorcraft were one and the same. A quick google agrees:

"As a division of the Honeywell Corporation, Autolite is the manufacturer responsible for the production of all Motorcraft spark plugs in North America for the Ford Motor Company. Both Autolite and Ford/Motorcraft spark plugs are built to quality standards using quality components. Autolite manufacture's the Motorcraft plugs based on the specific design requirements of the Ford Motor Company. Autolite and Motorcraft spark plugs are manufactured side-by-side at our facility in Northern Ohio."

 

[DerekTheGreat]

Welp, looks like I ought to check my facts before I say stuff. I could have sworn I made the switch to Motorcraft plugs after I bought some Autolites that said "Made in China" on them some seven to eight years ago. I began to assume all spark plugs are made in China, it is only a matter of time. So far so good with NGK's I put in my TBI 350. I don't know how I feel about putting Motorcraft/Autolite copper plugs in my GM engine. I know it's just some porcelain and formed metal but old guy mentality stuff dies hard.

I put A/C Smelcos in my Wife's truck about two years ago and I was treated to the same thing this guy saw:
Ac Delco plugs. Now made in China! | Bob Is The Oil Guy
Lots of speculation, some claim the box is the thing made in China, a few more claim Autolites are China and then others go back to the box being the only China item. Not sure what to believe, getting to the point where I just want whatever it is to work and fulfill it's purpose.

 

[LVJJJ]

I think my AC plugs were made in Mexico. They're great. I have a Fender Bass Guitar made in Mexico and its the best one I've ever had. Been playing bass since 1965 and have had many many basses.

 

[DerekTheGreat]

The plugs I had? I tried to thread them in by hand with the porcelain and whatever adhesive they used to adhere it to the metal broke. That's when I looked at the box and saw "China" on it. Never had that happen before. I know you're not supposed to try and tighten the damn things by hand but damn, there was literally zero torque applied when I felt the one start to wiggle on me..

 

[bhopthewelder]

Hi,

I just bought a 91 350 TBI with 267K km and i was thinking about doing the spark plugs, Wires etc. Maybe even distributor and other stuff. Its my first GMT400 and i love it so far.

First what kind of cable/Plugs i should use? Does high performance and iridium plugs help for power?

Is it worth changing the distributor if the engine runs well? Does it need to be retimed if i change it.

Any other preventive/Needed maintenance i should do on the engine or tranny?

Thanks for your help

Index your spark plugs for best performance of ignition.

 

[alpinecrick]

Any other preventive/Needed maintenance i should do on the engine or tranny?

Before you install a 30" lift with gangbanger wheels and tires tall enough to embarrass Bigfoot, before you install a bizillion watt amp driving a boombox left over from a Jimi Hedrix concert, before you install a purple LED bulbs everywhere, before you hang fuzzy dice from the mirror.....

Change all the fluids in the truck. ALL of them--diffs, T-case (if 4wd) trans, power steering fluid, coolant, and of course the motor oil.

If it's a auto trans the best thing you can do for it is get a pan with a drain plug or install a drain plug--keep the fluid bright red. Every third or fourth oil change pull the plug, drain oil, replace oil. Start with a new trans filter then don't worry about it until 30k or so.

Change the fuel filter--immediately. Then change it every 15-20k. If it's a quality fuel pump and hasn't been hurt by not changing the filter every 15k or so it may outlast the rest of the truck.

Flush the cooing system. A LOT of GMT400's have had conventional coolant mixed in with DexCooll--bad ju-ju.

Grease the chassis.

Electrical components and sensors think, AC Delco or Delphi. Although other companies have upped their game in recent times, I would still stick with the above for cap, rotor, and plug wires. If you can find a really dark spot tonight, light up the truck, let the motor warm up, lift the hood, let your eyes adjust, and check the plug wires for arcing. It might be entertaining.

Most (but not all) hard parts think GM OEM original when possible or affordable.

Odds are your truck needs steering parts, maybe suspension parts. Spend money making the truck "straight" before starting down the slippery slope of mods.

 

[alpinecrick]

Index your spark plugs for best performance of ignition.

Index?

You mean the ground electrode clocked in a certain position? What position?

 

[alpinecrick]

Okay then is there any way to add some HP to the TBI?

No.

Lots of other things have to happen before modding the TBI has any positive effect.