Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

I used the search function for info, and really only came up with more confusion :lol:

The 72 GMC Sierra Grande that I just bought has a 350; presuming it hasn't been replaced with something else, the SPID code is 1LS910.

This seems to be the only car I've ever had where I couldn't just look up the year and model and get an answer for plug type.

What are the basic plugs I should use? Same with wires, distributor cap and oil filter?

From the pic, is there anything non-standard about the engine? I keep reading about 'Vortec' heads and other things, and have no idea what options there were or what to look for.

https://farm1.staticflickr.com/480/1...00a2e63e_b.jpg

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

Take plug out. Read number and manufacturer of plug. Cross reference #. Looks like a later model crate motor with passenger side dipstick. Has 12si alternator conversion as well in addition to the long water pump and flipped alternator installation.
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Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

Flip the air cleaner lid so it's less likely to collect water. Take pic again with air cleaner removed so we can see if it has had an HEI converions. I would try and get the wires run from below again like the OEM installaiont on the 67-72.
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Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

I considered just using the old plug type, but since it seemed the PO rigged so many things, I wanted to get the right one, not just the one he used.

If I Googled correctly, it looks like the 12si is a later model alternator and puts out a little more?

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

I can't take a pic at the moment, but I believe it is HEI (the larger style cap, right?)

Which wires, the plug wires? How were they run 'from below'? Sure wish I had another truck, stock, sitting here so I could compare! :lol:

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

I have HEI, under wires, and r45tsx ac delco plugs at .045 gap. this will work on most sbc.

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

Thanks for that!

This looks a lot neater. I can't quite make it out, how do the clips that hold the wires attach?

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

Depending on what kind of heads you have you will need either a gasketed or tapered seat plug.

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

these plates are factory and the clips are a standard wire holding kit for the auto store

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

Thanks!

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

Here's another picture to study. The original routing for the front wires on each side was through a retainer clip on the oil pan then between the motor mount and block retained by the clip at the bottom of the head. The only things missing in my picture are the heat shields for the plugs. If you have an HEI, you'll need different plug wires than stock. The wires that I used (and learned about on this forum) were for late 70s (I think 75-82) Corvettes.

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

Thanks for the extra pic & details on the wiring - and especially for that hint about the plug wires!

It is complicated, trying to find the right parts and right methods of routing things on this truck, as the PO changed a lot and I have no details about what was done - and because I've never actually seen the engine compartment of a stock or 'correct' GMC/Chevy pickup in person.

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

for Gm trucks there is a heavy duty oil filter, Fram part number is PH 373. its a spin on 2 quart oi filter. I always use them ...when they fit. because they filter 100% of the oil even when cold and add an extra quart of capacity.

they screw on all right but on some trucks the exhuaste system does not have the clearance to remove and replace them. It gets old pulling your "Y" pipe to change the oil.

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

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Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

I'll measure the clearance and then try to get one if it looks like it will fit. Thanks!

Re: Confusion on which plugs/wires/filter - 72 Sierra Grande 350
 

I'm kind of shocked, but really glad, to see how many people here have multiple older Chevy / GMC trucks. My other car is a 2000 Jeep Cherokee XJ 4x4, and that community is a lot like that. I was actually planning to get another XJ when I came upon this '72 GMC Sierra Grande long bed, and got it instead. I'd still like one more of each :D