New owner of a 1991 Formula TPI 350, 36k miles

The standard plug for this seems to be the tried and true AC Delco R45TS. However, there are other higher priced ACD plugs and curious if any of you have done any comparisons or gained any benefit from spending more $$. ACD has a Professional Platinum and a Rapidfire Platinum. Twice the price.

Also, does the "45" heat range seem to work well in the TPI? I have no engine issues so no apparent need for a hotter or colder plug. I have seen some posts that these engines tend to run warm, but mine seems to stay in the 180-190 range in normal driving.

While AC Delco seems the obvious choice, I have had very good service from other brands as well (particularly NGK).

 

Yep, so many choices, and SO many more opinions....... Course, we all know about opinions and how they're like certain bodily orifices, everybody's got em, and they all stink

Threads about which brand of anything to use usually end up producing no good results because an item one person swears by, another will swear AT

This goes for sparkplugs, oil, batteries & tires, pretty much anything you could think of parts wise for our cars

 

How often do you want to change them?

Today's precious metal plugs, such as platinum, double platinum, iridium, etc., will last "forever," if an engine is tuned properly and runs cleanly and efficiently. It's the precious metals and their longevity that you're paying for, because you'll seldomly, if ever, have to replace them. Precious metals = one-and-done = higher price.

I realize that "tuned properly and running cleanly and efficiently" doesn't apply to a lot of Gen 1 SBC engines today, but there are still plenty that do meet that standard, so a set of modern plugs will last a very long time in them.

There's a nasty thread right now about Bosch plugs, but I had a set of the standard platinum in my Formula for about 10 years. They worked perfectly and still looked good when I replaced them. 3rdgens came with some "German" parts, lol, and they've worked well throughout the years, so why not spark plugs?

Changing plugs in modern engines is a big job because so much work is involved in removing parts, just to get to the coils and plugs, so most manufacturers now recommend 100,000 miles between changes because the precious metal plugs in them will easily last that long. They'll actually last much longer, but most people don't realize that, and no manufacturer will tell you that.

NGK platinum seems to be the OE choice these days. They were OE in my 2006 truck, and I put 300,000 miles on those original plugs. I assume they're also in my 2015 truck, as it's the same brand/model as my 2006 truck, and I'm currently at 390,000 miles on those original plugs. The plugs in my 2006 were still beautiful at 300,000 miles, and the truck still ran like new, so for the 2015, which also continues to run like new, better actually, I haven't worried about its plugs. 400,000+ miles should be achieved on the original plugs by year's end.

So, yes, modern, precious metal plugs in clean running engines can last "forever." To most car owners, "forever" is less than 100,000 miles, which means never having to change the plugs. To some people, "forever" is 200,000 miles, and modern plugs will get you there too, and beyond.

If your SBC runs well, then get the expensive plugs and never worry about them again. But if your engine slobbers all over its plugs, which a lot of SBCs do, then get cheaper ones because you'll have to change them regularly.

Brand, ethnicity lol, style of choice will work just fine, whether considered "gimmicky" or not.

 

I'd only bother with Platinums if I needed to go 40k+ miles between plug changes. The '89 FSM wanted R43TS in my TPI setup and the burn mark on my ground strap is still at least halfway down so they're working for my setup. Afaik you want the coldest plug that puts the mark halfway.

There's a lot of minor factors on what ends up being the optimal heat range for your application so really it's about whether you like what you see when you look at the plugs or not.

 

Perfect replies as to why you should run a precious metal plug.

Hot/cold plugs have nothing to do with engine temperature. It has to do with the heat of the plug. Typically you want the temperature of the plug to be in the 500-950* heat range. Too cold of a plug and it will foul up. Too hot of a plug and it will cause preignition and cause damage. Each engine is different. Which heat range works well in one engine may not be the choice for a similar engine.

The plugs temperature range is visible on the ground strap and can only really be seen with new plugs. You want to see a temperature dividing line about half way down the ground strap. Copper plugs are cheap and inexpensive to swap out to find the proper heat range. Gets a bit more pricey if you have to do that with platinum plugs. Technically, you want to run the coldest plug possible that doesn't foul up.

In my race engine, I run NGK copper race plugs. I buy them at the local NAPA. Something like $3/plug so they're cheap. Not like my engine is a high mileage daily driver. I bought a couple of different heat ranges to see what worked best. I also use indexing washers to position the ground strap up away from the piston. The high dome pistons in my engine will make contact with the electrode if the ground strap is pointing down. This isn't a problem with a typical street car with dish or flat top pistons.

Even with an older vehicle that was originally designed with copper plugs, the biggest advantage to platinum is never having to change them. A typical copper plug has around a 2-3 year life span. Platinum plugs are 5+ before needing to be replaced. A lot of newer vehicles, changing a set of plugs can be a whole afternoon job.