Well its been a while since I have been around the forums. Unfortunately life got pretty busy, nothing bad...just busy. Anyway, since I last posted, I was having issues with my brake lights/turn signal/hazards - I looked at it with a buddy of mine and we thought we had checked the simple stuff (fuses all looked fine) and we started looking at the turn signal switch in the steering column. I also started trying to find/comb through wiring diagrams to help me trace down any problems. But long story short...I should have just kept things simple. Before tearing too much of the car apart, my roommate said just change the fuse, even if it looks okay (this advice also came after I figured out that brake lights and hazards are on the same fuse). I changed the fuse and presto...all better. I also learned that if the fuse is out and you have a hazard switch in the on position then that screws up your turn signals as well, but once a new fuse was in, it was all good, no issues. Anyway, I thought I would post this real quick before asking my question, in case someone stumbles across it sometime and it helps them out.

I also had to have my suspension redone - but that is a longer story for another post.

My question today is about spark plugs, but here is some back story first. Ever since I got my '72 Z about a year ago she has been running really rich. This lead to a carburetor rebuild and then eventual replacement. I have recently been working on jetting her down and I changed the power valve from a 6.5 to a 3.5 because my idle vacuum is only about 7-8. She is running much leaner now, I definitely still have some work to do though. I cleaned my old spark plugs a while ago, but I think the best thing to do now is to just replace them and use the new plugs to help me further refine the tune of my carburetor.

My current plugs are ACDelco R45TS plugs. The question is should I simply get the same ones, or is there another company/spark plug design that would work better in my engine?

The engine (according to the documentation I got with the car) is:
1) 4-bolt main (010) block with a .030 overbore (machined, balanced and blueprinted by Golden Shamrock Enterprises) - so a 350 bored out to a 355
2) Crane cams flat tapped 0.500 lift, intake and exhaust 248n duration
3) Bowtie cylinder heads shaved to a 58 cc combustion chamber with oversized valves, big block springs
4) Chrome molly push rods, 1.5 roller rockers
5) Victor Jr. Intake
6) 670CFM Street Avenger Aluminum

Any ideas, advice, places to look for more info are greatly appreciated.

 

That's probably a good plug for your engine set up. I use an equivalent Champion plug, but brand really doesn't matter much to me. I think all name brand plugs are very close, regardless of what the various plug makers would like us to believe.
Here's a good cross reference site if you want to try another brand in the same heat range:
Spark plug cross reference

 

I run 45's in all my stock headed motors. They are right where you need to be. I just switched from NGK to Autolite in my Canfields. Not for any other reason than I researched what some engine builders were using. The NGK's were fine but expensive. I prefer Ac Delco on the rest of my vehicles. Again price driven. I dont put much thought in multi electrode plugs no matter how much advertising they buy. Never once seen a pro stock car with 8 E3 plugs sitting on the carb pan in the pits.

 

Very good point! Look at what almost all the pros use at the drag strip, and you'll see all sorts of brands, but never anything exotic. They use regular spark plugs just like we buy at the local parts store.

 

Thanks for all of the input. I changed out the spark plugs yesterday and ended up increasing the size of the jets on my primary metering block a little and now she is running great. I had apparently gone just a little too lean. I couldn't be happier. I know I still have some work to do on tuning the secondaries, but things are going great.

 

I have a AFR gauge in the truck. My first one and I couldnt be happier with it. It turns out I cant lean my idle out to where I want with the screws. I would have never known without the gauge. It has been pretty cool setting it up the way I normally would and seeing where I can tune it by ear. I wasnt far off but now I can tune the living snot out of and know for sure what I am doing. Best $100 upgrade I have gotten in a long time.