Spark Plugs for basic tune up? / Waking up a 307

SRD art

G-Body Guru
Jun 16, 2011
525
63
St. George, UT
Hey all I want to do a tune up on Grandpa, my 84 Cutlass more door. This is the first non Chevy engine I've owned, and for the cheapie tune up I've always used Delco R45TS plugs in SBCs. Any suggestions for the 307 Oldsmobubble? It's all stock, aside from removing the cat, adding a high flow muffler, and a K&N air filter. I'll bump the timing a little too to see if I can milk a couple extra hp/ mpg out of it.

The chain parts store online recommends an R46SZ, I'm not familiar with that plug number, is that maybe colder (?) than what the SBC's like? Your suggestions based on 307 engine experience? I'm not looking for a high dollar super platinum plug, unless they seriously make a noticeable difference in power/ mpg.

Thanks for any insight!

84 Grandpa Cutlass z6.jpg
 
Oct 14, 2008
7,201
113
Melville,Saskatchewan
NGK XR45, hottest or XR5, slightly cooler. Remember your 307 is barely over 8 to 1 compression. The Japanese NGK's are a better plug than the Chinese AC Delco and Autolite spark plugs.
 

SRD art

G-Body Guru
Thread starter
Jun 16, 2011
525
63
St. George, UT
Thanks for the reply. Looks like you're an Olds engine guy, another question for you /anyone else- any thoughts/ tricks to wake up the stock engine a little aside from what I'm already doing? I have a Chevy Vortec 350 crate engine that will eventually go in there so I'm not so inclined to go buy all the typical bolt ons for the Olds, just looking for the little things that will help the stock power levels or MPG a little.
 

bracketchev1221

G-Body Guru
Jan 18, 2018
965
93
I wouldn’t go crazy with ignition parts. A basic ngk plug and good parts will make it run as good as it’s going to. I put a set of replacement v-power ngk plugs in v6 and the car runs much better. Bumping the timing up a few degrees and a spring kit will probably get you more gain.
 
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SRD art

G-Body Guru
Thread starter
Jun 16, 2011
525
63
St. George, UT
Thanks for your insight. I've got an old G-tech so I plan to play around with things to see what each little tweak will do to it. Maybe I'll break into that hard to achieve 16 second 0-60 club. 😜
 
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CopperNick

G-Body Guru
Supporting Member
Feb 20, 2018
738
93
Canada
Instead of the 350 SBC, why not a 350 Olds? There are enough Olds fanatics hereabouts that among them they could direct you down the right rabbit hole to building a hot 3-5-0. Think you might even hear from the 403 and 455 crowd too. Don't misunderstand me here, that SBC will do the job and will respond to the correct combination of parts thrown at it. But the extra effort to drop an Old is worth the eyeball shock from the lookie-lous when you rumble into the cruise night at the drive in and pop the hood (or not. let 'em suffer).



Nick
 
Oct 14, 2008
7,201
113
Melville,Saskatchewan
Dual exhaust is a big one, guys have gained a second in the 1/4 mile with their 442's over the shitty factory exhaust. Your single exhaust is even worse. Full length headers like Hedman are worth 30 hp over manifolds on a hotter motor, hard to say on a 8 to 1 motor with a peanut cam. Any flat tappet Olds cam will swap in, a Vin 9 cam is an upgrade or the generic 204/214 cam, don't go any bigger. I would seriously consider a timing set replacement if your car has any amount of miles. They stretch and retard the cam timing or even worse the nylon teeth flake off and end up in the oil pump pickup. All this swaps directly over to an Olds 350. You will need new mounts, and accessory brackets to put a sbc 350 in your car.
 

airboatgreg

Royal Smart Person
Oct 2, 2016
2,221
113
I would stay with the AC Delco plugs that are recommended. Why do you need a "hotter" plug? You have the finest ignition in the world. If it ain't broke don't fix it
 

spidereyes455

G-Body Guru
Mar 6, 2013
611
93
Northeastern PA
Another plus of staying with a larger displacement small block olds is that ALL of your current parts will swap over. That means no having to hunt down sbc accessory brackets, pulleys, transmission, starter, motor mounts ect. That will save considerable time and money in the long run. Plus a 350 olds is a better engine overall according to many people, myself included.
 

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