Turbo Kyle

I'm going to put a fresh set of Spark Plugs in the Vette. 67 327/300HP. Stock. Weekend/Daily cruiser. Occasional rips at full throttle here and there.

Going with the AC45 heat range. Thanks to Duke and others for the info as I was searching the Forum.

Denso: The exact Part number I got for the Denso is 6008 W-14U. That Correct?
https://www.densoproducts.com/denso-...ove-spark-plug

Also they come Gaped at .028 is that good or should I open it up a bit? .030-.035

NGK: I could not find the exact part number for the NGK B4. Need help with that.

Also the car gets parked on a Stacker. Easier to get to the plugs from the bottom or top?

2009stanger

I used the Denso’s that you listed. I gapped them at .035. They work well. I changed mine from above except for numbers 6 and 8. I tried to get them from above, but it was easier for me to change those two from underneath.

DLowe

I went with the NGK plugs and i'm happy with them. I'm sure the Denso plugs are great but i just don't have any experience with them. If you're also thinking about replacing plug wires i used Napa- Belden 700103 for my '66 L79. They are lifetime warranty and 7mm so they will fit under ignition shielding. These are precut and correct length to fit under your shielding with routing through all the shielding. Napa website list the wire lengths as well. Just installed these and love them. Cost roughly $43. Good luck.

Dwain

Turbo Kyle

Thanks Dwain. Its got new wires and cap and rotor. Do you have the Part Number for the NGKs?

67:72

The NGK XR4 (#5858) plug is equivalent to the R45S, which is recommended today for modern fuels. The B4 you are asking about is #3210.
Attached is the NGK cross reference guide.

Turbo Kyle

Thank you very much. If I remember right the R45S is the "extended tip"? So the XR4 is also an extended also?

DLowe

I went with the NGK - XR4 (Part#5858) equal to ACDelco R45S (S means extended) - Both resistor plugs.

• NGK-B4 and Denso-14U are Non-Resistor plugs like the orginal OEM plugs
• Resistor plugs are the best choice if you have static/noise coming through your original radio other wise non resistors plugs work just fine with ignition shielding.
• Best prices I've found for the NGK plugs were on RockAuto or Amazon. RockAuto can be costly with shipping if you are just ordering plugs alone.

Dwain

67:72

Yes, but a 300 hp (~10.25:1CR) should be fine - it's the very high compression engines that may have piston interference with the extended tip.

Turbo Kyle

Thank you. Lastly, what gap would you guys suggest?

DLowe

I gapped mine at .035 per the GM spec

leif.anderson93

NGK and Denso are both very good spark plugs. I, personally, run Denso 14U. Almost 4 years and 24000 miles on the current set and they're still performing fine.

Turbo Kyle

Thanks for that info. I ended up grabbing a 10 pack of NGK B4 3210's off Ebay (New Old Stock). $33.00 shipped

DLowe

You'll be please with your choice. Could not have gone wrong with either brands.