Spark Plug Lengths - shorty's
 

Read lots of conflicting info on forums from past posts, so I thought I would share some details. I have some cheap Chinese headers, and they don't have the best plug clearance. Here is a photo of the different length spark plugs commonly mentioned for small block Chevys. We have:
ACDelco 41-905
Autolite 145
NGK YR5
Champion RV92YC
Accel header plugs 0576S

Accel are the shortest, Champion are not far behind at a lower cost.

Hope this helps someone!

Re: Spark Plug Lengths - shorty's
 

Thanks for the info!

Re: Spark Plug Lengths - shorty's
 

A Denso u11 is just shy of 2.25" from taper to end of plug. Can you measure any one of the ones you got pictured? Just to be able to reference to what the reader has on hand.

Alex.

Re: Spark Plug Lengths - shorty's
 

I'm out of town for a while, but here's a thread with some reference.
http://nastyz28.com/threads/spark-plug-length.60539/
I believe the UR5 is the same as my YR5 at 2.072"

Re: Spark Plug Lengths - shorty's
 

Which, if any, fit your header setup?

Re: Spark Plug Lengths - shorty's
 

The NGK/Champion fit everywhere but #5. It needed Accel. You can get a pretty good deal on the Accels at Advance Auto with a 25% off deal. I also have the fiberglass spark plug wire protectors.

Re: Spark Plug Lengths - shorty's
 

I used the accel's on my last 2 trucks with V8s and headers, They made a huge difference in clearance. Neither engine had much mods and they ran very well also for my situation.

Re: Spark Plug Lengths - shorty's
 

And here's a picture comparing two non-tapered seat plugs for older heads and aftermarket aluminum heads. Not just shorter, but smaller body diameter and wrench size, too. Great for keeping plug boots away from header tubes. That's an NGK on the left, but Bosch and others also make plugs in that same size (called "ISO").

http://pic100.picturetrail.com/VOL38.../321822811.jpg

Re: Spark Plug Lengths - shorty's
 

MikeB,
Can you share the NGK part number? I’m seeing BKR5 and an 11 under that but can’t make out the rest.

Thanks!
B

Re: Spark Plug Lengths - shorty's
 

They are BKR5ES

B = 14mm thread
K = hex size 5/8"
R = resistor
5 = heat range (comparable to AC 44 or 45, as I recall)
ES = standard 3/4" reach

Got them 10-12 years ago, so their part number scheme may have changed since then.

I have an NGK chart that shows "11" means the gap is 1.1 mm or .044". I guess that refers to the out of box gap.

Re: Spark Plug Lengths - shorty's
 

Great info! Thanks MikeB!!

Re: Spark Plug Lengths - shorty's
 

Here's a link to the NGK chart:
https://rb30det.com/wp-content/uploa...7/ngkchart.jpg