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What spark plugs are you running ?

Lunatic

Lunatic

1/2 ton status
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Jul 27, 2008
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Location
Ft Hood, Texas
On my stock 350, I've used AC Delco R43TS - heat range 3, 0.431 in. reach for quite some time. Just recently, I changed to Bosch HR9BPX Platinum Plus - heat range 9, 0.875 in. reach.

The change got me to wondering about all the "results" of what is found at the auto store computer, and what the optimal heat range and reach is for a stock 350. Just because it "will work on this application" doesn't mean it is "meant for this application".

So, what's the brotherhood running ?



Troy B
Ft Hood, TX
 
AC Delco "rapid fires" in my 350. not sure what the part # is. not a big fan of bosch though. i've been wanting to try the E3 plugs. pricey though
 
Been running NGK V-Power plugs for 20+ years now, best plug i've ever run.

Unless an engine was designed to use Platinum plugs DON'T use them. I have seen many melted pistons from them being used in the wrong application. Most times the engine doesn't even like them and doesn't run very well anyhow but not always.
 
I usually run the plug that was from the manufacturer....so mostly AC's
 
Thanks for the quick replies guys.

I am more curious about the heat range and reach differences - Trying to learn something I guess.

I'll do all the leg work - Thanks for posting your plugs ! :waytogo:




Troy B
Ft Hood, TX
 
If you run a shallower reach plug then the electrode will be further inside the head and it will cause the plug to have to work harder to ignite the fuel charge in the cylinder, if the reach is longer you could end up with the piston hitting the electrode and smashing it closed or even worse knocking a hole in a piston. As far as heat range goes, just run the stock heat range unless you are running aluminum heads and require a different heat range.
 
Ive always ran Delco's in a 44/45 range

Also ran NGK's with good luck, cant remember the numbers though :haha:
 
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I run the AC R45TS in my sbc406.That's what is spec'ed for it.And I RC my 87 350TBI 5.7 uses the R43TS.
 
The Rapidfire plugs have a different number of styles- I've seen numbers 1, 5, 9, 11, 12, 13. WTH ? :dunno:

The NGK Vs 2771 = heat range 5, reach .460

I've read somewhere online that the reach of the plug should not exceed the depth of your cylinder head - For reasons already stated. And shorter plugs will have issues when removing due to carbon build up. Installing the proper plug if chasing a shorter plug will present the same issue, being carbon build up in the threads of the head.

Finding a stock heat range is difficult for some reason. I would like to believe somewhere between 3-5 from most results I have found on the web but still haven't been able to nail it down.





Troy B
Ft Hood, TX
 
My favorite plug has been an ngk yr5.

Has the factory heat range listed for my 79 350 and it is almost as short as the accel header plugs so they clear my headers.

I also like acdelco but Ive had such good luck with ngk that I have no reason to change.
 
Thanks, Brady.

I've been browsing through any website I can find looking at plugs and noting differences. Those AC Delco Rapidfire1 plugs reach 12.3mm (.484) which is further than the more common NGK Vs (.460) or AC Delco R43TS (.431).

I'm not suggesting they won't do the job or do it well, but I am trying to figure out where exactly the reach should be for a stock head along with the correct heat range.

I already know that tomorrow I'll be pulling my #3 plug and measuring the spark plug hole. I'll probably pull them all - I don't really like the reach of the Boschs - There was a very notable difference when next to a R43TS. But who knows, the reach might be acceptable (technically).

I'll know more once I have a definitive measurement.





Troy B
Ft Hood, TX
 
GM said to.... Crate engine 454HO.... it was in the spec,,,so I run 'em....

They must have a reason......:dunno:


454HO Engine Specifications:
Compression ................................................................... 8.75:1
Cylinder Head: ................................................................ Cast iron, rectangular port
Valve Diameter (Intake/Exhaust): ............................... 2.19"/1.88"
Chamber Volume: ........................................................ 118cc
Camshaft:........................................................................ Hydraulic roller tappet
Lift: ............................................................................... .510" intake, .540" exhaust
Duration: ...................................................................... 211( intake, 230( exhaust @ .050" tappet lift
Centerline: ....................................................................... 112( ATDC intake, 112( BTDC exhaust
Rocker Arm Ratio: .......................................................... 1.7:1, stamped steel
Oil Pressure (Minumum): ............................................... 6 psig @ 1000 RPM
..................................................................................... 18 psig @ 2000 RPM
..................................................................................... 24 psig @ 4000 RPM
Recommended Oil: ......................................................... 5W30 synthetic motor oil (after break-in)
Oil Filter: ......................................................................... AC Delco part # - PF 1218
Valve Lash ...................................................................... Torque bolt to 45 ft. lbs.
Fuel: ................................................................................ Premium unleaded - 92 (R+M/2)
Maximum Engine Speed: ............................................... 5500 RPM
Spark Plugs: ................................................................... AC Delco MR43T
Spark Plug Gap .............................................................. .040”
Firing Order: .................................................................... 1-8-4-3-6-5-7-2
 
I change thousands of plugs a year, literally.. there's a reason Merc recommends AC's...

platinum's suck... and I've never been a fan of any split/quad tipped hype... from what I've seen they seem to actually load up quicker than a standard plug..
 
I tried the 4 strap quick fires back when they hit the market - Such a noticeable difference that I forgot I had them - Point being, they were just different with no truely noticeable gain. I haven't been aboard the "specialty plug" wagon since.

I found this informative little write up at Car Craft com. It's just a generalization of plug types and info. The one thing I didn't like was one of their pic captions....

The spark-plug companies don't make heat ranges easy to remember. Companies like AC, ACCEL, Autolite, Bosch, and Champion use lower numbers for colder plugs, while NGK and Denso use higher numbers for colder heat ranges.
Click to expand...


You would think there'd be a standard. So much for trying to make sense of the heat ranges.... :doah:





Troy B
Ft Hood, TX
 
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