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Gen2 Hemi spark plugs

Posted By: ProSport

Gen2 Hemi spark plugs - 07/20/22 08:35 PM

Hi guys, I don't come here much anymore so this topic has probably been beat to death but what spark plugs do you prefer for a Hemi. Mine is an aluminum 528 with Indy Legend heads, pump gas compression, 100% street car with a 1040 cfm APD 4150 carb.
I'd prefer a plug that doesn't come with the washers installed if possible. I tried running w/o the washers lately and the tubes seemed to stay cleaner inside that way.
I've been trying the NGK plugs, R5671A-7 and -9. Still doing some carb tuning but wanted to see if there's something else better for the street.
Posted By: NITROUSN

Re: Gen2 Hemi spark plugs - 07/20/22 10:32 PM

On my iron headed 528 the R5671A-7 worked well.
Posted By: ProSport

Re: Gen2 Hemi spark plugs - 07/21/22 08:13 AM

Ok thanks, I'm interested to hear more opinions as well.
It seems like the 7's run richer than the 9's in my car but I'm also tuning the carb so I'll keep playing with it.
Posted By: Cab_Burge

Re: Gen2 Hemi spark plugs - 07/21/22 04:40 PM

The only spark plugs I know of that don't came with gaskets are the tapered seat plugs shruggy
You don't want to use them in any Hemi motors I know of currently: confused:
As far as heat range I like to run the coldest plug I can that runs clean and doesn't get black at light part throttle driving up twocents
On your deal I would try a Champion RN9YC or maybe a Champion race plug. Autolite street plug # 3923 or maybe their 3922. Autolite # 3911 or 3910 on their race plugs.
I'm not current on NGK plug #s blush shruggy
Posted By: an8sec70cuda

Re: Gen2 Hemi spark plugs - 07/21/22 05:12 PM

I've always run NGK 4554 plugs (R5671A-8) on pump gas when I run it naturally aspirated. Never bothered to remove the washers.
Posted By: DoubleD

Re: Gen2 Hemi spark plugs - 07/21/22 05:33 PM

I run the autolite AR 3911 - been happy with and I have 8 sets in stock in the garage if you want to try them
Posted By: ProSport

Re: Gen2 Hemi spark plugs - 07/25/22 08:47 PM

Originally Posted by Cab_Burge
The only spark plugs I know of that don't came with gaskets are the tapered seat plugs shruggy
You don't want to use them in any Hemi motors I know of currently: confused:


Some plugs have the washer loose in the box so you have to screw it on yourself, that's what I meant.
Doesn't matter, I'll just use the washers, running without them didn't help anything.
Posted By: ProSport

Re: Gen2 Hemi spark plugs - 07/25/22 08:48 PM

Originally Posted by an8sec70cuda
I've always run NGK 4554 plugs (R5671A-8) on pump gas when I run it naturally aspirated. Never bothered to remove the washers.


Ok thanks Chip, I'll try those this week.
Posted By: ProSport

Re: Gen2 Hemi spark plugs - 07/25/22 08:49 PM

Originally Posted by DoubleD
I run the autolite AR 3911 - been happy with and I have 8 sets in stock in the garage if you want to try them


Thanks Dave, there's only 6 in stock at Summit right now. I'll let you know if I need to buy some from you, I'm gonna try the NGK-4554's first.
Posted By: quickd100

Re: Gen2 Hemi spark plugs - 07/26/22 01:49 AM

[i][/i] I first started with 9's and kept going hotter to until I stopped at 6's and stayed there . The 605 runs it's best on 91 octane and #6 plugs.
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