1 Step Colder Than R42LTS?

[TT/Ameasap]

Im pretty sure I need to go to another brand, but what #'s do I look at for 1 step colder than my current R42LTS plugs?

 

[BEATAV8]

Vern just switched to autolite AR474. You could also use AR473 and AR472 for even colder.

AR474 = NGK 8 heat range
AR473 = NGK 9
AR472 = NGK 9 or ~9.5 (colder than 473)

I think the AC 42 crosses to an NGK 6 heat range. So the AR474 is about 2 steps colder.

I run the AR474 in my champion heads. These are 3/4 reach thread, tapered seat. cut back strap. non projected tip.

 

[TT/Ameasap]

Steve,
My timing mark is 1/4 up on the strap (running 93/alky). I am also getting pre ignition brown specs on the porcelain. Is there another plug that is one heat range cooler that you know of?

 

[getdowngranny]

NGK BR6FS (4323) and never look back.


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[Nick Micale]

Steve,
My timing mark is 1/4 up on the strap (running 93/alky). I am also getting pre ignition brown specs on the porcelain. Is there another plug that is one heat range cooler that you know of?

If you are seeing specs on the porcelain, my opinion is for you to use a non-projected tip plug as it is getting very hot in the combustion chamber and the plug tip will become the major hot spot.

The Autolite AR 3931-3935 series plugs are 3/4" reach, the coldest plug starts with 3931. For street use the AR 3933 would be a good place to start, with boost in the mid-20's, start with the AR 3932.

Actually I think the spots are detonation, pre-ignition results in this or worse:

 

[BEATAV8]

According to sparkplugs.com the R42LTS actually crosses to NGK TR5, not TR6. So a NGK TR6 (6 heat range) would be 1 step colder.

As Nick mentioned though, best to go with the non projected tip.

 

[kidglok]

What about the ar133 and 132? Or we talking about aluminum heads here?


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[BEATAV8]

What about the ar133 and 132? Or we talking about aluminum heads here?


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TTA needs the longer 14mm thread .7" reach

 

[TT/Ameasap]

Bought AR3932(all the store had) and they don't thread in the TTA head. Now what?

Edit:
The shoulder at the base of the plug contacts the heads counter bore.

 

[BEATAV8]

Bought AR3932(all the store had) and they don't thread in the TTA head. Now what?

Edit:
The shoulder at the base of the plug contacts the heads counter bore.

Go for the AR474. It has 14mm thread like the AR3932, but the AR474 has the correct tappered seat like the delco plug. The AR3932 has a gasketed seat.

Also for consideration:
14mm tappered seat plugs with .708 reach thread. These plugs have projected tip though.
AR94
AR93
AR92

 

[BEATAV8]

I have some spark plug cheat sheets I can send you. Got an email? PM me.

 

[TT/Ameasap]

Pm' you Steve
I just went ahead an ordered the AR474 plugs.. Be here tomorrow. Thanks for all the help

 

[buickGN3:16]

is it really necessary to do a plug change for street & race? I mean would it benefit the cars e.t? Im around 17lbs on the 93 pump gas & i use a eric marshall race chip burned for 22-25 psi & 108 octane, but i use 110 octane.


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[TT/Ameasap]

is it really necessary to do a plug change for street & race? I mean would it benefit the cars e.t? Im around 17lbs on the 93 pump gas & i use a eric marshall race chip burned for 22-25 psi & 108 octane, but i use 110 octane.

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Reading plugs are a big part of tuning.

 

[buickGN3:16]

I run a r43ts delco, am i anywhere near correct on this plug choice? i hear thats a good middle choice btween street & race..?


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[1fastcobra]

Bought AR3932(all the store had) and they don't thread in the TTA head. Now what?

Edit:
The shoulder at the base of the plug contacts the heads counter bore.

I run the tr5 in my tta. Gap at 30.
And run 10's. No issues.

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[TT/Ameasap]

Built cars are different. Cam, timing, afr are all factors. Some run lean and mean and some run rich with more power. It is wise to start with a cold plug and move up if needed. I chose what worked for my low 11 second TTA and it didn't work for my built TTA. Steve was gracious enough to lend me his chart and recommended a good plug. At 21psi the plugs are perfect. Car moves out for sure now! Good timing mark, brown ring and no speckeling on the porcelain.

 

[1fastcobra]

Are u running race gas or 93. I run 93 low timing 20-23 psi and twin alky
(With a 255 pump in the smc alky tank)
I'm allways open for a better plug and learn more
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[TT/Ameasap]

93/alky for now. 21 degrees of timing. I have enough room on the plug now for a little more timing when the time comes. My blue annealing mark is just befor that bend, where the 42's were almost to the base of the strap. Car runs great now.

 

[1fastcobra]

What plug did u end up using?

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