prc stage 2.5 heads....tr6 plugs what gap?

**jmatt07** · 03-04-2009, 01:17 PM

i have the stage 2.5 5.3l ported heads 10.75:1 compression ratio on my 98 ss and hsw single nozzle 75 shot dry. i bought tr6 plugs, what gap do i set them as .35?

**jmatt07** · 03-04-2009, 02:31 PM

THEY ARRIVED TODAY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

My prc stage 2.5 5.3L heads arrived today. fully assembled with dual springs, titanium retainers, seats, seals and chromoly pushrods. im so happy right now.
They are almost too pretty to put in the car

**Firebirdjones** · 03-04-2009, 02:37 PM

I'd say your .035 gap is a good starting point. I run that gap on both of my 4th gens and they are NA motors.
With your nitrous plans it would be even better.

**Justin93** · 03-04-2009, 03:13 PM

I run the TR6's with 11.0:1 compression gapped to .40 without spray, so with that said, .35 would work fine for your setup.

**Jumper** · 03-04-2009, 03:19 PM

Originally Posted by jmatt07

THEY ARRIVED TODAY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

My prc stage 2.5 5.3L heads arrived today.

It`s always cool when your parts show up!! When did you order your heads? I am waiting for mine to get here. I had the same question about the plug gap, but I bought the tr 55 IX iridiums, I don`t want to hi-jack your thread so I will start a new thread later. Have Fun.

**Justin93** · 03-04-2009, 03:28 PM

Originally Posted by Jumper

It`s always cool when your parts show up!! When did you order your heads? I am waiting for mine to get here. I had the same question about the plug gap, but I bought the tr 55 IX iridiums, I don`t want to hi-jack your thread so I will start a new thread later. Have Fun.

We have to know what setup you have to make that call.

**Jumper** · 03-04-2009, 03:46 PM

346ci stock bottom end , 228R 112lsa cam, 2.5 5.3 heads, milled 60cc, stock mls gasket . no spray or boost. Street car only.

**Justin93** · 03-04-2009, 04:12 PM

Originally Posted by Jumper

346ci stock bottom end , 228R 112lsa cam, 2.5 5.3 heads, milled 60cc, stock mls gasket . no spray or boost. Street car only.

I have the same setup except I run a 224R with 112lsa and my heads are milled to 69cc. I'd do .40 gap on yours as that is what I run. However I would return those TR55's and get the TR6's as You will run more of a chance of issues with detonation with the TR55's as they are too hot for a higher compression Ratio. I run the TR6's on 93 octane and have zero issues. Do your self a favor and get the TR6's they are NGK P/N4177.

**Jumper** · 03-04-2009, 04:18 PM

Thanks for the info. I will look into it. What numbers did you make with your setup?

**Justin93** · 03-04-2009, 05:00 PM

Originally Posted by Jumper

Thanks for the info. I will look into it. What numbers did you make with your setup?

428rwhp 407Ftlbs. Note these numbers were with my MAF all messed up. Once I get a new maf im sure it will be a Tad higher. Reguardless I am very happy with the setup and numbers.

**jmatt07** · 03-04-2009, 05:04 PM

my setup is stage 2.5 heads 10.75:1 compression ratio. longtubes ory, bbk intake, 85mm tb, slp maf, 228r cam, 75 shot dry nitrous, 42# injectors, tr6 plugs. what gap yall think?

**Firebirdjones** · 03-05-2009, 08:09 AM

Like I said, .035 would be fine. No sense in making the coil packs work any harder than they have to.
I never run any more than .035 on anything, even the high energy ignition stuff. It has been shown many years ago by Smokey that opening the plug gap does nothing for HP and just makes the ignition system work harder than it has to.

I verified this quite a few times on the dyno, most recently with my 638hp 454 using an MSD digital 6 setup and found nothing with larger plug gaps.

**Firebirdjones** · 03-05-2009, 08:13 AM

As a side note, we didn't care for the NGK plugs either. It seemed even the cooler TR6 plugs were still hotter than a typical AC plug, but found the Autolite APP104's (which is the stock heat range for LS1) ran even cooler than the TR6's.
And if you want to drop a heat range the APP103's are the ticket, and have worked as intended for me.

Those TR6's just seem to be a hot running plug no matter which heat range was used.
Added benefit is the Autolite is american made verses that NGK jap crap.

**Marc 85Z28** · 03-10-2009, 11:24 AM

Originally Posted by jmatt07

my setup is stage 2.5 heads 10.75:1 compression ratio. longtubes ory, bbk intake, 85mm tb, slp maf, 228r cam, 75 shot dry nitrous, 42# injectors, tr6 plugs. what gap yall think?

.035"

Sell that BBK intake and SLP MAF sensor. Get an LS6 intake and either a stock MAF or if you insist on the 85mm route go with a Z06 MAF.