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Author Topic:   Spark Plugs and Gaps
carver101
Dirt Roller

Total posts: 21
posted May 20, 2005 07:41 PM  
Did a search on this site, came up with alot of varying opinions, mostly from years ago. MY QUESTION: Motor is a Dart Block 414 CID, 12.5 to 1, Vortec Heads(tricked out) big cam, best of everything, running 110 octane racing fuel. I have been running an AC Delco R42T plug with a new D.U.I. Ignition, gapped at .45 due to the fact that DUI says you can run gaps up to .55.
I was told by a very respected car and engine builder (at the racing school I just attended), who said I definitely needed to lower the gap, and switch to a racing plug. So I bought some Racing NGK stock #3442, part #R5673-9 plugs, but did not trust the bonehead at O'reillys autoparts and did a cross reference of the r42t to the NGK. I do not think he gave me the right plug, numbers are totally different. QUESTION 1- what is the best racing plug at a reasonable price. QUESTION 2. what is the best heat range for my application. QUESTION 3- What is the best gap for my application.
Thanks to all, I appreciate the responses greatly.

Cally66
Dirt Full Roller

Total posts: 65
posted May 21, 2005 02:23 AM  
just we use 133 autolite all we use is autolite

Steve Dupree
Dirt Freak

Total posts: 316
posted May 21, 2005 05:00 AM  
All i can help you out with is the gap should be .35 for any engine we run. There was a big topic on this a little bit ago and some guy even gave a site to go too and look. Have a good one

carver101
Dirt Roller

Total posts: 21
posted May 21, 2005 10:08 AM  
Yes, I used the search element of this forum and went through every post pertaining to spark plugs and gaps. The opinions were all over the place, and many were 2 to 4 years old. I was hoping to start a new thread, with more recent post'ers, mainly because there were not any historical posts geared toward the 406 type motors with vortec heads.

redneck racing
Dirt Forum Champ
Total posts: 860
posted May 21, 2005 09:55 PM  
We run a 45 gap and i have used the NGK plugs and have liked them also have run the Champion truck plugs and have liked them to have done the cross referensing my self,the cross reference from the Delco to the NGK will give you the standard NGK, that is what i have run. Eddie

carver101
Dirt Roller

Total posts: 21
posted May 22, 2005 04:14 PM  
Yes, I realize I can get a good cross reference if I wanted to use a standard plug, but NGK does not have any data whatsoever on any website anywhere pertaining to their racing plugs. I would like to find out what other guys are using for a RACING Plug, who have similiar motors as mine. Not necessarily NGK, any racing plug.

hsracer158
Dirt Full Roller

Total posts: 33
posted May 22, 2005 07:41 PM  
Can't help you on cross reference. But my engine builder, told us to you ac delco r45t and to run gap at 45 thousands. Seems to work good, plugs look good.
Rick

redneck racing
Dirt Forum Champ
Total posts: 860
posted May 22, 2005 09:37 PM  
Carver I will look in the books tommorrow when i get to work if need be I can get a wholed of NGK, Autolite or whoever and see if they can send me literature on there racing plugs. Eddie

carver101
Dirt Roller

Total posts: 21
posted May 23, 2005 10:17 PM  
Thanks Redneck, I look forward to your response. To HS Racer, is your set-up the same as mine? Thats is a much hotter plug than the R42T that I am currently running. My motor ran closer to its potetial (7200 RPM) and sounded much better this last weekend, Still with the R42T plug, but jetted the Carb down from 84's to 80's(2 barrel). I am getting a popping kind of sound when letting off the throttle at the end of the straight, it did clear up just a little after the dowsize in jets. Hoping the plugs will eliminate the popping all together.

leapinlizard
Dirt Freak

Total posts: 402
posted May 24, 2005 08:03 AM  
Exhuast leak will do it too. Carb idle mixture screw adjustment can and help.

Todchester
Dirt Roller

Total posts: 23
posted May 25, 2005 03:25 PM  
I have used AC Delco MR 43 LTS plugs in Vortec headed motors for the last 5 years. Gap no more than .040 (in my book anyway) This is a marine plug and heat range is a little cooler than a standard AC 43, but hotter than a 42. This is the plug that Bob Cross ( GM Racing) told me to use and have had no problems.

The Flash32
Dirt Maniac

Total posts: 120
posted May 26, 2005 09:16 PM  
I haven't seen where anyone uses Accel plugs? I have been using them for 17 yrs. now. #137 in 461 heads.

carver101
Dirt Roller

Total posts: 21
posted June 01, 2005 11:23 AM  
UPDATE: I called the NGK Tech, he told me to try the R5724-8 VGroove Racing plug, Which I did, with poor results, fouled the plugs immediately and ran poorly during the heat, so I put the old R42T's (which by the way are the short reach plug; I should be using the 3/4 inch plug with the vortech head)....Ran great, finished 5th. NGK racing tech says to go hotter, so is now suggesting the NGK TR-6, then a -5 if that dont work. Anyone using this plug?

bobaluuu
Dirt Freak

Total posts: 474
posted June 02, 2005 08:56 PM  
what ya wanna bet ngk isnt offering to supply any of the plugs your gonna experiment
with till you get their research done.

carver101
Dirt Roller

Total posts: 21
posted June 02, 2005 09:26 PM  
Yea, I hear ya, he did recommend that i buy the buck fifty plugs untill I find the right heat range, then switch to their 12 dollar plug only then. Is there something about NGK you dont like, bobaluuu? Maybe I should be using Autolites. Your thoughts?

waynedogg2003
Dirt Roller

Total posts: 15
posted June 03, 2005 06:57 PM  
I have pretty much same motor except darts and 2-barrel. I run ac delco R45ts gapped at 35 with much success.

racerss10
Dirt Full Roller

Total posts: 31
posted June 03, 2005 09:29 PM  
from what ive seen on ngk heat range a r5673-6 standard tip or r5674-6 projected tip crosses over from r42t, r42ts the higher the last number the colder the plug on ngk

[This message has been edited by racerss10 (edited June 03, 2005).]

hsracer158
Dirt Full Roller

Total posts: 33
posted June 05, 2005 05:35 PM  
Carver,
With out getting into to much detail, we run a 30 over 350, with a set of 55cc 305 heads, a canadian 2 barrel intake, and a rochester 2 gc that came from speedway. We run an isky cam and 76 jets in the carb, with the 45t plugs and a 45 thousandths gap. Plugs are pretty much cocoa brown, and we index the plugs. Compare to what you have. thanks
Rick

carver101
Dirt Roller

Total posts: 21
posted June 07, 2005 12:15 PM  
UPDATE: I tried the NGK TR-6's last sat with good results. Motor definitely woke-up...plugs however were sooty, So I leaned it down from 80's to 74's by the end of the night, was running well, finished 6th. I will next put the TR-5's in it, but fatten in back up then lean down from there. Getting Closer, Should of listened to poster waltonjr1 on the engine tech board, he recommended: [quote]
NGK Tr5
Champion RS12YC
Autolite 103 racing AR764
Ac Delco R44 LTS
All 14mm .708 reach

Looks like he nailed it with the NGK tr5 heat range, that explains the AC Delco guys running the hotter 45TS plugs, where I was running a 42T short reach plug("S" meaning long reach for votechs, FYI).
NGK is hotter going down in number, so the TR5's should be mean this coming weekend, once I dial in the jetting.

J3
Dirt Maniac

Total posts: 188
posted June 08, 2005 06:01 AM  
Does what kind of plug you use really make that much of a differance? If so, what plug would you suggest to use in a 315W, 30 over, flat top, with gt40p heads?

    

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