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iTrader: (21)

I've heard that switching to a tighter gap spark plug can yield gains on mildly modified cars. I read that Alan from tick said that there was a noticeable improvement from switching from a .055 to a .035. Can anybody chime in?

Car has full bolt ons and a cam spinning to 6800.

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iTrader: (21)

nobody noes anything bout this?

teke184

iTrader: (5)

doing plugs soon....so i'll be watching this thread

$750 L98

iTrader: (7)

Good question, I have an LQ9 with a cam and headers. Currently running out of the box NGK gap on TR55s, which looks to end up being about .055-.06"

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iTrader: (21)

bump, anybody?

twitchtwice

iTrader: (12)

im intereseted in this as well. im a bolt on car and i just put the out of the box gaps on my tr55s as well

01ssreda4

iTrader: (96)

I know NGK recommends something like .05 decrease in spark gap for each 50 hp increase over stock. So if stock gap is .060 and you have 100 hp over stock then you should drop it to .050. Also, didn't GM revise their recommended spark gap on our cars to .035?

KCFormula

iTrader: (4)

As long as the spark is strong enough a bigger gap should theoretically make more power.
There are a lot of variables here. Increase plug gap and optimize coil dwell *should lead to more power.

Blackhawk777

From what I've read, our spark gap is supposed to be at .040. That seems a little bit on the tight side don'tcha think?

Hemi2Slo

I've always been told by GM to run a .045 gap. But if a different gap either way will make more power then I'd definitely be interested to know what it is.

NHRAMAN

iTrader: (1)

A/C DELCO IRIDIUM plugs come at .050.

S10xGN

iTrader: (11)

I tried going down to a 0.030" gap and fouled the plugs so bad it wouldn't start. Went back to 0.050" gaps and all is well. YMMV, as mine is carbed and prone to being fat at idle and off-idle...

DaveX

This would be a good one for the mythbusters.

thewholefnshow1

iTrader: (2)

Your right.

LS6427

iTrader: (2)

There is absolutely nothing that will be gained or lost from going from a .060 gap to a .040 gap...I can tell you that from experience with my bone stock car....then after I had my 427ci put it.

I tried them all with both engines. .060 - .040 performed identically.

Conclusion: There is not a single bit of performance change from .040 - .060. I have since been using .050, right in the middle.

Spark plug gaps can be the same (.050) for a bone stock LSx all the way up to a 600+ RWHP LSx.

Its when you start boosting and spraying an engine where gaps make a difference. And big *** high compression bad *** engines.

Also, there's really no such thing as a plug that is gapped a certain way....you just buy the proper plug and gap it yourself. TR55 and TR5 plugs are identical and may come gapped from the manufacturer differently, but you can change the gaps to whatever you want. And if you do buy a certain plug and expect it to be gapped a certain way...always check them before putting them in to make sure they are where you want them.

I guess the best of both worlds would be as big a gap as possible BUT still have enough power to make the spark. They make something that increases the power that goes to the spark plugs so you can make the gap bigger and still have sufficent power to make the spark.

.

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iTrader: (21)

thanks for the good input man.

Paul57

I was under the impression that opening up a plug from say .030 to .060 would be similar to advancing your timing...albeit very slightly???

LS6427

iTrader: (2)

Ya know...maybe gas mileage will change ever so slightly between different gaps, but I'm talking from a performance standpoint, smooth idle, smooth acceleration throughout the rpm range and smoothness of a hard acceleration during a hard run.........I saw absolutely zero difference going from .040 - .060 gap on both my bone stock engine and my 427ci.

I never tried to go any lower than .040 because that really is getting just too small...for an N/A engine. And when you get too big of a gap you start having issues of the spark being able to make the jump from the plug tip to the electrode.

.

Johnnystock

iTrader: (6)

I always felt this way...^^

I changed from TR55 to TR6 with nitrous gap and no difference.

Paul57

I would agree on the performance aspect. It is unlikely there would be any real noticeable gain. Although, if I knew it was worth 5 free HP's, I would gap to whatever it could take. And, from a timing perspective...you shouldn't be relying on your plug gap to adjust timing...correct???

As long as your plug is firing "completely" every time, I would tend to think that wider is better...kind of like rear tires . OK...not really like that .

From what others are saying, GM has reduced the plug gaps. I am guessing this has a fair amount to due with emissions and making certain the plug never even "slightly" missfires or has a weak spark.

After all is said and done, it sounds like .050 is a good number for N/A on most street rides. Even if someone could prove that .040 or .060 was the absolute best, at least you only missed it by .010 rather than being on the extreme end of low or wide gaps.