legacycentral bbs

Used to be id put fresh sparkplugs in my car when I bought it then forget about it.. though generally I dont think I kept a car long enough for it to be an issue. But as I recall it was recommended that you replace the sparkplugs every two years.

Angel is now my standing longest *running* car owned. I had a 1969 Baracuda project that spanned several years. but I digress.

It seems like every 6 months I end up replacing the spark plugs. Angel gets a hesitation under heavy throttle. Poor throttle response, and eventually begins to backfire about 3k RPMs under moderate throttle ( about where the turbo starts spooling). Jerk the plugs out. put fresh ones in and everything goes away and she feels snappy and peppy again.

The old plugs are always clean with a light brown ash on them. the electrodes show no corrosion or tac.

Spark plugs are cheap and Im quite willing to put up with it. But is it usual? Anyone else have the same issue? When was the last time you replaced YOUR plugs?

Funny... I was thinking about this the other day. I think I put 20k max on a set of plugs, but usually change them every year. I'm NA, but I still notice a considerable difference before vs. after. I think these motors like the nice clean, tight and controlled, low resistance spark that you can only get from brand new plugs.

I used to think that it indicated something was wrong with the running condition of my motor, but this is the third motor, and second car w/ brand new sensors that display the same behavior.

There's a lot of variables in your post, so I gotta answer with some questions:

-How many miles does 6 months of driving equal for you?

-What particular plug are you using (brand, heat range, part#, etc)?

-What are you setting the plug gap at?

Either way, if you're spending around $20/year on plugs, I don't see that as a big deal, especially if they always look clean coming out.

6 months = about 5k miles on average

Im using the NGK R BKR6E11

After my frist two sets comming in within range out of the box I quit checking spark gap. I dont recall what the gap was I was checking for but it was out of the Chilton Manuel.

Those plugs are pre-gapped at .044", same as the manual specifies. You should try closing the gap on your plugs, especially seeing as you have an MBC in your sig...implying higher-than-stock boost levels. I personally feel .044" is too big a gap for any forced-induction motor anyway, both the turbo Leggies here have the NGK's gapped at .028" and run great.

currently only running 8.5 lbs boost. but intend to run more as future upgrades allow.

Ill break out the feeler gauges and regap the sparkplugs to .028, give that a try.

Thanks for the advice!

Slodrive - I've always wondered what lowering the gap a bit on the NA plug would do... as it is, I always bring it down to the minimum of the range even though they come pre-gapped. Do you think a tighter spark would negatively effect the NA, or just clean up the timing a bit?

I definitely see the reason for it on the turbo, particularly at higher boost.

fishbone79 wrote:Slodrive - I've always wondered what lowering the gap a bit on the NA plug would do... as it is, I always bring it down to the minimum of the range even though they come pre-gapped. Do you think a tighter spark would negatively effect the NA, or just clean up the timing a bit?

I definitely see the reason for it on the turbo, particularly at higher boost.

I'm not sure it will do you any good, especially if you can get 20k+ out of them as it is. Bigger plug gaps will burn the air/fuel mixture better up until the point of misfire, and a low-to-medium compression NA engine with a good ignition system can normally handle a .044" gap just fine, sometimes more. However, every car is a touch different due to condition, driving style, environment, etc. so there's some trial and error involved if you're trying to get max performance or life out of your plugs.