rcwilbur

I have just finished putting on TSP 5.3 heads and a 224R Cam on my C5 corvette with M6 transmission. I am tuning it and getting knock at WOT. I am still finishing the tune, but am wondering whether the spark plug gap could have any effect.

I have NCK tr5 spark plugs that are gapped .040 out of the box. They seem to run fine. Good power and performance. However, I've seen suggestions that .050-.060 is the appropriate gap. Just wondering if the spark plug gap can itself cause knock.

HCI2000SS

iTrader: (2)

I have those same heads and a similar cam, and run NGK TR6's gapped at .040, and everything runs great

RPM WS6

iTrader: (3)

Assuming that everything is correct with your A/F and timing, you might want to try the TR6s mentioned above. They are a step colder and might help to resolve your knock issues using the 5.3 heads.

rcwilbur

Do you know what timing you have at WOT? In the stock tune it is something like 28. My car is retarding timing down to 15 in some cases--I have A/F ratio at 12.9 during PE/WOT.

HCI2000SS

iTrader: (2)

No I don't know as of yet (only recently got the car) but I will soon as i'm having it thrown on a dyno next month when I slap the nitrous on. IMO you should just try a colder plug since you have a HCI combo. I think the gap is fine. For $20 you might just solve your problem

rcwilbur

Thanks very much. I went out and bought some TR6's at lunch and will install them this weekend. It is a real pain in the *** to get the rear spark plugs out and in on this corvette. Wish I had considered this when they were easy to get to, but who would have known? Thanks very much for your help.

HCI2000SS

iTrader: (2)

Not a problem man! I wonder if it's harder to change the plugs on your ride than it is on mine. The passenger side rear was the only one I couldn't get to from the top, so I had to get it from underneath. It really is a pita on these cars lol. Good luck

rcwilbur

I am a neophyte and was going to ask what a colder spark plug meant. However, went to NGK website and they have an excellent explanation. Following is the link for anyone else interested:

http://www.ngksparkplugs.com/tech_su...x.asp?mode=nml

Thanks for the help.

rcwilbur

If you don't mind, I would be curious to find out what your timing is at WOT (before the Nitrous install) just to see if I am in the ballpark. I have heard from others that on this install would need to be in the 23-25 range, but some have suggested it could be as low as 21 to 22.

HCI2000SS

iTrader: (2)

Sure i'll let you know when I get it dynoed. According to Texas Speed (where my heads and cam were purchased) they would usually set the timing on a car like mine at around 27-28. We shall see though