"In spirit", at any rate!

 

It is not bogus or lore, having raced cars, indexing is done today. Go ask any pro 1/4 or 1/8 mile driver or mechanic and ask them.
You can get 5-10hp from indexing, but you only get it at full throttle and you need to buy washers as mentioned earlier, plus 20-30 spark plugs of different length threads.

 

Does the top-fuel man's traditional dread of hydraulic lock have anything to do with it also?

 

No, but all spark plugs HAVE to be in the same heat range and if the plug goes into head off center, you want the plugs facing the center, if the plug goes into the center, you want the gap facing the toward the intake valve.

For a DD, it is not worth the expense, only race engines are worth doing this too and that is because race heads are usually not design with optimum spark plug gap location in mind, factory heads usually are made to get the gap in a good location.

BTW: you have to have the heads removed to do this the first time and then you notate what plug w/what washer goes into each cylinder and you need to try 2 or 3 plugs of the same type to make sure you have the right plug for each cylinder.
Plan on 5-6 hours the first time.

 

Uh randy i dont agree with heads off for spark plug location, just draw a line on the porcelin with a sharpie to indicate the ground electrode and youre set. Thet use the differant washers to set each plug in the orientation you want. And you have to do this each time you replace plugs in my experiance since plugs are differant of the same manufacture, part number, etc.... One of the reasons i quit doing it on the 580. Just not worth the hassle. When i indexed or not it never changed my mph in the qtr so it didnt give anymore or less hp

 

Unless you can see exactly where the SP gap is pointing, how do you know if the gap is pointing to the premium spot in the chamber?
But yes, for heads like the jag, you could get a way with a mark on the plug, but it would not be as accurate and could be why you did not see any HP gain.

 

Some of you blokes misunderstood the issue here. Few, if any, question the efficacy of race proven technology and tricks on high performance race cars.

The question is how much of it makes sense in street car application. Most of our Jags, regardless of year and model, are GT/street cars and Jag has crammed in as much performance enhancing stuff as is practical.

Most of the after mkt. performance upgrades available to Jag owners produce little or no performance improvements and certainly few are worth the expense. Excepted are such things as Super Charger pulley and perf. chip upgrades. Yep, there are guys that have transformed their Jags into dragster's but that's a whole nother story. For the money they would have been better served with a Mustang or Camaro. IMHO