A couple of weeks ago I posted the question about my son's '97 454. I asked what was the difference between the '97 and a '98 454 in the carbs? Also I wanted to know if I had the carb updated (with a complete new one) by AC in late '98 would they have put a '98 carb on it? Unfortunately nobody replied (I won't have replied either!) LOL [img]i/expressions/face-icon-small-smile.gif[/img].
Well I bought the K&N kit for the '98-'99 454 anyhow. While waiting for delivery I caleed Dynojet and asked if the thought it would work on my son's '97 with the updated carb? They did'nt know.. they also could not tell me what carb model the '98-'99 jet kit was developed for. Go figure that!!!!
Undaunted by their lack of knowledge and thinking that I must be smarter then them, I received my power kit and began tear down and installation. What I discovered is an interesting story.
I found that the AC had a Mikuni BST34 on it. I also found out it is a pain in the butt to get off! However, once I got it on the bench and started opening it up I found it had a 152.5 main jet. I found that the stock needle was at position 4. And lastly I found that bottom of the air box was filthy! Note to self "Clean the air box at least once a year!"
The Dynojet kit has very detailed instructions for the main jet and needle and idle adjustment based on modifications and elevation. It recommended that I install a 138 main and set the needle on postion 4, and finally give the idle adjustment 3 full turns. My reaction to that was "Holy Sh^& that is 14 points and 7 jet sizes different! No way! That will be way to lean."
Thinking that I am smart I decided that I would run the biggest jet that came in the kit... a 144 and run the Dynojet needle on pos 4 and run the K&N airfilter.
After installation I tried to light it up. It would'nt even idle, it was just to fat! So off came the carb and I put in the 138 as they siad and it is running great! Although it seems to run better at 1 3/4 turns rather than 3.
So the lesson I learned is combine a little knowledge, humility, ask as many questions as possible, and don't be afraid to try stuff.

I hope this helps anybody thinking about or doing this mod.

If you have any questions, email me at schmelin@aol.com and I be happy to help

Later

Max

 

have you checked your plug yet? That does seem like a big change in jet sizes for just a filter kit. Your plug should be a nice golden brown color.

 

ttaylor,
I have ridden it around a little, the plug is new and is not significantly colored one way or the other. If any thing it seems it is a little dark in color. I'll know more this weekend when I take it for a longer ride.
The original plug was really black because the idle setting was way to rich, therfore I re-adjusted the idle mixture to 1 3/4 turns (the service manual says 2 turns +/- 1/2) from 3. Then I put in the new plug and let the AC idle for 15 minutes. When I removed the plug it was no longer sooty black like the old one, so I am assuming that if I have a good idle quality and the plug is not getting sotty black that the idle mixture is set correctly. Is this an acceptable method?
One thing that I did not mention is that the needle that came with the Dynojet kit is .007-.009" smaller than the stock needle, thereby making up for the difference(?) in jets in those 1/4 - 3/4 throttle situations.