Just curious on what u guys running the 250 see as o2 readings ?

I see 4.7 on mine , I cut open plug and It looks good .

Im running 67 bottom 41 top , two alky carbs , 582 it makes about 2.8 lbs boost goes 4.52 in good air 153 mph

PM sent

Whatever the number is, AFTER i get the plug looking the way i like it. Anywhere from 4.9 - 5.3 makes power on alky

Abitz If you dont mine me asking. What did you cut your plugs with?

quote:

Originally posted by 329L:
Whatever the number is, AFTER i get the plug looking the way i like it. Anywhere from 4.9 - 5.3 makes power on alky

Those numbers will make aluminum not power. I know the baby blowers don’t need nearly as much fuel as a real blower but they need more than that.

Abitz, If you’re cutting plugs on alky to read then, you need to ask for some help with plug readings.

quote:

Originally posted by BJs Wild Ride:

quote:

Originally posted by 329L:
Whatever the number is, AFTER i get the plug looking the way i like it. Anywhere from 4.9 - 5.3 makes power on alky

Those numbers will make aluminum not power. I know the baby blowers don’t need nearly as much fuel as a real blower but they need more than that.

Abitz, If you’re cutting plugs on alky to read then, you need to ask for some help with plug readings.

I agree on the last paragraph!

quote:

Originally posted by Footloose:
Abitz If you dont mine me asking. What did you cut your plugs with?

I use a high speed cut off wheel to cut off the threads. Your question got me to search a better method. Search, spark plug cutting tool. I'm just going to buy the cutter & not the billet aluminium holder. farmandsandtoys.com has just the tool, I've done business with them in the past with our drag quads.

Just to be clear about my earlier comment:

cutting the threads off the plug on an alcohol motor will tell you absolutely nothing.

I have just tried to read the straps. Maybe I am wrong for 40+ yrs.

quote:

Originally posted by Footloose:
I have just tried to read the straps. Maybe I am wrong for 40+ yrs.

I'm all about technology, and efi. But as far as my experience with o2 and alky.......it just adds to confusion. Look at the plugs. No need to cut them and destroy them. As BJ said it tells you nothing with alky.
Now after you get the plugs in the ballpark, sure knock yourself out with o2 readings. Frankly I have found them worthless. And when you are getting started, if you splash one with fuel or anything that can happen on early startups and tuning.....the sensor can be damaged and be misleading.
I know some efi folks on alky will use the o2 to constantly adjust. With the unreliability I have seen with o2s and alky, I just wonder if they are out of their minds.

BJ and Bucky.

A trend would be more helpful to show how it’s going

I rely heavily on my O2 readings but like others have said they are useless until you get a good tune up and that is done with dyno time, track time, MPH and ET and reading plugs. Then when you get it right look at your O2 and that is your baseline for that motor. You increase boost that number will go down it needs more fuel with more boost.

A lot of people get caught up in what old So and So says like he said "You have a BBC so you need to run 38*-40* timing"

Well I have done a bunch of testing and dyno time and my motor likes 28*-30* timing and if I did like everyone says I would be leaving some on the table and harder on my motor to.

Same with the O2 readings I do not think anyone can really say what your motor needs there.

What I care about are ET, MPH and tuning to a certain O2 number will not get you there. Tune to ET and MPH then after that your O2 will help you keep it there and give you an indication when something changes.

Another for instance when I first started recording data was using EGT.

One of the older guys who was really nice and helpful was telling me to tune the car on alcohol the EGT has to read 1050* in the 1/8 mile and 1100* in the 1/4 mile. Well on my car at those temps it was stupid fat and would not run good at all. I ended up getting best ET and most consistent at 1350* (1/8 mile) and 1400* (1/4 Mile) on my that motor. 1050* and 1100* may have been perfect on his set up but did not work on mine.

Some say tune it to get 10* water temp rise during the run. Nope, tune it to best ET and MPH.

I do not use EGT any more I believe O2 are much better, more reliable and repeatable but still I tune to ET and MPH then use my O2 to help keep that tune up.

quote:

Originally posted by Footloose:
Abitz If you dont mine me asking. What did you cut your plugs with?

I insert the Porcelain part of the spark plug in an electric drill and as it spins u use a cutoff grinder just about 1/8 inch below the bottom of threads , takes 10 seconds .

quote:

Originally posted by TD1964:
https://www.dragstuff.com/tech...hol-spark-plugs.html

I've been using the dragstuff spark plug tuning articles for a long time; the one above & they have others that are referenced for spark plug reading.

Below is the current tech article I'm using for our ProCharged gas motor.

https://www.dragstuff.com/tech...ing-spark-plugs.html

Alot of good info in here but how did this thread derail so fast. Went from asking about o2 readings with the 250 blower to mostly how to read spark plugs

Go learn at a test and tune what your setup likes. No 2 combinations are the same. It would be nice if you bolt something on with no work involved.

quote:

Originally posted by MorgretNation:
Alot of good info in here but how did this thread derail so fast. Went from asking about o2 readings with the 250 blower to mostly how to read spark plugs

Because the spark plug is a better indication of what it needs and the O2 number is not the same for everyone. The more boost you run the richer it needs to be.
tune to ET, MPH and then use your O2 to keep it there.