I'm looking for a method to help me tune my carb, just to help give me a push in the direction I need to go (richer or leaner). O2 tuning is out of the question due to cost.

As far as reading plugs go:

My plugs in the motor are ~700miles old. motor break in was with them. I'd rather not buy all new plugs, as these are probably still good. They're just kinda dirty, and hard to clean well enough to be a good tuning tool. R42T plugs.

Can I just put a new plug in my #1 cylinder (easiest to get to), and just read that? What if I use an R43 plug? The R42T's that I have are rare enough to be hard to find, i'm thinking just any new spark plug for tuning would work?

Would this register with a single, 500yard long WOT blast? (secondaries locked out, to tune primary jets?) I'd shut if off as I was driving, coast to side of road and check?

Then say clean it or replace it, and do a steady throttle cruise test, say 1-2 miles long?

Does this sound like it'd work for me?

Thanks

 

Its easier to read old plugs that have a bit of buildup on them. They show lean/rich readings alot faster.


For the WOT run put it too the floor, pop it in neutral and shut it down ASAP. be careful if you still have a functional steering lock. It could get hairy...

 

yea, I found that out last time note to self, don't turn key all the way back....

hmm, so if the plugs are kinda worn, the newest buildup is what i'd be watching for, trying not to pay attention to the old stuff.... would I just be looking at the center electrode tip? still looking at the top of the threads?

 

i pay more attention to the electrode but technically they should both change at the same rate since its all in the same place at the same time!

 

ok, checked 'em out today. After wiping the plugs relatively clean, a WOT run from first to 80mph or so, didn't put much on them... A little bit of black on the top ring, i'm going to jet down one size and try again.

My plugs are pretty dirty though, compared to a brand new set of champion RV17YC's that I hold in my hands now... Are Delco's (R42T's to be exact) black oxide coated or something? I can't remember if they were painted black to begin with...?

I'm going back out there, one jet size smaller, and i'll also try the a new plug in #1, and see if it registers... This is a stock heat range plug, compared to what I run in the motor, will this throw off my results?