So since I put on the 2280 Holley it seemed pretty lean, I was getting a lot of detonation more than part throttle and especially under load. Seeing that there is little to no aftermarket availability for the 120-6 Jets, I decided I would make some of my own. Some internet research concluded that the stock jets in that carb were .055. So doing a little homework I found that my 1/16" drill bit works out to a .062. So, after some precision cordless drill / vice work, I had a couple of .062ish Jets for my carb. Slap them in and go for a test drive.
Driveablity was way up, and engine manners were better as well as a little more power. detonation came in way later, and is faint at worst case.
So....where some is good more MUST be better RIGHT? LOL. So I stopped by Home Depot yesterday and picked up a 5/64 bit, wich miked out to about a .078 Jetting. Knowing that that was going to be a pretty huge step, I only did the outboard Jet. Car fired up good last night, and I have a 40 mile hilly commute to work every morning with about 12-15 stop lights and signs on the way to my daughters school. I'll post results.

Check your timing lately? could be a bit to much advance that your just covering up with an overly rich condition, i did that for awhile on my holley390

Kev

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Drive to work this morning put me on a really good mood. Ping is almost gone, just very light at WOT. I have access to much better bits at work, so I am going to go step by step until I get rid of that lean ping.
Current jetting is .0625 ish on the inboard, .079ish on the outboard. Next up size will take the onboard up to .066ish.

I would check and know your total spark advance numbers before going much fatter on jetting... you have already taken some big steps to the rich side.
DD

Timing is good, vacuum is disconnected, and it is at 34 total. I even had to lengthen the adjusting tab with a rat tail file to get the timing low. I'm going to get it phased and dyno'd by a local shop that has a dizzy spinner.

34 degrees of mechanical advance "total" is more than a SL6 usually likes...
30 degrees total is about right... and being able to set the initial at 8 to 10 degrees BTDC.

It sure sounds like you need to "shorten-up" the mechanical advance a bit(distributor re-curve) and then get back to the jetting.
If you successfully "cover-up" pinging caused by excessive timing, with an overly rich mixture, performance and your fuel economy will suffer.
DD

All right, dialed it back, we are now at 8 BTDC Idle and 28-29ish Total with the vacuum still disconnected. I'll take it for a spin like usual tomorrow and post some results. If I get in a good place this week on the race car and have the spare time and the local 1/8th is open, we'll do some base runs.

Drive to work was good, no real noticeable change, but ping is still there at WOT, or heavy throttle and load. I'm wondering if it the limit of the carb without going too heavy with the jetting. I'd hate to mess up low and mod throttle. Gonna play with the idle a bit, its a bit too rich and fast, and see how the afternoon drive.

Is this a stock motor?
If not, what is the compression ratio?
What is the timing at 2500 rpm?
What is the timing at 3000 rpm?
What is the timing at 3500 rpm?
If the rpms keep going up, your secondary spring is too week......and over advancing
or you have a heck of vacuum leak and it's going lean.....
What are the engine temps at WOT?

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

.030 over 225, decked block 9.3:1 cr
Ported and polished head, 1.70/1.40 valves
Comp .440 cam
Feather duster aluminum intake
3-1 headers, y pipe, 2.5 into sidepipe.
If I get the time, I'll check the progressive timing, but its pretty steady once its in. No vacuum leaks, thing idles low.
Engine temps never go over the "warm up" line on the guage.

Alright, its been a while, but we've made some progress, so its time to post.
Went and got some dyno time so I could see what I was really dealing with. Found out a few things.
1. Way too rich
2. Way too much timing
3. Transition tubes are way too small
4. Baseline was 117hp before the pinging got out of hand at 3500rpms

So I had my speedshop guys do a full recurve on the Dizzy, and got it set up so that it only has 14 degrees of mechanical advance, vice the 22 it had out of the box. Ended up setting the timing down to 26 all in, which netted us 145rwhp, and 190ftlbs. It still has just a bit of ping, very light, I'm wondering if it might be crappy fuel distribution? I ordered a set of stock jets and put those back in the car, which has leaned it out quite a bit, and bored out the transition bleeds as well, which has turned the low-no throttle stall into a slight bog, so thats is a bit of progress.
I'll take it back and throw it on the rollers in a couple of weeks to get the final tune set in.

Huh? Yeah, there is. Walker supplies a full range of them.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

What's your cranking compression numbers? 170-180psi is pretty much the limit for 93 octane on carb engine. If you STILL have ping with headers & only 26 degrees advance, you might consider retarding cam timing 4 degrees to bleed off a little cylinder pressure.

Also, what spark plugs are you running? You might try going one or two heat ranges colder. Once you start modding a slant, stock plugs don't always work so well.

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63 Valiant Wagon
225 - 4 bbl

Not so much Dan. If you actually click on most of the sizes to order, they show that they are out of stock.

Cranking compression was pretty low, 115psi. I'll have to look at the plugs, I forget what I put in there, but I'm pretty sure they are Autolites that are a few ranges cooler than stock.

How are you mounting a 2280 Holley onto a Feather Duster intake?

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Slant Cecil