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1965 F100 352.
.30 over "street performance" can, Mallory electronic ignition,
Frankenholly 600 cfm, #64 main jets, with a light spring in the vacuum secondaries.
Ignition timing at idle with manifold vacuum to the can is @30° btdc. Limited to about 36°@3200 mechanically.
Running 91 octane from the pump. These plugs have been in about a month of daily driving that includes a 40 mile freeway commute.
I pulled these out last night after a spirited twenty mile freeway run home from work (80+mph) and then less than a mile on surface streets with minimal idling.
They look like I put them in right before I left work. What say you spark plug gurus?
Last edited by Thunderkiss1965; Aug 31, 2019 at 06:01 PM.
Reason: Need pic of plugs.
Either they haven't been run or a cleaner was used. I've never seen plugs that clean from any engine...modern or classic.
Swear on my momma's grave these plugs have been run just as stated in my original post.
I agree that they are crazy clean, but they were still hot when I took the picture.
How do you even get it to start hot at 30 degrees timing? And you definitely have the vacuum advance hooked up, so at 30 initial, plus vacuum advance, it's going to be WAY over 36. Something's way off on that. It doesn't ping like a can of marbles? It's possible the ring on the dampener slipped and it's not reading correctly. Check TDC on #1 and verify that the ring is in the right spot.
Plugs being that clean, you're running WAY too lean, and/or the plugs are not the right temperature and are getting too hot. What part number are they? One thing, maybe the flash from the camera drowned out any discoloration, I do see a hint of brown on one insulator.
Also, what compression ratio was the engine built for?
One of the most important areas to look at is way down inside the plug, where it transitions from the ceramic to the plug shell. This is called the "fire ring" and gives an indication of the wide open throttle or acceleration air fuel mixture. A lot of guys use those lighted magnifier ear scopes that doctors use, or cut open the plug to get a better view. Those pics are too blurry to tell much, really need close up pics.
The flat base ring of a plug shows jetting, the ground electrode shows heat range and ignition timing. A "throttle chop" cut and check is the only way to tell jet, idling time will show rich. The color of the ceramic at the tip doesn't really mean anything with modern gasoline. Use a stock heat range plugs for baseline tuning, in most cases they will be fine in a stock engine. Step down in heat range for extended high speed highway use in the summer.
How do you even get it to start hot at 30 degrees timing? And you definitely have the vacuum advance hooked up, so at 30 initial, plus vacuum advance, it's going to be WAY over 36. Something's way off on that. It doesn't ping like a can of marbles? It's possible the ring on the dampener slipped and it's not reading correctly. Check TDC on #1 and verify that the ring is in the right spot.
Plugs being that clean, you're running WAY too lean, and/or the plugs are not the right temperature and are getting too hot. What part number are they? One thing, maybe the flash from the camera drowned out any discoloration, I do see a hint of brown on one insulator.
Also, what compression ratio was the engine built for?
The vacuum advance is hooked up to manifold vacuum so the static or base timing is only 16-18°. The vac adv doesn't come into play during stArting, and falls away on acceleration, no pings. As for the plugs, should I go up 2,4,6 jet sizes? I'm just building the carb now and that's why I showed the plugs. I'll have to pull one out and get the number. I do know that they are recommended plug
You're not drag racing right? One indication is it will surge or misfire on the highway at steady level cruise if too lean on the jet. The old school way was to jet down two sizes at a time till it surges, then jet back up a size. The ignition timing curve and vacuum advance has to be squared away first before carb calibration.
From the David Vizard book on Holley tuning:
"Strange as it may seem, the main jet on a Holley carb is not what you should be using to calibrate the WOT mixture delivered to the engine. That job is the function of the power valve and the PVRC. The main jet, however, is the most often changed jet; the one changed in an effort to optimize the mixture for maximum power. While a main jet change for a raceonly vehicle may be suitable, it isn’t necessarily the case for a true street vehicle because in addition to power, both emissions and mileage are concerns. It is time to examine in detail the calibration of the cruise and WOT power mixture."
The goal in jetting is to run clean, there's no load (very little anyway) at cruise condition. Want to run fat and rich under acceleration though. Meaning when the power valve comes in under low vacuum. You'll have to run fat on the jets if the wide open throttle AFR isn't tailored. This means getting into the PVCRs, they are basically fixed size jets, only for the power circuit. The power valve determines when extra fuel comes in, not how much. If you have an AFR gauge can really dial it in. Without that though, it's a little risky, cannot go lean under power or acceleration.
The vacuum advance is hooked up to manifold vacuum so the static or base timing is only 16-18°. The vac adv doesn't come into play during stArting, and falls away on acceleration, no pings.
The vacuum advance seems to be (according to the pic) in the ported vacuum port on the Holley ?
No Tedster, I'm not really drag racing it, per se. But I am tuning for performance. I have not opened your link yet but I will shortly. I was as surprised as anyone when I pulled the plugs out. There really was no idle time on them. While not quite a throttle chop, I had just done a brisk 20 mile freeway run in the cooling evening sir and got all green lights from the freeway to my driveway, barely stopping for one stop sign and keeping my foot in it, with plans to pull the plugs. Before leaving work. I adjusted the af with a vac guage and confirmed that it was spitting a bit of h2o out the tail pipe. That has always signaled to me that the idle mixture is pretty dialed. I don't know the specs on the cam, I didn't build this motor. I was pretty impressed with it when it came into my Shop after being rear ended. (I'm a mechanic at a body shop) the owner had only had it about two months, and I think it scared him. With the insurance check and what I gave for it he did good. All I really know about the motor besides what is obvious is that the PO had it rebuilt about ten thousand miles ago, and didn't cheap out on it.
Yeah, definitely, check the link out then, I think you should find it useful. He talks about performance and street driven cars and trucks. Drag race only vehicles are a different deal, and they setup engines and select components for reasons that would be a mistake for driving on the street.
How do you even get it to start hot at 30 degrees timing? And you definitely have the vacuum advance hooked up, so at 30 initial, plus vacuum advance, it's going to be WAY over 36. Something's way off on that. It doesn't ping like a can of marbles? It's possible the ring on the dampener slipped and it's not reading correctly. Check TDC on #1 and verify that the ring is in the right spot.
Plugs being that clean, you're running WAY too lean, and/or the plugs are not the right temperature and are getting too hot. What part number are they? One thing, maybe the flash from the camera drowned out any discoloration, I do see a hint of brown on one insulator.
Also, what compression ratio was the engine built for?
Here is the motorcraft part number The rest of it Can you see down in there? Or are we looking for the timing mark on the ground electrode How about now? I basically just wanted to get the part number to you guys without writing it down, I'm lazy, decided to see if I could get a look inside
I took a pair of 64 main jets and drilled them out to the next size up in my drill index, didn't write it down. So last night on the way home from work, at the end of a spirited 20 mile freeway jaunt, I killed the ignition at around 80 and coasted to a safe spot and pulled a plug. Only one cause it was dark and on the side of the freeway. These plugs still look new with a couple (4) tanks of gas burned. A little fuzzy Better shot You can see the timing marks here. This is mostly for background so you can see where I was.
Coming in late to this thread, but I had a 390 with the same specs. Ran 44 autolites in mine, for years. As for the plugs you have, I don't know if the heat range is comparable to the 44's but, if they are, I would suggest that you are running very hot plugs. This will make reading them difficult in the best of circumstances. If you are running a lot of highway miles I would go to a colder plug. Assuming this and the plugs still look the same, I'd suggest running larger jets until you get some color to read.Probably 2-4 higher than what you have now. I absolutely HATE intentionally running an engine lean, so I'll never suggest that. Rich is never really harmful, but lean can be. At 10/1 compression 91 octane is usually sufficient. I ran it for years and never had a single knock or ping.
Wideband O2 sensors are reasonably cheap anymore, they are big with the EFI crowd but they are just the ticket to tune carburetors. If you really want to get into tuning a carburetor really well this is the only way to go. There's no substitute for careful plug reading, they don't lie, but it is really tough to do this with modern gasoline and plenty of experience. One way to get experience though is burning valves from running too lean. The wideband should give you a lot more confidence and safely experiment with different jets and power valves.
A stock heat range plug is the place to start tuning, or maybe a step colder. Improved high output ignition, leaner fuel mixtures, and lots of ignition timing calls for a cooler plug than was factory at the time, they used a fairly hot plug in those days to reduce fouling from city driving. I'd think the removal of Ethyl Lead from the fuel makes them less prone to deposits as well. I think the OP is just showin' off.
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