Starting to understand why building engines may be best left to the professional

[Drew Pojedinec]

To nerd up this post even more   (thanks Ross, hehehe)

Holley jets are rated by flow and not by actual size.  This is why if you gauged several jets, you may find many different jets are the same size.
That said, any given two digit Holley jet is rated for up to 3% variance in flow.

To get closer you need to use the three digit Holley Jet which are called "close ratio" and only allow 1.5% variance, but there will be three types available.

Jet sizes for a 66 jet:

66 (3% variation)
661 (1.5% variation between other 661's)
662 (1.5% variation between other 662's)
663 (yup, you guessed it)

In my case I've spent what? 10 years tuning the same engine to it's leanest, meanest configuration.  Of course, this once again goes back to the old adage "Give the engine what it wants."  Instead of any hard fast rule, especially when trying to attain perfection, you need to react to the clues that are given.

[Yellow Truck]

I would have thought 30 ft/lbs into aluminum would be a bit much. I do have some torque adapters that helped with the old ones, but the CJ style have 2 extra bolts per cylinder, probably a bit trickier.

I am going to run it tomorrow (better weather and a camera man), for what specific situations does it make sense to capture the A/F numbers. I am assuming idle and WOT (stomping on it), and the transition from 2,000 (cruise) to WOT gradually opening the throttle.

[Drew Pojedinec]

Ok, but remember:

[My427stang]

Paul, just a recommendation as you get closer. 

Maybe just get to know the truck if it's running decent now.  The weather is changing, fuel mix is changing, the engine will be breaking in.  All these things combined with looking at a/f numbers will have you chasing your tail.

FWIW, I don't even use an AF meter in a carbed vehicle, except for on a chassis dyno to make sure we aren't too lean during the first couple of pulls.  What I do is drive and pay attention to when it's doing something wrong, but you need to get to know your new motor now

Some rules of thumb though

1 - ignore idle a/f numbers and get it so it idles the best at the RPM you want
2 - if you want to do a WOT full-load pull, log it if possible, but if not have a passenger pay attention, 12.5:1 is likely pretty good, but it has to be a constant load and stay at WOT so the PV and the mains are both feeding the boosters.  Remember, you are evaluating both primary and secondary.  I generally add to the secondary to save a little mileage

Everything else, let the engine tell you.  If it surges at part throttle, go with an earlier PV, if it doesn't, leave it alone. 

I'd say in general, other than the run on, which will likely cure itself as it loosens up, get as many miles on it as you can, get a few oil changes under your belt, as the idle creeps up and you readjust it and idle a/f, take notes and see where you end up before you go back inside.

Now in my EFI builds, I can log load, vacuum, timing, a/f, different story because I can see everything that my foot tried to do and how the car reacted, but a/f ratio alone is a bit harder without the added info you will get from getting to know the behavior of the truck

[Yellow Truck]

Ross, I have noticed slight surging under part throttle. By surging I mean it lunges, then backs off, then lunges. Not enough that it is obvious, but it is there.

[My427stang]

Ross, I have noticed slight surging under part throttle. By surging I mean it lunges, then backs off, then lunges. Not enough that it is obvious, but it is there.

If that is at operating temp, if you have vacuum advance, I'd first disconnect and plug it and see if it goes away.

If it was the same unhooked, and at operating temp (all warmed up), that is when I would put an a/f meter on it and only look at it when it is doing it, noting both the vacuum and a/f ratio.

So, thinking about this, realize you are likely seeing a slightly lean surge (assuming it isn't ignition), this is AFTER you added jet and put an earlier opening PV, it also shows that you likely do not need to put a smaller IFR in it.

Does it have a 5.5 or 6.5 PV in it now?  If 5.5, look close at the vacuum gauge when you feel it.

[Yellow Truck]

The PV is a 6.5. I will check to day if it is there when fully hot. The jets are at QFT's recommendation (2 sizes down from factory to compensate for altitude) and the PV is factory.

I have a nagging feeling the reason I may not have paid too much attention to it is that it was only present in the first couple of minutes of driving.

[My427stang]

So, keep in mind that you have no heat to that carb with your intake and you are running it a smidge leaner with their recommednation.

It takes a while for a cold FE to get warm enough that the gas in the manifold acts normally (doesn't fall out of suspension)  That's why stockers had exhaust crossovers.  Hopefully it is doing well when fully warm.

Heck, mine isn't very happy for a while with the chokeless 1000 Holley and was the same when I had the 3310 and could jockey the cable.

[Yellow Truck]

I got it out today. First I put 3/4 of a tank of 94 octane with up to 10% ethanol. Had to take some stuff to the dump to clear the space in a friend's garage where I park it. Yes, I take my restored '69 to the dump. It is a truck.

It took 1/2 an hour to get there and get out onto the highway. Due to construction it took another 20 minutes to get to a nice bit of open highway clear of traffic to run her up and down the gears. No noticeable surging. The wind noise is really bad at speed - most of the rubber edges have come loose and I need to remove the old glue and re-attach them. Result is you can only really hear the engine at WOT. It pulls really hard in 3rd from 3,000 to 6,000. Bit weak below 3,000 but not shocking. Definitely need better splits a proper 4 speed or 5 speed is in the future.

Brought it home and shut it off - nice and hot - and it shut off cleanly. It is a bit rough idling at 7-800 but not terrible. I had the A/F sensor hooked up before I took it out but was getting an error signal so pulled it and put the plug in the exhaust. It was black with soot and I expect the plugs will be very black as well - before taking the carb back to factory the plugs almost looked polished. I suspect I've gone from scary lean to fat rich. I'll pull the plugs and get pictures on Saturday - it is supposed to rain tomorrow.

One last thing - the tick is back. I'll put the missing header bolt in and check the others, but I suspect it is the #5 lifter that is loose again. Only started after the last hard part of the drive - pulls up to 6,000 rpm.

Since I am really out of good weather I'll park it soon and wait for spring.

[My427stang]

Well, first, it's reliable and running well.  So in terms of your comment "scary lean to fat rich" remember, don't over correct.

If you have been running primaries only and it's rich, check float level front and rear, check the choke to make sure it isn't closing on you.

If it's all good, I recommend you track your vacuum while driving and see how often you are below the PV value.  Additionally, finding out the size of your PVCR (the 2 small jets behind the primary PV) could give us an idea of total area available to the main circuit. 

I do not recommend jetting any lower yet, as you are already low.

One last comment, realize that in town traffic may not get you EFI-like clean pipes, we can get close, but it will likely never be as clean as a modern car. 

[machoneman]

I can only add to Ross's suggestions by saying from here, only change one thing at a time. Otherwise, you may be chasing a few carby adjustments that don't help. Do so as recommended on a fully warmed engine.

And yes, w/o the heat crossover and even with it, it can be tough with a carb to get the cold to warm transition right. I live with it and once warmed, all is fine. 

[Yellow Truck]

Guys, I'm actually pretty happy. As I was driving it Drew's words were in my mind - it can be rich many times but lean only once!

After they shop changed out the jets and PV I noticed the plugs were shiny, and it scared me. Right now I expect they will be sooty, but that is not a terrible thing. I won't be messing with the carb until next year - I'm just out of nice days to test drive it. I'll be back some time in the summer looking for advice on making small adjustments to the carb, it will probably be summer because I hope to get my hip re-surfaced in the spring and won't be able to depress the clutch for a couple of months.

BTW, watching the vacuum I've seen around 7-8 inches at idle but at cruise it is closer to 15, and I have not experienced any surging, so I think the PV is not the problem. I am very happy it shut down without any run on. That was with 3/4 94 octane and 1/4 91 in the tank.

[My427stang]

Guys, I'm actually pretty happy. As I was driving it Drew's words were in my mind - it can be rich many times but lean only once!

After they shop changed out the jets and PV I noticed the plugs were shiny, and it scared me. Right now I expect they will be sooty, but that is not a terrible thing. I won't be messing with the carb until next year - I'm just out of nice days to test drive it. I'll be back some time in the summer looking for advice on making small adjustments to the carb, it will probably be summer because I hope to get my hip re-surfaced in the spring and won't be able to depress the clutch for a couple of months.

BTW, watching the vacuum I've seen around 7-8 inches at idle but at cruise it is closer to 15, and I have not experienced any surging, so I think the PV is not the problem. I am very happy it shut down without any run on. That was with 3/4 94 octane and 1/4 91 in the tank.

That is certainly good to hear!

[Yellow Truck]

I just looked at the forecast and I may have one more chance...looks to be high 50's and mid 60s next week.

[My427stang]

One last comment, the standard cold plug a guy drag racing may use may not be the plug for a heavy(-ish) truck in traffic with a very wide ratio 3+1 speed.