MG - Ya those electrodes look real good & I'm with you on the black soot. I would do exactly what you are going to do, new plugs with the 52 jets and run them for awhile & check the plugs again.

In the time period of this plug test check every little ignition, vacuum, carb item you can think of to make sure ever thing is operating as it should. For sure you need to do some thing about that early shifting as long as you have the 3.00 gears. That is killing your high end performance.

I think your getting real close to the best you might get out of the current setup. Then when you think you have it you might try a 2100 1.21 or 1.23 venturi carb that flows more CFM & will take a bit more jetting, along with making a little more power.

 

I agree old28. The only other thing I can think of to try is a plug chop where you run it at full throttle and then kill the ignition, shift to neutral, coast to a stop and pull a plug a see what it looks like. That way you're sure you are reading the main jet/PV mixture instead of the idle mixture you were running when you drove through the neighborhood and pulled in to the driveway. It's another motorcycle thing I've done before that I'm not sure crosses over to this situation but it might have value here as well? I live out in the country a bit so there are plenty of open lightly traveled roads near me where I can do this on safely.

I was originally thinking I would eventually do a 460 swap in this truck but the more I read about that the less inviting it becomes. I was thinking the 360 and 460 trans bolt patterns were the same but since they are different it becomes more of a challenge to make the swap. If I go the 390 route I can put short tube headers and a 4bbl intake on this engine before I build the block and spread out the expense a bit. I'll get to enjoy the upgrades on this engine before I pull it for the 390 upgrade.

 

What is the vacuum reading, engine warm, idling? If that is somewhat low, check for a loose timing chain like I posted earlier. A worn timing gear and chain can cause all kinds of drivability issues.

 

When I adjusted the timing using the vacuum method i was able to get about 18.5" of vacuum. The PO told me that the engine had been rebuilt at some point but just judging by the condition of the paint, it's had some miles put on it since then if it was in fact rebuilt. When I first got the truck it was so weak I was thinking the PO might have gotten the timing off by 1 tooth but I don't think that any more.

 

MG-- Your plug reading (MC way) will carry over nicely to your setup, give it a try & see what you come up with. First I would put some miles on the new plugs, get them up to running temp a few times then pull a couple & see what they look like. Then put them back in, run the truck out on the road & get it up to temp & try your WOT method.

My truck is a 4.9 300, I understand the Autolite/Motorcraft carbs but have no experience with the V8 motors. My 71 was a 360/C4 out of the factory but the PO had converted to a 300/C4 when I got it. Your 18+ idle manifold vacuum is good, mine runs 18.5. Did you try the timing chain test by setting the mark on -0- with distributor cap off & turning the motor a bit to see how many degrees it takes to see any rotor movement?
At this point I don't think you have a timing problem but I could be wrong. Good luck.

 

I took it out for a plug chop but the plugs look pretty much the same so either it is spot on or the test doesn’t work on a truck like it does on a bike. The good news is that it hit 80mph which is the fastest I’ve gone in it. It took about a mile to get there but it did finally get there. I figure with my gearing and tires with the 360s reputation, 80mph is a gift…lol

I also played with manually shifting the trans and it felt pretty good if I didn’t let it shift so early. 1-2 is happening at about 10mph and 2-3 at 35mph via the modulator regardless of how far I’m into the throttle. Looking forward to the new modulator and have my fingers crossed it will be better.

i have not tried the timing chain test but will do that once it cools off a bit.

 

MG -- Was the plug chop with a new set of plugs? If they were new did the plugs show the soot that the old ones did?
No pinging on hard throttle up to 80mph?

You could be right, a smooth pull up to 80 with your tire diam. & rear gearing might be all it has, maybe you will have to just enjoy it like it is. Your getting there.

 

It was with the same plugs but that’s typical with a bike. I haven’t had time to source a new set of plugs yet. Still no pinging. Sounded good with a nice intake note right up to the shift points and a smooth steady pull. Here is the #1 plug. It got just a touch darker but not so much that I’m concerned. I may order a set of 50s just for giggles but I don’t think I need to go any richer.

 

MG - I would put in a new set of fresh plugs and run them for awhile with the 52 jets that are in the carb now. Then pull one plug to see if they soot up like the ones you have in there now. At this point I would not go richer or leaner on the jets.

Get your early shifting problem taken care of and run it for awhile. You got to live with the tires & rear gears you have. Would not look for a 2100 1.21 or 1.23 until you have put some miles on this current setup.

 

OP, have you done a dry and wet compression test on that 360?

 

I have not done a compression test. I have a set of plugs coming and will do the timing chain check and a compression test when I change the plugs.

 

On my last fill up I checked gas mileage. There was some running with the larger jets and a lot of full throttle pulls with the smaller jets but mileage was down around 7.5mpg.

 

mg -- As a good fair test on new plugs & mileage maybe you can install the plugs, fill the tank, drive it normal for a tank, fill again & check mileage & pull one or two plugs to see if the electrodes are dry & nice light tan color. All this with the 52 jets in place.

 

MG - Any new information on the new plug test with the 52 jets?

 

There have been a number of new developments. The new modulator came in and I installed it. The adjustment screw on the old Duralast modulator had backed completely out on its own so it was shifting as early as possible. The new modulator is working much better and the trans is shifting nicely now and the truck feels better for it. The 1-2 shift is happening at about 25 and the 2-3 at about 40 under light throttle which works much better with my gearing.

I put in the new plugs but it turns out my compression gauge doesn't have the right size adapter for these heads so I couldn't run a compression test. I don't really think there are any issues there but it would have been nice to get some numbers to confirm.

Timing chain test was good, very little slack in the timing chain.

I installed #50 jets just for grins and it seems to run fine. Not much difference other than it's more sensitive to the choke now. The electric element in my carb is bad so I have the choke adjusted to where it doesn't close and it's been that way for a while. With the #56 jets it didn't matter and even without choke it would drive away with no issue cold which is another sign it was running too rich. With the #52s you could tell it was having a little trouble cold and with the #50s it's even more noticeable but once warmed up it runs perfectly fine. I've only run it a little bit with the new plugs but here are the old plugs after running a bit with the #50s. I think they still look really good. I'll have to give it some time and then pull the plugs again to see how they look and see if they are still building soot like the old ones. I'm not sure at this point if i will stay with the #50s or go back to the #52s. I have a choke element on order so I'll get that installed and see how it behaves with a functional choke system with the #50s. I also want to check mpg with the #50s and see if it's any better.



The big news is that I converted it to full 65kv HEI ignition with new 8mm wires. I gapped at the new plugs at .045. I still need to finish the resistor wire bypass so for now I have a jumper to 12v that I have to connect and disconnect to start/stop it. I have driven it though and it's running really well right now. WOT in first gear is almost impressive and it still pulls good up to 80 at least. It feels like it might do a bit more but I pretty much run out of road by then. At WOT the 2-3 shift happens at about 70 and 3rd gear with my gearing is more than the engine can overcome I think. It's not exactly aerodynamic and the wind resistance at 80 is probably significant with the windows down. Driving around town at light to part throttle is very easy now. From where it was when I first got it to how it is now is dramatically different. I used to be at half throttle driving around town and now I'm barely in the throttle at all.

I'm looking at some different header options for the next effort since everyone says that's the real limiting factor on these engines overall. I've found a set of long tube headers from Jegs that they say will clear the steering gearbox and a small starter. They are affordable but come painted with paint that they tell you up front will burn off in seconds so you have to do something to account for that or live with rusty headers. I've read that long tube headers favor the top end and short tube favor the bottom end and I need more help on the top end.

And still looking for a 1.23v carb to see what that might do for it.

I'm going to do what I can for the 360 with options that will still work if/when I convert it to a 390 or better just to see how good it will get. I hated this motor when I first got the truck but after all we've been through together I've kinda grown fond of it....lol