Hey man, sorry to hear that your truck is still fighting you, and don't worry about bugging me lol, I'm always up to toss out my thoughts. I enjoy trying to diagnose stuff like this. You're damn right about the misfire, and since you're actually with the truck you probably have a better idea of which cylinder is the problem then I can give you.

Does it smooth out at higher rpms? Can you pull the spark wire off of the dead cylinder and notice a difference in every rpm range?

If you have your doubts about it being a specific cylinder you could get fresh spark plugs, slap them in, and run the truck for a while until they are good and warmed up. That way you could read them for fuel air mixture too.

If you have spark at the wires then your plugs may be poorly gapped. It's always good to check for good airflow (I've had intakes eat rags before without my realizing). Is the fuel pump doing its job? Does it have one pump or two? I've cussed at those damn things before, they can definitely cause greif if they are failing.

Scotty Kilmore has a video of how to find vacuum leaks with a cigar, which is a cheap way to tackle that issue. Speaking of vacuum leaks, if you haven't plugged off the egr fully at the intake end of it you would have a pretty big one. The video gave me the impression that the exhaust port for your egr was un plugged, so if the intake side is too you could try that.

Beyond that if your timing marks line up on the belt (chain? ) you're golden there... Im assuming you've already fiddled with the distributor cap, and IIRC your mixture screw on the carb is already ****** (but it's probably around the right spot anyway). That leaves vacuum and fuel starvage...

Don't beat yourself up over it man. You're doing better than I did with my first head swap, and for every wacky problem you solve on an engine you walk away with more skill than you had before. It doesn't matter how good you are at mechanics, it's always possible to hit roadblocks like this. I found that out while building my truck with a bunch of old timers. They could solve a whole bunch of problems in seconds that I never would have gotten, but it was a lot more than once that I found them scratching their heads along with me at idle and starting problems.

Oh, and sorry for the 20 questions, you know how it is though, kinda hard to diagnose it when I'm not there.

I usually use autolites, but I have a set of champions in right now. Is it a bad thing to run different kinds? I still have the original spark plugs from when I first got it and did a tune up, just in case I fouled one but this is the only set of champions I have. Just curious if it would cause any kind of issues if I were to put two autolites and two champions in there. I tend to hoard old parts. The problem with the truck when I got it was the hydraulics were froze up, and I got new ones but I still have the old ones in case I ever decide to rebuild them.

No, it doesnt really go away to my knowledge. Ive avoided putting too much load on the engine since it doesnt have any coolant. I dont know for sure, but Id assume it has two pumps, I know it has one manual pump riding on the cam, but Id assume theres still another electric one in the tank. I thought of plug gap, and I looked it up and from what I can find it should be at .32, so thats what I gapped them to.

I totally forgot about checking for vacuum leaks, I can do that for sure. I quit smoking a few months ago so the thought hasnt really crossed my mind to use smoke. I cant actually adjust the carb. Theres a pin thats blocking the screws, and somebody must have tried to burn it away with a torch because its all melted around it, and the pin is still there all fused with the aluminum. Its belt driven, I kinda wish it was a chain. Its a non interference engine so if I do break the belt I should be ok.

Cylinders 2 and 4 plugs were gassy and carbony, 1 and 3 were white, with a little carbon. Cylinder 3 had the lowest compression reading. From cylinders 1-4 they read: 150, 148, 135, 150. I only put oil in the third cylinder because it was so low and after oil it boosted it to 170, so I guess the ring is bad in that one. Still, its not way too low that it shouldnt fire, but also the tubes that recirculate the gasses feels hot on 3, so I know its firing. 1-3 will feel hot, but the 4th will feel cold like its not.

Could it not be getting ENOUGH spark? Like I said Ive used an inline tester and all of them light up, but then I pulled them out one at a time and had a friend crank it over and they all spark, and even arc to the head from about an inch and a half away.

Let's start with the little things. Double check the firing order and make damn sure that the wires are in the right spot, and that the distributor rotor rotates in the direction that you think it does. It's easy to make a mistake there. If that is correct, then try spraying some ether down the carb while it's running to see if that smooths it out. After that look for any and all vacuum leaks. If that puts you back to square one then read through my thought process below and look for stuff that you may have missed. This paragraph is the last one I wrote in this post so the structure below may seem odd. Apologies in advance for the wall of text.

Ok let's start off with the spark. If they were all arking an inch and a half to the block then you have plenty of power going through those wires, and you have the plugs gapped to spec as well. That doesn't really leave much to go wrong. If you still feel like something is going haywire there you could swap the wires around (maintaining firing order of course) to put a nail in that one for good. I'd bet that you already have the spark dialed in just right though. You are right about that compression as well, that isn't your problem (yet at least, those rings will go eventually, but im sure they're plenty good for now. )

There is smoke coming off the hot side of your motor in the video right after it fired over, so it would have to be exhaust related unless she was already warmed up. The hard start suggested that it hadn't been started in a good while...

Speaking of the start, anything more than one or two gas pedal pumps on a cold start is pretty overkill for a 4 banger, but nevertheless I can see that it was necessary to start the truck in your case. If that is a new development since the head swap then either you have an airflow stoppage, really bad timing, really bad fuel pressure, or a vacuum leak. If it isn't new then you fuel air screw is probably the culprit (that or bad carb jets/a malfunctioning carb in general. That's a whole other round of troubleshooting) None of those jive well with cylinder 4 specifically being dead.

Nothing to do about that carb, and if it ran before, you are probably good in that department anyway.

It sounded in the video like you either had it uncorked at the manifold, or you had a reeeeeally big exhaust leak before the muffler, maybe even before the cat. Are you sure that your EGR is hooked up on the exhaust side? Those recirculating tubes you referred to sound like an egr setup to me. If they are hooked up properly and the one leading to 4 is cold, then 4 is dead for sure.

That's a tough one for sure... An exhaust leak bad enough to do that to your idle would have to be pretty big, and it wouldn't explain just #4 being dead. Meanwhile the spark situation seems fine and you also made sure that the timing dots were correctly lined up, so that's out too... The head is new, and being both non interference and never warmed up your valves are surely straight and doing their job. That leaves fuel and air (and kinda vacuum).

Ok, on both of my carbed mini trucks I had only a mechanical fuel pump to feed the engine. If it's pumping, the carb has all the gas it needs. That's all I've got for now, that video helped for sure though. Let me know when you've tried some pf the steps above, or if you find anything else important. Another video probably wouldn't hurt if you get everything else in order to where you can safely warm it up and test drive it to learn more symptoms.

Good luck man.

That wasnt the first start, it was started like 15 minutes prior and fired right up no problem, thats why in the video I only did it with one foot in. I only ran it for about a minute, I get nervous since it has no coolant. Its always been kind of a bitch to start, I usually needed to hold the gas down until it fired, then let off then tap it to coax it to life. After the head was put back on it usually starts right up the first time, but then after a second time its a bitch again.

Ive turned the crank and watched the rotor button, it turns clockwise, just as the haynes manual says. According to the manual, Ive got it spot on. Nothing was different from the manual, when pulled out the gear has a dimple and a hole you have to line up and when it sets in its ready to fire on cylinder one, it does just as it said in the book. With cylinders labeled 1, 2, 3, 4, and firing order being 1, 3, 4, 2. Pic related, its from the manual I have. I have checked, double checked, and checked again to make sure I had this set according to the book.

This book kinda pisses me off though, because a lot of times what Im looking for is not included. They tend to say stuff like, "installation is the reverse of removal". **** these authors. I got a little hasty in taking it apart, Ill admit, so when I couldnt figure out where the electric choke wire went the book was no help. I later learned it plugged into the alternator, but when the book spoke of the alternator or the carburetor all it said was, "unplug electrical connections", or "reconnect electrical connections". Nothing specific, just the basic **** I already knew that was not helping.

Ill try finding any vaccuum leaks, and new plugs and a more thorough video next time Im out messing with it. Ive held off on going to work on it because I dont like the cold and winter is coming, but its been pretty nice so I went to mess with it the other day and the very next day it was sleeting like crazy. I left it becasue **** the cold. It will probably be awhile before I go back again because I start work jan. 4th. Seriously though, thank you for your help immensly. Youre a gentleman and a scholar.

Well I had to ask on the firing order but I must say I'm a little bummed that it is correct lol. Oh, and mixing spark plugs is fine if they're similar in condition. Spark is spark for the most part. Im guilty of hoarding parts too lol. Got two carbs, a blown but not dead tranny, tons pf electrical **** and a smattering of engine accessories in the bed of my temp truck right now lol.

I'm with you on working in the cold. I had to tear out the aforementioned blown tranny while laying on rain soaked concrete a month ago and **** that noise. Those Haynes manuals piss me of too. They are too vague when you need the specific info and will straight up tell you to **** off and see a mechanic with some things. I only use them for the torque specs, firing info, misc engine specs, and rarely for the (hopelessly incomplete) wiring diagrams in the back.

The vac leaks are your best bet right now as far as I can see, so good luck with that. Baring that, you can always try to source a new carb. That would solve a ******** of problems right there. Buying a new one is usually pretty expensive, but obviously a new part is the best possible fix. If you don't want to blow the cash on a new one, there are other options.

I have the fortune of having a carburetor god in town who can help me out, and if you know of anyone like that in your area i'd check them out. Your other option is to pull one yourself from a wrecking yard, which allows you to take a million pictures while you're at it to make sure that it will go back on smoothly.

www.car-parts.com is a godsend for finding cheap car parts. It searches the wrecking yard databases and gives you some info and the location of every listed part in the US that you specify im a list. I use the **** out of it when im building something, and you can usually snag some random doohickeys from your makshift donor car while you're at it, like interior parts, relays, oh **** handles, running lights, you name it. You may have to go on a drive to get it, but some parts can't be gotten any other way.

The catch of course is that somtimes you end up needing a part that is rare and hundreds of miles away. One trick I use with that website is to look for general things that I don't necessarily need from a vehicle I know came with the part I do need. Often times if they have, say, a drivers seat for your donor car, they also have the whole rig there waiting to get scavenged. Some yards are pretty bad about listing all of their parts, so you just have to make an educated guess if they have it.

You've got me pretty curious now. Could I get the year and specific model of your Mazda again? Im going to do some individual research on it.

Anyway feel free to contact me with this or any other mechanic project man. Im happy to help out. Don't kick yourself over that truck, you've got me and my old man scratching our heads over it to lol. Pretty weird issues that you have happening. Good luck at the new job by the way.

I am gonna save up and get a weber 32/36. I hear great things about it, and it eliminates a lot of vaccuum lines and electrical connections. Since I know very little about carburetors Im gonna get one new on amazon. I hear its actually an imitation, but still it doesnt seem too bad to me. Ive felt this carb was a piece of junk since I got the truck, but I definitely didnt help it when I had the cam sprocket on wrong and was pushing all the fuel back through the carb. After cranking for so long it finally fired because there was just so much fuel in the cylinders, there was about a two foot flame shooting out of the carb. Then I couldnt get a compression reading, so thats how I knew I had the timing ****** up.

No problem man, I've learned everything I know about mechanics from self motivated research and old-timer advice (which usually kicks ass), and I'm always happy to pass on what I know to others.

Glad you got it running man, little mistakes like that are usually a prick to find. My damn truck wouldn't start for 2 days because I accidentally put two weather seals on a distributor plug, causing an incomplete circuit despite it appearing to be plugged in.

The old rebuilder's standard is 500-1000 miles, but you shouldn't really need to re-torque them if you used a modern gasket. Ultimately it's up to you, but the worst case scenario is that you waste a few hours taking it apart to find that they're already to spec, so there really isn't any harm in doing it.

While you're torquing you head bolts I'd suggest that you change the oil too. That'll flush the system of any fine particulate crud that will inevitable come off that new head as it settles itself in.

Damn, you're good