Captain Obvious

Yeah, That's the Kameari tensioner that I see mentioned in threads about this topic, and the only problem with it seems to be the price. Nice piece of engineering: So in summary, here's the issue in a nutshell... When you remove material from the bottom of the head, it brings the centerlines of the cam and crank closer together. With the cam and crank closer together, the valve timing becomes retarded and the chain has more slack. One solution to these issues is to shim the cam towers upwards and use either longer valves or thicker lash pads. Another solution is to account for the timing change using an adjustable cam pulley, and adjust for the chain slack with a different tensioning design, such as the Kameari tensioner.

Haha!! I understand completely. I went to Penn State, and the EE department forced all the other disciplines to take one introductory electrical class for non-EE majors. Every one of the other disciplines had to take it, and every one of the students universally hated it. So... By the time I got there, the ME department had retaliated and made the other disciplines take one introductory ME class for non ME's. It was thermo and fluid flow, and of all the classes I ever took, I think I despised that one the most. Now that I have identified so many automotive related applications, I'm sure I could get much more out of it. But at the time, it was pure torture. It was even rumored that sometimes people would swap... Your ME friend would take your thermo test for you and you would take their Intro to Circuits tests for them. Not that I ever participated in anything like that, of course.

Yup, I'm an electrical engineer. And I don't usually read the directions either.

Thanks guys. I did some searching around online and the issue with the .080 cut seems to be more about the chain tension, rather than the valve timing. The valve timing can be adjusted using an adjustable pulley or the stock holes as I described, but with that much of a cam drop, the tensioner can't deal with that much slack. There are other options to take up the slack, but I haven't gotten to the bottom of the details yet. But the bottom line seems to be: Yes... You can relatively easily mitigate the cam timing, but you can't easily mitigate the chain slack.

I don't think slimming the head results in advanced timing. I believe removing material from the head results in retarded valve timing. I think about it this way... The distance between the crank and cam got smaller, but the length of chain between the two did not. So the cam will trail the crank by that additional length. Did you mean slimming or shimming?

The FSM says that each different alignment hole in the cam sprocket adjusts the cam timing forward by four degrees. To make sure I knew what was going on with that I checked it out using the cam gear. Here's a quick sketch I whipped up using the cam gear off my P79 head. I traced the holes and sprocket teeth in the three different positions, and guess what... They are two (cam) degrees apart. That's perfect because two cam degrees is four crank degrees. Note that the direction is backwards because I could get a better registration with the cam gear flipped over, but the delta between the different positions is what's important. Here's what I whipped up: It would appear from the calculations, that you could take .080 off the head and advance cam the gear to it's next setting and pretty much be exactly back to where you started. Probably showing my inexperience, but assuming the tensioner can account for the difference, why can't you just do that instead of different valves and a whole bunch of shims under the springs and cam towers? Seems like the only thing you would need to do is move the cam gear.

Thanks for the input everyone. All that sounds like fun, but in the cause of expediency, I'm really hoping to leave the crank and pistons in for now. Diseazd, Question for you while you're here... I remember talking to you in Atlanta (over drinks and pool) about that .080 cut off the P79 head. So how far can I cut the head before I need to shim the cam towers? Do you know how much change can the chain tensioner account for before needing to mitigate with shims?

Well the lack of a pattern doesn't concern me that much. It's supposed to click the injectors every third ignition event, but doing it with a wire as I suggested is likely to result in a lot of contact "bounce" and what you are thinking is one connection may actually create two, three, or even more contacts. So I'm not too concerned about that. Yet. The complete lack of spark, however, is something that needs investigation. So what happens if you connect everything up normally and pull one of the spark plug wires off and stuff a spare plug into the wire and lay it on the valve cover while you crank the engine? Do you get a nice snappy blue spark? Is the ignition system stock 77 style? Or are you running some aftermarket system? And I'm not exactly sure what you mean by this... Are you saying that the fuel pressure gauge you are using tops out at 21 psi? And you are pegging it at that value? If that's the case, then you might not have a pressure problem. You just don't know what the pressure is... Only thing you know is it's higher than 21?

Yeah, I have no reason to believe there is anything wrong with the bottom end and I'm reluctant to pull the pistons and crank. I was going to pull and replace the oil pan gasket because the old one is seeping a little, but other than that, I was hoping to not mess with the bottom end. Oil pressure was great and no unusual noises from the lower end. I was hoping to let it be.

A while ago, I picked up an 83 ZX non-turbo and (with my recent calamity with my Z motor*), I've been working on pulling the motor with the intention of moving over into my 1977 Z. It's a stock F54/P79 combo and I'm not going to do a big time rebuild at this time, but I do want to do some clean-up and maybe some easy low hanging fruit improvements. I'm no engine expert and I'm going to have some questions for the collective along the way. I think there was a slight head gasket issue with the engine, so one of the things I wanted to do was replace that. Here's where I am right now. Head is off and block is stripped ready to be pulled from the donor car: So my first question is.... After I pull the block and have it on the engine stand, I have aspirations of removing the freeze plugs and sticking a power washer into all the block orifices and blasting out as much crud as I can. Anyone want to talk me into or out of that plan? Is the installation of new freeze plugs a straight forward and reliable process? I've never messed with them in the past. *https://www.classiczcars.com/forums/topic/62173-complete-misfire-on-three-cylinders/#comments

Glad to help. Hope you figure out what's going on. And thanks for highlighting a year related issue with the FI Bible. I never looked into it that deep and didn't know there were surprises like that in there. That could potentially save some other 77-78 owners major confusion in the future now that we're aware of that shortcoming. FYI, there is a later version of the FI Bible from 1980. It suggests grounding the negative side of the coil and doesn't talk about that single wire connector at all. Despite that, I still like the earlier version better than the 1980 version.

Man... That was confusing, but I think I figured it out. First, the simple (Obvious) answer... If you look at the prior page (32) of the FI bible, they show you how to locate the "ignition lead wire" and there is even a picture to show you what they are talking about. What they want you to do is disconnect and re-connect the wire that goes to pin 1 of the ECU, and the way they suggest to do that is to make and break the single wire connector under the dash next to your fuel injection relay above the driver's knee. But here's the rub..... You don't HAVE that single wire connector. You see, what happened is that the FI Bible was written in 1975, and hence, it referenced the 75 design and documentation, and in 1975 (and 76) there WAS a single wire connector there. But by the time they got to your (and mine) 77, they did away with that separate single wire connector and ran all those wires (including the input trigger signal) through the same connector that mates to the under dash harness. You do not have a single pin connector that funnels the ignition lead signal from the firewall under-dash harness to the FI system. That whole part of the FI bible does not easily apply to 77. All that said... What they want you to do is make and break the connection to pin 1 of the ECU (which is the ignition input signal). Easier to do in 75 or 76 than in 77. So here's what I would do instead: Pull the center high voltage wire out of the distributor and place it close to a good ground like the intake manifold or strut tower nut. Leave the other end of that coil wire connected to the coil as normal. Turn the key ON. Connect one side of a piece of test wire to ground. Ground and unground the negative side of the coil a bunch of times. You should get a spark from the coil wire to ground every time you unground the coil negative, and you should get an injector click on every third.

Man... I am IMPRESSED!! Now mind meld your way over here and fix my engine.

I doubt there is any easy answer. Probably a bunch of small vacuum leaks spread out all over the system. How long are you planning to keep these carbs in service before the RB swap?

Johnny, As eluded to above... If you're running carbs, there's no effect when you remove the oil cap when the engine is running. That's only an issue for the fuel injected cars. Carbs could care less.

Haha!! I could possibly be convinced to make more. You know they aren't metric though, right?

Never underestimate the rust of the dark side.

Yeah, I'd avoid the spoons too. From what I've heard, they can make you fat.

They don't filter for squat either. What he said.

Mark, I wouldn't pull the carbs apart to get the old oil out. I just roll paper towels into a narrow cylinder and stick them down into the damper hole to soak up the old oil. Give it a few minutes to sop up the oil and then pull the paper out. Takes two or three rounds of paper wads to get the old stuff out. Taking the pistons out and turning them over to dump the oil out certainly works, but I consider it a risky maneuver with very little gain over just keeping them together and sponging it out instead. Respectively submitted, of course.

So do you think this is an issue on ALL of the carbed Z cars, or is this something specific to yours?

He also said "A man's got to know his limitations."

Looks great. Can't wait hear how it runs!

Like Ricky "Wild Thing" Vaughn.

Back when I started my degree, they gave the orientation speech... "Shake hands with the students to your right and your left. Because many of those students won't be here come graduation day." As I shook those hands, I was pretty much 100% positive that I was the one that wouldn't make it. What a surprise...