Captain Obvious

Yes, I understand those subtle points, and that's where some of the problems are. For example... If you change the pin height spec in the calculator here>> http://www.atlanticz.ca/zclub/techtips//calcs/engine builder/index.html The compressed volume changes, but the un-compressed volume does not. It's a bug. It's not accounting for the fact that the piston height at the bottom of the stroke is raised as well. I'll clean up my spreadsheet some and maybe post my numbers.

No. Says who? I'd rather have the new one.

You should be able to very easily measure the base circle to at least determine if it's a stock grind or not. No calculations, no degree wheel. If it measures out to a stock base circle, you're done. If not, we can talk about that later? Don't pull that cam gear off now. Absolutely not. Way far down on the list of things that might get done. Or not.

I guarantee it!! Glad you found another starting point, and here's hoping it's a better start than the last one.

No.

I got the chamber volume "off the web". That 53.6 is the number that "everybody uses". Of course, because of that, I cannot attest to the accuracy. So I've been messing around with the calculators a little more, and I believe they messed the math up some. I've got an excel spreadsheet with my own measurements and calculations and I get pretty close to that 8.8 using data that I measured or derived myself. When I use my measurements in my spreadsheet, I get 8.86. I have not measured the chamber volume myself, so some small differences there could explain the remaining discrepancy. I do not think they are calculating the uncompressed volumes correctly. Also, my measurement of piston stick-up above the block deck back-calculates to a significantly different pin height than what they're using.

Now that the dust has settled with my broken camshaft project, I'm trying to get back to my F54/P79 motor. I was messing around with the handy-dandy Atlantic Z engine calculator app found here: http://www.atlanticz.ca/zclub/techtips//calcs/engine builder/index.html and I can't get it to give me the correct compression ratio. The FSM says the F54/P79 combo (used in the later ZX NA cars) yields a compression ratio of 8.8: But using the calculator app, I don't get that result. I get 8.43 instead: I get 8.43 instead of 8.8. What am I doing wrong? I know some of the numbers (like the head gasket thickness) is off a little, but not enough to explain my delta.

And @thetwood, You're doing a good job of becoming your own expert. Good work!

It's clearly a OEM Nissan cam, but it's not clear if it's been reground, right? If I'm understanding correctly, couldn't he just measure the cam base circle in-situ and determine if it's a regrind?

Hope you guys are all OK!! And when I heard Alabama was going to get hit, I was worried about you too. Thankfully, however, it was just the fake news and you guys were never in danger.

Well you aren't planning to put your sealed beams back in and run tests for me, are you? If so, that's certainly not necessary. I mean, if your incredibly bored and don't know what else to do with your time, I think the results would be interesting to discuss, but other than that, it's a lot of work for some academic discussions. I don't know what headlights I'm running. I know they're halogen somethings, but I don't remember the brand. Probably Sylvania. And with that said, all the real world effects of current drop and the like will diminish as the current draw goes down. So all that stuff like power being lost in switches, wires, and connectors will be much less with the LED's as compared to the old sealed beams.

I found measuring the headlight parameters to be a lesson in "real world" effects. Stuff like... If the engine isn't running, the battery voltage changes (drops) while you are trying to take measurements (because you're pulling capacity out of it). The currents are high enough that any amperage measurement results in a noticeable drop across the Ohmmeter, thereby affecting the results. Voltage measurements need to be taken both at the battery and right at the bulb. That'll tell you how much you're losing in the wiring and switching. Here's the best I could come up with... Three meters at the same time. One measuring voltage on the battery terminals. Second measuring bulb voltage right at the back of the bulb. Third measuring current draw of one bulb. Here's an example from after I finished my headlight relay upgrade. Both bulbs are lit, but measuring one side. Voltage measured on the battery terminals while under testing load (two bulbs lit) = 12.26V Voltage measured right on the bulb prongs of one bulb = 11.56V Current draw of one low beam bulb = 2.64A This is low beam: And this is high beam: If you go through the math, I'm consuming about 30W per side on low beams and about 50W per side on high beams. One thing that seemed odd to me was your current draw numbers were higher than mine. My total current draw on low beams should be approx. 5.3A (doubling my 2.64). And that's with relays installed which should increase the current because the system drop is lower. Questions are... 1) Did you have relays in place when you took your reading? And 2) What was your system voltage? (Was the engine running at the time?)

That AFM has been messed with in the past. Don't know if it's been adjusted, but that cover was definitely removed and reinstalled in the past. The glue's wrong. That said... Other than trying to verify that it's the correct AFM for the system, don't spend any time worrying about adjusting it right now. That would be one of the last things to mess with. Get the fuel pressure correct and tracking intake manifold vacuum first, Fix the PCV routing so you aren't pulling huge amounts of unmetered air. Get the AFM mounted properly so gravity has the correct effect. Search out and fix any other vacuum leaks in the system. Do all that first and go from there. BTW - I recently stripped down an 82 motor and it has the same fuel rail and regulator system as the stock 78. If you just can't seem to get the aftermarket stuff working, we can work out some sort of trade for your aftermarket stuff. I know it's a "downgrade", but it comes with the advantage of being a known entity.

Yeah... Yours was way worse. I'm relieved that mine was as minor as it was. Not that I ever need to do that again. Ever. But your experience is evidence that all things considered, I got lucky.

Looks great. So about your measured current draw values... Your original sealed beams drew 6.8 Amps for the pair and the new ones draw 1.7 Amps for the pair? If so, your new bulbs are consuming about 11W each on low beam. Does that make sense compared to the LED bulb specs? I took a quick look and they say they are 25W, but I don't know if that's for a pair, or if that's high beam, or what.

Thanks for the well wishes everyone. I took the car out today and other than the cosmetic, there doesn't seem to be any other ill effects. Wow! What a coincidence! That must've scared the crap out of the wife. (Would explain the pants... )

I think if I had been going faster, I would have swept his legs right out from under him and he would have rolled up the hood into the windshield. As it was, the only thing that happened to the windshield was the mess. I saw this blur, felt the BANG, and the windshield got sprayed. Took me a fraction of a second to even figure out what happened. I always thought you would see them coming. Not true. Never saw him coming. Happened in the blink of an eye.

Actually the speed limit was 45. I had just turned onto that road from a cross street and wasn't up to speed yet. Diseazd, LOL. Thanks for the help! Yeah, it's running great. Better than it ever has since I've owned it. Amazing what happens when all six cylinders are contributing like they should be! I took it out that night... Beautiful low humidity night. I went out and got gas and hit the deer on the way home. I checked my gas mileage and I've gained about five percent after the engine work. Another benefit of having all the cylinders firing I assume. I was all happy with myself, and then that happened.

Yeah, I didn't get away unscathed, but it could have been a whooooooooole lot worse. It was completely dark at the time and I never saw it coming. Huge BANG!!!! and a flash of brown, a couple big splashes of deer snot up on the windshield (I knocked the snot out of him), and then I saw him slide off across the oncoming lane into the brush. I was probably going 35-40 at the time. I went back today and took that pic. No fun at all for anything involved.

Last night I did this: I got off pretty easy. You should see the other guy: Say what you want about my park bench bumpers......

Ol' Blue!!!!

Agreed. Hopefully no revisit. I used an OEM Nissan gasket because after all the problems I had with my motor, the last thing I wanted to do was mess around with the head gasket again. Not saying that's any better or worse than what you used, but just that "if it's good enough for the dealer"... And there is a note in the FSM about re-torqueing, with the assumption that your using an OEM gasket of course. I figured what could possibly go wrong. Go wrong. Go wrong.

As mentioned prior, there's a whole lot modified on that system, and much of it done poorly. PCV connected, but valve cover vented to atmosphere. AFM mounted sideways. Static fuel pressure instead of varying with manifold vacuum. I don't think that's a stock throttle body. Looks like they threw an aftermarket one at the car because it's supposed to be "better". What's with the short stub of tubing that comes off the throttle body and goes to where the cold start valve used to be? Which side of that throttle butterfly does that tube come from??? It looks like the butterfly may be completely bypassed by that tube? Hopefully on that aftermarket TB, it comes from the high vacuum side, because if not... Sheesh! My humble opinion? The easiest route forward is to put most of it back to stock. Either that, or you will need an expert. Pay for one, or become one yourself. See if you can get the box of old parts the neighbor kid took off and put most of them back on. Someone threw a lot of time and effort at that engine, but I don't think they did it any good.

Excellent! Sounds like great progress. I don't know if it's really necessary, but I re-torqued my head bolts after about 100 miles or so.

I've only ever seen two length head bolts*, and the positions are pretty easy to figure out... Long ones go through the cam towers and the short ones go everywhere else. Five long ones for five cam towers. *I did see in the 1972 FSM where they referenced three bolt lengths. So that's either a feature of the early cars, or a typo. I've never worked on one that early, so I can't verify the lengths.