amplogic

Sounds like a plan. I went ahead and adjusted all the valve clearances to where they are supposed to be. The fuel system will be the next thing I'll dig into when I get some time. I did check the bowl level, and they were a tad high, even with the adjuster very nearly at its lowest limit. I'm pretty sure I also have a vacuum leak after really looking all around and under that carb. I see a couple of small fittings that aren't connected to anything, and I'm pretty sure that they are supposed to have vacuum lines connected. I'm going to feel like a big dummy if all these issues are from vacuum leaks.

I do have a timing light, but the engine won't idle long enough for me to check the timing. That, and with fuel blowing all over the place every few seconds, and having had excess fuel in the carb ignite a couple of times, it will be a little tricky. Never mind about the #4-#6 valve comment. It was a dumb way of stating that the mark most definitely didn't line up with #1 cylinder lobes in the correct position.

This is probably a dumb question, but I've never been one to shy away from an entertaining dumb question :-) Theoretically speaking, would it be possible for enough fuel to enter a cylinder to raise the compression enough to force a valve open? The PO installed an electric fuel pump and disconnected the mechanical one. There isn't any sort of pressure regulator or return line, and I have no idea what the fuel pressure is. I haven't really messed with the Holley carb, other than to wire up the electric choke, but I need to check the bowl levels to at least see if they are right.

I loosened up the bolt enough to slide the fuel pump cam out of the way. The sprocket didn't seem loose, and I wasn't able to spin it on the shaft at all. So I don't think the dowel is broken. Yes, and yes. I more or less assumed that the PO did know what he was doing. Aside from the am sprocket not having the standard timing mark groove, I haven't seen anything that really looks awry. I mentioned in my previous post that I found something that looks like a center punch mark in one of the sprocket holes. It could be nothing more than a mark left from the casting process, but it sure looks like a punch mark. No idea what it's there for, and it may be nothing at all. I just thought I would mention it in case someone has seen it before. I lined it up with the cam reference mark just for giggles, and it hits right on #4 exhaust and #6 intake.

I just looked at it again, and did find a mark that looked like a center punch. No idea why it's there, but it's actually inside one of the holes and not on the collar of the sprocket where it would normally be. I'll post a picture in a little while, after I've had a chance to get it off the camera and resize it.

Sorry, I missed the 2 posts previous to this. I live west, a few miles north of Douglasville. Maybe a half hour or so from the downtown ATL area. I bought the car from a guy in Monroe, about a couple months ago or so. The ignition issues were all electrical. The previous owner had installed a used MSD 6AL that had a blown output diode. But he didn't know that, and I didn't either until I drilled out the rivets and took it apart. I have a GM HEI module installed right now, because the module that came with the distributor doesn't work. The HEI module works pretty well though. Strong blue spark at every plug, even with a cheap generic coil I had lying around. And as inexpensive and butt simple as it gets.

Ok. I just double checked everything. Again. The sprocket is an S-462. And as far as I can tell, there isn't a timing notch cut into it anywhere. The bright link on the chain is line up with the #2 mark on the sprocket. The chain is stamped "Made in the USA", so it's not the original either. Also, the chain tension is fine. I must have made my final bump in the wrong direction the other day when I was looking for TDC. Everything still lines up exactly the same now as it did before, even with the chain tight.

Update : Just checked the compression and it looked pretty good, so I'm inclined to think that the valves are OK. I guess the next step is to get the cam sprocket lined up where it's supposed to be. Guess I need to make one of those chain tensioner wedges that I've seen mentioned. These are all dry numbers #1 170 #2 170 #3 170 #4 172 #5 172 #6 175

Upon further inspection, it looks like the cam is oiled by the towers. The back side of the lobes are drilled, and the end of the cam is plugged.

Thanks for the helpful info guys. I'm not sure about the spray bar for the cam. This is the first time I've had the valve cover off, and aside from the other day when I took the photos, I haven't had much time to work on the car to see what all is going on. I'll definitely watch the video, and try to get the cam sprocket lined up with the correct hole. I assume that the #1 hole is preferable? Thanks again.

Gonna do a compression test today to try and rule out the valves. The head has been off before. The previous owner had the head shaved, ported and polished, so there is a chance it was reassembled incorrectly. The firing order is correct according to the service manual. I checked it several times when I was trying to sort out the electrical issues the ignition was having when I first bought the car. Thanks for the replies.

Yeah, I agree. No idea how everything else can seemingly be in the correct position (cam lobes, piston, crank pulley, distributor rotor) and the cam sprocket be so far off. I'm glad to have any and all info I can get! Thanks for the reply.

Hi all. I recently bought a 260Z as a project car to work on with my son, and I'm having some engine issues. The car definitely needs a paint job and needs a good bit of interior work, but the body is great and has very little rust to speak of. The engine wasn't running when I got it, mostly because of electrical issues with the ignition. The ignition has been corrected and it working properly now. My main problem at this point is that the engine is "blowing back" through the carb at times. I say blowing back because it doesn't really seem like a backfire, although it has backfired through the carb before when the ignition timing was way off. The engine will crank, and it will stay running, but only if I feather the throttle. It will run ok for a second or two then either surges like crazy from too much fuel (my own fault), or sort of sputters and stalls if I just try to let it idle. Sooner or later (within seconds usually) it will start blowing fuel and air back out of the top of the carb. I'm not 100% sure if it's happening during compression or exhaust, or both, but it did briefly ignite the fuel in the carb once when it had flooded a bit. I forgot to mention that the old Hitachi carbs were replaced by the previous owner with a 390 CFM Holley 4 bbl. I assumed that this problem was caused by a timing issue, or possibly bad valves. I don't really have a whole lot of time to work on the car right now, but I had a few minutes yesterday, so I pulled the valve cover off to take a look. These are some of the things that I did/checked/observed: -Put the cam lobes for #1 intake and exhaust at 10 and 2. -Made sure that #1 was at TDC. It was. -Checked the timing mark on the crank pulley. Looked fine -Checked the position of the distributor rotor to make sure that it was pointing at #1. Probably not perfect, but close. -Attempted to verify that the cam sprocket mark lined up with the reference mark. As you can see by the picture below, NONE of the sprocket holes were in the correct position to be able to see the reference mark. This is obviously wrong, but I'm not sure if that alone would cause the issue that I'm having. Also, the timing chain seemed to be a bit looser than I think it should be. Again, I don't know if that alone could cause my blow back problem. Also, for whatever reason, someone had set the valve clearances to .005! All of them. Intake and exhaust. Easy enough to fix, but it makes me wonder what else the previous owners may have done incorrectly. Has anyone ever had a similar issue? Any suggestions on what is the most likely cause? Thanks in advance for any and all comments.