ISPKI Posted May 26, 2014 Share Posted May 26, 2014 Hey guys, I got my 77 280z running fairly reliably now and I just had my buddy over messing around with it. The vehicle has been having a vacuum issue where the vacuum pressure in the manifold is low (around 12ish). Also - It idles very rough and low and would bog out and die if I gave it any gas. We retarded the timing and measured timing with a light. By retarding the timing to about 25 BTDC it idled much nicer and the vacuum got up to about 16-17 at around 750RPM and was quite steady. Plus, I could give it some gas and actually drive it, although it still hesitates when I first gave it some gas. Now the issue is figuring out why it seems to run so much better with the timing that far off, I read that it is supposed to be either 10 or 15 BTDC? Any suggestions or insight or advice would be greatly appreciated. I am going to check compression on all cylinders as soon as I get an adapter for it as it is something I have not checked yet. Something else that my buddy pointed out is that the ring with the timing marks could have spun, he had that happen on an old truck of his and he was not sure if the ring is bolt to the crank/balancer or if it is like his where it just held in place by some kind of gasket ring material. Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 26, 2014 Share Posted May 26, 2014 Going from 15 to 25 is advancing the timing, not retarding. The obvious next step is to confirm that your pulley timing mark is correct. The notch needs to align with zero at top dead center on cylinder #1. Have you adjusted the valves? If you're not filling the cylinders fully (too much valve lash), then advanced timing would probably help. Have you confirmed that valve timing is correct (groove and notch on the timing sprocket and retainer)?. Incorrect valve timing could have a similar effect. Piece-meal is going to take you forever to get that engine running right but at least you're making progress. Quote Link to comment Share on other sites More sharing options...
AdreView Posted May 27, 2014 Share Posted May 27, 2014 I'm with NewZed, I got my 2+2 running smooth following the directions posted in my thread: http://forums.hybridz.org/topic/117526-l28e-tdc-verification/ Quote Link to comment Share on other sites More sharing options...
ISPKI Posted May 31, 2014 Author Share Posted May 31, 2014 (edited) Hey guys! I purchased a new compression gauge (could not find an adapter for my vintage foxvalley gauge) and did a compression test on my 280z. I unplugged the high tension cable from the ignition coil, unplugged all the injectors and all spark plugs and my pops cranked it over for me. Tests seem good: Cyl1: 170 Cyl2: 165 Cyl3: 165 Cyl4: 170 Cyl5: 175 Cyl6: 175 This actually seemed sort of on the high side to me. The vehicle has 75500 miles on it, so it has not seen much driving over the years, or maybe one of the previous owners replaced the rings? Next on my list will be checking verifying timing marks, valve timing, etc. This vehicle does have a distributor out of an 81ZX with the matchbox ign unit. Also - What is the spark plug firing order? Mine is setup as 1-4-2-6-3-5. Also - My previous post was somewhat innaccurate. With the timing ADVANCED to about 25 degrees, it idles much better, but I cant really drive it. It moves, but when I give it some gas it just bogs and pops a little out the intake and barely makes any power. I pulled out of the driveway and up the road about 500ft before turning around and parking it again. I dont think it would be good for the engine to drive it like that. Edited May 31, 2014 by ISPKI Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 31, 2014 Share Posted May 31, 2014 Google is full of "280Z firing order" posts and images. Probably easier to look at too, than the attached picture. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 27, 2014 Author Share Posted July 27, 2014 (edited) Got around to checking timing. Everything seems to line up perfectly, except the distributor housing appears to be rotated CCW further than it should be. With Piston 1 at TDC, notch on balancer lines up very close to 0, Valves 1 and 2 are up, marks on cam shaft and sprocket are right on each other, and distributor rotor is pointing to position 1 (pointed towards the adjustment bolt). Vehicle runs poorly, gently surging idle between 500rpm and 1500 rpm, has no power and bogs out if I press thr throttle down. I can tap the throttle and it will pick up and sound ok while I do that, but as soon as I stop tapping the pedal, and just hold it down, the RPMs drop and it bogs out hard. Vacuum gauge bounces around in the low 10s with the idle speed too, it sounds sort of like a vacuum leak problem, but I cannot find any leaks and I did not think that it would make the engine bog down so hard Edited July 27, 2014 by ISPKI Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 27, 2014 Author Share Posted July 27, 2014 Now, when I compare my images to the ones from Atlanicz It looks as though my cam sprocket is rotated about very far CCW. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 27, 2014 Share Posted July 27, 2014 It's in between before adjustment and after adjustment, it can't get better. The distributor rotor orientation is fine. If the distributor housing is twisted too far, that means the ignition timing is off. Get a timing light and set timing. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 28, 2014 Author Share Posted July 28, 2014 The issue is that it wont run without advancing the timing very far (25~btdc), and I am questioning why the cam sprocket appears to be so far off when the crank is rotated to 0 and the distributor is at position 1. Also - when advanced that far, it runs very poorly and cannot be driven Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 30, 2014 Author Share Posted July 30, 2014 It's in between before adjustment and after adjustment, it can't get better. The distributor rotor orientation is fine. If the distributor housing is twisted too far, that means the ignition timing is off. Get a timing light and set timing. I hooked up my timing light and started adjusting. At 15 btdc on the crank pulley, it is difficult to start and will idle for about 10-15seconds. The idle drops until it dies. at 20 btdc, it is easier to start, it idles very low (around 600rpm) but stays running. At 25 btdc, basically the same situation but it idles slightly higher and more stable. Vacuum gauge reading is around 10ish at the 15 degree mark, 12-14 at 20, and 15ish at 25, but it bounces around quite a bit. Fuel pressure is relatively steady around 35psi before fuel rail. The engine bogs hard if I give it any gas at all three timing settings. If I tap the throttle, it bogs and coughs out the intake, then picks up the RPMs to around 1200 and smooths out nicely after letting off the throttle. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 30, 2014 Author Share Posted July 30, 2014 I pulled the vacuum advance off the distributor to check to see if it was stuck. Movement was smooth but firm, I dont have anything to replicate vacuum but it seemed to be OK. Question: this is a dizzy from a 1979ZX, my vehicle is a 1977 280z with an automatic transmission. I noticed Rockauto has a separate vacuum advance, one for automatic and one for manual. Should I pickup an advance for an automatic transmission and see if that works or am I looking down the wrong avenue? Quote Link to comment Share on other sites More sharing options...
Josh280z Posted July 31, 2014 Share Posted July 31, 2014 Stop. You have low vacuum, fix that issue. Replace vacuum hoses, your PCV valve. Check everything. Are you burning oil? What color is your exhaust smoke? Are there any black sootey marks around you intake/exhaust manifold? Check them. Also do valve adjustment as stated. Ugh your vacuum advance sounds fine. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 31, 2014 Author Share Posted July 31, 2014 Thanks for the reply josh. I replaced the PCV and hose when I took the intake and exhaust manifold apart. I also replaced throttle body and manifold gaskets as well as almost all of the vacuum hoses in the engine bay and tested them with starter fluid. I noticed the other day that my valve cover studs are 1/4-28 thread and the threads on two of them are stripped out almost completely. The one closest to the firewall doesn't have a single thread left in the hole so I will helicoil them all and see how it runs after that. The engine is not burning oil from what I can tell but I can't really drive it either. The exhaust has no color to it Quote Link to comment Share on other sites More sharing options...
Josh280z Posted July 31, 2014 Share Posted July 31, 2014 That is odd your valve cover has standard bolts instead of metric. Got a video of it "running"? Quote Link to comment Share on other sites More sharing options...
ISPKI Posted August 1, 2014 Author Share Posted August 1, 2014 I do have a short video but I get an error 404 once it finishes uploading. The 1/4-28 thread is odd, it just feels like a PO cranked some 1/4-28 bolts into the holes and ripped them apart. The threads are not in very good condition to say the least and I cant tighten a couple of them down at all. I am in the process of drilling and adding helicoils to them all as we speak. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted August 15, 2014 Author Share Posted August 15, 2014 Not much of an update. One of the helicoils that I was putting in near the timing chain broke and fell down behind the front cover so I am now in the process of removing it to pull the coil out. Quote Link to comment Share on other sites More sharing options...
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