stemo76

I have a 76 280 and it was smoken bad (with new plugs). Would foul them out in about 5 days. I found a 78 280 engine and swapped in the head and block, keeping my intake and exhaust and dist. so all the wireing would match up. Now the engine sounds fine but has no power and when I take the oil cap off it does not die like I was told it would. I have the dual reluctor dist so my timing is set to 13 per the book. I tried 7 and it was no better. I can't figure out why the car ran fine before and now with a better block and head it will barely get out of its own way.

theramz

Sounds like it's retarded. If you have a timing light make sure your getting advance as soon as you throttle up. Check your intake hoses. A good tool to have is a vacuum gauge. You can check your advance with the dizzy cap off with it.
Also your manifold vacuum.

stemo76

My timing is set to 13 I have tried 7 with the same results. I have no vacumm at idle but 18lbs when reved up. I have also noticed that my plugs are burning rich, heavy black powder on them. Reved up in neutral my total advance is 33

NismoPick

Sounds just like this guy's prob: https://www.zdriver.com/forum/showthread.php?t=17135


Have you adjusted the AFM? Also, make sure the head temp sensor on the right side of the head & properly connected... that will foul out the car real quick.

theramz

I think your afm is fubar. When it fails your ecu gets a cold start condition and fires the cold start injector located on your manifold near the throttle body. This explains the rich mix and poor performance. Disconnect it after it starts and see if it leans back out. I found a paragraph in a repair book that states that the 75-76 manual trans cars have a "transmission controlled spark advance that disconnects the vacuum except in 4th gear". There is quite a proceedure for setting the timing on those years. I suggest you check your afm first and then do the rest. If you need the rest of the info let me know via pm and I will scan and send it to you.

stemo76

I have not played with the AFM. The strang thing is the car was running good until I swapped the block and head. I took off my intake, exhaust, dist, and therm housing and put it on the new engine. so all the sensor are the same. On the front of the therm housing I have 4 temp sensors. does anybody know the specs on these. I would like to test them and replace any that would be out of spec.

By the way my afm looks near new. The guy I bought the engine from had a hard time getting it to run so I have a new AFM and injectors. Found out it was just junk in the tank.

stemo76

Thanks, I do have several manuals, one of which is a year specific factory manual. From what I read to set my timing I don't have to disconnect the vacuum. I have tested it and there is no suction at ideal from the throttle body port.

Doesn't it seem strange to not have any vacuum advance until you hit 4th gear. I wonder what will happend when I swap in the 5 speed.

I will disconnect the cold start injector and see what happens.

stemo76

Well I think I am on the road to recovery. Somehow my mass airflow sensor became way unadjusted. I have a rebuild on it and has a set screw on the side. I didn't want to mess with this because it ran before. Had to lean it way out lots of turn to get it to run. Now it dies when I take the oil cap off which I guess is a good thing.

Any idea how to get this set without a sniffer?

jfairladyz

you could try using an air/fuel ratio guage and a digital multimeter to get it somewhat close to where you want it.