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Low vaccum
I have been fiddling with my engine, trying to get it to run properly. I thought i had it good, until i pulled it out to move another vehicle and it died 3 times, and took a while each time to get it to start. I have checked the TDC marks, and there correct, the oil pump is timed correctly. I have new plug and wires.New electronic fuel pump, and new lines. Installed electronic ignition in distributor. Have great oil pressure, and my compression is avg 95. I also rebuilt the carb with a MWM kit. I finally put a vacuum gauge on at the manifold and it wavers between 16 and 17. I also capped wipers, and no change. I have the timing set 5 btdc and runs best there, any where else and it will die after short time. When i have the vac gauge on it says early timing as well, no matter what changes i do. So i also clocked the oil pump a few different ways, and when i was 2 teeth clock instead of the 1, it still fired, and even got rid of the studder/dodge cough on accel, but timing marks where way on the passenger side, not even near the gauge (also vac gauge still said early timing). I think one of my tappets is slightly out, i can hear it in the exhaust, just not quite smooth, but not bad, no tapping sound. So i can't imagine it would affect vac that much. I am absolutely stumped, in the end i know set up by manual std im on 5 btd or can get to td. No matter what im pulling 16/17 vacuum. I am wondering if the carb or governor is affecting it, just not sure how carb could be affecting vacuum, espec at idle.... I know on my m38a1 i could get great idle or great driving, but not ether, and i had it professionally rebuilt a couple times, engine only worked great when i put a civi carb on. Any help or input would be much appreciated, and no i don't have an extra carb i could try with. It also has a new head gasket.
Re: Low vaccum
Saberr,
I'm a bit confused by your description of setting the timing. You may want to start from scratch to make sure your baseline is correct.
An easy way to find TDC is to pull the pipe plug over cyl. #6 and use a dial indicator to put the crank at TDC. This way you can check to see if your timing pointers are accurate. Once this is sorted you can check the relationship between the oil pump and dizzy. I can't recall what plug on the cap is #1 from the couch, but it's in the manual. Make sure the rotor is clocked correctly to fire #1 at TDC and you're good to go. Once you get the engine fired time it to 4 deg BTDC and you should have a good baseline.
On my truck small adjustments in timing have an large effect on idle vacuum. Currently when warm I run around 20inHG at around 750RPM at sea level. Playing with timing and idle speed can drive this down by 3inHg easily.
The carb on these trucks is a bit restrictive, but works pretty darn well when it's sorted out. The carb's governor won't affect your vacuum readings, but poor rebuilds and vacuum leaks are its enemy. Check carefully for vacuum leaks and make sure your PCV system is working properly.
Hope this helps,
Andy
I'm a bit confused by your description of setting the timing. You may want to start from scratch to make sure your baseline is correct.
An easy way to find TDC is to pull the pipe plug over cyl. #6 and use a dial indicator to put the crank at TDC. This way you can check to see if your timing pointers are accurate. Once this is sorted you can check the relationship between the oil pump and dizzy. I can't recall what plug on the cap is #1 from the couch, but it's in the manual. Make sure the rotor is clocked correctly to fire #1 at TDC and you're good to go. Once you get the engine fired time it to 4 deg BTDC and you should have a good baseline.
On my truck small adjustments in timing have an large effect on idle vacuum. Currently when warm I run around 20inHG at around 750RPM at sea level. Playing with timing and idle speed can drive this down by 3inHg easily.
The carb on these trucks is a bit restrictive, but works pretty darn well when it's sorted out. The carb's governor won't affect your vacuum readings, but poor rebuilds and vacuum leaks are its enemy. Check carefully for vacuum leaks and make sure your PCV system is working properly.
Hope this helps,
Andy
Re: Low vaccum
I did spray around carb with starter fluid for leaks, and nothing, guess ill try again. As for top dead, just to double check it, i used the bubble method. Used spark plug adapter attached to hose, ended in jar of atf/oil. Connected into #1 spark plug port. Turned fan by hand, turned until no bubbles coming out. The bubbles stopped, and i was matched up dead on with my pulley marking for tdc. Did it a couple times to verify. As for timing, with engine at tdc, i pulled distrib and oil pump. clocked pump just like manual says. I did play around with moving it a gear forward or back, to see if it changed anything. As of right now, everything is by the books and its at 5 deg btdc. Hope that help clarify anything.
Re: Low vaccum
95 compression is ok but on the low side if my memory serves me well. do you get any ting ting ting sound in the exhaust?
Re: Low vaccum
tight tappets dont make noise .....valve adjustment time? also if your mixture screw needs to be out more than 2 1/2 turns you could have a worn throttle shaft, poor sealing of intake gaskets or a cracked manifold
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