As part of my ongoing saga with the truck (Mission Creep on a D-150) I'm looking for guidance from those who know what they're doing, a group that excludes yours truly.
To make a long story short, as noted in my build thread the brand new engine only got 700 miles on it before I spun a couple of bearings - operator error no doubt. So I yanked it back out and completely rebuilt it again. I did a break-in on my buddy's run stand and it ran OK. Bring it home, put it back in the truck and it's a dog when I take it for a test drive. I tune, adjust timing, adjust the carb, re-lash the valves, all to no avail. It's hard to start when hot and will often stall coming into a stop sign.
I was thinking the carb (a Holley 390, freshly rebuilt) is the issue so my buddy that did the work stopped by to check it. There was a check ball for the idle circuit that was stuck so he fixed that, but it still runs like crap. I swap in a known good carb (Edelbrock AVS2 500) and it still runs like crap. Both carbs are boggy, have no power under load, hard to start, etc.
I'm thinking maybe it's a vacuum leak but it has none. I plugged the line to the power brake can, plugged all the ports, and sprayed starting fluid all over the intake, carb base, and carb - no change or RPM increase.
The truck has terrible compression and vacuum. This is a brand new engine with no more than five miles on it and maybe an hour or two running in the shop while I work on things. I checked the head bolt torque to make sure it was all tight, it was good. The rocker arms are tight. The valves are lashed correctly. However, compression is running 90 PSI in every hole, and the vacuum at the manifold fitting is a measly 5-6". The cam is barely bigger than stock so I should have 15" or more vacuum. The VC on the distributor does function correctly when I put a vacuum pump to it, advancing properly but of course with no vacuum it doesn't work at all in the real world. That makes getting the timing set impossible.
I did a leak down test, each hole shows good - no leakage from any valve, and the blow-by from the rings is less than 10%. Nice tight engine, just no compression and no vacuum.
Any suggestions what to look for next? And as if I'm not having enough fun, I have a serious rear main seal leak so I'm going to have to pull the engine again to get that fixed. Before I do, I'm looking for bright ideas what's wrong so if I need to run the engine for diagnostics I can do so before it comes out.
TIA, hopefully there's something I'm missing here to get this turd running right. It seems to me until the compression and vacuum issues are figured out it's not likely to get any better.
To make a long story short, as noted in my build thread the brand new engine only got 700 miles on it before I spun a couple of bearings - operator error no doubt. So I yanked it back out and completely rebuilt it again. I did a break-in on my buddy's run stand and it ran OK. Bring it home, put it back in the truck and it's a dog when I take it for a test drive. I tune, adjust timing, adjust the carb, re-lash the valves, all to no avail. It's hard to start when hot and will often stall coming into a stop sign.
I was thinking the carb (a Holley 390, freshly rebuilt) is the issue so my buddy that did the work stopped by to check it. There was a check ball for the idle circuit that was stuck so he fixed that, but it still runs like crap. I swap in a known good carb (Edelbrock AVS2 500) and it still runs like crap. Both carbs are boggy, have no power under load, hard to start, etc.
I'm thinking maybe it's a vacuum leak but it has none. I plugged the line to the power brake can, plugged all the ports, and sprayed starting fluid all over the intake, carb base, and carb - no change or RPM increase.
The truck has terrible compression and vacuum. This is a brand new engine with no more than five miles on it and maybe an hour or two running in the shop while I work on things. I checked the head bolt torque to make sure it was all tight, it was good. The rocker arms are tight. The valves are lashed correctly. However, compression is running 90 PSI in every hole, and the vacuum at the manifold fitting is a measly 5-6". The cam is barely bigger than stock so I should have 15" or more vacuum. The VC on the distributor does function correctly when I put a vacuum pump to it, advancing properly but of course with no vacuum it doesn't work at all in the real world. That makes getting the timing set impossible.
I did a leak down test, each hole shows good - no leakage from any valve, and the blow-by from the rings is less than 10%. Nice tight engine, just no compression and no vacuum.
Any suggestions what to look for next? And as if I'm not having enough fun, I have a serious rear main seal leak so I'm going to have to pull the engine again to get that fixed. Before I do, I'm looking for bright ideas what's wrong so if I need to run the engine for diagnostics I can do so before it comes out.
TIA, hopefully there's something I'm missing here to get this turd running right. It seems to me until the compression and vacuum issues are figured out it's not likely to get any better.
