Hopefully I posted this in the right place, I joined the HAMB back when I first got my 52 GMC as a gift from my Dad, I knew that eventually I would have a question, but most of them were already answered on other threads, well I guess I have a question now that goes beyond my knowledge lol *If you don't like to read long posts, just skip to the last paragraph, thanks, ^_^* Here's the background story, my truck came with a 283 V8 (not original of course), it had LOTS of blow-by but still had decent power and was plenty to get me to school and back. Eventually the blow-by got real bad and was getting worse by the day, and finally failed while i was going up a steep hill going 55. (somehow a chunk on the edge of the #3 piston broke off leaving a gap all the way down to the first piston ring So, I decided that since I did not know any good machine shops that I would just get a used long-block. I found a Chevy 350 long-block for $250 supposedly "recently rebuilt" with a new timing chain already installed and only 20k miles on it, through Craigslist (my first mistake probably). Over time, I put on a new electric fuel pump mounted under the cab, with a pressure regulator set to 5.5psi, Champion 3 stage radiator, aluminum high-flow water pump, aluminum Holley Street Dominator single-plane, Holley 600cfm vacuum secondary carb, rebuilt by me with a #65 jet and a 3.5 power valve, HEI distributor (from the 283). Here's where the weird part comes in, I start the engine when cold, everything is fine, sounds amazingly lopey too I love it! I can drive around and it has LOTS of power, but once the engine starts to get up to temp (190 - 200*F) the engine becomes weak, oil pressure with 5W-40 goes from 40psi and drops to almost 20 at times when idling, might be caused by the low idle rpm's at that time, not sure, but I do know that there's no power, does not like to accelerate or anything, and when I put in the clutch it either idles very low, or it dies. While this is happening I can see some light blue smoke coming out of the driver side exhaust. All of the plugs are black, wet with something that feels kinda like oil, and has a smell of gas. When I pull one of the vacuum lines on the manifold everything goes back to normal, but if i plug that vacuum port with my thumb, it all bogs down. When the engine is turned off, I get a whole lot of white smoke coming up out of the carb (i think it's fuel vapor right?) Manifold vacuum starts at 8in and when it starts to have troubles it's around 5in. I made sure that there were no vacuum leaks under the manifold by replacing the gaskets for a second time. I thought that since it runs better when a vacuum line is pulled that it would be running rich, but it does the same even with a small #52 jet, it does the same even if I adjust the idle screw, just takes longer for it to die. More things to think about: When I first got this engine and had all of the stock stuff from my 283 on it (327 cast iron intake, old Holley 600, stock radiator, stock water pump, and a cheap auto store fuel pump) It would not start till I pulled the valve covers and adjusted all the rockers to the exact point that the rockers wont wiggle (probably not the proper way), they were all tightened too far that I could tell, and some, annoyingly, were tightened multiple full turns with a wrench past zero-lash. The heads are sadly crack-prone I later found out with a cast number 462624. Last oil change I found a lot of metal particles draining out of the oil filter looking almost like metallic paint you would get for model cars. So, the big question that sums it all up, do you all think it is worth it to continue working on this engine, especially since ill need to get better heads later on to replace the ****-tastic abilities of the 462624's. The thing is, I can just get a modern fuel injected 305, from my cousins work for $800 with a computer and everything. But, I would still like to have something under the hood that is more cl***ic, with the self gratification to putting sweat and blood into something that works great. Im thinking the guy I bought this from had other motives of selling that 350 other than wanting to drop in a 383
Ok, when I changed the oil, it was late last week, I don't recall it ever smelling like gasoline, do you think running it for a bit, then smelling what's on the dipstick would give the same results? my used oil jug is full at the moment too
Without running it, pull out the dipstick and rub the oil between your fingers. Make sure it feels like oil, and smells like oil.
I decided to bear the cold, smelled the dipstick, took off the cap off my gas tank and compared the smells, it definitely smells like gas, yet still feels like oil. (lately I have only run the engine just long enough to burn off any moisture and keep everything lubed, hopefully I did not ruin anything then.)
I think you have a carburetor and fuel pressure problem combined with the heat activated choke mechanism. .02
hmmm... that's a possibility, I was thinking something similar when I replaced my old holley 600 with a newer model, then later replaced the fuel pump since it was not putting out pressure higher than 3 psi, that was a problem all on it's own making things even more confusing hahaha. But my fuel pressure gauge off the regulator stays reading at 5.5 psi even when the engine starts to get weak. I spent some time trying to get the choke to work perfectly, I wonder if I missed something that I should have noticed on both carbs.
It sounds like your carburetor is dumping fuel, possibly due to a stuck or improperly set float/needle and/or too much fuel pressure. This excess fuel is washing down the cylinder walls and into the crankcase, diluting the oil.
Seeing that it's a Holley carb I'd say a bit of **** got into the needle and seat. Next time you start it look down the carb and see if its dripping gas down into the manifold.
Ok, on my way back from work tomorrow ill pick up some of those clear fuel level check plugs, so I can watch the levels while it is running easier without getting gas on a hot engine (and don't worry, I get to carpool to work lol)
Ok, so I got the clear fuel level check plugs, and I have found a problem, It is amazingly cold outside for California, I thought I would have some problems getting it to start, nope, no problem, fired right up without pumping the gas or anything, let everything warm up, watching the fuel bowls, everything looked great. around 170*F the rpm's started to rise and the engine was getting nice and smooth, I decided to walk around my truck once more, and noticed that the exhaust on the driver side was back to blowing light blue smoke, put my hand up to it, felt kinda moist (probably just from everything being cold) exhaust was nice and warm, walked over to check the fuel bowl levels again, and as I was walking around my fuel pressure gauge was reading 12 PSI????!!!!! fuel level on the sight plugs were all the way to the top (probably flooding everything) I quickly turned it all off. It's very strange since the engine has bogged down in the past and I looked at the fuel pressure gauge and it was reading steady at 5.5psi and the old fuel pump that could not keep up would be reading around 3 psi (the reason why I got a new fuel pump). So I guess the pressure regulator is junk, but I doubt it is the source to all the problems...
when I get back from work ill see if I can work on that pressure regulator a bit. Hopefully ill have some good news soon.
alright, so it's been a while and I decided to make an update, managed to work out the fuel pressure problem, floats are set correctly, readjusted the choke, tuned the vacuum advance, and it ran great for a couple of days (yes i said a couple of days). Today, I went to let the engine warm up so I can use a timing light and really get the timing dead on, engine was warming up, I went to tap the gas real quick to let off the choke sooner, then the gas pedal just got ****ed to the floor. I saw the rpm's reach over 8 grand and the second before I could even cut the engine off it shot out blue smoke out of both pipes and died. I decided to tighten up the return spring some more and see if it would even start, it did, and the rpm's once again soared instantly, but at least I was ready and cut it off before it got past 4 grand. I cant think of how I could NOT have blown something, and I cant think of why it would randomly need a stronger return spring! so, until I go out to get a stronger return spring, then find out if I totally screwed something up, what should I look for before starting the engine again, and would a fuel-injected computerized engine be a better alternative for me. (obviously my bad luck/noob skills are getting out of control) ------------ EDIT: After being on the phone with my cousin, as far as we can tell (what makes the most sense) is that when i tapped the throttle, the secondary vacuum diaphragm pulled open the secondary ****erflies, got stuck and held the throttle open as my return spring was not up for the challenge. When I was looking around the carb and touched the vacuum secondary linkage I heard an audible "pop." I can turn the engine over by hand from the flywheel, I think im feeling compression on all cylinders (though I need to officially test that) and all the keepers on the valves seem to still be in place. I will be dropping the oil pan soon, will look at all the rods, and check for spun bearings. Then ill disconnect the vacuum secondary, attach a better return spring and pray to God that everything goes well!
The Jalopy Journal
