toxshox

iTrader: (3)

I probably know where this is heading to in the end but I'll ask the question anyways. On a old 1975 SBC 350 in a pickup I checked compression with no spark plugs in and without WOT just let it rip 5-7 cranks Cylinder 1 90-100 psi 2 = 125-130 3 = 115-120 4 = 105-110 5= 135-140 6 = 150-155 7 = 145-150 8 = 145-150 Something on #1 is differently worth looking deeper at but is it possible that something could be wrong enough with the rings to let fuel pass through into the oil? Truck seems to be running way to rich plugs are all black, and it had filled up the oil enough to push it out on either front seal or front of oil pan I didn't get to crazy to finding out exactly where just decided to drain the pan which probably was 2 quarts high lol. Thoughts and advice please just our service truck C20 with a 4 speed manual.

Gasoholic

iTrader: (1)

If your running a mechanical f-pump the diaphragm could be bad.
Just a thought.

You can squirt some oil in number one and see if compression comes up. That will tell you if its the rings or valves.
I always run multiple tests just to make sure I'm getting a good reading.

toxshox

iTrader: (3)

I guess the pump diaphragm slipped my mind it seemed like it was using a lot of fuel at the end there. It probably was burning rich but also leaking. I went back to #1 and checked again and it didn't get any better the 2nd try how much oil you think like 12ml squirt in and if compression goes up must be rings? and if it doesn't valves aren't sealing.

biketopia

iTrader: (5)

Could do a leak down test as well, that will pin point rings or valves. If it's running rich I'd dig into the carb and timing. A float could of sunk, trash in the needle, pump diaphragm, etc etc, thus causing it to run rich, fouling #1 and then washing the cylinder out... Could fix the running rich which could fix your other issues, and then live with the lower cylinder pressure on 1 for a while/might not even be too noticeable. What intake, carb, ignition is on it?

toxshox

iTrader: (3)

It's just all stock motor but it does have HEI on it not really sure if that was added on later. So 4 barrel quadrajet it will be until next week until i get a chance to tear into it Thanks for the suggestions

biketopia

iTrader: (5)

When you pull the carb, check the screws on the base plate of the q jet. They tend to loosen up over time and will cause all kinds of weird things to happen. My high school shop teacher was an absolute wiz with Q jets, learned a few things, but not sure what I remember 15 years later.

B52bombardier1

+1 on the fuel pump internal rubber diaphragm - it's leaking. Seen that on an old Nova I once owned.

Rick

toxshox

iTrader: (3)

Well this took way longer to get back to than i had thought. Pulled fuel pump it really didn't look like it was leaking but how would i know for sure it's hard to push on the flipper for the pump but when i do you can hear it suck. As for #1 cylinder added a squirt of oil compression came up to like a 140 psi level to keep it in check with other cylinders so probably some ring issues there. Next steps perhaps pulling carb?

B52bombardier1

Check the oil level on the dipstick. If a small block fuel pump diaphragm is leaking fuel, it winds up mixed with the engine oil. The oil level will be high on the dipstick, the oil will be thin and will smell like gasoline. It got so bad on my old Nova that the hydraulic lifters got noisy due to the thin oil.

Rick

Gasoholic

iTrader: (1)

You can test the pump by plugging one line and putting pressure on the other. I have a hand held vacuum/pressure pump I use. Pump it to about 15 psi and let it set. shouldn't leak down at all.
If your too rich, having cyl firing issues, especially missfires, etc it stands to reason you may be washing down the cyl walls with fuel and over time it will find its way into the oil as well.
Another thing that could be happening is your carb could be leaking down. As in, the bowls draining down into the motor after the engine is turned off. Symptoms of the carb leaking are after the car sits it has to turn over several times before it will start and run. You can also look down in the venturis with the motor off and if its leaking real bad you can see it dripping.

toxshox

iTrader: (3)

Yes fuel was for sure in the oil level on dipstick was high and oil was thinned out. I drained that out right away. Not really sure how long it's been adding fuel to oil even.

toxshox

iTrader: (3)

Ok thanks will do that here to the fuel pump yes that carbs been running rich i think for years and getting it to start you have to pump the **** out of it. I might be looking at multiple issues but will take one at a time i really appreciate the help.

toxshox

iTrader: (3)

the fuel pump didn't leak much it actually seemed to leak around the outer housing and not where the pump flipper is bolted to the block. It goes to show why the fuel pump was so messy. My guess is carb must be just dumping to much fuel and over time it's found it's way to the oil perhaps. that and the bowl might be draining.

B52bombardier1

The float needle could be sticky or stuck open by who knows what. Might be time for a carburetor rebuild.

Rick

toxshox

iTrader: (3)

Finally have an update on that fuel in oil situation, I stuck a bunch of parts onto it hoping the issue would be solved for the most part Replaced the fuel pump, intake, dist, and carb. I wasn't sure if the fuel pump was leaking or not after my vacuum/presser test i still was unsure since it was leaking out where the two halfs come together. Figured the carb always sucked on the truck so through on a edelbrock carb and figured i'd swap out the cast intake for a pretty one lol and then noticed mice where hungry on the distributor wiring and cap needed replace anyways so swaped that all out for another hei system.
Timing is set maybe 10 advance without vacuum advance connected. Seems to run good at idle and give it some throttle pretty responsive and normal sounding. Took it out for a drive once you get off idle low rpm to mid rpm have backfiring and popping out the exhaust sounds terrible like wtf if you give it high rpm to wot it seems to be doing what it should So what might be going on, this is what it did i guess when before we started swapping parts. My father said he started it on a cold morning and it kept dying on him so he gave it a bunch of gas and it popped and started backfiring ect... so i'm not really sure if timing is so sloppy that it could be causing this issue or if it is that sloppy could it have jumped a tooth? I'm not really sure what my next step could be to solving this issue. Thanks in advance

Gasoholic

iTrader: (1)

Sounds like you had a lot of stuff to fix.

I'm not there to see what your working on, but "normally" when I see backfiring its due to either timing or spark. You could also have other mechanical problems with the valve train.
I've seen a weak HEI coil cause backfiring. Usually it will happen when you step on it.

Since this is an old mid 70s motor does it still have the air injection reaction "AIR" system in place? If so the diverter valve could be defective or not connected properly. That will cause a big back fire in the exhaust when you let off the throttle. Been a really long time since I worked on a vehicle with AIR, but I do remember those diverter valves causing big time backfiring in the exhaust.

I would say best bet, if it ran good before you replaced the distributer stuff I would go back to that first. Make sure the timing is right, and your spark is good.
If memory serves me correct the peak voltage on your HEI coil should be able to hit at very least 17kv or higher. Any less than that it is not acceptable.

toxshox

iTrader: (3)

I took off the muffler/y pipe to check if that butterfly thing on the passenger side didn't break appart and had it running idles really nice. connected my timing light back up to it set it for 20 degree advance so that i could see the mark while getting into some higher rpms and it will run fine and spark will seem ok then all of a sudden spring gets out of wack and it starts back firing and popping like it's loosing spark but the funny thing is timing light keeps flashing away but the mark isn't where it's suppose to be and if you go up or down in rpms it seems to correct itself and timing mark will be back and it will run ok again. now i dont know if it was doing the same thing before all the work was done to it but i do think it was backfiring maybe not as bad but my father moved it while i was gone and drained the oil since there was quite a bit of fuel in it already. But should i be looking at the new hei system or timing chain. It seems to be sparking but not at the right time. So i'm not sure if something if just really wrong with the distributor, while typing this up i decided to pull off the vacuum advance on the distributor and see what happens well it didn't seem to backfire and timing mark stayed put until some higher rpms were reached. So could something be wrong with new distributor vacuum advance? I guess it was new so Never Ever Worked

biketopia

iTrader: (5)

You need to set base timing with the vac advance un-hooked and plugged off so it's not causing a slight lean out. Set it to 8-10* at idle and then lock down the distributor and hook your vac advance back up and take it for a drive. Have the advance springs, weights, or bushings been messed with? Unless you have a timing light with advance retard or a balancer with markers up into the 30/40s you won't be able to read total timing.

toxshox

iTrader: (3)

Yep timing was set without vac advance connected and it was set about that 10 degree at around 650 ish rpms's locked down it's a brand new hei distributor all stock never messed with anything. Yes have timing light with advance feature so that i can read up in the 30/40's I actually had the vacuum advance plugged into the timed vacuum for emissions controlled engines right away whoops plugged that port on the carb up and plugged it in the manifold vacuum for the non emissions controlled engines and damn thing could hardly run checked timing and it was all over the place terribly. i dont know but i think i'm going to return that damn distributor and go for a higher $$$ unit unless anyone knows how to make it work. I know the port on the canistor for the advance on the distributor was bent a bit in shipping i'm not sure if there is damage that could be done from that but it didn't look like much to me.