Greetings everyone, I have a 1974 Comet 250 - 6 cyl. and am getting blow-by I believe. Oil coming out from the oil filler cap, through the attached air tube and into the air filter (smokes) and oil coming out from the dipstick. Am I screwed? Do I have to rebuild the engine or could it be something else? Any troubleshooting advice? Thanks!
The ultimate fix might be an engine rebuild but there are some things that you should try first. 1. Check the PCV hose to see if it is clogged. 2. Replace the PCV valve (there is no way to check them without a flow meter) 3. clean the cap and hose in laquer thinner or tolulene and air dry. 4. Check the condition of your spark plugs. If one is oilier or more fouled than the others take a compression test or leak down test to see if your compression (or leak-down) is even - within 10% low to high.
Thanks Paul. I replaced the PCV valve already but will check the hoses as well as the sparq plugs. Worse case - a rebuild...sigh....
Checked the sparq plugs - 4 seemed caked in oil and burnt while 2 others were dry but brown. So - guess I'll take it in for a compression test. The dude I bought it from said the compression was 120 down the line, but I don't see how that's possible. I also happened to notice the EGR valve is the orginal one the car came with and it looks pretty sad. What kind of effect could that have, if any, on the problem I'm having? Thanks for your time - it's most appreciated. I attached some pictures of those plugs as well.
The EGR valve is just a vacuum operatred valve that allows exhaust gasses into the intake manifold to fool the engine into running a leaner mixture than it should. I can't recommend that you remove it but if you were to do that and install a carb from a pre-1970 engine it would run better. The reason I can't recommend it is that there is a $10000 federal fine (and probably state fines too) for removing or altering any emission controlling device or system.
With 4 oily plugs you probably need to refresh your engine. You can do a full rebuild or you can do a "refresh" in-car overhaul. You can try running the hotter plugs to keep fouling down to a minimum. If that doesn't work then the cheapest way to go is a "back yard rebuild". Pull the head and replace it with a head from a 200 six. Ream the ridge out of the top of the cylinders, pull the pistons and rods and install new rings and bearings. While you have the rods out replace the main bearings, seals and oil pump. Have the head reconditioned with perfect circle guide seals and a three angle valve grind. Have a two barrel adapter fitted to the intake log - requires milling a flat spot and boring two holes to fit the adapter. Use a Ford or Holley two barrel carb. Install an RV cam and lifters (hydraulic) and bolt it all together. you will have well over two-hundred HP and a brand new respect for that 250 engine. Nothing fancy - or expensive - just a cheap back-yard rebuild with a bit of HP added. The expense is a rebuilt gasket set, rings and bearings and the oil pump, cam, lifters and timing gear set. You can rent a ridge reamer and ring compressor. If you need measuring tools you can get a six inch dial caliper pretty cheap at Harbor freight tools or any of the discount tool houses. It won't be precision work but it will be usable for at least another five years or so.
