1977 porsche 924 compression test results-help Its really weird?

Question

So my 924 has been acting really odd. My mechanic though it was a bad intake valve, but he told me to do a compression test first.

Here are my results (piston one is closest to front, piston 4 to the back)
with no spark plugs in.
piston 1 170lbs piston 2 170 lbs piston 3 0 lbs piston 4 0 lbs

with all plugs in except the one being tested

piston one and two the same

piston 3 and 4 now have 50 lbs.

wtf mate? Is that a bad valve, or is it a blown head gasket leaking across 3 and 4?

any advice on what it might be?

It is the head gasket, I just did a check and air leaks between 3 and 4.

Answer 1

blown head gasket

Answer 2

Busted cam on back end,
valves are not closing,
damaged piston rings, damaged head gasket between #3 and 4 cylinders,
crack in block between said cylinders,

Answer 3

It's one of two things.... either you have burned valves in two cylinders or the head gasket is blown between them. You are going to have to pull the head either way so just pull it and check. If the gasket is blown, be sure to have the head resurfaced.

Answer 4

yep, lol squirt some oil in the two bad cylinders and see if it changes anything during the compression test. dont worry about the "with spark plug" in test as that is not the correct way. but i weould say you have a fire hole burnt inbetween the 2 cylinders. another thing you can do is pressurize the cylinders in question and see where you hear air coming out of, if its coming out of the other cylinder there is your answer, just make sure the velves are closed though

Answer 5

that's strange, because i'm 16 and performance a 1977 Porsche 924. nicely, what you could favor to look ahead to is a leaking gas distributor. If that leaks, you want to deliver it to someone to get a refurbished one which is $2 hundred-three hundred. you also wish to envision the gas tank. there's a good danger that the gas tank has water, rust, and likely airborne dirt and airborne dirt and dust in it. The gas filter out could get the airborne dirt and airborne dirt and dust and rust, besides the undeniable fact that the water will be undesirable. likely the most substantial element of examine is wether the battery container is rotted out. If there's a hollow in it then water will leak into the passenger compartment. you could't merely weld a clean piece of metal over this because the metal is inspired and also you could't weld onto galvanized metal (my father and that i attempted, did not artwork). What works merely as well is to positioned a clean piece of metal over this section, seal with some type of caulk, and riveti it to carry it there. We also fiberglassed it to further advance the spot. in case you listen a knock, that's timing may be off, yet on the different and larger likely case is that some lobes on the camshaft are worn. That replaced into my case and that i purchased a clean head that replaced into fairly worn. I were given fortunate and were given it for $50. many times, the elements for the vehicle are low-cost as they're specially Audi/VW. What you could also favor to look ahead to is the cost of insurance. it is going to bypass lower than your mothers and fathers call for sure and into their plan, yet I regarded what it can be for a 16 3 hundred and sixty 5 days previous and not using a intense college degree and massive insurance could value you $600, a MONTH! I freaked out at this, yet I were given insurance for $100 a month that is ahhh, ok as long as you've a job. To finally answer your certainly answer, if that vehicle isn't in only about pristine condition with a clean interior (which contains reliable seats), runs nicely, and looks reliable, i could attempt to diminish the cost. elements may be low-cost, yet they take a large type of time.