Zero10

I have the intake manifold off, and am changing the timing belts right now, and I noticed that I have little spirals of soot inside the intake passages in the head, and all 4 runners in the intake manifold are covered in soot. Curious, I turned the engine over by hand. 1 cylinder blows quite hard out the intake valve. Turning it over at maybe 1/4revolution/second, it gave a pretty good breeze. 2 others give a whistle, and if you put your hand there, they are definately blowing out air pretty quick, and the last (cylinder #4) just hisses, but I can't feel much air moving.

From what I understand, a little bit of leakage past the intake valves is normal, but this seems excessive.
How much is too much?

The car's past is really sketchy. The last record on the belts is 8 years and 100,000km's ago. It sort of seems like maybe they snapped, and new belts were thrown on, without checking the head?
I heard the intake valves were the first to go when the belt snaps.

Here's my compression test results
#1 - 105psi - Worst intake valve blow-by
#2 - 110psi - tied for second place
#3 - 102psi - tied for second place
#4 - 100psi - intake valve seems to seal the best.

Those results don't really reflect leaking intake valves, at least not in my head.

Any suggestions on what I should do?
I have already condemned the engine, and am planning a swap next year. Do you guys think it will last that long?

I'm amazed it didn't burn the tips of my fuel injectors... but the valves are a rainbow color around the edges.

Thanks in advance for any help.

seb928s

Those numbers are really low they sould be around 150.

Zero10

Yeah, the compression is definately bad. The numbers are all 170-180 wet though. So I would presume most of the issue is rings. Which lead me to think it's not losing that much pressure to the intake valves.

I don't know what to do about it...

early85944

You need to do a leak down test.

Zero10

I can't do one. No air compressor, no leakdown tester.
Should the intake valves leak at all, or is are my valves messed up?

SoCal Driver

Sounds like a rebuild or exchange to me.

Zero10

Hmm... no rebuild, no exchange.
I am planning on installing an inline 5 2.5L turbo diesel (or maybe the 1.9L TDI PD if the 2.5L won't fit) within 18 months.
I am wondering if there should be any blowby on the intake valves, or whether they should seal perfectly.
There is some minor blowby on the exhaust valves as well.

The part I don't get, is the 3 cylinders with intake blowby seem to have the highest compression numbers. And a wet compression test gives me 170-180 on all 4. Does this mean the intake blowby is insignificant?

jd944

Sounds to me like you have a very tired motor. In my opinion, the valves should seal 100%. When I lap valves into a head, I check the seal by turning the head upside down and filling the combustion chamber with water. If it leaks past any of the valves, the valves are leaking and must be re-lapped.

Zero10

Hrm.. mine would leak like a sieve....
I think I have a pre-85.5 motor... in an 86 car, so who knows what the mileage is... just little things are making me suspicious.
I don't know most of the history on the car.
Well, it looks like it will run for another year, then it's diesel time *fingers crossed*

David Ray

I just read mine and they're 157, 158, 155, 156, but the turbo is gone.

Zero10

Those are great numbers for a turbo!
Although your sig doesn't say it's a turbo...
If it's N/A, then they are getting a little low, but not too bad. 180ish is good, 200+ is wonderful =)