I’ve a 73-914 With a the original 2.0L Fuel Injection engine. Has about 75k miles. Set for about 10 years, brought back to life about 6 months ago. Checked compression and got readings of 90-95 psi across all 4 cylinders. Engine seams to run pretty good with that compression. Doesn’t seam to smoke any while driving but some bluish smoke when you first start it up. Pulls good up to redline. I was hoping to get the compression up to a range of 135-150 psi. Without spending a lot of money, what would you recommend to improve the compression? Valve job, new rings? Who would you recommend to do the work in the area? Estimated cost, Located in Oregon. Thanks

Ok just confirm the compression check was completed with the engine warm and throttle wide open.

Best place to start is with a leak down test. That will tell you where you are losing compression through the valve or past the rings.

Realistically if you are going to pay to have the engine pulled to do a valve job then I would count on putting in new rings as a minimum.

I do all my work myself so I cant help on the pricing.

I was planning on rechecking the compression today and doing a leak down test. Thanks

. I pulled the plugs and after maybe 50 miles of driving on new plugs the ends are really black, of course that could be due to some other issues.

That could be inline with the low compression. Old trick and not really all that reliable but if you add a few squirts of oil to the cylinder and recheck the compression, an increase in the numbers could indicate ring wear is the issue. No change points more toward heads and valves.

Far from a leak test and really not the sole test to make any decision on it but can provide a general direction on what may be happening.

90-95 is low, but its probably a good sign that they are all there, sort of.

Just for giggles, when did you last adjust valves?

Make sure the engine is fully warmed up.
Throttle should be wide open.
do the test will all the plugs removed to stop compression in the other cylinders from showing up, and just run the test with the starter.

Each cylinder, test, note the results of the test, add a few drops of oil to the cylinder and run the test again, noting any change. But simply having your engine warm is going to bring your compression numbers up.

The oil trick can be hit or miss in a flat opposed engine as you'll only get the bottom part of the cylinders oiled.

If your plugs are black, you are more than likely rich on the fuel mixture, and could be exacerbating the rings not sealing due to washing the cylinders with excess fuel. It might not be that bad, but it's possible.

Sometimes an engine that's sat up for a long period of time can develop more compression as the rings re-seat, but not always. You can also have bad rings from sitting up too long. I'd say it's highly unlikely you'll see 150 on that engine, and all things considered 125 is a good number, where you're at now is borderline top end time.

If the rings are marginal, then you'll typically run on the rich side, because it's not holding compression.

I'd say drive it for a thousand miles or so, and keep close monitor on your oil and fuel consumption.

Re did the Comrpession test with engine warm and as described. Compression test bumped up to 105-115 across all cylinders. Then added some oil to the cylinders and the compression bumped up a little but not much 110-120 range. The valves were last adjusted about 10 years ago or probably about 200 miles ago. Working on a leak down test.

I think I will try to put some miles on it and watch the oil/fuel consumption and recheck the compression as I get some miles on it. Thanks again.

please adjust the valves
you are really only guessing if you haven't done that
might as well just throw dollar bills out the window as you drive.

I would NEVER even start a 10 year sitting motor without doing a valve adjustment...


your motor is tired
rebuild it or live with it
I have lived with many tired motors
it may even get better

if you do a lot of work to bring the compression back on a tired motor, you are now most likely stressing the also tired bottom end... the results will likely be that you have now changed what is the weak link in your engine... often in these scenario's you have wasted money on the top end and get to respend it when you rebuild the bottom end....

If you have 115lbs with less than 5% deviation the engine is well loved but good to go.

Get some miles on the car and recheck the plugs after a good hot run.
If the plugs look the same try a hotter plug.
If you are burning oil it will be the guides, you likely wouldn't have even numbers if it was rings or valve seating.

This.



Also this.

With modern fuels your plugs will only show you what the engine was doing when you turn off the key. Its really hard to read plugs these days and get an idea of how the engine is doing under load.

Zach

I agree, but there is a way you can get a accurate enough reading for heat range through plug colour.
I only mention heatrange because what is the plug brand? Blue stripes ...Beru?

Plugs, Bosch or NGK, old school copper core only.
Beru are OK, Bosch clone, but they have a different numbering for heatrange.

Anyways....

Drive the car till hot, then run a freeway for 15-20 minutes, then shut it down at speed, coast to a stop, let it cool a bit and check the plugs.
Plan it out to coast stop somewhere you like and safe, you're going to be there for at least half hour or more.
You want tan but clean of soot. Can be other colours, grey, red, brown, all comparable to tan.

Everything suggested by others here, timing, valve adj., , etc should done first.

I agree with everyone’s comments. I plan on getting the valves checked/adjusted tomorrow and then I will drive it for a little bit and do another compression check. From my past experience over the years I realize if and when I do decide to rebuild the engine, there really isn’t any shortcuts! Do it right the first time and rebuild both the top end and the bottom end with good parts along with a machine shop that knows what there doing. Thanks again.

Amazing, I took it in and had the Valves readjusted and yes they were way off! Re checked the compression which showed 120 psi across all 4 cylinders! Running great, I just need to get the fuel mixture set correctly and then enjoy driving it again! Thanks again for all your suggestions! have a great week.

Nice!

Great!