lost compression

scotty · Post by **scotty** » Sun Mar 28, 2004 9:14 pm

I got the car back from the electrician and was driving it for a week, 80 miles round trip every day, and everything seemed fine, and then I think I really screwed things up. I'm just wondering if there is a correlation between what I did and the new problem. It's pretty simple, I re-connected the spark plug wires wrong(lack of sleep). It coughed and sputtered and wouldn't start. It finally started once I re-connected them correctly, but it was running so bad that I thought I still had it wrong, so I got the compression tester on #1, to see if I could find TDC from the pulses, and there is no compression-none! The others test around 175lbs. I know the head has to come off etc...I was just wondering if I could have really damaged valves by mis-connecting the plug wires? I saw the motor reverse itself for a half turn as it was dying on the first attempt to start it. I'm guessing that was it. How much should I flog myself? Thanks

scotty · Post by **scotty** » Sun Mar 28, 2004 10:52 pm

I figure IÃ¢â‚¬â„¢ll get started, so if anyone knows where to get the best deal on valves, springs, gasket etc, I would appreciate the help. Basically I need valve job parts for a Ã¢â‚¬â„¢66 1600. Thanks

TR · Post by TR » Sun Mar 28, 2004 11:31 pm

Scotty,

It is really hard to get absolutely no compression on a cylinder, that is really odd! Unless the connecting rod is broken or there is a huge hole in a piston, you typically see something on the gauge.

Did you hear any metal on metal bangs? Usually you will get a pretty good clack when a valve hits...

I bought a 510 once that the owner had driven almost 500 miles with the plug wires on wrong. Granted that was an L-series motor, but I put a ton more really hard miles on it after correcting the wires...

Maybe take the valve cover off and see what you can see in valve movement...Good Luck and fill us in when you figure it out! TR

oilleak · Post by **oilleak** » Mon Mar 29, 2004 9:07 am

Put air pressure into the cylinder through the spark plug hole while the piston is at TDC / firing. You need a compressor obviously. If you have air comming out of the intake (air filter) or exhaust it's one of the valves.

Dave · Post by **Dave** » Mon Mar 29, 2004 11:20 am

...and if you shoot your dipstick through the garage roof, it was a big old hole in your piston!

DatsunBucky · Post by **DatsunBucky** » Mon Mar 29, 2004 12:10 pm

Scotty, don't flog yourself.

There is a mechanical connection between the pistons and the valves via the valve train. Does the valve/piston clearance really care which direction the engine is turning?

I agree with TR. I am a big fan of a visual inspection being the first order of business. I also believe in listening, really listening to a problem. I spent over 30 years at "The Phone Company" (TPC for those old enough to remember "The President's Analyst" with James Coburn) as a tester, and you'd be amazed at what you could learn by listening to a circuit before testing for trouble.

You could pull the plugs and look in the hole to see if you can see anything obviously wrong. Remove the valve cover, and make sure the valves on #1 appear to have about the same play that the rest of them have. Then turn the engine over via the pulley and listen and look for anything that doesn't seem right.

If the intake isn't opening, then there wouldn't be much air in there to compress. Could be something as simple as way to much intake valve clearance on #1, or a bent pushrod. It's hard to do sometimes. but try not to overlook the simple things before getting all P.O.d and tearing everything apart. Then discovering it's something easy. Don't ask me how I know this...

We drive simple cars, and we should all be grateful for that. Too bad some of the parts are getting so hard to come by. Good luck!

Minh · Post by **Minh** » Mon Mar 29, 2004 12:12 pm

Dave wrote:...and if you shoot your dipstick through the garage roof, it was a big old hole in your piston!

Actually

(too funny), it wouldn't be the dipstick. It would be air coming out the breather hole.

Guest · Post by **Guest** » Mon Mar 29, 2004 2:22 pm

Oh OK, fine. Hole in the piston AND a plugged crank case breather = oil dipstick through the roof...

Dave · Post by **Dave** » Mon Mar 29, 2004 2:24 pm

Oops. Forgot to log in. That was me making that crack about the plugged crank case breather.

scotty · Post by **scotty** » Tue Mar 30, 2004 4:19 pm

I did hear some banging, and saw the extra gas pumping out of the carb and shut it off. It will be a few days before I can take a peek in there. Thanks for your guidance.

scotty · Post by **scotty** » Tue Apr 06, 2004 3:40 pm

I was busy then I got sick, but I finally pulled the cover off and the #1 intake valve is stuck open. You can about put your finger between the spring and rocker arm. So I guess I'm doing the valves. Can I get these parts from Nissan's forklift division? Where is the cheapest place to buy stuff.

Thanks.

Minh · Post by **Minh** » Tue Apr 06, 2004 6:18 pm

I think someone here can pull up the part number. Maybe Nissan can still get for you. Oh, Si-iiiiiiid...

Otherwise your best bet is through our vendor. Unless there is interchangable valve from another vehicle. Anyone got an inside skinny on this one?

Don't forget to examine the piston for any damage too.

Post by **itsa68** » Tue Apr 20, 2004 9:49 pm

Scotty:
I replaced valves in 68 R16 metric non-smog head last summer using nissan forlift parts for less $.

Part numbers were found to be same as nissan car part#'s.
in valve 13201-F1800
ex valve 13202-P5100
outer spring 13203-T7200
(forklift did not list inner spring,obtained from another vendor)

None car part#s
ex guide 13213-30002
in guide 13211-01W10

I did not require any new outer valve spring seats because the new valves were identical to my stock ones and existing seating could be used as is.
You might need to get new spring spring seats (washer spring sits on) to use the the new valves (if engine# is before R49885).
outer valve spring seat 13205-14600 (-D0020)

Hopefully someone else knows what other parts might be required to suppliment with the new valves if you currently have the old stlye set-up.

SLOroadster · Post by **SLOroadster** » Wed Apr 21, 2004 12:36 am

I hate when my engine compression runs off. I went from showing 190 ish (+/- 5 lbs across all 4) to showing 145 on my best cylinder and 105 on my worst. Good thing I have the money for a rebuild. The new engine will be illegal as all get out to race CSP autoX, but oh well it should be the most awesome U20 on the west coast ( that is still streetable and not supercharged or running NO2). Lots of internal machine work. 5lbs less weight in the crank. Ballanced, blueprinted, ect. Oh yeah, it will be using .060 oversized pistons.

Will

scotty · Post by **scotty** » Sat Apr 24, 2004 3:05 pm

Thanks for the help everyone. There is a forklift dealer about 30 minutes from me.

My aluminum head was too thin, so I picked up a cast iron head. I was wondering if there are any different considerations for setting up the iron head?