Hot Rods engine question, low compression

I bought a 32 five window back in the 60's that had a Pontiac motor in it. So WTF! Were talking motors here.

 

Great thread up until the time the police showed up. Bob

 

In before it gets locked. Nothing wrong about helping a guy out if you can. Keep an open mind, you may learn something!

 

I'm more than reasonably certain that big spaces, giant letters, and bold writing is much better suited to selling used cars than such is used for proclaiming that your panties are in a knot. Even if the above method is equally effective at developing the idea that the panties are indeed knotted.

 

Ok heres my three cents. I agree with beaner on the jumping time. I had a 67 (sorry) GTO with a 400. I shut it off was running fine, went out next morning and fired it up. It would idle but thats it. It died then would not start. Checked the dist and it was off. Pulled it apart and the nylon-alumimum timing gear was shot. Pulled the pan and there was nylon everywhere. Even in the oil pump screen. It CAN run after jumping time, but it will not run well. Check that timing gear. And that will cause low compression. Oh yeah it had 60,000 mi. JMO Lippy

 

Fwiw, I had a '52 Willys Aero Eagle HT with the intake valve in the head and exhaust valve in the block that sat for a while and it wouldn't fire off.

The old Mechanic across the street told me to put a couple of squirts of good old MMO in each cylinder, turn her over, then put the plugs back in and fire it off!!

Worked like a charm!!

The old guy said it had sat too long and dried everything so just needed some oil to wet it down so the rings and valves would seal was all.

Made me a firm believer in MMO!!

pdq67

 

looking in through fuel pump hole, looks like a new double roller chain, with steel gears. tight in both directions...............resisting the urge to pull this thing apart...........resistance may be futile.

 

Years back a '68-ish Tempest with a 350 comes in for a tune up.... that thing was beyond a plug and point change. It chugged in, barely had any power whatsoever. Popped the hood... vacuum advance was clocked against the firewall and the cap wiring was also very creative.

But they got it running, it had jumped time. The chain itself looked within reason, but the big nylon gear had shed about 1/2 of its teeth. We did the chain and gears, put the distributor in straight, whole major tune up and the car ran great. The customer was amazed that we pulled it together in a single day for her.

 

I hope the thread doesn't get locked. I'd like to know what's wrong. I've seen the nylon pieces get into the oil pump and plug the relief valve. It would blow the oil filter seams. We put on a Baldwin filter and the oil pressure light started coming on. I tore it down and found that the high pressure blew a drive in plug out of the lifter galley behind the timing gear. That's when I started tapping those holes and using screw in plugs.

I doubt that there are many nylon tooth gears left around and I don't know if anybody sells new sets with nylon teeth.

 

It's my understanding the nylon gears were never available aftermarket. No one wanted them anyhow. Since this engine was supposedly rebuilt by the previous owner, it would stand to reason the nylon gear is long gone. Unless of course the guy did a krylon spray bomb rebuild. I'm leaning more towards peeled off cam lobes now. I'm curios what the machine shop has to say.

 

Have we identified the offending problem yet? I'm just curious to see what it was that went wrong? thanks.

 

had a little time and pulled off the intake and valve covers, and removed the lifter tray, rocker arms and pushrods. i can spin the engine with one hand using the flywheel.
pulled one head, motor was definitely NOT rebuilt, although the cam, lifters and timing chain look new.

 

i just pulled the pan, the other head and timing cover. then i pulled number 1 piston. definitely not rebuilt.
piston rings frozen to piston and wore down even. i could not get them to move with my fingers and i actually slid the piston back into the motor without a compressor.

 

interesting pics

 

Ok but is there a way to tell if the piston ring situation was caused by the attempts to start it and the real culprit was simply hung valves from the engine sitting? The engine has not jumped time and exhibited normal compression on 2 holes. It has fuel and spark. I'm gonna suggest that there were hung valves, and the attempts to start/diagnose the engine is whats wrong with it now. The OP stated that the engine would spin over by hand with the valve train disassembled. What became of the two holes with good readings. Those 2 holes should still have compression since the valves are now fully closed. Some of the observed conditions don't make sense. OP, can you comment on all of the valves in both heads being fully seated after the heads were pulled?

 

the valves "looked" ok. and the 3 i did the leak down test to [worst three] all had no air coming through the exhaust or the carb.
i would also like to know what would cause the rings to freeze to the piston. the piston shown is the only one i pulled, the piston was removed with the crank up [motor upside down] and when i tapped the cap bolts down, the piston slid [gravity] to the bottom of the hole and would have fallen out if not for the ridge.
i was hoping an engine guy could explain.

 

There is no mystery really. tb33 told me earlier this year, that this car was a long time project.

The rings likely stuck long ago from varnish. When the car was finally assembled after cosmetic restoration, the car ran ok. With completely stuck rings, each time the motor is run, the blowby gets worse. That is from minor cylinder taper, and the stuck rings and the bores wear rapidly as the piston rings wedge tighter at the bottom of the bore.

I have an early Olds motor that did the same. It got worse the more times I ran it. I was running it each day to try to unstick the rings, but they never did. The engine got more difficult to start over time. Ran fine, if you could get it to start.

 

@F&J, your post gave me the "ah hah" moment. this makes sense now. we were under the impression this motor was rebuilt. it wasn't and was marginal, at best, and the final straw was the customer flooding it and his trying to get it started. the customer told me today he was putting a quart of oil in every 500 miles.
good thing is, it happened at the end of the season.

 

Why is they leave this stuff out until we're about to pull the last hair out of our heads.

It was running good until he parked it.
I keep messing with it because its a decent running car.

Oh yeah, it was burning 1 quart of oil every 500 miles.

It had to be smoking like a mosquito fogger no?

 

Read the first line in my post number 4.... only 13 words..

at that post, I did not know if this was the long term project car that tb33 told me about many months ago.

When he finally mentioned "GTO" much later, then I knew it was the unfinished project that got dumped at his shop.

I am not surprised it did not smoke; my 303 Olds never smoked a bit, but blowby at the filler pipe was very excessive. tb33 mentioned blowby early in the thread.

If the owner was told the motor was redone before he bought the car, then most shops hired to reassemble the car, would return it to the customer if it ran ok. Ifthe shop noticed it had some engine quirks like some blowby, it would be assumed it would need to break in.

 

i never noticed it smoking.
i never drove the car, i got the car and "all it needed" was the doors and nose aligned, the windows put in and all the lights and dash. it went to the upholsters before it had plates and he picked it up from there. i only saw it again to find a couple electrical ghosts.

 

I've had my share of mysteries & spent hours on diagnosis and forensics after that "is there anything else you can tell me or remember" question is asked. Then when you come up with a answer for them the say "oh yeah ,,,, "

Check that "he's got SBC woes" thread of mine.

Few weeks ago, OT car though so shhhhh. Comes in a little noisy and a SES light on for an EVap code. get it up in the air, pull rear wheel and inner fender to inspect fuel filler neck. Got scanner dialed up and start it to watch data stream and control the valves and the thing cranks like the plugs are out of it. WTF??? It drove in here 12 mins ago??? Zero compression. Somedays its just no fun I tell ya.

 

I've seen motors like this that ran when parked but wouldn't a couple weeks later. The excess fuel in the oil was the final nail in the coffin. The rings were already sticking and probably had plenty of sludge around them from the oil consumption and resulting sludgy blow by. The flooding of the engine washed the sludge away from the rings and they no longer held enough compression to run. My wife drove her Chevy home one day with smoke billowing out of the breather and every other possible opening in the engine. It had had the oil changed and was flushed to clean it out the day before and all the sludge that came out was keeping it running to that point. I was able to spin it over with my hand on the crank pulley. Flooding didn't destroy the rings, it cleaned them which removed the sludge that helped them seal.

 

^^^ I like that theory Too_Crazy, Welcome to the HAMB. Bob

 

As I said back on page one, the piston rings are stuck.
Now soak the pistons in diesel fuel for a few days.
They will come out with effort.

 

good call!.......for a mermaid
that will be a job for the engine builder, he may have to bore it and the pistons will be replaced.

 

Interesting thread tbanda3rd.I have been following it. Let us know what finally happens. Bruce.

 

those are factory pistons , have several buckets of them in the garage with and without rods , do not waste you time reusing them as the tin coat is worn and you will get a slight tick when cold like a forged piston ,
the rings are gummed from the carbon build up , if the motors heads have been changed to a low compression large chamber style head ( thats how you change compression ratio in a Pontiac and most people just swapped heads when a valve job was done and accidently give there proper chamber heads away (always check the ac bracket casting number for cc's )) with the low compression the piston tops will carbon up and the motor runs hot anyways now it will run hotter and the rings start gumming up . when we would re ring them they often were so stuck you had to pry them out even after soaking in a solvent tank for 2-3 days and then you had to clean the grooves with the ring tool ( or broken ring ground down ) , as for the bearings not bad shape if they are factory ,

 

thanks, the bearings look a lot better in the photos, the cap bearing is worn bad in the center. the crank and bearings both feel like a record when you drag your finger across it. [ for our younger readers; a record was a round disc with grooves. it was used to play music when spun on a machine and a needle ran in the grooves.]

 

as long as there is no copper or burn marks your Ok, make sure you get the same crank you send in for a regrind/polish (can cut as much as .030 with no problems ) as that's a Nodual Iron crank ( Pearlitic iron ) ( notate it on the work order ) , they are the good ones , I have been seeing lots of std grey Iron cranks ( low performance motors and motors built after 75 exc 77-78 w72 ) being handed out as they are plenty and a pure junk , if the bearings show signs of blistering that means there was detonation .