Compression Test Results with white smoke

[rutkak]

Gurus,

I did a compression test on my 1970 302 and the results seem shockingly very high. I tested with a warm engine, all plugs removed and WOT. My plugs are always a nice tan color.

Bottom Line: 6 cylinders were 210 psi and two of them were 215 psi. I rented the compression tester expecting to find 2 or more cylinders notably lower pointing to a head gasket leak or worn valve. I did not find any wide variation in testing, but I think the numbers seem REALLY high compared to what I've read elsewhere.

Any thoughts? My car still pushes white smoke when and only when she is warm. I have a intake manifold gasket and new bolts are in the mail so I'll reseal her later this week. I have a tad bit of an oil leak at the back of the intake manifold.

KR

 

[[email protected]]

Oil leaking around valve stems. Usually worse cold but if the cylinders are sealed well, thats where it has to come from

 

[rutkak]

Thank you Jenny, you rock.

Is replacing the valve stem seals a difficult process off the top of your head? I'll do some research on-line, but I'm thinking it's not that difficult for the average Joe.

KR

 

[jbojo]

Gurus,

I did a compression test on my 1970 302 and the results seem shockingly very high. I tested with a warm engine, all plugs removed and WOT. My plugs are always a nice tan color.

Bottom Line: 6 cylinders were 210 psi and two of them were 215 psi. I rented the compression tester expecting to find 2 or more cylinders notably lower pointing to a head gasket leak or worn valve. I did not find any wide variation in testing, but I think the numbers seem REALLY high compared to what I've read elsewhere.

Any thoughts? My car still pushes white smoke when and only when she is warm. I have a intake manifold gasket and new bolts are in the mail so I'll reseal her later this week. I have a tad bit of an oil leak at the back of the intake manifold.

KR

Typo on the readings? That would give you over 14:1 compression. If the numbers are in the 1XX:1 the the ratio is about 7.8:1. These would be really good compression readings and what I would expect for a 302.

-jbojo

 

[MotoArts]

Maybe that gauge is off.

Yes, those are tall numbers, especially if you think it may be stock or a mild rebuild.

Are the pistons domed or ???

That can cause detonation, and potentially popped head gasket(s).

Hopefully you'll be able to see a crown through at least one plug hole. A cylinder taking on leaking water will have clean piston crowns, no carbon.

Cam may have not enough overlap (to bleed compression), creating big static compression figures?

I'd guess something is amiss in the compression department for starters... That would worry me a little before white smoke.

 

[rutkak]

Yeah, 210ish is definitely very high for a (presumably) stock 1970 302. I'm going to check my 289 with the same gauge tonight...the gauge must be off. I'd expect that one to read even higher since it's a 1966 C Code.

KR

 

[71mach351]

I checked my 73 302 recently and all cylinders were in the 125 to 130 range. I also changed the valve seals with the heads on the engine. Very easy to do.

 

[rutkak]

Thanks 73Mach1.

The gauge is definitely functional. I tested the compression on my 289 C Code and all cylinders were 145ish. I'll recheck the 302 when I get back from work but I'm pretty confident the engine is stock as stock can be.

On both tests I pulled all the spark plugs, warmed up the engine, disconnected distributor and zip-tied the throttle wide open. The only difference in the two engines is that the 302 has an HEI dizzy but I disconnected it. It's supposed to rain pretty heavily today so we'll see what I can get to. Yeah, 210 is pretty damn high.

I take a look Moto and see what I can see.

 

[Jeff73Mach1]

Gauge readings are high, but the important thing is they are well within 10% of each other.

Valve seals will help, but usually valve guides are due to be done when there is leakage. I'd consider going ahead and pulling the heads and having them overhauled. That would also give you an opportunity for a full visual inspection of chambers and piston tops and bore condition. It is an afternoon's work, but it isn't hard.

 

[Don C]

I've seen some heads and pistons that had a lot of carbon due to oil burning, but I don't know that carbon could raise the CR that much and that evenly, even if all the valve guides/seals were bad.

 

[[email protected]]

KR,

Valve guide seals can be done with heads on. only reason to pull head would be if you suspect excessively worn guides. You know your cylinders seal well already. So if you replace guide seals and the problem comes back then you know what you gotta do. But if it cures the problem, be happy. If you are really concerned about whats going on in your cylinders, get a scope and see yourself. Good luck

Jenny

 

[72HCODE]

what can make changing valve seals more of a challenge is if you have aftermarket Rockers and hydraulic lifters. with solid lifters and original rockers you can follow the manual and lash things correctly hot or cold depending on method used. with aftermarket changes things get a little more questionable.

for example changing my valve stem seals was a huge pain because my engine builder used double springs required a specialized valve spring compressor, i had crane rockers which had a huge range of adjustment and hydraulic lifters which required a certain amount of pressure, it took me and my engine builder hours to replace all of mine, when we put it all back together we had major problems and required a few more hours of adjustment.

It was not rocket science but in my case i could not of done it by myself, do to all the modifications my engine had.

there was additional issues with the machining on my heads that required specialized vitron seals, that required my engine builders "box o left overs".

Also thankfully i was present for the valve stem seal replacements on my engine, because i caught my engine builder making a HUGE screw up with the retaining clips, had i not been there and let him work on my engine alone, my engine would of never made it 6 miles before dropping a valve and destroying the engine. <--my engine builders own words when he thanked me for spotting his screw up after arguing with me that morning about how he did not want me present to work on my own engine. yeah he drank his morning Joe and i field stripped my engine after driving it 60 miles to his shop, man was i pissed that morning and livid on the verge of murder that night driving home.

 

[rutkak]

Jenny and crew,

Thank you for a lot of sound advice. I'm moving in 3 weeks but have a friend here that is familiar with replacing valve stem seals so I may enlist his help prior to heading up to Virginia.

The engine is definitely stock or at least hasn't been touched in 30ish years. It was a true barn find (complete with mice) and not maintained at all but really kind of not driven much. The PCV was stuck and probably had been for god knows how long so the valve covers were pretty nasty. Inside the valve covers looked pretty decent though and not to gunked up. The oil was pretty cruddy when I got it changed and I'll do the next oil change this week to see what's coming out since I just started 30 days of vacation.

I'll do a pressure test on the radiator in the next 2-3 days as well to ensure I don't have a head gasket leak, but I'm sort of assuming I do because of the smoke. Hopefully the heads aren't warped.

The engine runs strong...and I mean very strong with my other carb on it. For a 302 it can certainly break one's neck giving it some gas.

I'll post the 2nd compression test tonight assuming it doesn't starting pouring rain (which is expected).

KR

 

[rutkak]

2nd compression test yielded the exact same results. All readings were about 210 psi. Recap: The compression test on my 289 engine showed 145ish for all cylinders.

 

[72HCODE]

Seriously don't worry about the high compression numbers. To calculate the actual compression ratio of a motor you need to know the volume inside the cylinder. That all changes with type of pistions and cam duration, etc. somebody could of dropped a stroker into that 302 you will never kow unless you take it apart. I know vetts with 200psi compression test numbers and they run fine on 93 octane.

Basically what you are looking for is making sure all the cylinders fall within 10-15% of each other for a healthy motor. So if the lowest reading you got was 180psi and the highest was 210 and everything else fell between those numbers you are fine. If everything fell between 200-210 even better.

A leak down test would tell you more then a compression test but I don't know if its worth it In this case.

So I would just go with it now and replace the valve stem seals and see how you do without spark plugs getting contaminated with oil In the future.


Replace the pcv or clean it out....

One thing is if the motor oil is as crappy as it was try not to dislodge it let the motor work it out with more oil changes and Maybe a shot of marvels mystery oil inside the motor oil for a day then another oil change. If you clean the gum out a chunk might break loose and clog an oil gallery. You sort of want to let the build up melt away slowly. Like oil and filter change with a good filter with a leak back valve. Drive it drop some mystery oil in the crankcase then put 20-50 on the motor oil and filter change again then oil filter change again after 500 miles. And you can pop the valve covers and check how the new PCv is doing its job.

Some guys attack the build up with a scraper to get the valleys all cleaned out and you have to make sure things are really clean after and drop the oil pan. Not easy to do in the 71-73 mustangs, better to let it work out with MMO or seafoam to breakdown the build up slow over time. The valve covers you can clean out just make sure nothing is left hiding in the corners.

 

[rutkak]

As Mark recommended I did a coolant pressure test (based on a different thread about the car surging) and I pumped 13.5 psi into the radiator. In the morning she was about 5-ish.

Here's Marks73 note "Stop driving it. Pistons hate water! Sounds like a zipper crack that only opens when it gets hot enough. Get a radiator pressure tester and pump it to about 13 pounds. Let it sit overnight and determine if it will hold that pressure. If it does, it's a metal crack in either the intake, head or block that only seperates when hot. Gaskets don't do that."

Tracking all 72HCode and I sincerely appreciate your reply. I've been running a little Marvel's Mystery Oil in it since my initial oil change. I changed the oil this morning expecting the worst, but it's not that bad. It's certainly very dirty but there aren't chunks of crud or metal flaking out. I really expected more than just dark oil...no coolant...no foam...just oil. I'll do as prescribed, but I just put in 10W30. I replaced the PCV recently and it's definitely functional. I sprayed it out this morning to clean up the tad bit of oil in there but it's looking pretty new. The one that was on the car when I bought it was seized up and pretty much gross.

It's amazing that a few basic things on a classic car can keep her running pretty decently. It's also amazing that if you don't do them...she'll get gunked up and run like crap.

 

[72HCODE]

as far as the coolant leak. you could have a crack in the radiator itself.

could be a few things as others have said, head gasket a crack in the block. is there evidance of coolant underneath the car from the pressure test?

was there coolant present in the oil when you changed it?

i discovered i had a crack in my original radiator by accident. I wasn't loosing coolant at the time but i had the engine running and i leaned over the rad to make an adjustment and i heard a hiss..

Stopped the motor and tried to recreate what i did while the engine was still hot. turned out a solder joint cracked on the top hose of the rad..... I threw that rad out and got an original 72 rad, took that to a radiator shop and had them install a high efficiency core with a Trans cooler upgrade it cools like a 4 row radiator but inside a 2 row case and looks like OEM except the fins are very close together, but it has the oem part number on the top of the radiator case .

it would be great to see a puddle under the car that could be traced to a bad hose or bad joint rather then inside the motor.

just realized you said you didn't find coolant in the oil...

might be worth to keep an eye on the coolant level, and see. A bad rad cap can cause coolant to disappear. if you put the wrong cap on it same problem. you have vented and non-vented caps. the vented caps are used with coolant reservoir they open at 2 different psi. the non-vented is original equipment it only opens when "Their SHE BLOWS" occurs. overflow just went out the drain tube. some people install a vented cap on our cars and the coolant just goes right out the vent at normal running temperature and they think they have a cracked block. a bad cap will cause the same problems the seal is no good or the spring has died and it starts to let coolant out before 11-15 PSI for the test you did the cap wouldn't matter but you could have a weeping coolant hose that is dry rotted. with your engine it sounds like you could spend money redoing the entire cooling system and you still may have head gasket or internal damage trouble.

you have some options to explore as far as coolant loss. if you do have wet plugs and its coolant then obviously the heads need to come off.

 

[marks73]

The motor I toasted never showed the leak just kept dropping level in the radiator. And ran about 10 degrees hotter after the rebuild. When I dropped the oil pan, I found 1 small bead of coolant hanging off the bottom of #5 piston. :s $1200 down the drain in less than 100 miles of rebuild. . Machinists helper bored my sleeve .030 instead of replacing it.

 

[72HCODE]

ARUGH! @mark73