Compression test results - looking for ideas

[signorc 31]

Hi everyone,

Here are the results for my compression test on my 302 2bbl stock 69 mustang.

There is a little oil on the back of the engine by #4.  Could it simply be a bad gasket seal?

Cilynder     dry      wet

#1               125      140

#2               117       135

#3                117        135

#4                 105        115

#5                120           140

#6                125          148

#7                120            133

#8                 122          140

All ideas and thoughts are welcome!  

All the best from sunny Tuscany!!

[Brian Conway 264]

 Greetings from Southern California.  The test results for you stock 302 are about what you would expect.  Actually not to bad and having one or two weak cylinders is to be expected.  ' Ideas and thoughts ' meaning exactly what ?   . Brian

[1969_Mach1 333]

Normal for an older motor.  Rings have some wear and not sealing as good as they should.  How does it run?  Number 4 cylinder compression is getting close to where a slight miss at idle will be noticed.  That usually happens when a cylinder's compression test is about 90 psi dry.

[Bob & Sue 110]

Those are close except for #4, if it were me I'd warm the engine up to temp again & check it. Not much you can do about it for now.

The oil by #4 might be from your PCV valve if it's located above #4 or you have a breather there check the seal on it. One of my breathers gaskets was bad leaking down the side of the valve cover, I have 3 breathers plus the oil fill on mine.

[signorc 31]

Hello,

It's def not the pcv cause the valve covers are not wet. it's oily below the head and now onto the bell housing.  

Would a thicker oil help the lubrication out on the cylinders? I'm pretty much against synthetic oils.

The engine runs great with the only issue that it stalls when in stop-and-go traffic. then I have to wait for the engine to cool off a little to restart.

I was thinking that maybe the low compression on #4 is due to a gasket leak, which would then explain the oil leak by there.  Was thinking to replace the head gaskets. Ant thoughts on this?

ciao! 

[Bob & Sue 110]

Do you have some pics of the spark plugs? What did #4 look like oiled up, dry etc? Google " reading spark plugs ".

The only other test I know of would be a leak down test to determine what is causing the low compression.  It could be caused by several things rings, guides, burnt valve etc.

If your going to change the head gasket you'll find out what is wrong. The only time I've seen a blown head gasket leak oil it blew oil everywhere not a slow leak.

You say it stalls when hot how hot is it 210* F 240* F ?

Does it use any water or oil?

Maybe some others will have some other ideas.

 

[1969_Mach1 333]

There are no oil passages going through the head gasket.  For the oil leak, also check the back of the intake manifold.  Are you certain it's not a small amount of coolant seeping through the head gasket?  That is a possibility.  If the engine stalls in stop and go traffic and you have to let it cool to restart it could be fuel related, i.e. vapor lock, or an ignition issue, coil going bad.  Is the tune up and carburetor in good condition?

[Dave R. 85]

6 hours ago, 1969_Mach1 said:

There are no oil passages going through the head gasket.  For the oil leak, also check the back of the intake manifold.  Are you certain it's not a small amount of coolant seeping through the head gasket?  That is a possibility.  If the engine stalls in stop and go traffic and you have to let it cool to restart it could be fuel related, i.e. vapor lock, or an ignition issue, coil going bad.  Is the tune up and carburetor in good condition?

I've never had a 302 apart but doesn't the oil from the valve springs/rockers drain back through the head gasket?   Dave R.

[1969_Mach1 333]

That's a good thought, I didn't think of that when I made that post.  The oil from the rocker arms drains back into the valley below the intake manifold.  As best I remember last time my intake was off, the oil drain back did not go through a hole in the head gasket.

[unilec 57]

If its stalling in traffic it could be the carb is getting too hot, try a spacer it may solve that issue.

[signorc 31]

Thanks for all the discussion so far!

I've ordered a phenolic spacer so I hope the carb won't get as hot to make it stall.  The car has been tuned and I rebuilt the carb so all good there.  I was debating getting an aluminum intake manifold....but don't want to go to a 4 bbl.

Also, there's no gas tank vent hose on the car. Don't know if the pressure that builds up can screw up the gas flow to the carb and make it stall. 

The car doesn't stall cause of vapor lock (I've checked this).  

It stall around 210-220 but ONLY when idleing or in stop&go traffic.

Spark plug #4 is dry. but #1 & #3 are slightly oily.

I have to check if the leak in the back of the engine is oil from the manifold or coolant from the LH header.

[1969_Mach1 333]

For 1969, the gas tank is vented through the gas cap.  Make sure you have the correct gas cap on the tank and it vents correctly.

[Midlife 814]

An unvented gas tank can cause a car to stall out due to the fuel pump unable to overcome the vacuum induced in the tank.  How can you check for this condition?  Drive a bit, pull over, and remove the gas cap.  Do you hear a loud "whooosh"?  If not, then the tank is vented.

 

I'll bet you though that I was going to recommend after removing the gas cap to use a match to look inside and see what's going on, eh?  Nope...you need to use a Bic lighter for that.  *G*

[Bob & Sue 110]

Your oil returns passages in the block could be plugged on that side.

Like I said I've only seen oil come out of a head gasket after a run down the track 2 dead cylinders blew the gasket out, it can happen when you blow an engine.

I'd start by pulling the valve covers to see if the oil is returning to the pan.

The best test you could do now without tearing it apart is a leak down test to determine what is failing. Just google "engine leak down test" plenty of videos watch a few. At least you'll know what your dealing with.

Best of luck

Oh yeah propane torch would be quicker than a Bic Lighter.  NOOOOO

If your cap isn't ventilating there should be a pinhole relief valve thats plugged if it's the correct cap. My John Deere plugs up about every 2 years if I forget to blow the vent hole out. 

[Dave R. 85]

The '69 filler neck has a small notch on the rim of the neck where the cap gasket seals against the neck. I think the notch is located near the 12 o'clock position on the neck rim. That small notch is the vent for the tank. If the gasket is being forced into the notch, maybe the gasket is getting old and soft?, that might seal the notch closed. I think the '70 used a smooth neck and a vented cap.  This was just discussed a couple of weeks ago on one of the Mustang forums but I don't remember which one.   Dave R.

[signorc 31]

So, after a closer look and cleaning.....there's oil seeping from the back of the intake manifold cause there's oil there and leaks all the way down both sides of the heads to the block and oil pan, as well as under the distributor.  It's all cleaned up and now I gotta keep a good eye on it to see if it's only leaking from the intake manifold and/or somewhere else.  Right now it looks like whoever put the RTV on last time didn't put enough on the front & back in between the block and manifold.

FYI - I did look into the gas tank with a long reach Bic lighter which explains why I'm writing this post with my new best friend St. Peter here in heaven! lol

[1969_Mach1 333]

I suspected the intake leaking somewhere at the back might be the issue. If it's a stock cast iron intake manifold, when you replace the intake manifold gaskets the cork or rubber end seals that come with the gasket kit should work fine.  Just glue them to the block and use a dab of silicone in the corners where the end seals meet the gaskets at the cyl heads..  There are gasket glues but what's often used and works fine is 3M weatherstrip adhesive.  If it's an aftermarket intake manifold you should use a bead of silicone for the end seals instead of the cork or rubber end seals. 

[signorc 31]

Update! 

So after cleaning the oily substance from everywhere on the engine I've found out that it's leaking a small amount of oil (not antifreeze) from:  around the distributor & from the back of the engine.  Issue is I can't figure out if it's from the intake manifold or the RH header.  I've attached a pic to get your opinion. I think it's coming from the corner where the intake and the header meet but could be wrong.

Also, I need to order new brake pads (I have 1978 Granada spindles installed with a 1 piston caliper) and would like to know if anyone has a favorite brake pad and exact part number.  I'll be shipping them to Italy so don't want to make a mistake ordering them. I've attached a pic of the ones on my '69 now.

Thanks in advance for all your input!

[1969_Mach1 333]

That oil leak looks like its from the back of the intake manifold.  Now that it's cleaned some, drive it a bit and make certain its not a valve cover gasket before replacing the manifold gaskets.

For stock replacement brake pads I like Raybestos brand.  I don't have any part numbers for your application.  Keep in mind, anything with a semi metallic lining material will provide better braking but will create a high pitch squeak at some point in its life and usually also wears out the rotors.  Squeaks from semi metallic linings are more common in cold temperatures.

[signorc 31]

the leak is definitely not from the valve cover.  

Thanks for the Raybestos suggestion. Never gets below freezing here so I'll be ok :)

[1969_Mach1 333]

My fault, I wasn't clear regarding semi metallic brake lining and squeaks.  Some, not all, will squeak in cold weather for the first few brake applications until they warm up.  During hot summer months that doesn't seem to be an issue.  For me, I don't like it.  Others don't seem to mind it.

Raybestos might offer several different brake pads with different lining types for your applications.  Then it's just personal preference.  I drive fairly mild.  So I usually get something that is considered an OEM replacement.