Did a compression test

[crazy_canadian]

Saturday I was bored after my oil change and I decided to pull the front plugs, since the back ones are hard to remove, and I didn't wanted to pull the intake, plus the firewall is all messy from the rustproofing grease.

So all front plugs looked fine, no oil in wells. White plugs (Motorcraft platinium) with accel wire. Compression checked at 160psi on each one. I assume the rear bank should look the same.
Problem is, the car is Slowwwwwwwwwwww. O2s aren't old, so is the timming belt. My injectors are noisey and I can hear my rod bearing knock a very little bit on cold startup. (to be fixed soon)
I have a weak motor mount in the front. This is a non-egr and non-cats car.

I just have no clue where to start from, or should I just start working on rebuilting one of those 3.0Ls I have laying around in the sister's garage.

 

[SLoW_SHO_316]

Start by cleaning your MAF sensor

 

[F-22 Raptor SHO]

did you run that compression check when the engine was cold? If so the numbers will read lower.

fix what is running, its alot less work. cold start up knocking on the bearings is normal for my 3 sho's....all have new bearings...understand the tolerances on the bearings is low 0.003..you are trying to pump oil thru that on cold mornings.

 

[dantheman68]

check the back cylinders anyway (atleast do it with the eec).. my buddy had a rod knock, and it turned out one of his pistons was cracked (we found this after we parted the car out) i always thought it was slow too, and figured that the plugs/wires were bad... we didnt think the piston was cracked... matter of fact the PO said that it was a transplanted motor with less than 70k on it... BS

 

[clintonk]

Try running a cylinder balance test.

 

[TT SHO PROJECT]

So all front plugs looked fine, no oil in wells. White plugs (Motorcraft platinium) QUOTE]
white plugs??? as in what? whats white? if yer checking plugs and the electroid is white then u have a fuel problem... white=running way lean.

 

[crazy_canadian]

I'll snap a pic of my plug tomorrow, but what color they should be ?

 

[Storm-Chaser]

....

fix what is running, its alot less work. cold start up knocking on the bearings is normal for my 3 sho's....all have new bearings...understand the tolerances on the bearings is low 0.003..you are trying to pump oil thru that on cold mornings.

Where did you read this?

If this were true, the new "tight" engines would be more suseptable to bearing knock than high-mileage "loose" engines. And what's to say the noise is not from wrist-pin slap or piston-skirt slap? I've even heard some exhaust gasket leaks that sounded suspiciously like a bearing knock.

This is the reason for multi-viscousity oils - even among synthetics. A 10W30 oil exhibits the characterists of a 10-weight oil when cold, and 30-weight oil when hot. This allows good flow characteristics when cold, and high-viscosity protection when hot. It is done through the addition of chemical additives, which reduce the amount of shearing at the molecular level as oil temperature increases (basically it's a modified 10-weight oil). This concept was further enhanced with the development of synthetic oil.

One of the engine-building tricks in drag racing applications was to build the engine "loose", that is during blueprinting process to set tolerances on the high-end of the acceptable range. This allowed running higher-weight straight-weight oils at higher oil pressures to protect the bearings during high-rpm operation. Of course this was before synthetics became common and manufacturers began shifting to lighter weight synthetics and even tighter bearing tolerances that reduces friction and results in incremental increases in mileage.

The general rule of thumb was to use 0.001 of bearing clearance for every 1" of rod/main bearing journal diameter. Due to the tighter tolerances used in the blueprinting process, "loose" high-precision tolerances combined with balancing allows the engine to rap faster, due to the reduction of fluid friction and out-of-balance harmonics (among other beneficial results).

New bearings will not "stop" bearing knock in many cases depending on the extent of damage before the change. Wear occurs at both the bearing *and* journal surface (slower in the latter), not to mention that over time oil pumps loose efficiency (ie. pump lower volumes at reduced pressure). In extreme cases bearings will spin in a matter of seconds if journal damage was bad enough and only the bearings are changed. Damage to the journal surface often results in grooves which serve to channel the oil inspite of the smoothness of the new bearing surface.

 

[Storm-Chaser]

I'll snap a pic of my plug tomorrow, but what color they should be ?

Cylinder balance is based upon firing/mis-firing, not compression, but still should be run to see if you have a plug that is not firing.

Almost any parts store should have some product literature that will include a picture-chart of the various plug-colors associated with the various types of ignition problems (eg. tan = good / white = lean / black = rich / wet black = oil in the cylinder / these are generalizations of course).

Take the plugs with you, in case they only have one "reference" plug identification chart.

 

[crazy_canadian]

I know how to check a plug with a 2 stroke engine, so I'm a bit lost here.

And IF i do run lean, where, or more How can I read the fuel pressure ? I don't have any special tools here.

 

[F-22 Raptor SHO]

Where did you read this?

If this were true, the new "tight" engines would be more suseptable to bearing knock than high-mileage "loose" engines. And what's to say the noise is not from wrist-pin slap or piston-skirt slap? I've even heard some exhaust gasket leaks that sounded suspiciously like a bearing knock.

This is the reason for multi-viscousity oils - even among synthetics. A 10W30 oil exhibits the characterists of a 10-weight oil when cold, and 30-weight oil when hot. This allows good flow characteristics when cold, and high-viscosity protection when hot. It is done through the addition of chemical additives, which reduce the amount of shearing at the molecular level as oil temperature increases (basically it's a modified 10-weight oil). This concept was further enhanced with the development of synthetic oil.

One of the engine-building tricks in drag racing applications was to build the engine "loose", that is during blueprinting process to set tolerances on the high-end of the acceptable range. This allowed running higher-weight straight-weight oils at higher oil pressures to protect the bearings during high-rpm operation. Of course this was before synthetics became common and manufacturers began shifting to lighter weight synthetics and even tighter bearing tolerances that reduces friction and results in incremental increases in mileage.

The general rule of thumb was to use 0.001 of bearing clearance for every 1" of rod/main bearing journal diameter. Due to the tighter tolerances used in the blueprinting process, "loose" high-precision tolerances combined with balancing allows the engine to rap faster, due to the reduction of fluid friction and out-of-balance harmonics (among other beneficial results).

New bearings will not "stop" bearing knock in many cases depending on the extent of damage before the change. Wear occurs at both the bearing *and* journal surface (slower in the latter), not to mention that over time oil pumps loose efficiency (ie. pump lower volumes at reduced pressure). In extreme cases bearings will spin in a matter of seconds if journal damage was bad enough and only the bearings are changed. Damage to the journal surface often results in grooves which serve to channel the oil inspite of the smoothness of the new bearing surface.

Didn't "read" it any where. I've got 3 that have done this. You start up a cold sho motor with ambient temperatures in the 10 to 20 deg F and you will hear a slight knocking noise under initial mild acceleration. Lasts for a very short time and is barely noticeable, but its there.

 

[thecrew2999]

forget the slight engine knock best bet to do is what i do. since when you give the pedal WOT during starting i turns off the injectors as if the engine was flooded. just floor it let it crank for a few then take your foot off and let it start normally so the engine is well oiled before it gets pushed under stress and no oil condtions.

start up is one of the hardest thing on a engine so why not help it out some?

 

[Storm-Chaser]

Didn't "read" it any where. I've got 3 that have done this. You start up a cold sho motor with ambient temperatures in the 10 to 20 deg F and you will hear a slight knocking noise under initial mild acceleration. Lasts for a very short time and is barely noticeable, but its there.

That sounds more like piston-slap - that's why changing the bearings didn't eliminate it - and why it is only present the first few minutes as the internal engine components come to normal operating temperature and reduce the excess tolerance gap. A true rod bearing knock should be more a function of engine load (primarily rpm).

There is one test that may help you eliminate that it is a rod bearing knock. While the knock is present, short-out the plug wires one at a time and listen whether knock continues or is reduced/eliminated.

Rod bearing knock results from the connecting rod bearing smacking the crankshaft journal when combustion rapidly forces the piston assembly downward and the oil film layer is not strong enough to prevent shearing of the film layer due to insuffcient oil pressure (whew!). Shorting a plug-wire removes spark from that cylinder. When the plug does not fire, the explosive force of the compression stroke is absent, and the force behind the downward movement of the piston assembly is reduced to the point that the oil film layer is sufficient to protect the journal surface.

 

[SeanMc]

On cold morning, I have a hard start and a slight knock that goes away after a few revolutions. Piston slap? Hmm. I had that when my motor blew and it was very loud.

 

[Storm-Chaser]

On cold morning, I have a hard start and a slight knock that goes away after a few revolutions. Piston slap? Hmm. I had that when my motor blew and it was very loud.

If it is a bearing, those characteristics are usually associated with a main bearing knock. But remember, these are simple generalizations. Why didn't you take it to a shop?