Where are those block numbers?

[afgunn]

From what I have been able to read here the block number is under the intake manifold (in the valley) or inside the bell housing beneath the passenger side head. True or not? If true, then is there any other way to tell which block you have - without having to remove something major from the engine? I most likely have the questionable and infamous '506 block! And I already hear a knock (or diesel rattle - not sure - not a diesel head!!

[john8662]

I'd put some money on the table that you have a '506 block, it's pretty certain.

But, which '506, only tearing it down will identify for sure.

The cast numbers are "beaded" into the intake valley, so pulling the intake will reveal that. You can also see the number by getting to the back of the engine with a light and mirror on the driver's side and just looking at the number. Remember all you need are the last three to tell, the rest of a waste of your time.

We just don't like the '506 because it has the piston oil spray coolers. That modification has it's pro/con's the main con being, well, cracking.

J

[afgunn]

I am 99.99999% sure that it is the weak 506 block as well. Just want to make sure before I make a assumption and buy something that I do not need. I will try to take a look over the next 3 days on my time off to confirm this.

I think the knock I hear is a lifter - rattles rather loudly (with other rattles as well) when first started up and quiets down as the engine warms up at which point it sounds like a dull knock (very light at cruising speed) that varies with engine speed. The knock disappears completely under heavy throttle. Could this be the timing chain? Piston wrist pin? Or worse?

[Inspector]

It could be as simple as dripping injector. With fuel already in the cylinder when compression starts can cause what is called injector knock.
Denny

[afgunn]

Would a leaking injector sound quieter after the engine warms up and disappear under heavy throttle? I hope the answer is yes!

[DmaxMaverick]

Would a leaking injector sound quieter after the engine warms up and disappear under heavy throttle? I hope the answer is yes!

Yes. And that's usually the case. These engines very rarely have a knock that is either not normal, or isn't caused by a leaky injector. Abnormal knocks, excluding fuel knocks (injector), are usually the finally words uttered by the engine. They grenade quickly when they knock like a fading gasser.

[afgunn]

Is a leaky injector something that I should take care of immediately (or it may cause more severe damage) or can it wait until I rebuilt an engine ~ 1 year, I hope.

If I must replace the injectors now, can I use the high flow, high pop injectors that I want to use on my rebuild?

[DmaxMaverick]

Is a leaky injector something that I should take care of immediately (or it may cause more severe damage) or can it wait until I rebuilt an engine ~ 1 year, I hope.

If I must replace the injectors now, can I use the high flow, high pop injectors that I want to use on my rebuild?

You shouldn't wait any longer than you absolutely have to for the injector. A leaky injector can burn up a piston over time. It can also cause an imbalance with the combustion event, which introduces damaging harmonics into the powertrain.

You can use any injector. If your IP is healthy, it will pop them. The drawback with mis-matched components is economy loss, uncertain EGT's, noise, and possible starting issues (unlikely with a healthy LP and glow system). Theoretically, high pop injectors should provide more efficient combustion, but the timing is more critical. Generally, the purpose of high pops is to allow you to inject a higher volume of fuel in a shorter duration, and/or a more atomized spray pattern. Beware of "shimmed" high pop injectors (read Ebay special). The correct "marine high pop" injectors will have the correct spring and shim, rather than just increasing the preload on an OEM spring with shims, like the old shade tree trick to keep valves from floating in the old SBC/BBC (worked good until valve stems shot through the valve cover). Unless you are intending a rebuild designed for the high end of the HP scale, HP injectors are not recommended.

[afgunn]

I agree, Dmax, I was thinking of this today. If the leaky injectors are causing a pre-combustion knock then this could lead to worse problems for sure. Still not used to thinking in DIESEL.

Seems if I have one or several leaky injectors then, to keep the system balanced, I should change all 8 at one time. Also, for me at least, it would be hard to find the 1 or 2 injectors that are leaking. I am thinking of using a quality brand of high flow, high pop so, I will not need to buy another 8 when I do my 300HP rebuild. At that time, I am planning to have the IP rebuilt as well because of the miles, to have the latest improvements and for the ULSD.

Thanks much for all the help guys! It is very, very helpful!

[JohnC]

Finding the leaky injectors is easy. If you have a scanner, use the cylinder balance test to turn off the individual cylinders one at a time. Otherwise, loosen the B-nuts on the injector lines one at a time to stop that cylinder from firing.

[afgunn]

I do not have a scanner but, I can loosen the nuts (letting the fuel leak I assume) to find the faulty injector(s). Thanks John, good call!

[JohnC]

I can loosen the nuts (letting the fuel leak I assume)

Yes. It won't be much at idle. It keeps the injector from building enough pressure to "pop".

[afgunn]

An update. I started using a Performance Formula fuel additive as recommended on this site for the coming ULSD. At least until we know if the ULSD lubrication is adequate for the older engines like mine. The engine is running much better and much quieter. Usually the light knock is totally gone and only barely audible at worse. So, I think I have bought a little time and maybe the fuel additive will clean the leaking injector(s) so, I can wait until the rebuild to replace all 8.

Thanks again for all the help!