New 408 engine started rattling -what to do?

[matt63]

After a nice long cruise the engine started clattering.  So much for tuning. At first I thought it might be a bad rod bearing, piston pin, etc.  I pulled over and listened to it but it was hard to pinpoint where the sound was coming from.  I took a walk to think about.  The oil pressure was the same so I decided to idle it home.  It started smoking bad from the tailpipes.  I pulled the plugs and found #5 was covered in oil. #6 was much cleaner than the rest and the porcelain was very white while the others were brown??.  I pulled the valve covers and found that #7 intake rocker was sideways (stud mounted rockers - Edelbrock Magnum heads)  The locknut was almost completely off.  I guess that the valve was not opening and that the lifter was probably bouncing around on the cam.  I can't see the cam so I'll probably pull the intake to have a look.  I'll replace the stud and locknut just to be safe.  The only thing that leaves me scratching my head is why the engine started smoking so bad.  Would it draw oil down the valve guide if the intake valve was opening?

[Chryco Psycho]

Ahh the joys of ball stud rockers , shaft are so much more reliable
anyway the only place the burnt fuel in the cylinder could go is back into the intake so the smoke was caused by misfiring from the polluted intake

[matt63]

That makes sense.  Also, I pad $78 for intake gaskets as FelPro doesn't seem to make them for the Magnum.  They come with molded front and rear gaskets.  I was wondering if they would work if I cut off the locating "nibs".  Ay idea?

[Chryco Psycho]

I have not tried doing that

[matt63]

I'll guinea pig it then!

[daves70]

Good luck!!!

[matt63]

The head gasket now leaks badly.  I should of gone with the Cometic MLS gasket but didn't realize how short a life the std ring type composite gaskets could last.

[moper]

If it went away that fast. Its not the gasket's fault. Did you retorq the heads after a few heat cycles? This is necessary, tho not frequently spoken about. The MLS gaskets need a very fine finish. The heads may have it altho the factory finish on them is almost too rough out of the box. The block doesnt unless you told them you needed it. Seeing as there are issues with things loosening up, it may be worth your time to take a lap with a torque wrench. You'll need to get under the headers and stuff, but I'll wager you find a lot of the head bolts are coming loose.

[matt63]

I didn't retorque them.  The engine is coming apart as the gasket is probably shot now and new MLS gaskets are coming my way.  As soon as I can get the headers to drop another inch or two I'll remove the head bolts and we'll see if they are loose.  If I remember correctly the surface finishes are pretty good although I might get the heads checked again for flatness and the engine shop can tell me if they are good enough for the MLS gaskets.  The block was decked last fall.

[daves70]

I didn't retorque them.  The engine is coming apart as the gasket is probably shot now and new MLS gaskets are coming my way.  As soon as I can get the headers to drop another inch or two I'll remove the head bolts and we'll see if they are loose.  If I remember correctly the surface finishes are pretty good although I might get the heads checked again for flatness and the engine shop can tell me if they are good enough for the MLS gaskets.  The block was decked last fall.

[moper]

I'm sure they are flat. MLS needs better than flat. They need a very smooth Ra value. The manufacturer of the gasket can tell you how smooth. They arent all the same. If the block was decked as a typical HP rebuild, it probably has too rough a surface for them. Just an FYI..Also, in some circumstances, the MLS may seap slightly until heat cycled a few times, and they will DEFINATELY need to have the torque checked after.

[matt63]

According to Cometic they do not need to be retorqued.

[matt63]

I now realize that my block will have to be resurfaced to get the 50 Ra surface finish.  I'll have to get moving if I want to drive this again before winter.