Engine Rebuild on' 73 302 Coupe

[danumkc]

White smoke and Very low compression (10 psi) in cylinder #5 after only a few hundred miles of owning it.  Bummer! 

A reputable machinist is going to rebuild the heads and assist with the head gaskets etc.  We are not planning to go below the heads to do any additional work.

My question is would you recommend doing the extra work to change the timing chain (to a double roller), water pump, and possibly the cam and lifters.  The reason I mentioned the cam is that is a Comp cam currently, but I find it the idle rough.  I am a little concerned the cam contributed to my engine problem. The previous owner did the engine work 3-5 or so years ago and I am not sure what else has been done to the engine besides an aftermarket intake and carb and how many miles have been put on the car since the last engine work was done. I would love to start with a clean slate so I don't need to redo anything engine-wise for a long time.

I am also thinking about pulling off the oil pan to clean it and replace the oil pump.  I imagine it would be okay to do the under at a separate time.

Would you recommend replacing anything else in that area while the heads off?

Unrelated, but I am also replacing all of the fuel components (a few tank leak), headers, and exhaust (exhaust leaks) at the same time.

 

[Don C]

What engine upgrades?

I would wait until the heads are off and inspected, and the cylinder bores are inspected before making any decisions. The condition of the heads and lifter valley (sludge buildup) will help make the decision on what needs to be done. You can also see at that time what the timing chain is, hard to imagine someone putting in a cam and not upgrading the timing set. What you thought was cam making the engine lopey may have been burned valves, recessed valve seats, or head gasket.

 

[danumkc]

What engine upgrades?

I would wait until the heads are off and inspected, and the cylinder bores are inspected before making any decisions. The condition of the heads and lifter valley (sludge buildup) will help make the decision on what needs to be done. You can also see at that time what the timing chain is, hard to imagine someone putting in a cam and not upgrading the timing set. What you thought was cam making the engine lopey may have been burned valves, recessed valve seats, or head gasket.

Thank you so much, Don. 

Would you remove and clean the oil pan and replace the oil pump at the same time or could that be done at anytime? I am a little nervous there is sludge or metal shaving of some kind in the pan, and would like to start with a clean slate.

 

[73pony]

If you are pulling heads etc and considering a cam swap I would pull the motor, mount it on the stand and begin disassembly and inspection. Dropping the oil pan and changing oil pump with the engine in the car is a PITA, so is removing and installing heads. Should only be a couple hours of work to pull the motor. This will also allow you to check bearing clearances on the main etc.

 

[jowens1126]

I agree with 73pony here.

If you remove the heads, go ahead and pull the motor. 302's leak like a sieve anyway, so it will need all of the other gaskets changed at a minimum. Personally, I would take the whole engine to the machine shop and have them go thru the motor and see what they find. Your loss of compression could be a valve seat problem, but it could also have worn rings to go with it. Since your going that far, its not that much more trouble to pull the whole motor and let them go thru it. Put all new bearings in it, line bore the crank bores, resize the rods, polish the crank, check piston bores and repair as needed. If you want more power, get a 347 stroker kit for it. That is if you have sufficient budget to do all that.

 

[Don C]

Personally I would just pull the engine to start with, much easier than trying to do a piece at a time. It takes longer to pull the oil pan with the engine in the car than it takes to pull the engine and transmission. Then, it's easy to pull the pan and oil pump, change timing set, check bearing condition, and so on. If you do have metal filings in the pan it's likely cylinder walls are scatched and the bearings and crankshaft have also suffered damage. Anything that happens in the top of the engine drains down onto the bearings and crankshaft.