To start things off, I have a 97 F150 with the 4.6 Romeo engine. I had rebuilt this engine about 20k miles ago when a head cracked and was leaking coolant. All pistons and bores were good so rebuilt with the original pistons/rods. Ended up the head was over torqued on the front intake manifold bolt where the thermostat is...caused it to crack. But regardless, the engine didnt burn oil. After the rebuild it had a slight burn and progressed. At startup I would ave a cloud of smoke covering the truck, then 5 min later it would calm down and just smoke when revved or over 3k rpm. This past week I had to rebuild my top end due to a oil pump failure. So I installed a ford racing pump and replaced the damaged heads. because of the oil burn I inspected the bores and there was zero scoring, I was expecting to see evidence of a damaged ring. So I checked the bottom end, and it was good. After the top end rebuild was done it seems the oil burn is back and is worse now. Rings seem good, compression check was within 3 PSI of every cylinder, new rebuilt heads, new motorcraft pcv. I cant find this burn. Its about 1qt every 100 miles. Please help me out.

 

Looks like i have to the one to say this. You obviously have problems rebuilding these engines I suggest you stop doing it. Get yourself a nice used motor one that ford built they know how to do it right. The modular is a complex engine not many can build them right so dont feel bad. Just find a low miles use one and you'll be good.

 

2 sets of head in 20k miles. Same person rebuild the heads both times??
Was the block surface checked? For each rebuild..

That bolt must have been waaaayyy over torqued to crack the head. If thats possible. I think its only 18inch/lb

 

Check that the oil fill cap has an O ring. Also make sure that the pcv baffle is in place directly under the cam cover beneath the PCV valve. If this is missing or damaged the oil from the valve train will shoot up directly into the PCV and generate excessive oil consumption. Make sure you are not overfilling the crankcase. To much oil will generate high oil consumption as well. Did you inspect all bores down to the bottom of the bore? A wrist pin that moves to the edge of a piston (usually rearward) can wear a groove in the bore and you will get oil consumption bigtime.

 

Heads were rebuilt buy a local head shop. Bores were all good, one was a little werry, but it was within ford specs. This isnt my 1st rodeo jethat, I have a 5.0 and a 4.6 cobra I rebuilt and they are running perfect. I am also a mechanic for the USAF for 9 years, anywhere from gas, diesel, to turbine engines witch are far more complex than a 4.6 . So im not doubting myself nor do intend to stop. Ill inspect the PCV system tonight, that is about the only thing that makes scene. I went through the set of heads due to an oil pump failure, I hope the new FR one will treat me well.

 

When you had the heads off did any of the pistons or valves have the appearance of excessive oil burning,thick black deposits etc. If you could narrow the consumption down to one or two cyls it would be a good start. Do any of the sparkplugs look oil soaked or black from possible oil? Another possibility is that one or more piston rings were installed upside down. By now your sparkplugs should give you an indication of which cyl/cyls are giving you grief. A head gasket oil leak would usually migrate to the outside as the gasket bore fire ring is the highest area of head gasket to block compression. I doubt the oil would compromise that area and get into the cyl bore. Has to be a ring bore issue or cracked cyl head pushing oil into a bore. Again check your plugs for any indication of oil. Take care.

 

Yeah, I think your right. I has to be a ring. I check the PCV system, and it all looked good. I guess thats my weekend project. #1 and #8 had slight signs of burning.

 

After a teardown, I found the #8 piston had a crack in it. Having Summit Racing so close is a blessing and a curse. This time a blessing The engine is rebuilt with 10 over pistons and is running perfect. Thanks for your help everyone.

 

Sounds like you all know. Installing pistons in 4.6 romeo with no notch on top have R on one side of piston. Does this mean R towards the rear when installing the piston into
the cylinder?