I dont post much here but read every single thread in this section of the forum, learning something each day and i first want to thank all you guys for your time and advice.

I have a 86 f350 dually, 6.9 litre. has an issue with the head gaskets leaking coolant from the corners, doesnt mix with oil or combustion, just trickles out the corner of the heads. i replaced the original fuel water seperator with a spin on seperator , napa base and filter that bolted to the original place on the firewall. other than this its the only issue other than having to replace every rubber item on the truck from front to rear. this truck was put in a pole barn and tarped 12 years ago and didnt see the light of day till i uncovered it a few months ago so dry rot was everywhere !! but the a/c still had pressure in it..woo hoo !! anyway here is my dilema , i have a 7.3 IDI i was told it was a year model 91. dont know this for sure but it looks real clean and well taken care of. dont know the miles it has on it just that when it was given to me they said it used oil. got me where just yet, could be leaking it or burning it but was told it used 5 quarts of oil between 3000 mile changes. the 6.9 has 48,000 miles on it and it seems just about every gasket needs to be changed as well as the oil cooler rebuilt ( i see moisture coming from where the orings i guess would seal the tube to the end caps, doesnt really leak any but i see a problem coming) so i just want to pull it and replace everything so i dont have to worry about it. not talking a rebiuld but from oil pan to valve covers replace all the gaskets. but should i just use the 7.3 ? All i know the difference is between them is bore size , 5 hp and the 6.9 would have a stronger cylinder and less likely to have cavitation problems. freshen the 69 ? or rebiuld if it needs it the 7.3 ? what would you guys do ? my feeling is to stay with the 6.9 , tear the 7.3 down and rebuild and save it but i wanted to hear what you guys thought.

http://i19.photobucket.com/albums/b153/eman28/f350seperator.jpg
http://i19.photobucket.com/albums/b153/eman28/f350motor.jpg
http://i19.photobucket.com/albums/b153/eman28/f350.jpg

 

My opinion is the 6.9 is a better engine, which is rebuildable.

The 7.3 is also a fine engine, but not rebuildable in my book.

 

If the 6.9 has only 48000 miles on it, it is a known quantity - whereas the 7.3 is a totally unknown quantity.

I'd do the gasket job on the 6.9 if it were me. Like Dave said, it is a very rebuildable block, whereas the 7.3 is much less so.

 

Pull the 6.9. bolt it to an engine stand, and replace all the gaskets. Before you bolt the valve covers on, swap the 7.3 rocker arms onto your 6.9.

Re install the engine, and be ready for hundred of thousands of miles from it!

 

thanks guys, i didnt realize that the 7.3 wasnt really rebuildable. but my gut said same thing you guys are telling me so i guess ill just find a home for the 7.3 doubt if ill ever use it and would take too much space up in my shop. freshen up the 6.9 and drive worry free. hey fonefiddy, why the rocker change ?

thanks again guys

 

Nice truck madriver . You should get the head gasket fixed sooner rather than later, the high compression in diesels is such that it will erode the head and block around the area if the fire ring if you leave it for too long. This will make it hard for the new gasket to make an effective seal, especially once the turbo goes in.......

 

The 6.9 rockers were made of white metal, with a steel pivot point, they are very prone to wear. The newer 7.3 rockers are a much better design.

 

thanks fonefiddy and david, this is why i like this place . did not know the rockers were different. and david ive seen that first hand, we have a truck fleet of 42 trucks, all volvo's. half of them with cummins N14's i would say, and have changed a few headgaskets that were leaking compression to find the same thing, i think due to design it seems not to hurt the block but liner top and head sometimes. i have yet to change a volvo engines head gasket due to leaks, they just throw the rod out the side

ive read that it is not uncommon for head gaskets to leak there do to design and the new gaskets will have a rubber oring around that gallery. do they still have a possibilty of a leak after the change ? ill also be putting arp studs in as well. who has the better gasket ? i have always used fel-pro for my stuff, still a good idea for this engine ?

 

Felpro is supposedly the standard for head gaskets. My 6.9 had them and those gaskets fought long and hard against my abuse, The fire ring was basically pushed back slightly until compression gasses finally dug around it.. Using ARP studs is a good plan too, the 6.9 bolts are weak.

The gaskets I pulled out did have a rubber insert at the cooling passage at each end of the block if thats what you mean??

 

i was under the impression the factory gaskets did not have a rubber insert at the cooling gallery and the new did ? and that the original head bolts didnt do the job of holding very well. the two added up to the leak in many of those motors. but this is all from reading here and there

 

Early versions of the 6.9 did have head gasket problems, and the newer gaskets are much better, but I don't know what differences there are compared to the old ones. The head bolts will probably do well enough for a non turbo, but if you ever want to add a turbo later on, you know that it is less likely to have problems.

 

The rubber inserts were added, taken out, added at least twice that I know of.
Fel Pro gaskets will do a fine job.
ARP head studs will give you more trouble free miles out of the engine.
7.3 rockers are a better design.
7.3 exhaust valves are made out of a better alloy.

86 and 87 was the best years for the 6.9

 

thanks for the info dave and all others who have posted. sticking witht he 6.9 and regasket her. while i have the engine out is there anything else you guys can think of i need to do? upgrade this or add this to that 6.9 ? dont think ill ever turbo it but.... ill put a new heating element while i have easy access

 

I would definately go with new returnline kit and check gp's for swelling. maybe even reseal oilcooler while it is out.

 

yeah good idea starmilt, i have all the oil cooler parts, i had seen some moisture coming fron the rear cap where it goes onto the tube. wasnt leaking but moist so i had ran to ford to get all those last week. i have the return line kit but hadnt put it on yet, eveything rubber item on this truck needed replaced when i got it out of the barn but i hadnt changed it out yet once i noticed the head gasket seeping coolant down the block and the cooler. figured i was going to pull the engine to fix everything at one time. or redo the 7.3 and swap but ive tossed that idea out . stopped in the ih dealer and ordered a new thermostat, should have it early next week. from the looks of it would be easier when its out than to mess with it in, way i see it take the belt off the alternator and vacum pump. remove vacum pump and set aside and take the bolts holding the bracket for the fule filter and alternator, move out fo the way and remove thermo housing. i think it could be done this way or change it when the engine is out !!

oh does anybody have a paint code for the engine color ?