FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: BigBlueIron on September 30, 2019, 11:21:32 AM
-
This is relation to an old engine not a fresh rebuild. I have, be it a waste of time or maybe even the wrong thing to do re-torqued heads on old engines. Method I use, take bolt out clean threads blow out with air and maybe even run a tap down the hole if nasty, light coat of oil on threads and pull to spec in one swing. Do this on each bolt in order. Intake removed.
I had to pull a head bolt for some reason I cant remember and reinstall, when I did I noted the position of the head and it ended up about 15* or so past where it was (tighter). So I did them all, this was on a junkyard 390 that has been nothing but abused since. I also did this recently on a Cleveland and got maybe 5* this engine had a "recent" rebuild.
Anyone else ever do this? Should I quit doing it? I can't see what it would hurt, obviously the gaskets have relaxed a little over the years and I feel this is bringing the clamp load back where it should be.
Just wondering what peoples thoughts where on the matter.
-
By using a three step torque method you can insure the bolt threads and the block threads "fit" each other.
-
I personally would not run a tap down each hole without being able to flush and blow them out completely. The threads are 3 - 4 inches down the clearance hole so it would be difficult to ensure that all the dirt was removed without removing the head. I would not want to risk any chips or dirt being left behind or finding their way into other parts of the engine. If I were to re-torque, I would simply set the torque wrench to the final torque setting and re-torque them in the proper sequence without removing any bolts.
-
I don't go back and re-torque head bolts, never saw the need if done correctly in the first place. As noted, if I did it would be to set the wrench at the final setting and test. Would not remove anything - why, that's just make-work. Also, just for full disclosure, I never use head bolts anymore. I prefer studs. On anything I can get, everywhere I can fit. Even the cheap, tiny. chinese 72cc engine I'm working on uses studs to retain the head.
Also - you clean the threads before final assembly and you would use a clean out tap, not a regular tap that is meant to cut threads. Using a full thread tap can weaken the existing threads by removing material.
-
On brand new engines, I always retorque head bolts/studs. First pass, I do in 3 steps to full torque. Second pass, I loosen one fastener at a time, then pull full torque in one swing.