Procedures for torquing manifolds
Group. I am getting immersion by fire on our first annual inspection. I helped my mechanic remove two cylinders for repair from our Franklin 165 and will help him reinstall then in a couple weeks. So here is my question regarding reassembly:
After the intake and exhaust manifold nuts have been assembled with new gaskets and torqued, is there a standard procedure for retorquing? Should the engine be ground run up, allowed to cool then retorqued?
Hi Bret; I will check the maintenance manual today, I doubt that there is a specific procedure, just don't overtighten.
I will get back to you later with more info. Glad to hear that you are learning more about the engine.
Thank you Jim:
I really enjoy working on the Franklin with the help of my mechanic.
It would seam to me that there would be a step to double check the torque after a run up. As I recall on some big industrial stationary engines and evenness some farm equipment there is some type of process.
Thank you for your help.
Hi Bret; Standard torque for intake and exhaust bolts and nuts; 60 to 75 inch lbs. I don't think there is a torque limit for the
type and volume of words used to install the manifolds. More important is the method and torque used to install the
cylinder hold down nuts.
Good luck Jim
Thank you Jim.
I hope whoever your mechanic is, had the Franklin manual and in installing the cylinders and the intake manifold that he followed the manual procedure exactly, which is to assemble the cylinders but not torque them or even tighten them. Then install the intake manifold WITHOUT gaskets and torque it tight. Then, torque the cylinders to spec and I like to install pal nuts as was originally done on the Franklins. Then, after the cylinders that have been removed are properly tightened, remove the intake manifold and install it with the gaskets. If your intake manifold has hex head retaining hardware, install the bolts with new star washers and torque as the manual says for the given bolt size and thread. When you install the mufflers on the exhaust ports, that is not important to do before the cylinders are tightened.
This procedure is because the cylinder hold down studs and the holes in the cylinder flange are not precisely located and if the procedure is not followed intake leaks will often occur because the intake manifold is very rigid and the only way to get a good fit is to let the cylinders move into alignment in the first tightening of the gasketless intake manifold. The exhaust pipes on the mufflers are somewhat flexible and they will fit up after the fact without problems.
The original intake manifold retaining screws on the F150 engines were socket head caps screws that were drilled for safety wire (they used lockwashers too) and after final torquing they were safety wired to each other and few if any problems were experienced later. Most 165s used the same length screws but they were hex head with a screw driver slot which made them a little easier to run up in the confined space, but some have had them loosen after a period of time, probably because they were not properly torqued to begin with or did not have new lockwashers. This whole procedure, done properly is pretty time consuming, as writing this is. The time factor is why many mechanics only experienced with Continentals and Lycomings often do not read the manual or don't follow it because of the time. This why I encourage owners to become more familiar with their Franklins than their mechanics, if the mechanics are only experienced on Conts and Lycs.
Larry Wheelock, A&P/IA working on Franklins for 48 years.
Larry; Thanks for the full procedure regarding cylinder and intake installation. This is the reason why I joined the club, to
access information from experienced members.
Many thanks for the guidance. I really appreciate your advice.
We will follow.
You are welcome.
But, it is all in the Franklin overhaul manual and everyone working on a Franklin should have one, read it and heed it. In fact, the FAA requires that the manuals be there and open when work is being performed.
Will do Larry.