Working on a 310Q S/N 1156 here in the shop. It’s a Colemill conversion done many years ago to install the IO-520. The left forward engine shock mount was distorted and sagging on each engine. I removed the mounts and replaced with new Lord units. The new mounts were pulled out of place when torqued. The right forward and rear mounts appear fine but the left forward upper mount needs to be pulled downward to the point I think the inner tube spacer will hit the outside of the mount cone. I tried a 1/4” cessna spacer above the Lord mount to the mount leg on the left mount and this helped reduce the distortion.

The problem is previously the mount attach bracket to the engine mount beam was wearing against the intake tube. Now it’s basically touching but oddly only on the left front mount for each engine. The other three are fine.

I believe there is a difference in the mount location from the old 470VO and the 520 rear alternator. Interestingly a call to Mike Jones / Colemill they said it’s an old STC and has been this way forever The engine they spec to order from Continental has totally different legs. I had Continental tech support send me a drawing copy to compare. Called back to Jones and he verified they reuse the VO mount legs. I asked about shimming or different mount and basically was told It’s been this way forever and if you change you violate the STC. Thanks a lot. The other thing I notice is the 520 case studs for the mount legs to attach are long enough to hit the top of the shock mounts.

I don’t see where any mount beams have been replaced on this airplane or gear up landings that would have bent something. It’s also odd it’s exactly the same left and right engine. But it can’t be correct as is and I don’t see any parts replacement that would help.

Any other Colemill owners out there notice a similar problem?

Hi Charlie,

If you could send some pictures, it would help.

Thanks,
VW

Working on it I don’t have a good photo hosting site to link to. I’ll see if the kids know how.

Anyway the main trouble is the left intake pipe hits the engine mount support which rises vertically off the engine mount beam

This is a known issue with all 310's and especiallly Colemil Converted ones. The engine mount case studs can be changed (recommended) to the shorter lenghts that the VO engine cases use if clearance is a problem. Mine were very close to touching the mount washers so I slightly beveled the stud to give it some extra clearance. Didn't need much because it is on the side of the mount that will not compress.

The front engine mount rubber isolator, and most noticebly the left one, tend to distort after a while but they also do this with the IO-470-VO's but not as quickly.

I intend to change my front mounts every 250 hours on my recently Colemil converted IO-550 310Q.

Thanks. The old left front mounts were distorted but I noticed after installing the new mounts they were also distorted and the intake tube was hard against the mount beam leg. I installed a 1/4” cessna mount shim on the opposite mount right front That appears to have made the fit better. I have clearance from the intake tubes to each vertical mount leg. I checked and the studs are very close to the inboard mount washers but not holding them away from the engine mount leg