View Full Version : c-85 stroker conversion

01-21-2022, 03:47 PM
Iím building up a Stroker conversion for my J-3 with a 65. I found a C-85 certified engine and have started building up the Stroker. I have had the case and camshaft inspected as well as the lifters by Central Cylinder in Omaha. I had a serviceable O-200 crank 0-200 rods also inspected. Putting it together all proceeded well. Case was closed and everything rotated well without problem. I When I put the cylinders on and rotated the engine on the engine stand there was interference at number one cylinder between the piston rod cap and the camshaft between the lobes. I havenít found any reference in the threads I have searched to this problem. I called aircraft specialists and they werenít helpful. I called Dons dream machine and they were not very helpful since I didnít buy their STC. Has anyone had this problem? All the rod bolts are new. What is the solution?

01-21-2022, 06:28 PM
We're all the cylinders on when you tried to rotate it? If the rods were not in a cylinder they would be out of alignment and the caps would hit


01-21-2022, 07:25 PM
Before I put the cylinders on there was not a problem that I noticed. The overhaul manual said to rotate and check which I did. The interference was noted AFTER I put the cylinders on. When I pulled the number one cylinder and have noted witness marks on rod cap and rod bolt, in the grease I put on it. I haven’t felt any interference of the other cylinders as I rotated the engine. The rod bolts are new and rods are the correct part number. Would it be appropriate to take the rod and bolt out and file down the small contact area as well as the bolt head? Has anyone seen this before?

01-21-2022, 09:00 PM
Rods in proper orientation - flat up? Proper bearing inserts for each journal? Proper rod bolts and length/head size shape? Just some quick thoughts. What STC and why no support from them?

Gary - not an A&P just the $ guy

01-21-2022, 10:15 PM
Rod caps placed per the overhaul manual (not clearly written but consulted A&P with experience in C-85 and O-200 rebuilds) . Rod bolts were correct part number as were the piston rods. I didn’t measure the rod bolts as they were new. There were witness marks on the rodcap, I put some lubriplate on cam shaft to see what rubbed. The STC came from Aircraft Specialities in Tulsa. I called them earlier this week and the guy I talked to had not heard of this problem but he said he would check with his coworker and get back to me. Haven’t heard anything back.
I haven’t found any interference on any other rod.

01-22-2022, 09:55 AM
weigh all the rod caps to the gram and see what you come up with.

01-22-2022, 10:16 AM
Removed, didnít read last post.

01-22-2022, 08:17 PM
Is the cam timed to the crank? Gears installed?


01-23-2022, 07:57 AM
If it's hitting between lobes timing shouldn't matter.

brown bear
01-23-2022, 08:54 AM
switch the rod that is hitting to another hole and see if it still hits

01-23-2022, 09:23 AM
Take it for what it's worth because I am going back 45 yrs. The 85-8 stroker that was in my J-3 had a small place machined out of the inside of the case for rod clearance when it was converted. Wish I could recall more, but it's been too long. Hope this doesn't muddy the water's.