Looks like I will be sending my engine in for an unexpected overhaul. On my last flight my oil pressure dropped to 1/2 of normal so I returned to my home airport. As it turns out I flew back 7 minutes with a broken crankshaft. No vibration, all indications normal except for oil pressure. With that said I was wondering if there are any firewall upgrades available for a Maule M4-220. Not sure if titanium is a possible option. My current firewall will work but has many holes drilled and could be cleaner. Didnt see any previous posts on the subject. Thanks.

Interesting, what was your oil pressure?

Interesting…I have a PZL Franklin 220. About 5 years ago I was flying and noticed my oil pressure drop to about 45 lbs. Other than that no change in the way the engine was running except the prop pitch. I was about 45 minutes into a two hour flight. I decided to turn around and go back home. Flew it back with no issues except low oil pressure. Turned out the crankshaft was broke completely in half.

Is yours a PZL?

My engine is not a PZL. Its an original Franklin off my 1971 M4-220. The engine has 3600 hours on it and about 1000 hours since overhaul 21 years ago. The oil pressure dropped to 29 psi and then dropped down to about 11 psi when I pulled the power back. Since I will be down for 3 or 4 months i would upgrade my firewall if it is a possibility.

I had a crankshaft on my Franklin break also. ( Do you see a pattern here? ) Mine didn't keep running. Luckily I was still a half hour from crossing the Rockies. That was the third time I had to walk home when flying a Franklin. I won't get in an airplane that has one hanging out front.

Well to add fuel to the fire, I’m currently stranded in McCook, NE with a cracked case. I like the franklin and it’s solid in a lot of ways. But I’m not excited about this new development. I seriously almost scrubbed my flight this am from this thread. Really wishing I had at this point. Luckily she still ran and I was easily able to get to my destination. That’s one thing I can say for sure is that all the bad stories I hear about franklins end in the pilot making it to safety as the engine just keeps going.

I assume Maule can supply you with a new stainless firewall right?

I have had a Lycoming cylinder come apart and the engine quit. I had a Continental throw a rod through the crankcase and the engine quit. I have yet to have a Franklin leave me stranded. (Knock on wood) Franklin is the only aircraft engine, that I know of that has never had an AD issued for the engine itself. An AD came out on the fuel pump's that were on the Franklin engine, but not the engine. You can print off pages of AD'S that have been issued for Continentals and Lycoming's. Not to say one is better than the other. I have an RV7 that has a Lyc in it and I am happy with it.

I got a new stainless firewall from Maule for my rebuild. Thought about titanium for a minute, but I think it was going to be about a 2lb. weight savings, and I didn't look forward to fabbing it myself. Plus the additional cost....

On the subject of the Franklin, so you know how many times the crank journals have been turned town? I have two- one that's 2000 hours SNEW, and one that is 0 SMOH, but the crank has now been turned twice, so it's on it's last run. Both are American Franklin's, if that makes a difference for this discussion.