Marvel Carb Experience

[cdoughty]

Hi Guys. First post but I have been lurking for a while sucking up all the great info on this site. Thought I should finally contribute.

I have a C140 with C-85, fresh overhaul. With the overhaul the carb was "upgraded" to the modern Marvel. The engine made good power, but really never passed a mag check. On one mag, either one, it would cut out almost immediately and start losing rpms, 200,300, 400, etc. If you ran it up to 2100+ and were really quick on the mag check you could trick yourself it was ok, and the story was "just needs to break in", "just loading up", etc. I flew it for 25 hours till broken in. It didn't improve and as the weather got colder (in Mass) it got worse, occasionally running rough in the pattern.

Check for induction leaks, checked, cleaned, gapped plugs, changed idle mix--no change. Called Marvel and sent it back. They claimed it checked out but admitted "sometimes they just do this". When I asked to see the flow data they claimed its proprietary. They said they would change the nozzle (in some undefined way) and that sometimes this helps. Got it back and it was worse, couldn't even get to 2000 rpm.

Pulled the old Stromberg out of the trash and engine ran great, other than the stumble on acceleration. So the Stromberg is on the plane, the Marvel is in a box somewhere at Aircraft Spruce and they still have my money. When these problems started I started searching the interwebs and this sort of issue is widely reported on C-85s with Marvels after the venturi AD in the 1990s. They essentially never bothered to really fix the problem. Some work, some don't. My advice with all the normal disclaimers--If you are thinking of uprading keep that in mind. If you have one that works don't send it in as a core on a rebuild.

[6643]

Thanks for posting this!

Interesting you would call 1938 technology "modern" compared with 1937 technology. I prefer to call it "complex". There is, however, that incredible performance increase you get from flying with a lighter wallet.

[2066]

Amen! Thanks for sharing. It seems that many folks keep trying to fix something that's never needed "fixin" -- the Stromberg worked very well when our planes rolled out and has continued to over the years. The proverbial leaks, stumbles and mixture control (that may not be effective or needed below FL30 ) are minor inconveniences compared to the costs & potential and serious issues with the "modern Marvel". Mac

[6863]

I wouldn't trade my Marvel for a Stromberg but then my Marvel is on a modern C90.

[6643]

My C90 sports an ancient Stromberg and in 30+ years I've never needed to buy a $125 accelerator pump or comply with an AD!

[2066]

I wouldn't trade my Marvel for a Stromberg but then my Marvel is on a modern C90.

...next thing we hear may be that you've installed "modern" ADS-B . (I'm reminded of David Lowe's comment to Sara Parmenter a few years back RE her fuel caps with "vent tubes". David said "I didn't say it wouldn't work, just that it isn't necessary".) Seriously, if it functions well and you need/want true mixture control and an accelerator pump, the modern Marvel just may be the ticket...different strokes. (I just prefer to "Make things simple..." ). Mac

[cdoughty]

Should have put "modern" in quotes I guess.

Whether a good one is better or worse than a Stromberg I don't know. But one that doesn't work is clearly worse. Unfortunately M-S seems to know that they often don't work right and doesn't really care to figure out why and fix them. Having cashed the check Aircraft Spruce says they don't actually sell these and that M-S was the vendor. And I guess the FAA just figures its all good if its wrapped in 8130s and has the right number on the dataplate--Form and Fit trump Function.

End of rant.

[2066]

Yep, sorry you had to go through that hassle, cdoughty. And, my feeble attempt at humor wasn't intended to criticize anyone who desires to "upgrade". In any event, here's hoping that you can get some $$$ back on the deal and that the Stromberg will work well, long term. Thanks, again, for wading in here to share the experience and please post more thoughts and ideas as the affair 'twixt you and that neat airplane evolves. Mac