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Marvel carb interchangeability help

Robin8er

Well Known Member
I have a Rotec TBI on my O-360, but its giving me problems and the easiest solution is just replace it. I came across a Marvel MA-4-5 10-3148-1. This is listed as the carb for a Franklin 6-A4-165-B3.

Would this carb work on a O-360 with low compression pistons putting out 170 HP?

If not, would I be able to use this as a core for the correct carb? The correct carb appears to be a MA-4-5 10-3878.

Any help is appreciated.
 
I cant answer your carb Q, but I also have a Rotec on my OX-340 and am fairly happy with it after a few tweaks. What problems are you having?
 
Its doesnt seem to matter how aggressively I lean, I always have dark black spark plugs. It runs way too rich.

It also fails to produce full power and stumbles at high power settings. I've spent lots of time trying to turn it and have finally just given up.

I came to the conclusion that it's too finicky and it requires mastery just to operate it. I couldnt hand the keys over to a fellow pilot and have confidence that they would be able to fly it because of the rotec TBI.
 
Its doesnt seem to matter how aggressively I lean, I always have dark black spark plugs. It runs way too rich.

It also fails to produce full power and stumbles at high power settings. I've spent lots of time trying to turn it and have finally just given up.

I came to the conclusion that it's too finicky and it requires mastery just to operate it. I couldnt hand the keys over to a fellow pilot and have confidence that they would be able to fly it because of the rotec TBI.
Sorry to hear that. I suffered vapour lock with my original Mk I Rotec, replaced it with a MkII and am quite happy with that, after wrapping my fuel lines and gascolator.

I needed to slightly drill out a couple of the spray bar holes in the first one, but beyond that, am very happy with the MkII. Starts first blade or two cold and instantly when hot and I can run slightly LOP with it.

IF you're running waaay rich can you start it with the mixture at ICO and then throttle up a fair way? If so, have you adjusted the idle mixture with a hex key? Mine will get to around 1000RPM before it calls it a day so could probably be a touch lower, but it idles beautifully around 650RPM hot. Another idea that comes to mind is the primer-override button that pushes the diaphragm down not returning, or a hole in the diaphragm?
 
I've tried all those things. I slowly drilled out the spray bar and it got continuously better. Then I drilled out 3 more holes slightly and then suddenly it was much worse.

Rotec recommended buying and installing an oxygen sensor to figure out exactly what was going on, but I've decided I just dont want to mess with it any more.

It works, and I trust it, but my entire flight consists of continuously playing with the throttle and mixture. The main issue is the engine stumble at full power. This means no full power climbs and reduced cruise speeds.

I've considered replacing the spray bar and trying again, but rotec wants $300 and I feel I'm better off cutting my losses and replacing it with a carb.
 
Carb for O-360

That model carb might run lean for your engine. I needed a 10-4164 on my RV4. The snorkel seems to cause it to run lean. I also ferried a RV8 with the 10-3148 and it ran lean. We later found a jet kit called the "Mooney Mod" and installed it. Engine ran great after that.

Best,

Mitch GArner
 
That model carb might run lean for your engine. I needed a 10-4164 on my RV4. The snorkel seems to cause it to run lean. I also ferried a RV8 with the 10-3148 and it ran lean. We later found a jet kit called the "Mooney Mod" and installed it. Engine ran great after that.

Best,

Mitch GArner

Am currently upgrading the 20 year old 10-3878 carb on my O-360-A1A with a rebuilt 10-4164-1 carb.

Spoke with the tech support engineer at Tempest/Marvel-Schebler today. They advise the 10-4164-1 carb should flow about 4.4 gph more at full throttle, full rich mixture, at sea level versus the 10-3878 carb.

Just chiming in here to provide for future reference some quantitative Sea Level flow data for the 10-4164-1 carb.
 
I've tried all those things. I slowly drilled out the spray bar and it got continuously better. Then I drilled out 3 more holes slightly and then suddenly it was much worse.

Rotec recommended buying and installing an oxygen sensor to figure out exactly what was going on, but I've decided I just dont want to mess with it any more.

It works, and I trust it, but my entire flight consists of continuously playing with the throttle and mixture. The main issue is the engine stumble at full power. This means no full power climbs and reduced cruise speeds.

I've considered replacing the spray bar and trying again, but rotec wants $300 and I feel I'm better off cutting my losses and replacing it with a carb.

I went through similar issues with the 4-5 TBI on my O-360. Ran too lean at WOT. Tried drilling the spray bar, plenum adaptor, insulator, A/F gauge... No support from the manufacturer unless I was buying parts. Replaced it after 100 hrs flight time, much wasted $ and many hours of mod time.

I installed a 10-3878. It was too lean as well. Put the Mooney mod kit in it and it has been great for the last 350 hrs. Some people drill the main jet. I went with the kit because it gives a new jet and a restrictor to give a richer mixture through the economizer cct at WOT.

My understanding is the Mooney mod 3878 is the same as the 4164. Don't know anything about the 3148.

Good luck.
 
Since this thread has been revived I thought I'd share what I did.

I sent my MA-4-5 10-3148-1 to Russ at D&G as recommended by N13BN and told him exactly what I was doing with it. They rebuilt it for about $500 including installing an epoxy float, which I thought was a phenomenal deal. He marked it for an experimental on the data plate and basically tuned it to work on a Lycoming 360. It has been flawless and resolved ALL of my rotec issues. They really know what they are doing at D&G, I can't recommend them enough.

As much as I wanted the rotec to work, I could never get it to run right. You shouldn't have to drill holes on something that is specifically designed for the application i used it for. It should be ready go out of the box, just like a carburetor. The most you should have to do is minor tuning with the mixture adjustment.

The other problem with drilling holes on the rotec is it voids any sort of return policy. They really don't provide any support, i can't imagine them taking back a tbi with holes drilled in it, even though that's what they tell you to do.
 
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