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Carb for 160 HP upgrade

cropdusterdave

Well Known Member
I had my O-320 E2A overhauled and converted to 160 HP. My origional carb is a MA4-SPA 3678-32.....But I'm wondering if I'd be better off with a different carb? My engine guy said the old one would be fine but I need to get a new or overhauled one anyway so figured I'd see if anyone has any useful input.
 
Your engine guy is correct, the 160 hp variant of your engine also uses the -32 carb. If it was my choice, instead of investing an additional $800-$1100 on a new or rebuilt carb, sell the one you have and take the money towards an Airflow Performance or equivalent fuel injection setup.
 
Same upgrade

I upgraded from 150-160. I was told the carb jet
Could be slightly opened up to allow more fuel. I had my carb
Rebuilt and they did this for me.
 
ReJetting the carb is a very common action to take, but Dave doesn't have the engine running yet, so if he were to open either of the jets up now, he may be needing that material back when he is in phase 1. With the external adjustments that can be made to the MA4SPA's accelerator pump and idle circuit, it will be easy to find out if the carb will need opened back up or can fly-as-is.
 
MA4-SPA 3678-32

I just bought the same carb from ACS. I have an 0-320 D2B 160HP. I have my DAR on the hook for next week so we'll see how it works shortly!
 
Just as a data point, I changed my 7:1 pistons to 9.5:1 pistons over 800 hrs ago.
I did nothing to the original carb and it is still running perfectly today. I'm getting approximately 175 hp.
 
I would suggest buying an Ellison TBI, it is more expensive than a carb but it is significantly more than efficient than a carb.

I flew one on my RV-4 O-320 160 HP, Lycoming for ten years and when properly set up never had a single problem with it. I could run much leaner than a carb which saved fuel. I also believed the engine produced a little more power cause my manifold perssure used to run approx an 1" higher at cruise settings.

I have no connection to Ellison in any way other than being a happy customer.

Glenn Wilkinson:)
 
I have been considering a Rotec TBI. (much less $$) I'm worried about the rigging as I've just ran all my cables and would hate to re-do everything when I could simply bolt on a carb. How does the Ellison differ setup wise from the carb?
 
Hey Dave,

I did the same thing as you about 8 years ago. The engine will run happily with the old carb - but after everything is broken in it is likely that yours CHTs will be higher than you really want. I worked really hard to ensure the baffling sealed well, and ended up enlarging the main jet by 0.004" - some have enlarged by 0.007". That got the CHTs under 400F most of the time. Adding louvres in the bottom cowl (6A) dropped the CHTs by another 40F - almost too cold in the winter. If I had a grand to spare I would install a Pmag - no question.

I would fly and see where you are.

Pete
 
Hey Dave,

I did the same thing as you about 8 years ago. The engine will run happily with the old carb - but after everything is broken in it is likely that yours CHTs will be higher than you really want. I worked really hard to ensure the baffling sealed well, and ended up enlarging the main jet by 0.004" - some have enlarged by 0.007". That got the CHTs under 400F most of the time. Adding louvres in the bottom cowl (6A) dropped the CHTs by another 40F - almost too cold in the winter. If I had a grand to spare I would install a Pmag - no question.

I would fly and see where you are.

Pete

I'm curious to know what the effect on fuel economy is before and after opening the jet?
 
Fuel econony will not be affected by opening the jet a couple of thousands. It can almost be like comparing an O-360's cruise consumption to that of a 320's. It is all dependant on the throttle operator. Many times the main reason in opening it up is to make the motor "happier", or closer to its most capable power curve, not to make more top end power.
 
I'm curious to know what the effect on fuel economy is before and after opening the jet?

I use the red knob to aggressively lean whenever I can, so the period of time spent at full throttle, full rich is not that long. Consequently I can't say I really noticed any great increase in fuel consumption. My max fuel flow is about 13gph (52 lit/hr). I typically operate around 6 to 7 gph (24 to 27 lit/hr), which is good for 135 to 140kt.

Pete

PS Link to Rotec TBI thread http://www.vansairforce.com/community/showthread.php?t=76405
 
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