I have a 8a with o-360 par valve engine, seems hot in climb with my cherokee carb (3878). I remember some threads on drilling the main jet out from a 43? to a 46?. Anyone know what the procedure actually is. I contacted a fuel metering shop and was told the drill idea works fine! Any comments/ideas? Thanks, Ed
Van's Air Force
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main jet drilling
- Thread starter whirlpool
- Start date
Frank
Active Member
MA4-5 Enrichment
After experiencing the same issues in my RV8, I purchased a re-jeting kit designed for the M20 with the same engine/carb combination. I will have to look up the documentation and get back.
This is an old thread from Matronix 1998:
I talked to Pete Nielson at Precision Airmotive tech support During that conversation Mr Nielson told me that he believes the MA4-5 carbeurator (part number 10-3878) that came with my O-360 (from Van's) is too lean for the RVs (something about the induction system on the RV, coupled with the use of the reusable air filter). He indicated a richer carb (MA4-5 part number 10-4164-1) is what he believes should be used in the RVs. He indicated he's discussed this matter with Bill Benedict a couple of times, including recently regarding an RV-4 that's running too lean. be sure that the carb is runing rich enough that you can lean the carb and produce a 75-100 rpm rise and a 150 degree (F) EGT rise. If you can't, the carb is too lean and needs to be swapped for a richer carb, or modified. Precision has a conversion kit, which lists for $240. I asked Van's about this, and got the following response: "At this writing, we have only about 1-2% of the aircraft that seem to be on the lean side and so it has not even been an issue here beyond helping those that individually have the problem to solve it" Tim: please refer to the archives for tons of useful info on this very subject, discussed as recently as this summer when I had the lean carb syndrome on my O-320 with the old Cessna carburetor. In particular, Gary Corde's posts were helpful. I ended up drilling out the main jet from a # 43 drill size to a # 37. this made a world of difference, but probably went too far. Now I have no more rpm surging in cruise, and make better takeoff power, but I have to lean about 8 turns on the ground for best results. I lean about 4 turns for T/O at 3000 ft density alt. The EGT rise I can get at cruise went from something like 90 degrees to over 200 deg. If I had it to do over, I'd buy the kit from Precision, so as not to jeopardize the certification of my engine, or else drill to # 38. I think for my application, # 37 is just too big of a hole, but not worth going back and changing at this point. I've learned the nuances of flying a rich carb, and prefer this to a lean one!
After experiencing the same issues in my RV8, I purchased a re-jeting kit designed for the M20 with the same engine/carb combination. I will have to look up the documentation and get back.
This is an old thread from Matronix 1998:
I talked to Pete Nielson at Precision Airmotive tech support During that conversation Mr Nielson told me that he believes the MA4-5 carbeurator (part number 10-3878) that came with my O-360 (from Van's) is too lean for the RVs (something about the induction system on the RV, coupled with the use of the reusable air filter). He indicated a richer carb (MA4-5 part number 10-4164-1) is what he believes should be used in the RVs. He indicated he's discussed this matter with Bill Benedict a couple of times, including recently regarding an RV-4 that's running too lean. be sure that the carb is runing rich enough that you can lean the carb and produce a 75-100 rpm rise and a 150 degree (F) EGT rise. If you can't, the carb is too lean and needs to be swapped for a richer carb, or modified. Precision has a conversion kit, which lists for $240. I asked Van's about this, and got the following response: "At this writing, we have only about 1-2% of the aircraft that seem to be on the lean side and so it has not even been an issue here beyond helping those that individually have the problem to solve it" Tim: please refer to the archives for tons of useful info on this very subject, discussed as recently as this summer when I had the lean carb syndrome on my O-320 with the old Cessna carburetor. In particular, Gary Corde's posts were helpful. I ended up drilling out the main jet from a # 43 drill size to a # 37. this made a world of difference, but probably went too far. Now I have no more rpm surging in cruise, and make better takeoff power, but I have to lean about 8 turns on the ground for best results. I lean about 4 turns for T/O at 3000 ft density alt. The EGT rise I can get at cruise went from something like 90 degrees to over 200 deg. If I had it to do over, I'd buy the kit from Precision, so as not to jeopardize the certification of my engine, or else drill to # 38. I think for my application, # 37 is just too big of a hole, but not worth going back and changing at this point. I've learned the nuances of flying a rich carb, and prefer this to a lean one!
Frank
Active Member
MA4-5 Enrichment - Follow-up
As promised, Percision's 10-3878 to 10-3878-M (10-4164-1) enrichment kit.
The service bulletin is A11-62. The kit is part number 666-660. The list price is $292.90. We have stock. You will have to purchase it from a distributor. Call National Aviation @ 800-359-1843. Have a good one.
Alan Jesmer
[email protected]
As promised, Percision's 10-3878 to 10-3878-M (10-4164-1) enrichment kit.
The service bulletin is A11-62. The kit is part number 666-660. The list price is $292.90. We have stock. You will have to purchase it from a distributor. Call National Aviation @ 800-359-1843. Have a good one.
Alan Jesmer
[email protected]
