Carb swop

·         matthew dovey

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Hi All, I have an early solid lifter 2200. I'm thinking about swopping the 32mm to the 40mm carb. The aircraft is running fine so far but I'm looking for a power increase as I operate out off a short strip and would like an increased safety margin that a bit of extra power will give. I've read that I should get a power increase. But I've also heard from other sources that it wont make any difference by changing carbs. Can you advise if all the expense and effort will be worth it

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·         Doug Smith

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Hi Matthew,
We have a venerable wooden "club" propeller that we use to do the ground running on the 2200 engines we overhaul. We've had it forever and by putting the same propeller on every engine we got a good idea of how each engine compares to the rest in terms of power. One of the best 2200 engines ever was built using a 32mm carb - beating many using the 40mm... so I would not start with the carburettor if you're looking for more power.

Depending how old your engine is there are various upgrades to heads, valves, intake manifolds etc which will give improved power. If you tell us the serial number and any changes made during overhauls we can figure out what you have and how it can be improved.

Regards,
Doug.

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·         matthew dovey

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Hi Doug,
Thanks for the reply. My serial number is 22A675. Its standard as far as I know. I replaced the heads the year before last with Camit heads. But they were a straight swop. Replaced the valves. They were again standard.
I do have an newer style used, upgraded sump and manifold that I can fit. The engine is in a Jabiru SK.
I'm interested to know which mod's I can perform to get some more power out of the old girl. Saying that I really don't want to have to take the engine apart again this winter.
This tech forum has been long over due. Good to get information straight from the horses mouth so to speak. Appreciate the advise.

Matt

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·         Doug Smith

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22A675... The old heads were likely to have been a restriction for sure. I'm not familiar with the fine details of the CAMit heads so not sure how they rate.

Depending how far you want to go, upgrades to the crankcases (better breathing with less windage losses) and manifold/sump assy should give you a little more... but pretty soon you'll end up with a "new" engine. I'm not sure if you're familiar with the old motor racing adage of "how fast do you want to spend???"

In the short term, especially if you're not keen to pull it apart again so soon, a different propeller might be the most effective upgrade: a little more diameter and less pitch should pop you off the ground quicker (at the cost of a little cruise speed). If it's a rough or grass strip some upgrades to the wheels/spats might be worth looking at too: bigger wheels obviously have less rolling resistance over a rough surface while spats will mean your wheels drag less in long grass (but of course they're a little fragile and will take plenty of care and attention to keep in one piece if they're in continuous use on a rough surface). Correct brake adjustment and wheel alignment are also key to reducing the rolling resistance.

Regards,
Doug.

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·         matthew dovey

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Hi Doug,
The Camit heads were the best option at the time. They were pretty much a straight swop.
I wont to keep the spend down if I can. I'm hopping to sell the plane. But planes sell when they sell so the aircraft is in use and I'm not in a hurry to get rid of it.
I have the sump and the manifold already. I've been told I'd have to replace or modify they induction pipe to get them to fit. What are your thoughts. Will the newer sump work well with the 32mm carb? Is there an adapter to fit the 32mm carb to the manifold. Would it be worth the effort.
I have previously thought about the prop. The prop I'm running is a GT 1510mm x 1050mm (59".44 x 41".37). That might be a good place to start.
Never been a fan of spats. I used to work for a flying school. The first thing to be roved was the spats. I have the big foot wheels and tyres fitted. I will look at the brakes and the wheel alinement.

Matt

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·         Doug Smith

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So if you have all the induction pipes that go with your new manifold (upper and lower sections for each cylinder) you should be fine. If not and you're mixing and matching pipes from different era intakes you'll probably need to do some persuading (up to and including cutting / welding) to get them to go together.

I think the 32mm carb can be adapted onto the "swept" manifold but I from memory it's not a bolt-together job: I think the welder would need to come out again. If you've got the whole manifold there it's probably best to see about finding a 40mm carb for it - especially if the aircraft is for sale: that way you can say the induction has been upgraded to later/std specs.

I've not personally flown behind a GT prop but as far as I know they're a good thing. It's a tough call with the aircraft for sale: spending big dollars on a propeller that may not appeal to the new owner. Depends how long you think you'll have it and how short that strip is I guess!

Fair enough re the spats. But if the grass is getting close to axle height or higher they'd make a positive difference and if you're only flying it yourself they can be kept in one piece. I put a set of spats and home-made fairings on the undercarriage legs of my UL (small wheels) and they've aged well - nearly 400 hours with minimal upkeep. It operates mostly from pretty smooth grass runways but sees the occasional farm strip.

D.

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·         matthew dovey

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Thanks for the advise Doug.

Matt