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Engine basics => Engine set up tips => Topic started by: Bootlegger on July 18, 2018, 08:18:49 AM

Title: OS LA 40 engine
Post by: Bootlegger on July 18, 2018, 08:18:49 AM

I have an OS LA 40 engine as for as I know it is stock, with a .257 venture, one stock head shim T/Bolt idle bar plug, turning an A P C 11x4 prop, 5-10% n 22% oil, and on the bench it runs well. It turns in the 9500-10,000 R P M range, so I am asking how you have yours set up, and THANKS a One other thing I forgot it has a R Smith P A 40 Needle assy in it also...lot.

Title: Re: OS LA 40 engine
Post by: Gary Dowler on July 18, 2018, 09:45:14 AM

I'm not expert on this, but I would think a 11-4 is more than this engine should have. I'd be inclined to try a 10-4 APC, and I'd think that you should get a lot more than 10k.  My 20FP with a 9-4 APC on 10% will make 13,800.

Gary

Title: Re: OS LA 40 engine
Post by: rich gorrill on July 18, 2018, 01:30:26 PM

I use 11-4 props on my la 40s. If the 257 venturie is bigger than the standard OS venturies you should be all right. I have never had to add a head shim. I launch at a wet two stroke and they work fine on a modifies twister and a Nobler.

Title: Re: OS LA 40 engine
Post by: rich gorrill on July 18, 2018, 01:33:09 PM

Forgot to include I use stock OS needle valve and OS large venturie. I also switched to a 4 oz. chicken hopper tank from Eric Rule, better performance than standard Uni-flow tank on the Twister.3

Title: Re: OS LA 40 engine
Post by: Bootlegger on July 18, 2018, 05:23:30 PM

  Motor man, it already has an aluminum back plate, but thanks for the suggestion..

Title: Re: OS LA 40 engine
Post by: Bootlegger on July 18, 2018, 05:25:12 PM

  Gary, I just didn't try to exceed  10,000 R P M on the engine, and thanks for your suggestion also...

Title: Re: OS LA 40 engine
Post by: Tim Wescott on July 18, 2018, 07:17:12 PM

Quote from: Gary Dowler on July 18, 2018, 09:45:14 AM

I'm not expert on this, but I would think a 11-4 is more than this engine should have. I'd be inclined to try a 10-4 APC, and I'd think that you should get a lot more than 10k.  My 20FP with a 9-4 APC on 10% will make 13,800.

I don't have any mileage with the stock 40LA, but based on my experience with the 46LA, an 11-4 and launch RPM of 9500-9800 is probably about right.  They don't want to turn as fast as the little engines, and they do unload in the air.

Title: Re: OS LA 40 engine
Post by: Al Ferraro on July 19, 2018, 06:42:21 AM

 My LA .40. APC 11.5x4 prop, OS stock .283 venture with Brodak air filter, PA needle valve .156, Sig 2003 idle bar glow plug, 1 extra head shim, 4 1/2 oz uniflow tank, Power Master GMA 10 Nitro 22 oil, fuel filtered before you put it in the tank, Scott Dinger muffler, 60' .015 lines, 5.1 lap times on my Vector ARF.
Al