SC 32 need advice

[Daniel Cardona]

Hello to everyone

 

i need advice about an engine that i recently bought second hand but still in the running-in phase, the engine is a SC 32. the is new but still didnt had full running in on the bench. i ran it with supaglo fuel and a 10x4 prop, the engine started instantly with one flick and it ran great.

 

using the normal running-in procedures for needle adjusments and making sure not to overheat and overstress the engine, all was going great.

 

after a while then i noticed that when the engine cools down and trying to turn the engine by hand slowly i started to feel and hear at TDC a slight squeak noise. feels like the piston is rubbing hard with the liner at TDC position.

 

when i flick the prop with my finger dosen't almost feel and when the engine is hot feels normal. on the bench it runs ok and now i changed the prop to 10x6, now i worried that it will give me some trouble. never had an engine feeling like this when turning slowly by hand.

 

anyone had experience like this? any toughts?

[Martin Harris - Moderator]

There's unlilely to be any problem as this is normal for a tight tolerance ABC engine. The bore is slightly tapered and expands more at the top as it reaches running temperature - hence it feeling right when it's warm.

 

This is the reason why you should run in at only slightly rich settings - rather than the slobbery rich settings needed for a ringed engine.

Edited By Martin Harris on 07/10/2010 23:49:40

[i12fly]

Tightness at TDC is normal for ABC engines. I have the same engine with the same characteristic and it has done about 18 hours running and still going great. It is to do with a taper on the bore, I think to allow for expansion when the engine is hot. They often 'knock' slightly as you pass slowly over TDC and is again quite normal.

[Graham Chadwick]

My ASP .32 is just the same.I am newish to  abc type engines but definitely not new to ringed engines. I could not believe that a engine could possibly be meant to feel like this, but that's just how it is. 

[Daniel Cardona]

so it is possible that an engine will feel like this? i mean if i turn it at TDC starts to squek and it literally stays there if i let it go. i'm new to SC engine's i only used OS engines totally different behaviour.

[i12fly]

Yes they feel like this. I have 8 engines all SC except 1 Irvine, 7 of them excellent and 1 mediocre (and it is not SC). Relax and enjoy

[001]

I would have thought that a 10 x 6 propeller is a bit on the large side for an 0.32 for running in purposes. Not that it would make much difference to the bore/piston fit.

Not getting the engine hot enough would though.

[Peter Miller]

The SC 32 is my favourite engine. I have 6 of them at the moment.

 

I do not bench run them but put them straight in  a model and fly them slightly (Very sightly) rich.

 

In flight you can do Cuban Eights as this will load and unload the engine alternately.

 

Slow rich running in is a quick way to ruin an ABC engine as the engine has to get up to temperature quickly . Otherwise that "squeaky" feel will mean that the engine is just wearing and when it does go to normal operating temperature you will in fact lose compression.

 

If you run it fast and then turn it over slowly before it cools down you will find that the tightness is much less until it does cool.

[Steve Hargreaves - Moderator]

I have an ASP32 (same engine different badge) & can confirm that yes this is how they feel.....!!! After about 8-10 tanks you will find that the squeak is gone but the compression is still good

 

Its a great motor....good power, stable idle & a fantastic throttle response....I've tried a 9x7 & a 10x6 APC on mine & the 10x6 certainly pulls better....the 9x7 unwinds nicely in a dive but seems to lack pulling power....lots of noise but not much go if you know what I mean!!!