IO-540 CIB5

I am preparing to rebuild my Lycoming IO-540 CIB5, and was thinking of going with 9 to 1 compression pistons (Giving me aprox 275HP) instead of the stock 8.5 to 1. (260hp) My airstrip is short so thinking a bit more power would be nice. Wondering if this would be a bad idea? Also would I still be able to burn premium auto gas as an option if I wanted to?

Thanks.

ZX-14 said:

I am preparing to rebuild my Lycoming IO-540 CIB5, and was thinking of going with 9 to 1 compression pistons (Giving me aprox 275HP) instead of the stock 8.5 to 1. (260hp) My airstrip is short so thinking a bit more power would be nice. Wondering if this would be a bad idea? Also would I still be able to burn premium auto gas as an option if I wanted to?

Thanks.

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Keep in mind that the design performance criteria of most, if not all Vans aircraft is to operate of Van's 600 ft grass strip. Also keep in mind that all Lycoming engines that come stock with 8.7:1 compression require 100LL fuel. So, no, I don't think you will be able to get high enough octane to run 9: compression pistons. Perhaps some have real world experience that will say they get away with that combination.
The real answer for your performance needs is to keep the plane light. You might consider a 3 bladed prop to give you the extra acceleration you desire.

Welcome to VAF!

Walter, welcome to VAF.

My 540 has 9:1, not an issue-------although I have never tried to use mogas in it.

Lots of these engines out there with higher C/R.

Thanks Kelly and Mike!

Much appreciated!

Walter

Walter, make sure that you fly a -10 before you make a decision as to whether it needs more power.

-Andy

What Andy said. I flew my -10 for the first time a gross weight and could not believe how fast I was off the ground. IO-540 V4A5 with 8.5:1 pistons and standard 2 blade Hartzell prop. Gets off the ground fast and climbs like a home sick angel!

Ok, thanks, will do! (Just going by the fact that nothing I have ever owned, flown, rode, driven or had a ride in so far in my life had so much power that it couldn't use more! Lol )

Quick response, take it or leave it.

9:1 sure why not
Mogas.....never.
Magneto's ONLY.

ANy further details PM me.