How to obtain the engine I want?????

[jscottpilot]

I am at the engine acquisition phase of an RV8 build and want to put an O-360 that will burn gasoline with an octane rating less than 100LL. I know the O-360-B1A and B1B fit this description and have a compression rating of 7.2:1 however, finding one of these engines used might be difficult. My question is, if I find an O-360 with the normal compression ratio of 8.5:1 can I rebuild it with the lower compression rating cylinders and pistons?

[cjensen]

You can burn Auto gas with 8.5:1 compressions without issue...that's the recommended limit. I have 8.5:1 and plan on burning Mogas when I can...

[Rivethead]

Frankh has some info about this, he should be chiming in anytime now. Apparently he runs mogas all the time in an 8.5:1 FI engine.

[Beancounter]

With 9:1 comp, I too am interested in this. Is it just a piston swap.

[mahlon_r]

7:1 compression ratio, in an O-360, is had by installing 75413 or equivalent pistons and it is generally accepted to burn mogas with 87 octane and above with that compression ratio. Take off Hp is in the range of 168 with those pistons.

8.5:1 is the standard compression ratio for the O-360 and it is attained by use of 75089 or equivalent pistons. It is generally accepted to run mogas of 91 octane and above with this compression ratio. Rated power is 180 HP with those pistons

9:1 compression is attained by use of the LW-15357 or equivalent, in the O-360, and it is generally accepted that you should use 100LL r above with this engine. Normally see around 185 HP at take off, with those pistons.

Good Luck,
Mahlon

?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[Sam Buchanan]

Originally Posted by mahlon_r

7:1 compression ratio, in an O-360, is had by installing 75413 or equivalent pistons and it is generally accepted to burn mogas with 87 octane and above with that compression ratio. Take off Hp is in the range of 168 with those pistons.

8.5:1 is the standard compression ratio for the O-360 and it is attained by use of 75089 or equivalent pistons. It is generally accepted to run mogas of 91 octane and above with this compression ratio. Rated power is 180 HP with those pistons

9:1 compression is attained by use of the LW-15357 or equivalent, in the O-360, and it is generally accepted that you should use 100LL r above with this engine. Normally see around 185 HP at take off, with those pistons.

Excellent info, Mahlon. I have made a copy of your post a sticky in the Traditional Aircraft Engines forum.

Could you give us the same rundown on the O-320 piston combinations?

Thanks in advance.

[jscottpilot]

Just what I needed to know. It seems a 12 hp loss in power is alot to pay just to run regular pump gas. I guess I must decide based on the tradeoffs of power and cost but I definately do not want to be dependent on 100LL.

[rocketbob]

I'm curious if anyone's done testing with 9:1 and mogas. I bet not.

[mahlon_r]

Originally Posted by Sam Buchanan

Excellent info, Mahlon. I have made a copy of your post a sticky in the Traditional Aircraft Engines forum.

Could you give us the same rundown on the O-320 piston combinations?

Thanks in advance.

The 320 and the 360 have the same bore, only the stroke is longer on the 360 to get the extra displacement. So you use the same pistons to get the same compression ratios as with the 360

7:1 compression ratio, in an O-320, is had by installing 75413 or equivalent pistons and it is generally accepted to burn mogas with 87 octane and above with that compression ratio. Take off Hp is in the range of 150 with those pistons.

8.5:1 is the high compression ratio for the O-320 and it is attained by use of 75089 or equivalent pistons. It is generally accepted to run mogas of 91 octane and above with this compression ratio. Rated power is 160 HP with those pistons

9:1 compression is attained by use of the LW-15357 or equivalent, in the O-320, and it is generally accepted that you should use 100LL above with this engine. You should see around 164 HP at take off, with those pistons.

Good Luck,
Mahlon

?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[Sam Buchanan]

Thanks Mahlon, sticky at the top of this forum has been updated to include O-320.