0320 150 upgrade to 160 hp

[Bob Hoffman]

I have a 0320 150 hp / FP prop,and would like to upgrade to a 160 hp.
I know that this has been done before and I'm looking for advice on how this is done . Is it just a matter of buying new pistons / pins & rings -- from who?
(or is that whom?) or is there more to it ? does everying need to be re- ballanced ? or can I just pull the jugs and replace pistons/pins & rings.
Is there anything else that can be done to eek more HP without overstressing the system?
Any help would be appreciated.

[sf3543]

I have done this and it is straightforward.
The cylinders must be either nitrided or chromed to handle the change.
New pistons and rings are required. (Can't recall the new compression ratio, but the 150 HP pistons have a flat top while the new ones will be domed and machined out for valve clearance.)
Once the cylinders are off, you need to have them honed, at a minimum. Depending on how much time you have on them, this would be a good time to have them inspected for valves, guides, etc. Also, take a good look inside the case through the cylinder holes.
You will need a top overhaul gasket set.
If you have been using 87 Octane w/the 150 HP, you will need to use 100LL. (For MoGas users, you will need to use the premium 93 Octane.)
Reassemble according to the Lycoming manual.
If you go to a cylinder shop for work, or to install the pistons, they will probably ask you for the STC. Tell them you are doing this in an experimental aircraft. They may ask you to sign a waiver for this, since there is no STC, but no big deal.
This is an easy modification and you get a top overhaul as part of the deal!
Good luck.

[Low Pass]

I converted mine some 500-600 hours ago, and did it with very little trouble.

Under the general guidance of an A&P (asked him just how stupid of an idea it really was), I basically swapped pistons and wrist pins to go from 7:1 to 8.5:1. The cylinders stayed steel.

The 8.5:1 pistons were not domed, but the 9:1 pistons may be.

There are questions to be answered, but it's not that big of an issue, IMO. One source of info is the O-320 TCDS (link below).

http://rvimg.com/tcds/lycoming-o-320.pdf

Call ECI and some of these other knowledgable part suppliers and just tell them what you have and that you want to up to 160-hp. Check several sources and form a plan based upon your existing configuration.

[penguin]

I did mine by installing new Superior cylinders. You may also have to open out the main jet in the carb by up to 0.007" to get the motor to run rich enough, especially when using a Van's airbox. Remember to only undo one cylinder's worth of hold down through bolts at once, otherwise the case halves may fret once its all back together.

Pete

[AZtailwind]

Sent mine out also and the shop bored oversized with steel (personaly don't like the break-in time of crome) but I think the Cyl's of my E2D 8.5:1 were choked unlike the standard 7:1. (??) Something to check- I would recommend sending them out to your prefered shop.

Brad
RV-6A- Firewall forward

[Low Pass]

Originally Posted by penguin

Remember to only undo one cylinder's worth of hold down through bolts at once, otherwise the case halves may fret once its all back together.
Pete

Even when retorqued? Can you explain more, please?

Thanks

[Scott DellAngelo]

The change is pistons and maybe pins. If you have the thin walled piston pins you need to get the thicker ones. If I remember right the difference in piston pins was big. With the thin ones I could put a small finger into them and nowhere even close on the thick walled ones. I have 9:1 pistons and there is no dome or valve reliefs, just more meat above the piston pin to change the compression. As someone else stated you may have to rejet and/or drill out your jet larger with the change.

I got just about everything for my engine overhaul from ECI.

Scott
#90598 - N598SD Flying - 72 hours

[Bob Hoffman]

Thank you all for your replies,I have learned a lot already - never would have thought about opening up the jet to richen mixture.
I knew about the 8.5:1 pistons but not about the 9:1 pistons,was there a productio 0-320 running with this compression,or is this just an after market enhancement ? What is the HP rating?
Penguin
Could you elaboriate more on the "only undo one cylinder's worth of hold down bolts at once" Are you saying loosen and remove one cylinder at a time? And if so is there a sequence to removing cylinders?
Again -- Thank you all
Bob

[Scott DellAngelo]

9:1 came in the H2AD, it is a Lycoming part. Horsepower something like 165 with those pistons, 160 with 8.5:1 and 150 with 7:1. To go higher you gotta get custom stuff from Lycon or somewhere like that (much more expensive too). Richer jet is because in simple terms more power equals more fuel needed (on the same engine). I definitely had to rejet but some have said they didn't. No ideas here as to why you can only do one cylinder at a time? I can think of no reason why it would matter?

Scott
#90598 - N598SD Flying - 72 hours

[Mel]

I went with 9.5:1 custom pistons and they ARE domed. If I had it to do over again, I would not go above 9:1. With 9.5:1 the engine is not nearly as smoothe. I got my smoothness back with the 3-blade Catto prop. Im getting somewhere around 175hp. In addition to the heavy pins, be sure you have a wide-deck engine.