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0320 150 upgrade to 160 hp

B

Bob Hoffman

Well Known Member
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.
 
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.
 
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.
 
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
 
Cyl's may be choked

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
 
penguin said:
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
Click to expand...
Even when retorqued? Can you explain more, please?

Thanks
 
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
 
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
 
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
 
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.
 
Mel,
Why wide deck? and how do I know if I have a wide or narrow deck ??
I think 9.5:1 is a little much for me but I might go for 9:1
Thank's
Bob
P.S. Thank you for all the replies everyone
 
cost of 160 hp upgrade?

I also have a "150 hp" RV6A. I'm sure the top end overhaul costs are different based on things like, whether or not you're going to use the existing cylinders, and how much professional help you're getting.

But I'm curious about what a modest (reusing the same cylinders with some treatment) 160 hp upgrade is costing guys?

Also did any one change or re-pitch there props after the hp increase?

Thanks
 
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C/R = H/P

This is a good discussion as there is a lot to learn as how to convert a 150hp o-320 to 160hp. I did this on my O-320 dash nothing by just changing the pistons and pins at O/H with the higher compression pistons and the thicker pins. My understanding the only difference in the pistons is that the pin location is relocated by a small amount, something like .045?, to let the piston travel further into the combustion chamber creating an increase in the mechanical compression ratio from 7:1 to 8.5:1 thus increasing the HP. We have all heard this and it is common knowledge that if you increase the C/R it will result in an increase in HP. But what is really going on with the physics to make this increase happen? Some have suggested that you must richen the fuel mixture for the increased C/R in order for it to make increased HP. If this was the case then why could you not just richen the mixture and not the C/R to get the HP? I think there is more going on there as an engine works best at a specific air/fuel ratio and increasing one with out the other will do nothing other than added cooling or leaning depending on which way you go. I like to get to the nuts and bolts of things like this so I posed this same C/R = HP question to a forum a few years back and in a nut shell this is what I got.
When you increase C/R you are creating more heat on the compression cycle thus subjecting the Air/Fuel (A/F) mixture to more heat causing it to vaporize/ atomize better in the combustion camber creating a more complete/efficient combustion cycle utilizing more of the energy from the fuel and wasting less out the tail pipe. That being said, there is no free lunch here as the increased C/R makes more heat which needs higher octane, more stable, fuel in order for the A/F mixture not to pre-ignite. But the bottom line is that a higher C/R makes the engine use the fuel more efficiently is my understanding. I am not an engineer but love all things mechanical and strive to understand why thing do what they do.
 
Bob,
The easiest way to tell is to look at the serial number at the top flange of the crankcase at the rear. If the serial number ends with the letter "A" it is a wide deck. Most 4 cylinder Lycoming engines built before 1964 were narrow deck. If you reall want to learn everything about operation, failure, and repair of Lycoming engines, I highly recommend the "Sky Ranch Engineering Manual". It is a great source of information.
 
Last edited:
Low Pass said:
Even when retorqued? Can you explain more, please?

Thanks
Click to expand...
Undo the through bolts/studs at the base of one cylinder and take it off, then get a plate the thickness of the cylinder base flange (several things can be used, Lyc even sell a special tool for $$$) and re-torque the through bolts only. Do the same on all the other cylinders. If you let the torque off all the through bolts at the same time bad things can happen to the main bearings and/or case halves. I think its all in the overhaul manual.

Pete
 
freegespeed said:
Also did any one change or re-pitch there props after the hp increase?
Click to expand...

Yes, you will almost certainly have to re-pitch your prop, or accept much higher rpms in the cruise. I re-pitched my Sensenich from 77" to 79" (on a 6A) and am now going to 80" as I keep exceeding the 2600 rpm limit by 50 rpm. Previously I was pulling 2500 to 2550 with a tired 150hp engine, now I can easily pull 2600 rpm (with the 79" prop) at just about any altitude. Climb has also increased by 3 or 400 fpm.

No idea how much it might cost to overhaul your cylinders, but several cylinder shops have prices on the web (for example Sentry cylinders at www.aircraftcylinders.com).

Pete
 
ECI Prices:
9:1 Pistons - $85ea
Piston Pins - $32ea
Ring sets depend on your cylinders but figure $40-$60 or so

So, average it out add shipping and say $700 for the parts to do it and then anything you might do to the cylinders while apart.
 
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Narrow Deck and 9:1

Mel

Are the narrow deck cases and cyls incompatable with 9:1 pistons?

Duane Zavadil
6A
IO-320-B2D
 
More To It

When the wide deck E2D on my 172 was overhauled, the mechanic noted in the log that the "case was modified for 160hp...". This has something to do with the front crank bearing; I forget exactly what. Since this prep had been done, I popped on 8.5:1 ECi cylinders in lieu of the standard 7:1 when applying a recent AD fix for certain ECi cylinders. The sales guy said the only difference between the two kits was the pistons; no mention of pins, but he's in sales not mechanics so...

Those of you contemplating such a conversion might want to talk to Lycon or RAM. Both have STCs for this conversion, which you don't need to buy for an experimental engine, so ferreting out info without prospect of gain may be a trick. Each has different approaches re jetting, pitch, and may shed some light on the bearing issue.

John Siebold
-7, 198 hrs
-7, -300 hrs and counting
 
It's really not recommended to "hop up" the narrow deck engines. The cylinder base flanges are not designed to support the extra compression.
BTW, I don't find a listing for a IO-320 B2D. or even an O-320 B2D. Hs the engine been modified already? The "B" would seem to indicate that it is already 160hp.
 
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B2?

Mel

It is an old Tripacer engine - certainly narrow deck but I may be missing the last digit. It is and was manufactured as a 160 hp engine. Same answer? Not advisable to go to 9:1? I've got a year or two before it will be ready for some work and probably would not swap out pistons prior to OH.
 
I know that Mel is a DAR, but the advice from others, regarding compression and a Narrow Deck engine differs from Mel's comments.

My understanding is that ratios of up to 9.0 to 1 is perfectly acceptable and safe with a narrow deck. There were several 160 hp narrow deck engines, and Lycoming engines with high compression and the same flange design as the narrow deck.

Just passing on the advice I got from several experienced engine shops, YMMV.
 
Besides being a DAR, I've been an A&P mechanic for about 35 years and I've built up a lot of Lycoming engines. It's experimental, so you can do what you want. Personally I wouldn't go over 8.5:1 on a narrow deck engine. I actually went to 9.5:1 on my wide deck O-320, but I wouldn't do it again.
 
FWIW Talked to ECI today and they also said 8.5:1 is as high I should go & no higher on a 0-320 narrow deck.
They also state that the STC for a production A/C upgrade also reguires a longer thrust bearing,they have been known to take the crankcase and weld up and machine an extension. BUT he says -- for an experimental we can do whatever we want (but make sure it's SAFE)
For those of us who are cost concious
Pistons - 53.30 ea
rings - 36.52 ea
pins - 46.92 ea
Tatal w/o tx 546.96 In the "old" days I have been known to spend more for a 10 hp boost
Bob
 
Just to clarify,

In my case, the recomendation came from Lycon, and was backed up by a local machine shop which has been building for nearly thirty years.

I can see how high compression, plus alot of ignition advance, etc could all combine to cause a problem. On the other hand design can help too.

In my case the actual c/r is slightly under 9 to 1, with custom, flat top pistons. The nice thing about it was that the pistons, pins and cylinders were weight and flow balanced as a set and in opposing pairs.

Rules of thumb are always just that, but it definitely pays to have a long and thoughtful discussion with your particular engine builder, and to check the claims with other engine specialists. I could not find ANY engine shop which recomended against 9-1 in a narrow deck engine.

Again, just passing on the information I was given by folks who specialize in engines, and only engines, and have been rebuilding them for decades.
 
changing props could be expensive

Thanks for the input all. It's what I was expecting to hear about props needing to be re-pitched. I have a wood prop that was already re-pitched once to bring the rpm's down at cruise settings. I kind of doubt I would do it again, so the this leaves me having to out lay some serious cash for a new prop. I guess I could control the power settings at criuse and just enjoy the new spunkier climb rate, but cruise would be about the same speed as before.

Another question I have is whether the cylinders on the 160 hp Lycomings are different in any way then the 150 hp Lycomings? I read somewhere that cylinders must be changed when the pistons, etc. are upgraded to the high compresions ones, (8.5 or 9.0 to 1). From the responces on this thread it seems that quite a few people just got the pistons and built there new top ends with their same old cylinders. A 10 to 15 hp increase in power is well worth $700 to me if it's a safe thing to do.

Cheers
 
Barrel material

freegespeed said:
Another question I have is whether the cylinders on the 160 hp Lycomings are different in any way then the 150 hp Lycomings? I read somewhere that cylinders must be changed when the pistons, etc. are upgraded to the high compresions ones, (8.5 or 9.0 to 1). From the responces on this thread it seems that quite a few people just got the pistons and built there new top ends with their same old cylinders. A 10 to 15 hp increase in power is well worth $700 to me if it's a safe thing to do.

Cheers
Click to expand...

Lycoming says that for the 160 HP you need nitrided cylinders (or chrome?) but the 150 HP engines ship with plain steel barrels.

Some of the STCs might make you change cylinders, but the one for Grumman Cheetahs (O-320-E2G) lets you just put in the new pistons.
I think they sort of limit the HP to 157, which is 5% extra, and within the Lycoming new engine tolerance, which reduces the FAA paperwork.... However, their is no effective control on you running a few more rpms... :) Note, this is a fixed pitch prop. installation. If you use the Sensenich metal prop, the 2600 rpm limit would probably keep you below this 5% increase point.

The cylinder wear might go up a bit, but I don't think it would be a big deal on the life of the engine.... I say go with the original steel cylinders if they are good to use.. if they need major work, a new ECI cylinder at $850 might work out cheaper...

http://www.aeroinstock.com/products/product_cat.php/subid=5819/index.html


gil in Tucson.... going to end up with a 160HP -E2G
 
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When doing 160HP you should use a hardened choked cylinder bore surface not plain straight steel. On a 150 HP engine it is permissible to use a hardened choked barrel or a straight, plain steel barrel. So some of the cylinders that are used on a 150 HP engine could be used on a 160HP engine. On the other hand, many 150 HP O-320's have plain steel straight bore barrels, these are not recommended for 160HP. Thus the controversy there....
On the n/d vs. w/d issue, if you have N/D O-320 cylinders that use the additional plates on top of the cylinder-mounting flange you are OK at 160HP. However, if you have n/d cylinders that don't use the extra plates on the cylinder-mounting flange between the cylinder base nut and the cylinder flange, you should only go to 150HP. Thus, the confusion and controversy there.
The non-plate n/d style O-320 cylinders have a spot-face on the cylinder where the cylinder base nut would go and the n/d ones that use the additional plates don't have the spot face machined into the flange. So by looking at the cylinder mounting flanges you should be able to tell which cylinders you have and what hp they could be used for.
You can absolutely use either O-320 main bearing set up for 160HP. There are many stc's to use the 4 piece nose bearing set up on 160hp conversions on certified engines and aircraft. Although Lycoming has never made an engine using this setup, we have converted many, many, O-320-E2D's and E3D's, using an STC, that use that 4 nose bearing setup to 160hp and have never had an issue.
Hope this all helps!
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 you own risk.?
 
Bolt count...

mahlon_r said:
On the n/d vs. w/d issue, if you have N/D O-320 cylinders that use the additional plates on top of the cylinder-mounting flange you are OK at 160HP. However, if you have n/d cylinders that don't use the extra plates on the cylinder-mounting flange between the cylinder base nut and the cylinder flange, you should only go to 150HP. Thus, the confusion and controversy there.
The non-plate n/d style O-320 cylinders have a spot-face on the cylinder where the cylinder base nut would go and the n/d ones that use the additional plates don't have the spot face machined into the flange. So by looking at the cylinder mounting flanges you should be able to tell which cylinders you have and what hp they could be used for.
Click to expand...

Thanks for the real details Mahlon...

As I read your text, it seems to imply that the narrow deck cylinders without a plate at the base use a different number of cylinder bolts that the cylinders with the plate.
Is this true?

gil in Tucson
 
No the number of studs are the same for either n/d with the plates or without. The visual difference between the cylinders is the spot face on the cylinder flange or no spot face on the flange.
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 you own risk."
 
Thank you soooo much Mahlon and everyone else (I never expected this much response).
Mahlon,-- My 0-320 has 50 hours since MOH (prior owner) and has "chrome" cylinders . I am trying to envision what you mean by "spot face on cylinder flange" Could you help me understand a little better so when I go home I can look and see if I have or have not.
Thank You ALL (WOW)
Bob
 
Bob,
By spot faced I mean it would look like you machined a small area for the cylinder base nut to mate directly against the flange. The nut would be directly against the cylinder barrel flange without a plate in between the nut and the cylinder and there would be a obvious machined spot for the cylinder base nut to seat against.
?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 you own risk.?
 
Mahlon,
Ok I checked , I have narrow deck chrome cylinders (50 hrs)with "hex"bolts.
Question -- The wide deck portion seems to be a plate that goes on top of the cylinder mounting flange. Can that plate be add to make it a wide deck or is there more to it than that ?
Regards
Bob
 
As far as I know, you can't use the plates with a spot faced cylinder. Never tried it but can't see how it would work properly. Secondly, the studs in the crankcase will be too short if a plate is added to the cylinder flange.
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 you own risk.?
 
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