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  #11  
Old 07-19-2019, 10:12 AM
theduff theduff is offline
 
Join Date: Jan 2012
Location: Fallbrook Calif.
Posts: 222
Default Case overhaul limits.

Quote:
Originally Posted by jacoby View Post
You would think so but it's not listed in the Lycoming table of limits.

As a data point, these guys list 4.475" min on their 8130s and it appears it's supposed to be nominally 4.5" for these crankcases.
James number must have been a typo. 4.475Ē is the minimum for certified cases. Uncut cases measure 4.500Ē measured from the case parting line to the cylinder pads. This can be measured with a standard set of dial calipers on a bare case if done carefully. When the case is overhauled it is cut a maximum of .025Ē per side to remove fretting and to shrink the main bearing journals and cam journals so they can be line bored. Even with this small amount the idler shaft pads hace to be moved to keep the correct back lash on the accessory gears.
Iíve seen cases decked on the cylinder pad side to increase the compression ratio from some biplane racers at Reno win the class required the old 290 Lycoming. Itís a royal pain to remove and reinstall all the cylinder hold down studs to accomplish this and with at least 2 after market manufacturers of high compression pistons there is no need anymore. Interesting side note Lycoming makes a 10-1 piston for a helicopter version and they were highly coveted by Hot Rodderís back in the day.
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  #12  
Old 07-19-2019, 10:31 AM
theduff theduff is offline
 
Join Date: Jan 2012
Location: Fallbrook Calif.
Posts: 222
Default Poor Mans deck height measurement.

I would take a stock piston and pin and hang it on the rod. Then take a tablespoon size chunk of modeling clay and put it on the center of the piston dome. Spray some lube inside the cylinder head ( to keep the clay from sticking) then reassemble the cylinder on the case. Rotate the engine through a couple of times then disassemble. Take the plunger side of your dial calipers and measure the thickness of the squished clay and voila you have a poor mans piston deck height measurement.
With that measurement and the number you shared for the 9.5-1 piston you should be able to interpolate the aproxŪmate comp. ratio with the stock pistons.
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  #13  
Old 07-19-2019, 12:17 PM
Jim Ball Jim Ball is offline
 
Join Date: Sep 2016
Location: Mobile, Alabama
Posts: 21
Default Deck Height

Quote:
Originally Posted by Ralph Inkster View Post
Jim- the 4.775 confuses me a bit as I just measured 3 engines (cases assembled, flange to flange) and come up with
360 wide deck = 9" across
540 wide deck angle valve = 9 1/16"
320 narrow deck = 9 1/16"
granted the measurement method was crude but result is a lot less than
4.775 X 2. Is there a raised surface between the two mating case halves that would account for the 0.275 x 2 dimension difference?
I'm sorry the correct minimum at ECi was 4.477 not 4.775. Divco and others may have a similar minimum to certify after lap and line bore.
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  #14  
Old 07-19-2019, 12:20 PM
lr172 lr172 is online now
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 4,325
Default

Quote:
Originally Posted by Zuldarin View Post
I know this is a long shot but are you sure its the piston hitting the top? The rings on these engines do have an upside and a downside. If you install the rings (any 1) up side down the piston will not go all the way to the bottom of the tapered barrel. You should have noticed this when installing/gaping the rings but just a thought.
DId you gap the rings? I just bought 6 superior cly kits and on each one, I had to shave a good 10-20 thou off the rings to get the minimum gap up in the choke area. If I didn't do this, I would have had the symptoms you describe.

That said, if the cyl mounting decks are milled, you definately don't want high compression pistons.

Larry
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Last edited by lr172 : 07-19-2019 at 12:25 PM.
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  #15  
Old 07-19-2019, 12:36 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 341
Default

Quote:
Originally Posted by jacoby View Post
You would think so but it's not listed in the Lycoming table of limits.

As a data point, these guys list 4.475" min on their 8130s and it appears it's supposed to be nominally 4.5" for these crankcases.
Is there a difference for narrow vs. wide-deck O320? They say these numbers are for a narrow deck. Mine is a D2J O320 - is that narrow or wide?
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0-320 AFP fuel injection, EFII Electronic Ignition, Sterba wood prop
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  #16  
Old 07-19-2019, 01:17 PM
jacoby jacoby is offline
 
Join Date: Jul 2018
Location: WNC
Posts: 176
Default

Quote:
Originally Posted by 1flyingyogi View Post
Is there a difference for narrow vs. wide-deck O320? They say these numbers are for a narrow deck. Mine is a D2J O320 - is that narrow or wide?
Check this out: Ask Paul: Wide deck vs. narrow deck engines

Basically, look for an "A" suffix in the serial plus hex nuts on the cylinders.
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  #17  
Old 07-19-2019, 02:05 PM
1flyingyogi 1flyingyogi is offline
 
Join Date: Dec 2015
Location: Long Beach, CA
Posts: 341
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Quote:
Originally Posted by jacoby View Post
Check this out: Ask Paul: Wide deck vs. narrow deck engines

Basically, look for an "A" suffix in the serial plus hex nuts on the cylinders.
Thanks! Looks like mine is a wide deck - I'll confirm when I get to the hangar, but I'm quite sure it's a wide deck based on the the link you gave.

So... does anyone have a number for what the deck height is supposed to be for a WD O320? The numbers given so far are for ND cases.
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  #18  
Old 07-19-2019, 03:12 PM
sailvi767 sailvi767 is offline
 
Join Date: Sep 2010
Location: Charlotte NC
Posts: 972
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Paulís article on narrow verses wide deck engines is interesting but contrary in some respects to what I was told. On the IO540 at least the narrow deck engine is preferred by racers and hard core aerobatic guys because it is viewed as stronger and more tolerant of raised compressions. I confirmed this with Barrett engines. They prefer narrow decks for their high performance versions. I wonder why the difference in thought?
George
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  #19  
Old 07-19-2019, 03:55 PM
theduff theduff is offline
 
Join Date: Jan 2012
Location: Fallbrook Calif.
Posts: 222
Default ND vs. WD

Quote:
Originally Posted by 1flyingyogi View Post
Is there a difference for narrow vs. wide-deck O320? They say these numbers are for a narrow deck. Mine is a D2J O320 - is that narrow or wide?
The deck heights are the same for both ND vs. WD . You have a WD engine based on the picture you posted. Keep in mind the same connecting rod is used in both versions ie same rod length.
Iíve even seen a factory Reman engine that utilized ND cylinders on a WD case. Apparently they donít have any new ND cases any more so the simply took a new WD case and drilled it for the smaller circumference ND stud pattern. Apparently when your the factory you can do such things ! 🤪
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  #20  
Old 07-19-2019, 04:02 PM
theduff theduff is offline
 
Join Date: Jan 2012
Location: Fallbrook Calif.
Posts: 222
Default High Performance ND engines

Quote:
Originally Posted by sailvi767 View Post
Paulís article on narrow verses wide deck engines is interesting but contrary in some respects to what I was told. On the IO540 at least the narrow deck engine is preferred by racers and hard core aerobatic guys because it is viewed as stronger and more tolerant of raised compressions. I confirmed this with Barrett engines. They prefer narrow decks for their high performance versions. I wonder why the difference in thought?
George
One of the reasons ND engines are some time preferred is because contrary to what you might think the ND case holds up much better. Ask any case OH company and theyíll tell you they crack far less.
One example is the National record holder biplane ran a narrow deck 360 for many years that produced over 260 hp at over 3500 rpm.
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