Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Piston ring question Napier second ring

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Ohio Rob
New Member
New Member
Posts: 47
Joined: Sat Feb 08, 2020 4:54 pm
Location: 44090 Ohio

Piston ring question Napier second ring

Post by Ohio Rob »

Hello all.
I’m building a 363 SBF that will be a dry sump engine. It’s for a drag race application. It’s going to be high compression (15:1 or so) and will have a sealed crankcase. I have a Peterson vacuum relief valve to set the vacuum (I plan on around 7” crankcase vacuum) and a Peterson blow off valve in case of positive pressure.

My question is in regards to what piston rings to use.
I’m thinking of a moly top ring and a cast Napier second ring and a low tension oil ring.
Is that sound thinking? Do I need the Napier second ring with the vacuum pulling on the bores?
The engine will be NA and I plan to spin it relatively high 7500 to 8000.

Any thoughts will be appreciated.
Thanks
Rob
User avatar
MadBill
HotPass
HotPass
Posts: 14757
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Piston ring question Napier second ring

Post by MadBill »

Not an answer to your question, but re crankcase vacuum the sweet spot between power, gasket sealing and pin and guide oiling is usually ~ 10-14". You should do some A-B testing once you've got your combo mostly dialed in.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
mt-engines
Member
Member
Posts: 148
Joined: Fri Sep 27, 2019 12:35 pm
Location:

Re: Piston ring question Napier second ring

Post by mt-engines »

Yeah thats fine. I like the total seal ap rings. they all come with napier seconds.. why not pull more vacuum like 15"-18"
mt-engines
Member
Member
Posts: 148
Joined: Fri Sep 27, 2019 12:35 pm
Location:

Re: Piston ring question Napier second ring

Post by mt-engines »

MadBill wrote: Sun Feb 09, 2020 10:09 pm Not an answer to your question, but re crankcase vacuum the sweet spot between power, gasket sealing and pin and guide oiling is usually ~ 10-14". You should do some A-B testing once you've got your combo mostly dialed in.
Unless he has done all the oiling tricks in the book to control windage, he woud still need to measure oil flow to determin its an oilling issue. You don't get the dreaded or feared pin issues unless you don't have the right wrist pin, clearances or run the very minimal amount of oil through the bearings. i have run 20" without issues. But then again some of them arent as dry as others.
Charliesauto
Pro
Pro
Posts: 246
Joined: Wed Sep 03, 2014 2:01 am
Location:

Re: Piston ring question Napier second ring

Post by Charliesauto »

Ohio Rob wrote: Sun Feb 09, 2020 9:02 pm Hello all.
I’m building a 363 SBF that will be a dry sump engine. It’s for a drag race application. It’s going to be high compression (15:1 or so) and will have a sealed crankcase. I have a Peterson vacuum relief valve to set the vacuum (I plan on around 7” crankcase vacuum) and a Peterson blow off valve in case of positive pressure.

My question is in regards to what piston rings to use.
I’m thinking of a moly top ring and a cast Napier second ring and a low tension oil ring.
Is that sound thinking? Do I need the Napier second ring with the vacuum pulling on the bores?
The engine will be NA and I plan to spin it relatively high 7500 to 8000.

Any thoughts will be appreciated.
Thanks
Rob
No reason to not run a napier 2nd, everything about it is a positive with no negatives. With good crankcase vacuum and a napier 2nd, you can drop the oil ring down to 5 or 6 lbs and still have adequate oil control. Like the other guy said, no need to limit yourself to 7" of vacuum, in a drag application I would be 20" or all the pump will make. That being said, more crankcase vacuum is a case of diminishing returns, the first 10" will net you a lot more performance gain than the last 10".
hoodeng
HotPass
HotPass
Posts: 593
Joined: Sat Mar 04, 2017 6:53 pm
Location: South Australia

Re: Piston ring question Napier second ring

Post by hoodeng »

In a P/S engine we ran we had 20" pan vac, on our data if we saw the pan vac start to decrease towards the end of the run we knew we were up for rings pretty much straight away. Is this also the case for you mt?
Ohio Rob
New Member
New Member
Posts: 47
Joined: Sat Feb 08, 2020 4:54 pm
Location: 44090 Ohio

Re: Piston ring question Napier second ring

Post by Ohio Rob »

Thanks for the replies. Much appreciated!
I can adjust the crankcase vacuum up some.
I was thinking too much would pull the oil off the bores too much and pull in the seals.
Thanks for the correction on that.

On that note, do the seals go in the block in the traditional way with the increased vacuum?

Thanks
Rob
LSP
Pro
Pro
Posts: 317
Joined: Tue Mar 16, 2010 12:33 pm
Location: Charlotte

Re: Piston ring question Napier second ring

Post by LSP »

Ohio Rob wrote: Sun Feb 09, 2020 9:02 pm Hello all.
I’m building a 363 SBF that will be a dry sump engine. It’s for a drag race application. It’s going to be high compression (15:1 or so) and will have a sealed crankcase. I have a Peterson vacuum relief valve to set the vacuum (I plan on around 7” crankcase vacuum) and a Peterson blow off valve in case of positive pressure.

My question is in regards to what piston rings to use.
I’m thinking of a moly top ring and a cast Napier second ring and a low tension oil ring.
Is that sound thinking? Do I need the Napier second ring with the vacuum pulling on the bores?
The engine will be NA and I plan to spin it relatively high 7500 to 8000.

Any thoughts will be appreciated.
Thanks
Rob
Do you already have pistons? If so, what width and depth are the ring grooves?

Is this motor for a specific drag race class?
Ohio Rob
New Member
New Member
Posts: 47
Joined: Sat Feb 08, 2020 4:54 pm
Location: 44090 Ohio

Re: Piston ring question Napier second ring

Post by Ohio Rob »

I have diamond pistons 1/16 1/16 3/16
Here’s a pic of the piston card and the pins.

The engine isn’t for any specific class. Just for hurting feelings on grudge night amongst friends.
:twisted:
You do not have the required permissions to view the files attached to this post.
LSP
Pro
Pro
Posts: 317
Joined: Tue Mar 16, 2010 12:33 pm
Location: Charlotte

Re: Piston ring question Napier second ring

Post by LSP »

Ohio Rob wrote: Mon Feb 10, 2020 9:11 am I have diamond pistons 1/16 1/16 3/16
Here’s a pic of the piston card and the pins.

The engine isn’t for any specific class. Just for hurting feelings on grudge night amongst friends.
:twisted:
I'd go with Total Seal ring set CRG0690-5 and gas port the top ring. Gap the top ring at .018", and gap the 2nd ring and top oil rail to more than that.

Doesn't have a Napier 2nd ring, but they'll substitute one in the set for a minimal charge if you want it.
engineguyBill
HotPass
HotPass
Posts: 1215
Joined: Fri Feb 26, 2010 11:15 am
Location: Gold Canyon, AZ

Re: Piston ring question Napier second ring

Post by engineguyBill »

Go with steel top ring, plasma moly or nitrided, Napier second ring for sure and low tension oil ring assembly. Ductile iron top ring with plasma moly face coating will work fine if you cannot find the steel top ring.
The Napier ring will work fine being manufactured from grey iron material. Second ring is primarily an oil control ring and doesn't come into contact with excessive cylinder pressure, nor combustion heat, therefore ductile or steel material is overkill and not necessary for this ring.
Bill

Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
Charliesauto
Pro
Pro
Posts: 246
Joined: Wed Sep 03, 2014 2:01 am
Location:

Re: Piston ring question Napier second ring

Post by Charliesauto »

Ohio Rob wrote: Mon Feb 10, 2020 6:00 am Thanks for the replies. Much appreciated!
I can adjust the crankcase vacuum up some.
I was thinking too much would pull the oil off the bores too much and pull in the seals.
Thanks for the correction on that.

On that note, do the seals go in the block in the traditional way with the increased vacuum?

Thanks
Rob
Call Signal Seal in Mooresville NC and get a set of high vac crank seals.
User avatar
MadBill
HotPass
HotPass
Posts: 14757
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Piston ring question Napier second ring

Post by MadBill »

LSP wrote: Mon Feb 10, 2020 9:42 am...
I'd go with Total Seal ring set CRG0690-5 and gas port the top ring....
Goodson sells a kit for drilling lateral ports; it works pretty well but working freehand is likely to cost you a couple of bits vs. using a drill press.
https://goodson.com/products/gas-porting-tools
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
mt-engines
Member
Member
Posts: 148
Joined: Fri Sep 27, 2019 12:35 pm
Location:

Re: Piston ring question Napier second ring

Post by mt-engines »

MadBill wrote: Tue Feb 11, 2020 12:11 am
LSP wrote: Mon Feb 10, 2020 9:42 am...
I'd go with Total Seal ring set CRG0690-5 and gas port the top ring....
Goodson sells a kit for drilling lateral ports; it works pretty well but working freehand is likely to cost you a couple of bits vs. using a drill press.
https://goodson.com/products/gas-porting-tools
Just send them to Rebco so they are done right and you can have 12-14 of them.
Ohio Rob
New Member
New Member
Posts: 47
Joined: Sat Feb 08, 2020 4:54 pm
Location: 44090 Ohio

Re: Piston ring question Napier second ring

Post by Ohio Rob »

Here are a couple pics of the pistons.
Gas porting has been suggested, but I have a 1/16” top ring. Thoughts?
You do not have the required permissions to view the files attached to this post.
Post Reply