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CVO Technical => Twin Cam => Topic started by: acengeist on February 10, 2021, 06:34:48 AM

Title: SE Piston Dome Volume
Post by: acengeist on February 10, 2021, 06:34:48 AM
Morning All.
First time posting.  Been doing a lot of searching, and I am trying to find the dome CC spec for the SE piston 22503-07B.  I know its made by Mahle, and I have emailed them.  I am currently doing my 110 engine build.  My machine shop said it was a 8CC dome but I want to be sure cause my Corrected Compression is close to being too high.  Tks for any info.

pz
Title: Re: SE Piston Dome Volume
Post by: johnsachs on February 10, 2021, 08:49:15 AM
I built a 110" engine for a customer last year, using the standard bore # 22502- 07B pistons.( 22503- 07B is a + 010" oversize piston). My build sheet shows that I removed .015" off the domes, and wound up with a 10cc domes. Have your engine builder cc the pistons if there are any questions.
John
Title: Re: SE Piston Dome Volume
Post by: acengeist on February 10, 2021, 09:02:29 AM
Hi John

Tks for the reply.  Well.....that would be frustrating because my builder told me 8 CCś (volume of dome itself not corrected for piston height) That is quite a difference.

pz
Title: Re: SE Piston Dome Volume
Post by: acengeist on February 10, 2021, 10:14:06 AM
John, I think you were right on the money.  I called Mahle and they were helpful.  I gave them the Harley Part number and they told me the piston dome is 10.94CC.  I have quite a bit of milling to do.  Tks!

pz
Title: Re: SE Piston Dome Volume
Post by: johnsachs on February 10, 2021, 04:18:19 PM
Here is a pic of the build with the cut domes. A "B"  88" carburator engine I converted to a 110" case bore engine. Doc tuned it . Made 124 and change, and 130.5 Torque. Piston in the pic.
John
Title: Re: SE Piston Dome Volume
Post by: acengeist on February 11, 2021, 06:04:40 AM
Nice, thanks......talked to my guy yesterday.  Based on the size Mahle sent me, I calculated that I need to get down to 5 CC on the dome, to  get me to a 9.3 corrected compression.......bringing the pistons back to him today.  I guess that would be about 1/2 the size the dome is now......

Can I ask you how you make a determination on the dome size?
Title: Re: SE Piston Dome Volume
Post by: johnsachs on February 11, 2021, 05:45:40 PM
FIRST THING you/they need to do is check the thickness of the crown. IIRC, the 110" dome pistons aren't like the similar 117" Mahle pistons, where weight is removed under the crown (.200" thick). Then go on a compression calculator, and figure how many cc's the dome needs to be for your target  Cut and measure. If the shop you're using doesn't understand how to do that, you may be in trouble. Possibly your contact at Mahle can tell you the amount that needs to be removed for your target. I would never run a Mahle piston, or any piston for that matter, with a crown much thinner than .200". :o
John
Title: Re: SE Piston Dome Volume
Post by: acengeist on February 12, 2021, 07:01:34 AM
Roger....Tks again I will contact Mahle I think.  Tks for the info!

pz
Title: Re: SE Piston Dome Volume
Post by: vtwinjim on February 12, 2021, 10:50:31 AM
Just for my own clarification.
When discussing dome volume, are they giving you the volume of the dome minus volume of the valve reliefs for total volume or just the dome volume? Maybe the dealer was just talking dome volume?
Title: Re: SE Piston Dome Volume
Post by: acengeist on February 12, 2021, 01:58:40 PM
Im definitely not an expert, so maybe someone that knows can comment.  I think I understand your point, but I would think that any specs HD would have would come directly from the piston manufacturer.  Also if they were both giving me the same number just one accounting for reliefs.......3 CCś of relief sounds like a lot.....but just not sure

pz
Title: Re: SE Piston Dome Volume
Post by: johnsachs on February 12, 2021, 07:34:58 PM
Dome Volume is the complete volume of the top of the piston, including the valve pockets, the dome, and the area from around, and above the top of the top ring, to the deck of the piston. Simple, like **** on a bull.
John