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Old 08-06-2013, 07:17 AM   #31 (permalink)
IronButt
 
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I have 12 CC dome pistons coming for my own 120. Will be testing a new cam of mine will see how it goes.. Don is right none of this is really off the shelf parts. I dont agree about flat top making power over a dome. But that my opinion, and until someone builds the engines both ways hard to prove.

I should have mine done in a month if I can get all the parts together and have enough time.. Time is the killer.

but basic parts list is as follows

My hand port work on the MVA head
a increase over the 5.5 cc dome piston to 12 CC dome
66 MM FBW and a 58 FBW oval from HPI
timken lower end, prepped crank
cam will be a 675 custom ground will also be testing the S&S 640 for a base line.

Static will be 12-12.3 gas will be 93 pump. CCP well wont know that for 100% until I pump the engine but should be in the 220 range.
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Old 08-06-2013, 06:09 PM   #32 (permalink)
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Ask StrokerJK. That one he tuned made 146hpSAE with flat tops at 200CCP and the crap for cams according to the internet, SE266. A duplicate of the HD dome certainly won't help HP any. Schrouding and flame travel issues. There is a way to get the domes to work too but I haven't seen one yet custom or otherwise and the 20 or 30 squish domes are way too top heavy, JMHO
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Old 08-06-2013, 06:23 PM   #33 (permalink)
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I'm guessing the head was probably cut .050-.060 thousandths to get 200psi with flattops.

Last edited by Olivepearl; 08-06-2013 at 06:33 PM.
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Old 08-06-2013, 06:24 PM   #34 (permalink)
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I am at 95 cc chambers with rework and I am not going to deck these as I am able to alter the set up etc. The dome on these are very mild compared to some pistons. As for the weight these are set up correctly. , again I am going in a direction to produce power and I have a target hell it makes 143 now with the 5.5 cc dome. That is not near my goal. SO more compression custom cam and see what happens.

I do not think one way is really better than the next when it comes to pump gas and street engines. Heck even my old 742 with massive domes never had one lick of issue, that engine was ran both ways as I lost a roller lifter. We ended up having to weld the heads I dropped chamber volume by a large % still have the same. ET wise it was a great engine..
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Old 08-06-2013, 07:12 PM   #35 (permalink)
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Stroker tell us about the flattop motor. Stock port MVA's? was it 140+HP and Torque.
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Old 08-06-2013, 08:40 PM   #36 (permalink)
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Due to HD pent roof design 12 to 12:5 is probably the best deal. I understand the conversation on flame travel and personally looking at CAD models we all can go crazy trying to sort it out, It seems me to hp and tq change more with port design and csa choices than the piston deck. 160hp plus is definitely doable if the heads are well thought out. The higher compression we run the earlier the exhaust can open and the smaller the ex valve can be and makes room for a larger intake valve. Better TDC lifts as well. One positive note with pop ups. If a piston is designed off a combustion chamber mold, valve control is better at higher rpm.
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Old 08-06-2013, 08:54 PM   #37 (permalink)
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All I would add is that we have been limited to 91 octane fuel here in CA for over a year now. I think I recently saw some 92 octane in either OR or WA on my recent road trip but I would not swear to it. They add so much "corn meal" it didn't work much better. Be advised. If your going touring on a high compression build on the "West Coast" bring a LOT of octane boost while traveling here in the West. Just sayin! Maybe Don can comment as he lives up in WA.

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Old 08-06-2013, 09:05 PM   #38 (permalink)
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I don't care to tell all but I do understand what Gordon is saying and that is a success recipe if the weight of the piston can be held down low, full skirts, and the dome is reversed on top so the flame kernel can be controlled and push straight down on the piston with the dish with less rocking of the piston by working up over the dome
Tutt, we have 92 here at almost every 76 station and some Chevrons. That is all I use if I am not forced to others.
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Old 08-06-2013, 09:06 PM   #39 (permalink)
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I regularly don't go west of Texas we got 93 and some 94 at every stop here plus non-ethanol too. 93 is pretty much all over the southeast.

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Old 08-06-2013, 10:01 PM   #40 (permalink)
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The whole dish > flat top > dome has a lot more to it than just flame travel. Think about what a dished piston does to the amount of room in the cylinder below deck for air to fill. It basically imitates adding stroke. It has been proved again and again, maybe not right here. There's a reason nascar, Indy cars and serious naturally aspirated engine builders use dished pistons.
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Old 08-07-2013, 06:26 AM   #41 (permalink)
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Quote:
Originally Posted by VDOP View Post
The whole dish > flat top > dome has a lot more to it than just flame travel. Think about what a dished piston does to the amount of room in the cylinder below deck for air to fill. It basically imitates adding stroke. It has been proved again and again, maybe not right here. There's a reason nascar, Indy cars and serious naturally aspirated engine builders use dished pistons.
I agree with the argument for the dish piston and the combustion chamber is considered to be another port for flow design but how many engines (air cooled) on the street do we see that are close to 2hp per ci. I have built dished, flat and domed and the power differences between them have not been eye opening. There is another problem here. And until its figured out maybe topics like these will lead us to our hp fortunes.
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Old 08-07-2013, 07:11 AM   #42 (permalink)
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Quote:
Originally Posted by gordonr View Post
I agree with the argument for the dish piston and the combustion chamber is considered to be another port for flow design but how many engines (air cooled) on the street do we see that are close to 2hp per ci. I have built dished, flat and domed and the power differences between them have not been eye opening. There is another problem here. And until its figured out maybe topics like these will lead us to our hp fortunes.
I agree it's probably not practical or worth the effort in these engines, especially with the huge combustion chambers we're stuck with. Which is why my motor is running domes. It's fun to think about though.
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Old 08-07-2013, 08:07 AM   #43 (permalink)
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Stroker tell us about the flattop motor. Stock port MVA's? was it 140+HP and Torque.
The wegner 2-1 don't make a lot of tq . It just carries it forever , allowing the hp to just keep on climbing .
Don did a fine job on these heads .
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Old 08-07-2013, 07:09 PM   #44 (permalink)
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Dang! table top flat torque. Stroker your torque didn't flatten out with the 266 and the wegner did it?
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