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Tyrap
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| Joined: | Thu Jun 28th, 2007 |
| Location: | Chandler AZ |
| Posts: | 22 |
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Posted: Thu Jul 5th, 2007 09:11 pm |
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Jason,
I have been looking at your engine build packages.
I noticed you only use the CP 10.5:1 piston on the 800cc Stroker.
I can see why you would use it there. Not sure why not elsewhere but I suppose cost is the biggest reason.
Kelly (PDMAZ) told me he modified several CP 12:1 pistons to lower the compression to a 10.5:1 (approximated) with very good results. That was quite a while ago. I personally prefer the CP over JE and am curios. Kelly also told me that CP will make that piston in any desired compression for anyone willing to pay the cost. Obviously, the cost is amortorized with quantity. He speculated at the time that the break-even between the cost of secondary machining vs custom ordered from the factory would likely be around ten pisotns.
I also noticed that since that time racer's edge advertises they use the CP 10.5:1 in their kits.
My questions are:
1. Is the CP piston you are using one that is modified by a machinist...custom ordered as a 10.5:1 from CP...or do they now make that piston in 10.5: off the shelf?
2. How much does it add to the cost over a JE 10.75:1 piston in a build.
3. Do you not use it on the less expensive builds to keep costs in line or for some other reason...
I have a motor I want to have built. Recreational use. Long term reliability and low maintenance is more important to me than hp. Someday I will pay someone to build this motor for me. You are the hometown favorite and now that you have this forum and have expanded your business it puts you in the driver's seat...literally...lol...
So far,
I know I will use a Carrilo rod and want it trued and welded. Factory stroke. Minimal bore. And unless things change...I will want a CP 10.5:1 piston...
The rest I am not sure about....porting, which cam, clutch mods etc.
Anyway, the Q's are geared toward pairing down options and cost...hope you don't mind...I ask a lot of dumb questions...
Yeah, I know...there are no dumb questions...only dumb people...lol...
TIA,
Ty
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Weller Racing
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Posted: Fri Jul 6th, 2007 05:55 am |
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Hi Ty,
I use the CP 10.5:1 on the 760cc Stroker Engine. The 800's use a Custom JE piston. I like both CP and JE they are both very precise and well made parts. I do not prefer one over the other, but that CP piston is a custom stroker piston that works very well for the 760cc engine. I buy them made 10.5:1 compression from CP - and yes, these are off the shelf. That particular stroker piston runs about $75 more than the JE. As far as using the JE in other engines, I have had very good experiences in dealing with JE, and they are always readily available. I am not a big fan of high compression on these big engines. Hope that helps. Jason 
P.S. You should stop by sometime.....  Kelly is a super nice guy with awesome products!
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Tyrap
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| Joined: | Thu Jun 28th, 2007 |
| Location: | Chandler AZ |
| Posts: | 22 |
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Posted: Fri Jul 6th, 2007 06:58 pm |
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Thanks for the invite. I will come by later this month.
You keep reffering to the CP 10.5 as the 'stroker piston'.
Is there any reason I can't use it with a factory stroke Carillo rod...???
Is there any reason I shoudn't use it with a factory stroke Carillo rod...???
Yes, PDM Kelly is a top notch individual in my book. I have known him for almost two years and he is a very good person indeed.
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Weller Racing
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Posted: Fri Jul 6th, 2007 08:20 pm |
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| Yes that particular CP piston is a +2mm stroke piston and will not work with a stock stroke/rod.
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Tyrap
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Posted: Fri Jul 6th, 2007 09:26 pm |
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Well alrighty then...
I asked the wrong Q...
Is there a CP 10.5 already made for the factory stroke or do I have to have one modified....
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Tyrap
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Posted: Sat Jul 14th, 2007 01:54 pm |
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The last time I checked with CP they only listed the 12.0 on thier site.
Now I see they make the Raptor piston in 11.0, 12.0, and 12.5...
I suppose I could go with the 11.0 since the CP has the anti-detonation design...
I know a lot of people say 11.0 is doable on pump gas...
I want to be on the conservative side for both octane and heat...
No racing...just want the most durable, low maintenance, motor with the most power available on low octane gas...
No need to jump through any hoops on this, Jason...there is plenty of time...11.0 might be the ideal piston anyway...I dunno...
I am inclined to go with the 11.0 rather than modify the piston...
If it winds up being too high compression for me I can always take it out and KC do his tricks...
I did see someone post somewhere that Racer's Edge uses a CP piston at 10.5:1...
Maybe they are ordering custom pistons...
I don't want to pay an arm and leg to have them make 1 piston...so maybe if there is enough interest in them a batch can be done and get the cost in line...
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SteveS
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Posted: Fri Aug 3rd, 2007 03:56 pm |
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Tyrap wrote: .............I am inclined to go with the 11.0 rather than modify the piston...... Ty, one way to compensate for an overly high compression ratio would be to use a thicker head gasket. It would take a little knowledge about the compressed chamber volume and some math to work out the thickness needed for half of a point change. Obviously, it can be overdone, but it would be a simple tweak.
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