right cam for high compression?
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Road Warrior
Joined: Oct 2009
Posts: 1,664
Likes: 99
From: P.E.I. Canada
right cam for high compression?
So I finally listened to you guys and went and got a compression test done. The guy at the shop laughed and said ok, i believe you now, no wonder you're pinging. My compression, which should be at 190 aprox, was about 220. So, what to do now? I can either put in a new head gasket and lower the compression that way, or I can find a better suited cam. He has no idea why it's up so high, but I have to do something about it now. One of the better builders around here says that he'd through a Red Shift 575 cam in it, which should give me great power, and he's pretty sure it'll help with the ping, but he's not 100% sure. Any suggestions?
HDF Community Team
Joined: Jun 2006
Posts: 12,774
Likes: 2,606
From: san antonio
Post the build details again, i.e., bore, stroke, chamber volume, head gasket and cams. A head gasket change isn't going to move you from 220 to 190. You need cams with a later intake close.
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Road Warrior
Joined: Oct 2009
Posts: 1,664
Likes: 99
From: P.E.I. Canada
I:25/98/41
E:49/105/17
246
246
.575
.575
Any thoughts? I'd rather do a cam swap then a gasket change anyways, but I want to keep my torque fairly low and lose the ping. Right now I have my timing set way back to stay away from the ping, but I'm losing power and can't get rid of it all together.
Road Master
Joined: Dec 2008
Posts: 872
Likes: 20
From: Niagara Falls Canada
255 comp will be higher
I have 255 in my build with se mva heads and 10.5:1 pistons the cold cranking pressure with the throttle plate at idle position pumps out 225 lbs so If i take a reading with the throttle plate open I caN ONLY IMAGINE HOW HIGH IT WOULD BE. I stuck the stock cams in and compression went down to 185 and 240 with throttle plate forced open. I still hAve to figure out what to do either pull the pistons and put flat tops in or change the cams or both. if your compression is high now it will be even higher with 255 they open the valves a few degrees past tdc and stay open all the way down to bdc .
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Road Warrior
Joined: Oct 2009
Posts: 1,664
Likes: 99
From: P.E.I. Canada
I already have the 255's in... that's my problem... and my pistons are flat tops already, so I'm left with the cam change. I'm thinking a se204, or I can get a great deal on a RS575, and I love those cams, but I don't know if the 575 will help or make it worse. Any help would be great because I need the bike ready for a 11 day run starting next thursday. 575 yay or nay?
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Road Warrior
Joined: Oct 2009
Posts: 1,664
Likes: 99
From: P.E.I. Canada
ok, that's a good start. So I'm thinking the 575 and maybe retard the timing a hair and I should be pretty drivable without a ping and racing fuel?
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Road Warrior
Joined: Mar 2010
Posts: 1,505
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From: Vancouver Island, British Columbia
My recent 96 upgrade build which included 103 flat top Hypereutectic pistons, .030 MLS and the 204 cams doesn't ping at all so far, (summer isn't here yet). The dyno tuner did a great job and used the TTS. I showed 220 front and 205 rear CCP, tested with the throttlebody wide open. Good luck, interested to find out how you make out.
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HDF Community Team
Joined: Jun 2006
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From: san antonio
Kirby is right, as one would expect; something is wrong. Your CCR should be under 200psi with a standard BB kit and 255 cams. The gauge is reading wrong or, as Kirby suggests, heads were milled. You need to know what you are working with before you start making any changes. I would check compression again with a different gauge, probably more than one before I accepted 220psi as CCR. Too many guys are running that combination without issues.