another cam question for 98" build
another cam question for 98" build
Hello forum, I know this subject has been gone over numerous times, and I know im going to get everyones opinion on whats the best cam and thats exactlty what im looking for! I have checked my crank run-out and im well within spec so im going gear drive. Picking a cam is starting to drive me nuts. I very rarely ride 2 up and i love torque but i dont want to run out top end either. any ideas are well appriciated.....thanks
what i have done so far:
98" forged CP pistons +10cc dome (10.75:1 comp)
.30 head gaskets
Heades have been ported and polished (big boyz porting)
manual compression releases
what i have done so far:
98" forged CP pistons +10cc dome (10.75:1 comp)
.30 head gaskets
Heades have been ported and polished (big boyz porting)
manual compression releases
Tourer
Joined: Sep 2014
Posts: 420
Likes: 5
From: Kingsport, TN
First obvious answer is to ask BigBoyz since they did the heads.
If you want to select cams on your own, you need to use the BigBoyz compression calculator to estimate the static compression for your build before selecting cams. If it comes out to much over 10:1 you will need cams with a later intake close to keep corrected compression down to around 9.5 or less (195 psi CCP at your altitude) assuming you will use high-quality 93 octane fuel. With 89-92 octane fuels, you will usually need to stay below 192 psi CCP and below 190 psi with octanes below that.
Most well-designed late intake close cams (say around 42-46 degrees ATDC) will deliver a good smooth rideable torque curve with 9.5 corrected cr (195psi CCP) and a good pipe and will blast off like a rocket at 4000 with a set of good flowing heads. Cams with early exhaust opening will help eliminate detonation too, but the resulting high overlap will make the motor very pipe sensitive.
Assuming your calculated static compression comes out to 10.5-10.7:1 and you use 93 octane fuel, look at the R&R 615. Maybe the S&S 585 if you want less lift.
If you want to select cams on your own, you need to use the BigBoyz compression calculator to estimate the static compression for your build before selecting cams. If it comes out to much over 10:1 you will need cams with a later intake close to keep corrected compression down to around 9.5 or less (195 psi CCP at your altitude) assuming you will use high-quality 93 octane fuel. With 89-92 octane fuels, you will usually need to stay below 192 psi CCP and below 190 psi with octanes below that.
Most well-designed late intake close cams (say around 42-46 degrees ATDC) will deliver a good smooth rideable torque curve with 9.5 corrected cr (195psi CCP) and a good pipe and will blast off like a rocket at 4000 with a set of good flowing heads. Cams with early exhaust opening will help eliminate detonation too, but the resulting high overlap will make the motor very pipe sensitive.
Assuming your calculated static compression comes out to 10.5-10.7:1 and you use 93 octane fuel, look at the R&R 615. Maybe the S&S 585 if you want less lift.
Last edited by dynawg1; Mar 15, 2015 at 11:30 AM.
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
If the OP truly has a 10cc dome piston and chamber volume is 85-86cc, a cam like the Andrews 60G or something similar with a 55* intake close, or thereabouts to keep corrected CR and CCP manageable. I would bet that Bean did not set the heads up for cam lifts above about .590" lift as his typical street port job retains OEM valves and springs.
ChangedBagger needs to contact Bean and get find out what the chamber volume is and start cranking that into the BigBoyz calculator as dynawg1 has suggested but cam choices with the 10cc dome will be limited. Additionally, the cams that will work will be hi lift, long durations cams that most likely will not deliver the torque where the OP would like but there will be plenty of power up top.
I suggest that the OP learn the chamber volume from Bean and start playing with the BigBoyz calculator to find out what dome volume will work with a cam like the S&S585, TMan590 or Andrews 57 and have the piston dome shaved to that dome volume. I don't believe the OP will be happy with the 10cc dome piston and the cams that will work with that much compression. JMHO.
ChangedBagger needs to contact Bean and get find out what the chamber volume is and start cranking that into the BigBoyz calculator as dynawg1 has suggested but cam choices with the 10cc dome will be limited. Additionally, the cams that will work will be hi lift, long durations cams that most likely will not deliver the torque where the OP would like but there will be plenty of power up top.
I suggest that the OP learn the chamber volume from Bean and start playing with the BigBoyz calculator to find out what dome volume will work with a cam like the S&S585, TMan590 or Andrews 57 and have the piston dome shaved to that dome volume. I don't believe the OP will be happy with the 10cc dome piston and the cams that will work with that much compression. JMHO.
Tourer
Joined: Sep 2014
Posts: 420
Likes: 5
From: Kingsport, TN
See what you mean about the pistons, djl. Looks like the OP has a pretty serious challenge selecting cams with those pistons and heads with only .590 lift (if they are). Much easier to go with flat tops and use head volume and headgasket thickness to get desired compression.
Elite HDF Member
Joined: Sep 2012
Posts: 3,791
Likes: 57
From: N Texas
Are yall thinking the static compression is higher than the 10.75:1 as stated? I would think that the OP has everything included to get that #, no? If not then definately more homework is required.
Last edited by HD Pilot; Mar 15, 2015 at 12:54 PM.
Tourer
Joined: Sep 2014
Posts: 420
Likes: 5
From: Kingsport, TN
Pilot, based on djl's post, wouldn't he need to go with something like the reaper 594 to get the corrected compression down to a realistic street level with those pistons? Would need higher lift springs and would be a decidedly high-rpm power motor.
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Elite HDF Member
Joined: Sep 2012
Posts: 3,791
Likes: 57
From: N Texas
All the HTT guys were telling me a 10.8:1 would be better than my 10.5:1 plan for performance out of my Tman 590s with an intake close of 44 degrees. The 574s close at 45 degrees, have not put the numbers in BB calculator but should be good, especially in Boston with premium fuel. I stayed at 10.5:1 because of Texas heat....
As always, with higher compression a very good dyno tuner will be necessary.
As always, with higher compression a very good dyno tuner will be necessary.
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HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
All I am suggesting is that the OP be smart about selection a cam; do the math and don't make the mistake many make and just throw the parts together with fingers crossed.
Elite HDF Member
Joined: Sep 2012
Posts: 3,791
Likes: 57
From: N Texas
Static, according to my calculator will run about 10.9 but worse is corrected CR at 9.75 and CCP at 206 and that is if Bean didn't take any off the heads and the chamber volume is 85cc. Without knowing chamber volume one cannot say for sure what cam will work with the OPs configuration. A cam like the Reaper 574 with a 45* intake close will hit the corrected and CCP numbers referenced above.
All I am suggesting is that the OP be smart about selection a cam; do the math and don't make the mistake many make and just throw the parts together with fingers crossed.
All I am suggesting is that the OP be smart about selection a cam; do the math and don't make the mistake many make and just throw the parts together with fingers crossed.