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Old 02-24-2013, 09:58 AM   #1 (permalink)
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Shovelhead Big Bore cam ???

Hey guys, need a little advise on cams. I've decided on building an 88" shovel engine (3 5/8 bore X 4 1/4 stroke) using between 9.5:1 to 10.5:1 comp, dual plugged heads, jims evo upgrade hydraulic lifters and roller rockers. I'd like to keep this engine pretty reliable and long lasting yet still good low end torque. Think the comp i'm using will give me the extra pony's i'm looking for but not sure what cam to use. should i go with like the andrews AB or BH grind, or bump it up a little with andrews c or #6 grind. Gonna use bike for everyday driver and long trips average rpm range will be between 1500 to 4000 rpm. want most my power built at mid rpm range. I would like to stick with andrews cams, and advice would be greatly appreciated, Thanks.
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Old 02-24-2013, 10:12 AM   #2 (permalink)
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In looking thru the spec sheets for an 88" Shovel the "7" looks to be in your range. It's a hotter version of the "B" grind. For 84"-88" and 2500-6500rpms.
I've never used one but the specs look right.
Maybe one of the racers here will chime in and give ya a better perspective.
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Old 02-24-2013, 10:46 AM   #3 (permalink)
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i really dislike how companys discribe there cams....they list duration as being the key factor with engine size....this is not really to be the case...i feel lift is more important....duration is the cam timeing and the cam timeing controls the power range and curve characteristics

if i was running an 88 inch motor i would want the heads ported with larger valves...i would go with a 1.9 intake and a 1.6 or so exhaust...not sure how well the exhaust port is on the old shovels...never been into one

then i would look for a cam in the rpm range i want
for street and reliability most want a solid midrange cam something that closes the intake valve around 45 degrees + or - a few degrees one way or another...it will be typicaly 240 -250 duration @ .050 lift
the exhaust timeing is alittle less important but typicaly if the exhaust port doesnt flow well u want more duration then the intake and keep in mind the point which the exhaust opens the earlier it opens the better it works for longer exhaust pipes and lower rpm

also look at overlap...this is the intake opening time added to the exhaust closing time...this gives the choppy idle...it will give higher power numbers but in a more narrow power range so it wont be as friendly off the cam

also look at lift i would consider .550 lift....duration is what people use to improvise lift with...yes it works to help fill the cylinder BUT also means the motor has to rev high to fill properly and make good power...not as friendly on the street

if it was me....id go with the andrews # 3 if still available if not the S&S 514 cam is the identical cam it has more lift then the others youve listed while still keeping the power range you would want for the road if wanting alittle more top end then go with redshift 580S grind

i found these cams on nightriders website...couldnt tell you if they are available or not...but on a big motor lift is important...you are looking at cams that would work well in a sporty 883....not a 88"

those are my personal thoughts but get ahold of some shops to back up my claims...tell them what you are building and the cams you are thinking about...im sure they would agree lift is going to better for you then duration

ALSO compression...be careful...make sure you know what your dynamic compression will be with the combo of of parts...dynamic compression is very important...pretty much the later the intake valve closes the more static compression you need to raise your dynamic compression into a friendly range

i would shoot for 190-200psi in your shovel...you may find installing a particular cam that you need 11:1 static compression to get your dynamic comrpession back up around 190-200 psi which is 9.2:1 or so

there are calulators on the web for this you will need to know
rod length, bore, stroke, intake closing point, static compression, and elevation (which i always use sea level 0 ft...that way i know i will never actualy GAIN compression when i ride....if you figure 200psi into your build at 7000ft and you ride to the coast well...you may find you are at in excess of 220 and will knock like crazy on pump gas...

let us know what you decide to go with...
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Old 02-24-2013, 10:59 AM   #4 (permalink)
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I was thinking higher lift = more valve train pressure= shorter engine life?
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Old 02-24-2013, 11:03 AM   #5 (permalink)
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Planned on headwork, dual plugged, light porting, and 2.0 intake and 1.7 exhaust. C grind is 278 duration and 525 lift and #6 268 duration and 510 lift. Both these cams are made for stroker engines. Is this considered low lift still for a shovelhead. Stock lift is .390"? Read several other forums and they are saying stay around .450 lift for street use. Both the AB and BH are .450 lift. This is why i'm so confused, everyone has a diff opinion, lol!!!
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Old 02-24-2013, 11:34 AM   #6 (permalink)
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I think I would try to keep to the lower compression side. 9.5-10.5 is pretty much in a Shovel. Especially with the shit gas we get up north here. I'm running 8.5 in my Shovel and can run regular E-gas without pre-detonation.
Maybe with the dual plug heads you would be safe at 9.5 but so many other variables come into play.
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Old 02-24-2013, 12:13 PM   #7 (permalink)
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Hey Schmidtys, I'v got an 82 FXS with Weisco 9.5:1 pistons, single plug heads, and an andrews AB grind cam and no issues with pre-detonation on pump gas. Had 8.1:1 before rebuild and the compression bump made huge difference in power on rebuilt engine, but your right we got shit gas up here, LOL!!!
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Old 02-24-2013, 01:38 PM   #8 (permalink)
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I did pretty much the same thing with my '77 Sporty when I rebuilt the top end. I went with Wiseco 10.5:.1 pistons and I think PB cams and it came alive ! I would see my speedo needle past the 120 mark pinned on many nights for the long freeway ride home after 2:00am !
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Old 02-24-2013, 04:20 PM   #9 (permalink)
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Re: Shovelhead Big Bore cam ???

Got a Andrews C grind in my 100" shovel. Doesn't turn on till mid range. With the 88" me personally would run BH for street and the 7 if you're street and strip.

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Old 02-24-2013, 04:25 PM   #10 (permalink)
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Quote:
Originally Posted by jhog4805 View Post
Planned on headwork, dual plugged, light porting, and 2.0 intake and 1.7 exhaust. C grind is 278 duration and 525 lift and #6 268 duration and 510 lift. Both these cams are made for stroker engines. Is this considered low lift still for a shovelhead. Stock lift is .390"? Read several other forums and they are saying stay around .450 lift for street use. Both the AB and BH are .450 lift. This is why i'm so confused, everyone has a diff opinion, lol!!!
2.0 is a big intake valve man...in my evo i have stock size valves 1.85 intake....its making great power, my motor is 83.5ci....if i was running an 88ci like you are planning on i would run 1.9 MAYBE 1.94 if you plan to turn higher rpms

and the duration you are wanting to run is going to kill the bottom end and make you have to spin the motor to start making good power

also i see the posts about 9.5:1 compression being high...again there are 2 compressions you need to be concerned with Static...which is what the piston is designed to make if the intake valve were to close at 0 degrees bottom dead center with the piston set at its manufacturers stated deck height
the other and more important compression is what you are actualy left with and is the dynamic compression....this takes into account all the things i stated before....

i strongly suggest talking to someone because i feel you wont be happy with what you are building

also when it comes to lift...you are installing new valves which are alot better then your factory ones, valve springs to handle the added lift, and i would hope you are installing new pushrods....for $100 you can have tappered solid pushrods made, that is what im running and i have .567 lift , also consider beehive springs because they run less spring pressure due to better design
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