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vdub
Samba Member
Joined: September 07, 2003
Posts: 442
Location: Valley Springs, Ca.
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 Posted: Thu Jun 16, 2011 12:44 am Post subject: Cam Question |
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I am building a motor for a 69 square and have a question.
The idea at the beginning was to build a mileage motor but now I really don't care about mileage. I want something that will have back breaking torque off the line.
This is what I have.
76mm CB crank
5.5 CB rods
90.5 Stroker Pistons
044 heads 40x37.5 w/ Single springs
solid rockers 1.1
44 webber IDF's
Lightened flywheel (12LB crom. I believe)
1700 kep clutch
I have 2 cam's
One is a KF41 and the other is CB's cheater cam.
I got the KF41 because it was close to the cheater but many people told me the ramp angle was to high for 1.1 rockers so I got the cheater cam instead.
The cheater cam is 222 duration with 394 lift.
I think I may want to buy a new cam to give me better off the line torque. I was recommended the CB 2241 with 240 duration with 424 lift but I wanted to know what you guys think.
I don't want to change my rockers, I want to stick with the 1.1's. At the same time I want torque not high RPM power. I only plan for this motor to spin around 6000. Its built for higher but I am more interested in a power band below. |
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Foxy
Samba Member
Joined: June 10, 2003
Posts: 379
Location: Birmingham , UK
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| Posted: Thu Jun 16, 2011 4:08 am Post subject: |
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I'm running a similar spec to you in my square, but I have a 78.4mm crank ( 2017 ), and slightly higher spec heads with dual springs etc.
I'm running an FK-7 with 1.4:1 rockers, and its got loads and loads of torque. I'm still running it in at the moment so haven't gone above 3000 rpm but it pulls up steep hills at 1500rpm easily!
If I were you I would be looking at running the FK-41 and changing the rockers for a 1.25:1 set. You really want to get more lift than what the cams are giving you with 1:1 rockers. |
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vdub
Samba Member
Joined: September 07, 2003
Posts: 442
Location: Valley Springs, Ca.
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| Posted: Thu Jun 16, 2011 11:00 pm Post subject: |
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| Foxy wrote: |
I'm running a similar spec to you in my square, but I have a 78.4mm crank ( 2017 ), and slightly higher spec heads with dual springs etc.
I'm running an FK-7 with 1.4:1 rockers, and its got loads and loads of torque. I'm still running it in at the moment so haven't gone above 3000 rpm but it pulls up steep hills at 1500rpm easily!
If I were you I would be looking at running the FK-41 and changing the rockers for a 1.25:1 set. You really want to get more lift than what the cams are giving you with 1:1 rockers. |
I always thought more lift meant higher RPM's. I want this to be a lower spinning engine. I want the power band to top off at about 6000. Plus I already spent a few hundred on the solid shaft 1.1's. I know i could always just change the arms but I want to stick with them for now. |
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Foxy
Samba Member
Joined: June 10, 2003
Posts: 379
Location: Birmingham , UK
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| Posted: Fri Jun 17, 2011 12:23 am Post subject: |
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I'm no engine expert but I've always thought its duration that affects where the power band is more than the lift, lower duration then lower the powerband ( although I'm sure its not quite a straight forward as that ).
Thats why i went with the FK7 with 1:4 rockers, I've got .500 lift with a 288 duration.
If you do want to change the cam then the 2241 you mentioned does look like a better spec for what you are after. |
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