bbc r.rockers 1.7 with 3/8" studs!!
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Lead Driver
Joined: Mar 2008
Posts: 7,165
Likes: 375
From: Near Los Angeles
bbc r.rockers 1.7 with 3/8" studs!!
I just found out that Crane Cams makes roller rockers for the 409 bbc with 1.7 ratio and 3/8" studs.
I just bought a set of the Pro/Race ones, p.n. 15750-16, $474 at Summit, for $100 at the auto swap meet. And they're cherry, not even a shine where the pushrod sits, or where it rolls on the valve end! The guy said he had a problem with the valves, so the rockers were bolted on and taken off, never run.
The engine they are made for puts out oe 360 hp, so I think my screw in hardened studs are plenty strong.
I'm laughing....
I just bought a set of the Pro/Race ones, p.n. 15750-16, $474 at Summit, for $100 at the auto swap meet. And they're cherry, not even a shine where the pushrod sits, or where it rolls on the valve end! The guy said he had a problem with the valves, so the rockers were bolted on and taken off, never run.
The engine they are made for puts out oe 360 hp, so I think my screw in hardened studs are plenty strong.
I'm laughing....
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Lead Driver
Joined: Mar 2008
Posts: 7,165
Likes: 375
From: Near Los Angeles
I am a bit leery though. It seems I am stepping into a rather questionable gray area is using performance cam with the higher ratio lifters, and I'm not sure that I want to be questionable or doubtful on long trips. I may simply sell the rockers on ebay and buy the Crane 503901 cam, or the 503941. I'm waiting to hear from a couple of trusted mechanics regarding this.
I will keep you posted.
Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
The only risk involved is valve to piston clearance. Do you know how to check valve to piston clearnance? I'm not intimately familiar with the 300, but my gut is telling me that there is no problem in this area, but better be safe rather than sorry.
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Lead Driver
Joined: Mar 2008
Posts: 7,165
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From: Near Los Angeles
I spoke with a guy on the other forum who is running the Crane 503901 cam with the bbc Crane 13750 1.7 rockers. I think that is a bit too radical for me, with over .500 lift on the exhaust, and close to it on the intake lift.
Postmaster
Joined: Dec 2006
Posts: 3,603
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From: Spokane, WA
The usual and recommended procedure for obtaining higher lift is with a cam rather than with rockers or high performance cam + rockers. The higher lift is best ground into the cam. On the other hand, the cam + roller rockers may alleviate some of the additional wear/strain that plain rockers would put on the valve train.
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FTE Legend
Joined: May 2008
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From: In my own world
The usual and recommended procedure for obtaining higher lift is with a cam rather than with rockers or high performance cam + rockers. The higher lift is best ground into the cam. On the other hand, the cam + roller rockers may alleviate some of the additional wear/strain that plain rockers would put on the valve train.
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Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
The usual and recommended procedure for obtaining higher lift is with a cam rather than with rockers or high performance cam + rockers. The higher lift is best ground into the cam. On the other hand, the cam + roller rockers may alleviate some of the additional wear/strain that plain rockers would put on the valve train.
Obtaining higher lift with the use of higher ratio rocker arms is actually quite preferable than grinding it into a cam. When grinding it into a cam it is necessary to increase duration to prevent having a cam profile that will promote rapid wear on cam and lifters.
Obtaining higher lift via rocker ratio allows for higher lift without the negative effects of added duration. It is a quite legitimate and accepted modification as long as the correct geometry is used and there is no valve piston clearance problems.
Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
Taller valves will NOT increase effective rocker ratio.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
Very true. The valve's length has nothing to with the distance between the pivot point and ends of the rocker.
Taller valves will change the rocker arm's installed angle, and can cause other problems, but do not change the rocker ratio.
Taller valves will change the rocker arm's installed angle, and can cause other problems, but do not change the rocker ratio.
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Lead Driver
Joined: Mar 2008
Posts: 7,165
Likes: 375
From: Near Los Angeles
Hey guys--
Thanks for all the feedback. I am still learning about all this stuff, so it is always good to hear from other with more experiance.
My valves are longer by .095 more than oe Ford, but my machinist does not know if that is above the seat length. My cam has .450 lift. With the rocker change I will have .475. That seems extreme to me. Crane is the only one making cams for the 300 with that much lift, to my knowledge.
I am going to set it up, check it, and if satisfied I will run it a bit. To tell you the truth, it does worry me with that much lift. But when I look at it on the mich,, it seems like nothing. If there is a problem, or I simply don't like it, I'll sell the rockers on ebay.
There is a guy on the other forum running the Crane Cams 503941, which has more lift than mine, with the same rockers.
Thanks for all the feedback. I am still learning about all this stuff, so it is always good to hear from other with more experiance.
My valves are longer by .095 more than oe Ford, but my machinist does not know if that is above the seat length. My cam has .450 lift. With the rocker change I will have .475. That seems extreme to me. Crane is the only one making cams for the 300 with that much lift, to my knowledge.
I am going to set it up, check it, and if satisfied I will run it a bit. To tell you the truth, it does worry me with that much lift. But when I look at it on the mich,, it seems like nothing. If there is a problem, or I simply don't like it, I'll sell the rockers on ebay.
There is a guy on the other forum running the Crane Cams 503941, which has more lift than mine, with the same rockers.
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Lead Driver
Joined: Mar 2008
Posts: 7,165
Likes: 375
From: Near Los Angeles
Hey guys--
I've decided to pull the plug on the 1.7 rockers. I just don't feel comfortable with that much lift. Because of the .095" longer sbc valves, I just feel it would be adding a risk factor that I don't want.
It would be fun to feel that much power for a short time, but it is my daily driver, and dependability is very important to me. When I am 18 hours into Mexico, I want to KNOW that all is well, and not have a nagging hunch that I'm going to suck a valve.
I may go with the next step up in the Isky cams, the 262 duration (as opposed to 256 degrees), with .005 less valve movement. Is that MORE power?
I've decided to pull the plug on the 1.7 rockers. I just don't feel comfortable with that much lift. Because of the .095" longer sbc valves, I just feel it would be adding a risk factor that I don't want.
It would be fun to feel that much power for a short time, but it is my daily driver, and dependability is very important to me. When I am 18 hours into Mexico, I want to KNOW that all is well, and not have a nagging hunch that I'm going to suck a valve.
I may go with the next step up in the Isky cams, the 262 duration (as opposed to 256 degrees), with .005 less valve movement. Is that MORE power?
Thread Starter
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Lead Driver
Joined: Mar 2008
Posts: 7,165
Likes: 375
From: Near Los Angeles
I just found something very interesting indeed. I was reading on the isky site regarding the 256 and 262 super cams. With bbc, bbf, and chevy inline sixs, the 256 is producing .492 lift on the valves.
It is the rocker ratio that limits the 300. With the proper springs, etc., it is 'normal' for that grind to produce much higher lift than the .475 I would be getting. And Isky still calls it an economy cam.
Yep, the Chevy inline is getting .492 valve lift with the 256 duration, and it is still an economy cam!! That says volumes.
It is the rocker ratio that limits the 300. With the proper springs, etc., it is 'normal' for that grind to produce much higher lift than the .475 I would be getting. And Isky still calls it an economy cam.
Yep, the Chevy inline is getting .492 valve lift with the 256 duration, and it is still an economy cam!! That says volumes.