Rocker arms question
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Postmaster
Joined: Apr 2004
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From: Santa Clarita
Rocker arms question
I'm running a 289 Ford in my truck. It has a cam with 480 lift 272 duration. A buddy of mine gave me a set of rocker arms. They are metal like the originals, but have the roller bearing on the end instead of the flat tappet like the original one have. The box also says they are 1.7. What would be the benefit of switching my stock rockers with these, or is there a benefit? Someone told me I would get more lope sound from the cam.
Postmaster
Joined: Jun 2004
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From: Riverside, So Cal
The roller tip means that the action is smoother. However, 1.7 is a huge ratio. It multiplies the cam lift. You'll be effectively running .816 lift on each valve (I think). Are you sure the pistons are cleared to handle that? Normally, rockers like that are used with a low lift stock cam.
At least that's my understanding of it. I could be wrong. But that setup sounds real iffy to me.
At least that's my understanding of it. I could be wrong. But that setup sounds real iffy to me.
Post Fiend
Joined: Feb 2001
Posts: 6,328
Likes: 124
From: Iowa
RJ
The .480 cam lift spec already accounts for a specific rocker arm ratio. Likely 1.6 was used.
Ed
Jumping up to a 1.7 rocker arm is frequently done by the Mustang crowd. You get a minor increase in lift and a VERY minimal increase in duration. It would take a good ear to hear it IMO. The custom cam I just bought has two sets of numbers on the spec sheet. One for 1.60 rockers and another for 1.72. You need to check for rocker arm geometry with a rocker change, and account for it with custom length pushrods in many cases. Not really worth the trouble for the gain potentially achieved IMO.
EDIT: Found my specs in my carry on bag. This should give you an idea. My cam with 1.6 rockers nets the following at the intake valve .5344, and .5678 with 1.7 rockers. Lobe lift at the cam is .334
Duration change is so minor it isn't even listed on the sheet. I have seen egghead pro cam grinders do the math on stang forums, and back it up with a degree wheel. Duration is what you hear. Valve overlap causes cam lope. 1.7s won't get you there with a mild cam.
The .480 cam lift spec already accounts for a specific rocker arm ratio. Likely 1.6 was used.
Ed
Jumping up to a 1.7 rocker arm is frequently done by the Mustang crowd. You get a minor increase in lift and a VERY minimal increase in duration. It would take a good ear to hear it IMO. The custom cam I just bought has two sets of numbers on the spec sheet. One for 1.60 rockers and another for 1.72. You need to check for rocker arm geometry with a rocker change, and account for it with custom length pushrods in many cases. Not really worth the trouble for the gain potentially achieved IMO.
EDIT: Found my specs in my carry on bag. This should give you an idea. My cam with 1.6 rockers nets the following at the intake valve .5344, and .5678 with 1.7 rockers. Lobe lift at the cam is .334
Duration change is so minor it isn't even listed on the sheet. I have seen egghead pro cam grinders do the math on stang forums, and back it up with a degree wheel. Duration is what you hear. Valve overlap causes cam lope. 1.7s won't get you there with a mild cam.
Last edited by fatfenders; Sep 23, 2006 at 07:25 AM. Reason: SPECS
Fleet Owner
Joined: Jul 2004
Posts: 27,290
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From: NM
Need to check for spring bind, too.
That seems like an awful lot of cam for a small-displacement engine in a heavy vehicle. Might be good with the stock rear end ratio (high 3's or low 4's) but aren't you hurting for low end torque?
That seems like an awful lot of cam for a small-displacement engine in a heavy vehicle. Might be good with the stock rear end ratio (high 3's or low 4's) but aren't you hurting for low end torque?
Elder User
Joined: Sep 2006
Posts: 630
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From: Dayton, OH
Are you running stock press in stud heads or do they have screw in studs?
I had the problem running stock rockers on a 302 and I had to relief cut each hole about .30 thats the slot in each rocker I mean. I was snapping rocker arms.
I played around with running guide plates and diffierent types of rockers. I just buy new GT 40 heads now instead of rebuilding old ones. The cost is about the same.
I had the problem running stock rockers on a 302 and I had to relief cut each hole about .30 thats the slot in each rocker I mean. I was snapping rocker arms.
I played around with running guide plates and diffierent types of rockers. I just buy new GT 40 heads now instead of rebuilding old ones. The cost is about the same.
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Postmaster
Joined: Apr 2004
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From: Santa Clarita
Thanks guys.
I'm not sure if I will go with these rockers or not?
Oldgreen- I originally had the pressed in rocker studs, but after putting this cam in, (timing gear was off) I tried to start the engine and studs were litterly coming out. I took the head off and had screw in stud put in.
I'm going to have to look at the specs for my cam. It runs good, but sure seems and idles like a stock grind.
Fatfenders- good to hear from you again. You back home?
I'm not sure if I will go with these rockers or not?
Oldgreen- I originally had the pressed in rocker studs, but after putting this cam in, (timing gear was off) I tried to start the engine and studs were litterly coming out. I took the head off and had screw in stud put in.
I'm going to have to look at the specs for my cam. It runs good, but sure seems and idles like a stock grind.
Fatfenders- good to hear from you again. You back home?
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Postmaster
Joined: Apr 2004
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From: Santa Clarita
Hey guys, I just found the specs on my cam. Let me know what you think.
Valve Lift: Intake: .450 Exhaust: .474
Lobe Centers: Intake: .108 Exh:. 116
Duration: Intake: .280 Exhaust: .289
.050 Duration: Intake: .204 Exhaust: .214
The guy who sold me this cam said it would be nice little loper without changing the valve train. No offense, my truck idles nicer than my wife's Nissan Maxima. With these specs, would the 1.7 rockers help? Thank guys.
Valve Lift: Intake: .450 Exhaust: .474
Lobe Centers: Intake: .108 Exh:. 116
Duration: Intake: .280 Exhaust: .289
.050 Duration: Intake: .204 Exhaust: .214
The guy who sold me this cam said it would be nice little loper without changing the valve train. No offense, my truck idles nicer than my wife's Nissan Maxima. With these specs, would the 1.7 rockers help? Thank guys.
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Post Fiend
Joined: Feb 2001
Posts: 6,328
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From: Iowa
Ed
Those are pretty mild cam specs. I wouldn't expect any binding problems, or stud pulling. Correct alignment between the rocker roller tip and the end of the valve stem should still be checked though. It's a bit tedious, and not worth it in my opinion for a slight change in sound. You use an adjustable pushrod to determine what length push rods you really need with the new rocker arms. Then buy custom pushrods of the proper length. Or you can just assemble it and hope nothing bad happens next time you wind up some RPMs. That's what many guys do.
And yes, I am home now.
Those are pretty mild cam specs. I wouldn't expect any binding problems, or stud pulling. Correct alignment between the rocker roller tip and the end of the valve stem should still be checked though. It's a bit tedious, and not worth it in my opinion for a slight change in sound. You use an adjustable pushrod to determine what length push rods you really need with the new rocker arms. Then buy custom pushrods of the proper length. Or you can just assemble it and hope nothing bad happens next time you wind up some RPMs. That's what many guys do.
And yes, I am home now.
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Postmaster
Joined: Apr 2004
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From: Santa Clarita
Thanks Dwayne, I think I'll pass on installing these. It almost sounds simpler to just change out cam. Glad I got the info before switching them over. I guess the guy who sold me the cam fooled me thinking my cam was suppose to be more than what it really is and that it would be a nice loping cam. Maybe I'll install a B&M Supercharger instead? 
Last edited by imlowr2; Sep 24, 2006 at 10:37 AM.
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