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Old 11-12-2007, 22:48   #1 (permalink)
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1.7 or 1.73 rocker ratio?

I'm ready to purchase the rockers now. I've decided on full roller rockers but I'm finding two different ratios, 1.7 and 1.73. My Lunati cam specs are based on 1.73 but I believe the factory ratio is 1.7. I've calculated (hopefully correctly) that the 0.543 exhaust valve lift becomes 0.534 and the 0.516 intake valve lift becomes 0.507 with the 1.7 rockers. From what I've read duration isn't significantly affected with the different rocker ratio. I'm thinking of going with the 1.7s because I'm looking for lower to mid rpm for towing my RV and the 1.73 rockers are $100 more than the 1.7 rockers. I think the 1.7s actually might work better, although I suspect the diference would be minimal anyway. Is that sound reasoning or am I off base?

Thanks for your input.

Ron
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Old 11-13-2007, 12:38   #2 (permalink)
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cool Re: 1.7 or 1.73 rocker ratio?

If they are Ford-specific rockers, then you are okay. If they are big block chebby rockers (BBC uses 1.7 ratio), then it varies from brand-to-brand and you need to know the detailed differences. Also, beware of the cheapo chinese BBC rockers that might be being sold as Ford applicable because the seller believes they are "close enough" to be used as BBF rockers (some BBC rockers you can get away with this, and some you cannot...in a mild build as yours, you are probably okay but I don't know wht brnd rockers you are considering).

Paul
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Old 11-13-2007, 14:20   #3 (permalink)
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Re: 1.7 or 1.73 rocker ratio?

Paul,

I'm considering Comp Cams 1330-16 (1.7 ratio) and 1130-16 (1.73 ratio). Both are Ford engine specific so I feel comfortable with that. The 1130-16 rockers are roughly $100.00 a set more that the 1330-16. Do you believe there will be noticable performance loss with the 1.7 rockers, especially considering it's application? I guess what I'm asking is - Is the extra $100.00 worth the minor extra lift for my engine? I'm somewhat concerned about piston to valve interference with the added lift as well, albeit only about 0.010. I have recessed pistons so I really don't think it will be an issue anyway but I hate to spend the money and find out there is an issue. Maybe I just worry too much................

Any opinion appreciated.

Ron
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Old 11-23-2007, 20:15   #4 (permalink)
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cool Re: 1.7 or 1.73 rocker ratio?

Quote:
Originally Posted by Rlzegers
Paul,

I'm considering Comp Cams 1330-16 (1.7 ratio) and 1130-16 (1.73 ratio). Both are Ford engine specific so I feel comfortable with that. The 1130-16 rockers are roughly $100.00 a set more that the 1330-16.
You have privided us with only one part number for both rocker sets. The rocker arms that you're considering are:
  • 1130-16 (Hi-Tech Stainless)
  • 1330-16 (Pro Magnums)
I am told the Pro Magnums are a CAST rocker arm, not my first choice. The other (more expensive) is a stainless steel rocker arm. Either will work in a hydraulic lifter cam application just fine. The Hi-Tech Stainless rockers are the superior rocker.

I know a guy that had a Pro Magnum rocker break under the trunnion bearing (air bubble). Comp replaced the rocker under warranty, and then he sold the set and bought aluminum roller rockers.
Quote:
Originally Posted by Rlzegers
Do you believe there will be noticable performance loss with the 1.7 rockers, especially considering it's application?

Ron
Technically speaking, timing events will be affected, but in a hydraulic lifter cam application, I don't think you'll feel any power difference between 1.70 and 1.73 ratios.

Paul
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Old 11-14-2009, 09:38   #5 (permalink)
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Re: 1.7 or 1.73 rocker ratio?

Quote:
Originally Posted by Rlzegers View Post
Paul,

I'm considering Comp Cams 1330-16 (1.7 ratio) and 1130-16 (1.73 ratio). Both are Ford engine specific so I feel comfortable with that. The 1130-16 rockers are roughly $100.00 a set more that the 1330-16. Do you believe there will be noticable performance loss with the 1.7 rockers, especially considering it's application? I guess what I'm asking is - Is the extra $100.00 worth the minor extra lift for my engine? I'm somewhat concerned about piston to valve interference with the added lift as well, albeit only about 0.010. I have recessed pistons so I really don't think it will be an issue anyway but I hate to spend the money and find out there is an issue. Maybe I just worry too much................

Any opinion appreciated.

Ron
Hello,
New member here.
I'm in the exact same boat you were in and wanted to know the outcome. Which rocker did you choose and was there a difference with the 1.7 vs. 1.73 ratio?

Thanks,
Jim
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Old 11-14-2009, 12:02   #6 (permalink)
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Re: 1.7 or 1.73 rocker ratio?

Hi Jim and welcome to the forums!

I went with the 1330-16 (1.7 ratio) because it was easier on the budget and I felt the .03 in ratio wasn't significant in terms of my application and not worth the extra $100 in costs. I have about 4000 miles on the engine and so far no issues. I'm using a Lunati 00096 cam and the engine performs well in the towing application my truck is used for. That being said I would suggest considering 1130-16 for the reasons Paul stated if the budget allows it because castings do carry a risk of air pockets. I suppose it depends somewhat on application. For my engine where RPM seldom reaches 4000 I feel comfortable with the 1330-16. If it's a more severe application 1130-16 might be the better choice.

Does that help at all?

Ron
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