66ninetyeightls

I have been looking at different rocker arms to replace mine since one of my rocker arms broke last Friday.

I have found a number of different options:

1) Sealed Power Stamped Steel 1.5 Ratio $14.50CDN pair = $116CDN (FULL SET)
2) Comp Cams High Energy Stamped Steel 1.6 Ratio $130CDN (FULL SET)


What would the difference be between these rocker arms? What difference would the ratio make???

Eddie Hansen

the ratio decides how much the cam will open the valves the stock ratio of olds motors is 1.6, if you think about it your cam pushes up on the lifter the lifter pushes up on the pushrod, which pushes up on the rocker, which pushes down on the valve. by going with the 1.5's you will decrease the amount of push down, thus reducing the valves opening so you will be restricting both intake and exhaust, lowering performance.

Other guys will jump in with more technical advice, but I would go with the stock ratio, unless your using a cam that requires less ratio.

you do know you need studs put into the heads for the roller tip rockers right?

Eddie Hansen

are these roller tips? just reread your post, now not sure

66ninetyeightls

No these are not roller tip. I was looking at those as well but didn't see the point of rolelr tip without going full roller. They are supposed to be stamped steel stock replacement rockers.

Eddie Hansen

craig, ok disregard about the studs then, but the ratio info is still valid.

svnt442

The stock ratio on all modern (64-90) Olds V*s is 1.6 so stay with that.

66ninetyeightls

The ones from Federal Mogul (Sealed Power) 1.5 Ratio are the only ones local parts suppliers can seem to find, which are listed as stock replacement units and they can get them in 1 day. However the Comp Cam units at 1.6 ratio will take 3-4 weeks to get.

I wonder if it’s just a misprint or something..... They are listed for 66+ Oldsmobile engines 260 - 455.

If that ratio of 1.5 is correct how much difference would that make in regards to power??? Would it be noticeable?? I am not really looking for a racer as you can tell by my vehicle choice (1966 98 LS) LOL, just a car I can cruise around in. However if it’s going to make a noticeable difference in power & fuel economy I might rethink it.

svnt442

Trust me when I say that 1.5 ratio is not correct. It is either a misprint or he looked up the wrong parts.

On a stock cam where the advertised lift is say .440 with a 106 you wold drop down to .412. If is was a .400 lift you would drop down to .375.

So you see it can make a big difference.

66ninetyeightls

I trust you. I have done the searching and come up with the same specs... Thats why I posted this thread to begin with.

I was looking to see if there was a way to contact Federal mogul to verify the specs but can't find anything.

geckonz08

[quote=Eddie Hansen;168189]the ratio decides how much the cam will open the valves the stock ratio of olds motors is 1.6, if you think about it your cam pushes up on the lifter the lifter pushes up on the pushrod, which pushes up on the rocker, which pushes down on the valve. by going with the 1.5's you will decrease the amount of push down, thus reducing the valves opening so you will be restricting both intake and exhaust, lowering performance.

Other guys will jump in with more technical advice, but I would go with the stock ratio, unless your using a cam that requires less ratio.



sounds like a mighty fime explanation to me Eddie.
Some of us (me) don`t do technical!!
mike

Eddie Hansen

craig try here?
http://www.federalmogul.com/en/ContactUs/NorthAmerica/

here is some good info
http://www.442.com/tech/enginearticle.html

also while your looking
http://www.streetperformance.com/par...8-1242-16.html

http://www.rockauto.com/catalog/rafr...856&a=FR8-R856

hope it helps

66ninetyeightls

I contacted Summit Racing and they gave me the technical contact number at Federal Mogul. 1-800-325-8886

I spoke with the guy at Federal Mogul and explained to him about the difference in ratio. He said it was most likely a misprint as they are straight copies of the factory rockers.

cutlassefi

One other thing, by changing your rocker ratio to something different than stock you also change your effective overlap. Although not much of an issue on a stock cam, by lowering the ratio you decrease effective overlap. By increasing ratio the reverse is true. You're holding the valves open more or less at that point of overlap depending on the rocker ratio. Gets to be an issue on bigger cams. Stick with the 1.6 at least. If you go with an adjustable setup then I might consider a 1.7.

InfoJunkie

If you are looking for stock replace parts from Federal Mogul this link takes you direct to the catalog.http://www.fme-cat.com/
It will give you the part numbers for what you need.