xtremerevolution Posted January 24, 2010 Report Share Posted January 24, 2010 I've always known about these. I know what they look like, but I don't know the differences they make from stock, with the exception of reducing friction, and I've always been curious. What's the difference between stock rocker arms and high performance roller rockers? For example, I installed 1.8 ratio roller rockers in my Regal, and I know that improved performance, but I don't know why or how. Does anyone know what the stock rocker ratio is for a Series 1 3800? What does changing that ratio do? How do these rockers affect lift/duration? Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted January 24, 2010 Report Share Posted January 24, 2010 Putting in higher ratio rockers increases your valve lift slightly. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 24, 2010 Author Report Share Posted January 24, 2010 Putting in higher ratio rockers increases your valve lift slightly. By how much? I believe the stock rockers are 1.6, so going to 1.8 I'm guessing would probably make a slight difference? Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted January 24, 2010 Report Share Posted January 24, 2010 Putting in higher ratio rockers increases your valve lift slightly. By how much? I believe the stock rockers are 1.6, so going to 1.8 I'm guessing would probably make a slight difference? It depends on your cam profile. Lets say you have a lift of .273" With a 1.6 rocker it would be .437" lift and with a 1.8 rocker it would be .491". It depends on your cam profile as to how much more lift and duration you get. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 24, 2010 Report Share Posted January 24, 2010 i believe the stock rockers are 1.6:1, but i'm not entirely sure on that. going from 1.6:1 to 1.8:1 is a 12.5% increase in lift. since the valves already move .378 and .373 with stock cam/rockers, it's now up to .425/.420. not sure on how much of a power bump it would be since i don't have all of the specs necessary for desktopdyno... Quote Link to comment Share on other sites More sharing options...
Addicted to eaton Posted January 25, 2010 Report Share Posted January 25, 2010 ok, i want to learn a little. so installing 1.8 rockers lets the car get more air? Quote Link to comment Share on other sites More sharing options...
90v65speed Posted January 25, 2010 Report Share Posted January 25, 2010 It basically does the same thing as putting a bigger cam in only it is easier to do. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 It basically does the same thing as putting a bigger cam in only it is easier to do. that is a very simple way of putting it. and entirely correct. it's basically the same cam with more lift right at the lobes. Quote Link to comment Share on other sites More sharing options...
Andrew Posted January 25, 2010 Report Share Posted January 25, 2010 their other advantage is that they have less/no deflection. stock stamped rockers actually bend slightly at their highest lift. roller rocks dont. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 roller rockers shouldn't. fixed. so installing 1.8 rockers lets the car get more air? potentially. up until you have so much lift that the heads can't possibly flow more... then you get to deal with port work/larger valves/more duration... Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 25, 2010 Author Report Share Posted January 25, 2010 I'm pretty sure I've reached that point with the regal. Remember how you said 3100 heads flow better than l67 heads? L27 heads flow even worse than that. I was a bit disappointed in the improvement the roller rockers got me over stock. Time for heavy porting work in March. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 I'm pretty sure I've reached that point with the regal. Remember how you said 3100 heads flow better than l67 heads? L27 heads flow even worse than that. I was a bit disappointed in the improvement the roller rockers got me over stock. Time for heavy porting work in March. it certainly sounds like you've hit that wall... or the stockers are higher lift than i'm thinking, in which case it won't make as large of an improvement... if you can find some L27 headflow charts/graphs/numbers, i can probably give you a realistic estimate of what you're pushing now... i had a hard enough time finding L67 flow numbers... if not, i can probably scale down the L67 numbers until it matches what a L27 puts out stock... Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 25, 2010 Author Report Share Posted January 25, 2010 I'm pretty sure I've reached that point with the regal. Remember how you said 3100 heads flow better than l67 heads? L27 heads flow even worse than that. I was a bit disappointed in the improvement the roller rockers got me over stock. Time for heavy porting work in March. it certainly sounds like you've hit that wall... or the stockers are higher lift than i'm thinking, in which case it won't make as large of an improvement... if you can find some L27 headflow charts/graphs/numbers, i can probably give you a realistic estimate of what you're pushing now... i had a hard enough time finding L67 flow numbers... if not, i can probably scale down the L67 numbers until it matches what a L27 puts out stock... I don't think its the lift that's the problem. The Series 1 L67 guys are pulling good numbers with these rockers. I don't think I'm going to find L27 flow charts. I don't think anyone has ever been quite that interested in Series 1 performance. Stock numbers are 170hp/225lb-ft. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 I don't think I'm going to find L27 flow charts. I don't think anyone has ever been quite that interested in Series 1 performance. Stock numbers are 170hp/225lb-ft. at what RPMs? and valve sizes? compression ratio? and either the TB size, or how well it flows? Quote Link to comment Share on other sites More sharing options...
Andrew Posted January 25, 2010 Report Share Posted January 25, 2010 its really impossible to compare flow numbers. different testers and testing techniques will have different results on the same heads. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 25, 2010 Author Report Share Posted January 25, 2010 I don't think I'm going to find L27 flow charts. I don't think anyone has ever been quite that interested in Series 1 performance. Stock numbers are 170hp/225lb-ft. at what RPMs? and valve sizes? compression ratio? and either the TB size, or how well it flows? HP 170 @ 4800 Torque (ft/lbs) 225 @ 3200 Compression 8.5:1 I have no clue on the throttle body numbers. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 25, 2010 Author Report Share Posted January 25, 2010 Got some more numbers. 1.71 and 1.487 for intake and exhaust valves respectively. I haven't found numbers on valve lift yet. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 25, 2010 Author Report Share Posted January 25, 2010 Got some info from the Bonneville forum regarding the roller rockers I'm using. well you aren't making any changes to duration.... just lift... But... with these rockers... iirc.. Your intake lift will go from .400 to .450 and you exahust will go from .408 to .459 I also got a lot of information there regarding reversion. It seems that the Series 1 engines are a lot more suceptible to it than the Series 2's, because of the flow restrictoins. My LIM is amateurly ported with a dremel (before I discovered air tools and porting wheels from summit racing), but I did notice a very big difference in the way the engine revved in idle after I ported that LIM, and a slight increase in performance. I have read in various discussions on the bonneville forum dating back to 2006 when the owner of Series1Performance.com was actually legitimate, that to get the full benefit out of these rockers LIM and Head porting were necessary. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 the stock lift on a L27 cam is .252/.255, so those numbers are close. you don't have any idea what size the bore is on the TB? i can calc theoretical flow from just size... Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 reversion is a tricky thing to deal with. the simplest way to ensure that it doesn't happen is to have make a small step when transitioning from different parts. reason being reversion seems to effect the air on the outside much more than the center of the airstream. mspaint is my friend here. that's how it's dealt with in exhaust, but i would think the same concept would apply with intakes as well... i believe stepped-tube headers are a perfect axample of this... Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 25, 2010 Author Report Share Posted January 25, 2010 the stock lift on a L27 cam is .252/.255, so those numbers are close. you don't have any idea what size the bore is on the TB? i can calc theoretical flow from just size... Got numbers for a 93 L27 TB, which I believe should be the same. 2.940 at diameter at the opening and 2.260 at the butterfly. As for exhaust, I do believe I have D shaped exhaust ports on the heads specifiaclly for the purpose of preventing reversion, which is exactly what you showed. My concern is more in regard to intake port reversion. I know the upper intake plastic insert was pretty well coated with an oily substance that also smelled of fuel the first time I took it off at 185k miles. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 that's roughly 57.4mm at the throat... so about 375cfm... here's what i came up with... Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 25, 2010 Author Report Share Posted January 25, 2010 that's roughly 57.4mm at the throat... so about 375cfm... here's what i came up with... According to that, I should have gotten a decent power increase, especially with an opened up exhaust and a CAI. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted January 25, 2010 Report Share Posted January 25, 2010 that's roughly 57.4mm at the throat... so about 375cfm... here's what i came up with... According to that, I should have gotten a decent power increase, especially with an opened up exhaust and a CAI. i see a peak increase of 4HP... and 3 lbs of torque.... from the rockers alone anyway. adding in the exhaust and CAI? i'd have to be much more familiar with 3800 stuff to know for sure. Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted January 25, 2010 Report Share Posted January 25, 2010 Different ratio rockers is really just a way to play with exhaust/intake tuning. Some motors might like a 1.65 ratio on the intake and a 1.5 on the exhaust. I personally know people that run these in their cars, although its older muscle carb'ed engines. Quote Link to comment Share on other sites More sharing options...
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