Hi ThereIam looking at upgradeing my rockers on my ls1 stock are a flat tip 1.7.1 ratio so iam looking at remanufactured 1.9.1 high ratio or a true roller tip rockers with a 1.8.1 high ratio after your toughts on which would be the better way to go as the the US has a lot more experience with these parts than we have here in Australia
one of your first issues will be valve clearance to the piston. easy test is to pull the head, put a lump of clay on the piston, then put the head back on and spin the engine over to get an idea of what the clearance is when every piece of metal is cold and hasn't expanded.roller tips will reduce friction, but you want to make sure either choice is hitting the top of the valve stem spot-on as it cycles thru its lift off the seat, up to full lift, then back down again. Can't be hitting the valve stem seal or guide, either.
Just because you can't do it...doesn't mean its impossible
HiThis is Greg I make roller rockers some things to think about are piston to valve clearance, fuel and a few more things that matter.If you have more questions call me at 440-242-5004 I can make you roller rockers at any ratio you want .
There are alot of things going on when you are pushing the envelope. For example. A .300 base lift cam. 1.5X.300= .4501.6X.300= .4801.7X.300= .5101.8X.300= .5401.9X.300= .570By increasing the rocker arm ratio you have taken your base .450 to .570 that is an increase of .120You have valve to piston clearance that was already mentioned.You have valve train geometry to worry aboutYou will have to use big block valve springs You will have to install atleast .100 longer valvesYou will have retainer interferenceWhy not install a bigger camshaft and use a 1.6 rocker arm.Your heads will need to flow some big numbersI don't know what your purpose is. I hope your not going to have us chase our tails for something that is not fesable. Bob
Hello BobThe purpose of the excerise i have looked at remanufactred ls1 rockers from 1.7.1 to 1.9.1 which they claim increases power by ave of 5% or 10-13 rwkw and another company claims the same power gains but with there 1.8.1 ratio with roller tips not sure what is the best way to go iam looking at these products as one way to increase power on a budget as i have tight budget also been informed that if i go 1.9.1 I will have to replace valve springs but with 1.8.1 roller tips i wont need to replace springs whats intresting is same power gains with diffrent ratios so they claim.
Rayssupu6 I think what happens in some worlds the heads just stop flowing. It's the same as installing a bigger cam and not doing anything to increase the cylinder head flow. Here is what I think happens. The 1.8 will still make power with the head flow and the 1.9 stops making any more power, because the head stops flowing. If you have the specs on your cam then divide that by your stock rocker arm ratio. Then with that figure multiply that by the stock 1.8 then by 1.9 rocker arm ratio. Ray when I did those figures I took a generic number I.E..300X each rocker ratio. I'm doing heads for guys that are using 1" of cam lift. NO CHIT...I apoligize it took so long for me to get back on the site. I hope this helps and hope your still on our site... Bob
Thanks BobLooks like after reading your post that I will go with the 1.8.1 ratio rockers with the roller tip (less friction better wear on valve tips)
Many thanks to you and good luck: Yeah we (my buddie crazy Dave the Dyno guy) and I test rocker ratios to see if we can make more power and where we can make it. Just by moving Rocker Arm Ratios around. You know when we run data acqusition the numbers will tell us this or that. The physical result is really worse. On certain engines we can touch it and the HP increaeses, and yet there are other's they won't move either way...LOL... It seems the cam that a customer may bring me is at it's limit, its at the end of its potential. So when I call a customer and tell them we need more camshaft I either get a yes or a no. Just for an example. I remember back in the early 70's when I worked developing Jet engines for recon. aircraft, everything revolved around Fuel. More or less made the difference. But then there were times when we ran a Government acceptnce test. We had to hold levels of power X amount of time and the jet would be low on power. So we would them to a ground idle and actually through ground up Walnut Shells into the intake and then shoot water in them to clean the blades off, and the power level would come back. Thanks again. Maybe you might installing the 1.8's on the exhaust side first, and see if that makes a difference,or put them on the intake an try that. There maybe hidden power with an intake or reverse change only...Bob