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Old 04-23-2010, 01:19 PM
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can any gurus explain "roller"

i hope this is'nt a stupid question. i'm not a full gear head yet but i'm trying I understand roller rockers but what does it mean to have a full roller motor. my reason is this

i am building a an sbc (casting #4088548 4bolt) and i am following a build i read on gm performance dot com. I'm using vortec heads(casting 12558062) and the build said it produced 440hp. i am bowl blending the heads which they didn't do in the build and was told this will up my hp from 15hp to 20hp. i will probably just get the part #'s from the site and buy the same valve train they used. but i would still like to understand the hole roller concept. i get that it reduces friction but is that it? what is a roller cam vs a hydrolic cam? roller lifters? roller ratios like 1.6 vs 1.5 or 1.7 etc. again sorry if this is a stupid question but I'm sure theirs a lot of newbie gear heads who wold like this knowledge.

thanks for any input in advance
brian

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Old 04-23-2010, 02:10 PM
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a "full roller" would be roller cam/lifters and roller rocker arms.
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Old 04-23-2010, 02:22 PM
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okay a full roller refers to a motor with a roller camshaft, roller lifters, and roller rocker arms, pretty much if you're using a roller camshaft then you will end up using these other parts anyway and you will have a full roller. a roller valve train does have less friction but as far as gaining a bunch of power from the less friction, there wont be much. you have 4 different kinds of cams, hyd flat tappet which uses a lifter with a flat surface that contacts the camshaft lobe. then you have a solid flat tappet camshaft, this too uses a lifter with a flat surface that contacts the camshaft lobe. the difference between a solid and hydraulic is a hydraulic lifter has a spring in it that compensates for the clearances needed in the valve train due to the expansion of heat and contracting of cooling while the engine is running a solid lifter does not and requires that you set the valve lash (gap between the rocker end and the valve stem) for the clearances needed as mentioned before. then you get into roller camshafts, both solid and hydraulic roller camshafts use lifter with a rolling wheel that contacts the camshaft lobe, but like the flat tappet lifters the hydraulic uses a spring and the solid does not. typically a roller cam can have a more aggressive ramp rate and is also has higher peaks on it's lobes resuliting in a higher lift to the valve, although a flat tappet is acutally able to start it's ramp at a more agressive rate the roller's over all rate will be more aggressive from begining to end.

all camshafts specs that are advertised in say summit/jegs/scoggin dicky etc are rated for a 350ci engine and for 1.5 ratio rockers, when you choose to use a 1.6 ratio rocker in the valve train you are actually increasing the rate at which the valve open and closes as well as how far it opens and closes,

example a cam with an advertised lift of .490" with 1.5 rockers will still just open the valve .490" but when you choose to use a 1.6 rocker then that lift now has to be mulitplied due to the higher ratio. the ratio of 1.5 to 1.6 can be mulitplied by using this number 1.0666, so take .490 X 1.0666 = .523" lift at the valve. now when talking about a solid cam you also have to take into acount the valve lash set. say your valve lash is .024" and your lift (w/ 1.5 rockers) is .550" but you chose to use 1.6 rockers, .550 x 1.0666 = .587" but you have .024" clearance between the rocker and the valve stem so now take .587-.024= .563" lift at the vale but as the motor warms up and the parts expand the clearance will get smaller and the valve lift will grow (some)
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Old 04-23-2010, 02:37 PM
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Currently, there are 4 types of cams being used.

1. Solid flat tappet. This is the cheapest cam to buy. Very basic, no frills or fancy stuff. Tappets (same as lifters, just a different word to describe them) are "solid", with no provision for an internal plunger or oil. Valve lash (there must be some play in the system, otherwise the valve could be held off the seat all the time) is accomplished by manually adjusting at the rocker arm or with adjustable pushrods from time to time, usually figure on adjusting the valves every other oil change for a street driver. Lots of roundy-round racers use this type cam. Will allow maximum revs compared to hydraulic cams. Bottom of lifter is cut on a long radius, can't remember, maybe 50 inches. Tie down a 50" long string to a nail. Tie a pencil onto the other end of the string and describe a short line (roughly 7/8ths of an inch long) on a piece of paper. That very shallow radius is what the bottom of a flat tappet should look like. I'm trying to get you to understand that the bottom of a flat tappet is not flat, but crowned. It rides on a cam lobe that has been cut on a downslope from one end of the lobe to the other, so the edge of the cam lobe rides on the crown of the lifter and spins it in the lifter bore. There is only a very tiny contact point between the lifter and the cam lobe. If lifters are too tight or too loose in their bores, they will not spin properly and the cam lobe rubs on the same spot again and again. This will destroy the bottom of the lifter, which then destroys the cam lobe and things go south in a hurry. Flat tappet cams can also be destroyed quickly with excessively stong valve springs. That small pencil point of contact at the lifter crown/cam lobe can't take but just so much pressure without galling the steel by wiping off the lube between the parts. Requires a complex break-in procedure to prevent premature failure. Also requires that extreme pressure lubricants be added to the engine oil with each oil change or use an oil that still has these EP lubricants in it (dedicated racing oils such a Brad Penn).

2. Solid roller tappet. More money. More complexity. Prettier parts. Roller tappet cam lobes are ground straight across, with no slope to the lobe as you look at the cam along its length. The rollers on the lifter are also ground straight across, flat, so that the roller rolls around the cam lobe making full contact between the lifter roller and the cam lobe. Because this is still a mechanical tappet cam with no automatic adjustment at the lifter, the owner must do periodic lash adjustments just like with a solid flat tappet cam. This is the cam of choice for anyone looking for max performance, regardless of price and freedom from worry about one of the lifters going south and taking a lobe out with it. No break-in process required. No special EP lubricants required.

3. Hydraulic flat tappet. Same basic design as solid flat tappet, except that the lifter is designed to adjust the valve lash automatically after the initial valve lash adjustment at the time of engine build. Will not rev as high as solid flat tappet due to the lifters "pumping up" and holding the valves off their seats at the upper rpm operating limit. Best used with reasonable valve spring pressures, stock rocker arm ratios, closely observing the break-in process and inclusion of EP lubricants in the engine oil in a daily-driver type motor where the owner does not wish to adjust the valves periodically. There is still a plethora of offshore (Chinese) lifters floating around in the marketplace. The price of these parts makes them very attractive to amateur engine builders who are unaware of the quality of these parts. If you are going to use hydraulic flat tappet lifters (which I do not recommend), then by all means try to find the best lifters money will buy. Get the whole mess as a cam/lifters/springs/retainers/locks/shims package from a well known cam grinder.

4. Hydraulic roller tappet. Same basic design as solid roller tappet, except that the lifter is designed to adjust the valve lash automatically after the initial valve lash adjustment at the time of engine build. This is the heaviest lifter among the 4 types outlined here, therefore it will have a lower rpm limiting range than a hydraulic flat tappet. The lifter actually begins to separate from the cam lobe at design limit engine speeds, requiring either reduced engine speeds or the inclusion of an additional "rev kit" set of springs in the lifter valley to assist the heavy lifter in staying in contact with the cam lobe. Generally speaking, this rev limit without the additional rev kit will be around 6200 rpm's. If the owner can absorb the initial cost of this design, it will be the most maintenance-free of the 4 types outlined here. No break-in procedure. No EP lubricants required. No worry about valve spring pressures roaching the lifter. This makes a great daily driver or street/strip cam.

To answer your other question, roller cams can have a much more agressive lobe design because there is no edge of a lifter trying to dig into the cam lobe like there is on a flat tappet type cam. You can WHAM, yank the valve open, leave it open longer and WHAM, slam it closed. The lobes on a roller cam look more rectangular than egg shaped like on a flat tappet cam.

Last edited by techinspector1; 04-23-2010 at 02:49 PM.
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Old 04-23-2010, 02:38 PM
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wow 87z that was great, thank you so much.... i had to read it a couple times to get it to click but it did

techinspector1 thanks that was great as well. anytime i see your post i always stop and read .... your kinda my hero
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Old 04-23-2010, 02:45 PM
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between what Tech1 and I said you aught to have a little bit of grasp on how the different cams and lifters work.
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Old 04-23-2010, 03:20 PM
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Quote:
Originally Posted by v8mazda
i hope this is'nt a stupid question. i'm not a full gear head yet but i'm trying I understand roller rockers but what does it mean to have a full roller motor. my reason is this

i am building a an sbc (casting #4088548 4bolt) and i am following a build i read on gm performance dot com. I'm using vortec heads(casting 12558062) and the build said it produced 440hp. i am bowl blending the heads which they didn't do in the build and was told this will up my hp from 15hp to 20hp. i will probably just get the part #'s from the site and buy the same valve train they used. but i would still like to understand the hole roller concept. i get that it reduces friction but is that it? what is a roller cam vs a hydrolic cam? roller lifters? roller ratios like 1.6 vs 1.5 or 1.7 etc. again sorry if this is a stupid question but I'm sure theirs a lot of newbie gear heads who wold like this knowledge.

thanks for any input in advance
brian
One first would need to understand what the engine will be used for, the vehicle, gear ratios, trans type, tire diameter, etc.

Going for big power is nice, but a 440 horse, vortec headed, I'm assuming 350 is going to take some cam. You can get 400 horses out of a Vortec headed 350 with something like 270 degrees of duration and 1.6 rockers. To go beyond that with Vortecs takes a cam around 300 degrees, these are measured at .006 lift timing not .050. It takes way better attention to the piston and given where the revs are going you need to look at a good quality crank and rods.

Porting the Vortec head by non professionals leads to disaster as much as power. The head's already been pretty well refined by the factory, just getting in there with a grinder is likely to mess them up. They didn't bowl blend, because there just isn't much if anything to be had there with these heads.

The bigger the ports become, the further up the RPM band the power moves. This is quite damaging to lower end and mid range power as it goes down as the RPM curve gets longer. This leads into vehicle weight and gearing. Same with the cam, as the timing gets longer the power moves the same way as big ports. The two together are additive. The solution is running the engine at higher revs to get it up in the power band. This means stiffer gears.

Adding rocker ratio, stock being 1.5, your options are 1.6 or 1.7 increases the working load where the lifter meets the lobe reducing part life. The Vortec head is limited to .45 maybe .47 inch of lift without cutting the top of the guide down for clearance. The 1.25 inch Vortec springs are inadequate for the cam you'll need to use. The spring pad can be cut for a larger 1.46 dia spring but this reduces the thickness of the casting and often leads to cracks. I guess where I'm going is for the money to make "race" heads out of the production Vortec, there's way better solutions in the aftermarket.

The Achilles heel of a roller motor, is failure of the roller parts. Be thee aware that when a roller rocker or lifter lets go all those roller bearings are headed for the oil pump. Typically the valley is used to capture parts from the rockers by placing veterinary magnets in the rocker box and valley to attract splintered parts. Stand off breather tubes are used on the SBC in the holes along the cam to prevent stuff from falling thru while providing a crankcase vent. The end drain-backs of the block are covered with screen epoxied into place to stop the shrapnel from going to the pan with the oil. In the case of protection from a roller tappet coming apart a finer screen wrapped around the pickup and some super magnets are about all you can do.

If you're going to race this motor or even have a very hot street motor it should have a really good windage tray and a seven quart pan with baffles to keep the oil by the pump intake.

The more RPMs a motor can turn and the more power it produces, the more critical this foundation building is as the motor will go away mighty quick when something goes even a little wrong.

Bogie
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Old 04-23-2010, 04:23 PM
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ok bogie you scared me ya i just wanted a mean street motor. i built a 430hp motor years ago but just followed the directions from the machine shop and didn't understand a thing. I'm on my 7th camaro and i wanted to put a nasty motor in it. but what your saying is making me rethink it. i don't want a short lived hot rod motor. OK so does anyone have any suggestions on my build?

my goal is 400hp+ motor. i just want to be over 400hp call me silly but well anyway. i was following the gm build just cuz it had all the part numbers and they said exactly what they did making it easy to replicate.

what would be a great build and safe for a 350 with vortec heads. i already have the lower end built. .060 over with flat top pistons, 4 bolt main. i have vortec heads and it is being bolted to a 700r4. the rear end will be a 7:73 posi and i will be using 15 or 16 inch rims. i have not bought the valve train or intake. i will be using long tube headers and i think that's about it.

gosh i love this web site. nothing funner then talking about motors lol
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Old 04-23-2010, 07:27 PM
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is it a roller block (86' and newer) or is it a originall flat tappet block (86' and ealier)
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Old 04-23-2010, 08:52 PM
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roller rockers

Full roller rockers have roller bearing pivots and roller tips.. cheaper are roller tip which use the pivot ball and a roller on the tip end. The roller tip does not put as much side push on the valve stem which increases valve guide life.
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Old 04-23-2010, 09:21 PM
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the casting # when i looked it up said it is from 86 to 88.
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Old 04-24-2010, 06:38 AM
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bump for any more info
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Old 04-24-2010, 06:26 PM
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then it should be a roller block with a 1 peice rear main seal
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Old 04-24-2010, 07:50 PM
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ya 1 piece rear main.
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Old 04-25-2010, 11:25 AM
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got any more questions?
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