upgrading from a flat tappet to a roller cam

[grumpyvette]

YEAH SIT BACK AND TAKE NOTES THIS WILL TAKE A WHILE IF YOU READ THRU THE SUB LINKS ,BUT ITS WELL WORTH THE EFFORT IF YOU WANT TO DO THINGS CORRECTLY

check list

roller cam
roller lifters
matching valve springs
correct length pushrods
cam button
cam change engine gasket set
roller timing set or gear drive
roller rockers (strongly advised)
and TALL VALVE COVERS CAN IN SOME CASES BE A NECESSARY OPTION TO CLEAR THE VALVE TRAIN CHANGES
read thru and follow the manufacturers instructions, and carefully check clearances

http://www.idavette.net/hib/camcon.htm

you might want to read thru the link above first, its got some good info...heres some cam suppliers

viewtopic.php?f=52&t=155

this will help
viewtopic.php?f=52&t=425

OK Ive done the conversion dozens of times, so on the earlier gen 1 sbc its not that difficult, you'll need , a decent quality roller cam and a billet core is superior to a cast cam core, the roller cam of your choice needs to match the rest of the components and the intended rpm and power band, failure to do so almost always results in a combo that runs poorly, if your limited to use of the original heads, gearing and exhaust system,you'll more than likely NEED to keep the cam selected rather mild compared to what can be used in a combo with better heads and the correct gearing ETC,THE KEY TO A GOOD COMBO IS MATCHING ALL COMPONENTS USED TO THE INTENDED HORSEPOWER AND RPM BAND.
that cam selection is critical to success of the swap, it needs to match the rear gear raio, engine compression and port flow rates of the heads and intake and the exhaust flow or restriction to flow needs to be considered as will the transmissions gearing and stall speed if its an auto trans.
Your probably, better off getting the advice of several totally differant cam manufacturers, before making your sellection if your not building engines on a monthly basis, as the cams offered change as does the technology availavlable.

read these
viewtopic.php?f=52&t=904

viewtopic.php?f=52&t=796

NEXT youll need roller lifters and those must be compatible , with the engine and the cam, theres two basic choices , hydraulic and the solid lifter designs, just like on solid flat tappet lifters, the hydraulic lifters tend to need far less frequent adjustment but are limited to about 6300rpm, while solid lifters easily add 700-1200 or more extra rpm to the valve trains potential, a few of the late model blocks that had flat tappet cams , but they had the taller lifter bores so a few retro roller lifters won,t fit (clearances) but in most cases a retro roller lifter fits fine, the vertical bar style

tends to be easier to fit than the horizontal bar type in some applications.

solid lifters generally require more spring pressure to reach those upper rpm limits, and those spring pressures can tend to negatively effect the long term durability.
remember the LIFTERS SELECTED NEED TO MATCH THE CAM AND THE SPRING PRESSURES, SO TAKE THE EFFORT TOO VERIFY WITH THE CAM MANUFACTURER

read these

viewtopic.php?f=52&t=480

viewtopic.php?f=52&t=788

viewtopic.php?f=52&t=399

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=121

you'll also need a valve train that's stable at the intended rpm band, and with the correct geometry and clearances. and you'll need a cam button as flat tappet cams have a slight bevel to the lobe that's used to spin the lifters in their bores as the lobe passes under them to limit wear, while roller cams must remain stable and roll over the lobe in a strait line, and ideally under conditions where the oil flow cools and lubes the total valve train correctly.

you'll also need a cam button to limit the cams movement in the block.

viewtopic.php?f=52&t=697

viewtopic.php?f=52&t=663

viewtopic.php?f=52&t=553

this should also help, durring the reassembly

viewtopic.php?f=55&t=293

viewtopic.php?f=52&t=196


BTW heres my current 383 roller sbc combo

viewtopic.php?f=69&t=263

 

[grumpyvette]

btw it should go without needing to be mentioned (BUT I WILL ANYWAY), that any upgrade to a roller cam on 40 year old fuelie heads, VORTECS,ETC, or almost any stock pre roller cam cylinder heads will require a MANDATORY VALVE SPRING upgrade and clearances will need to be verified, and the valve train geometry carefully checked on ANY AND ALL cam upgrades, simply because standard flat tapped spring specs are very unlikely to work correctly or be ideal for use with a hydralic roller cam. and once EITHER the duration exceeds about 225 @ .050 or the lift exceeds about .520 in a 383 SBC youll probably have clearance issues with stock connecting rods,and the cam lobes, aftermarket (H) or SOME (I) style stroker rods with 7/16" capscrew bolts are stronger and profiled to clear and use of both a small base billet roller cam and stroker profile rods will usually prevent that

The following Mechanical operating clearances must always be verified to ensure proper operation of the camshaft:
Spring coil bind clearance
Retainer to seal/valve guide boss clearance
Piston to valve clearance
Rocker arm slot to stud clearance
Camshaft endplay
Distributor shaft and gear endplay
Connecting rod to cam clearance
Proper hydraulic lifter pre-load or lash clearance
Proper valvetrain geometry
proper spring load rates
rocker to retainer clearance

keep in mind that at 7000rpm a lifter is accelerating and changing direction 116 times each second, and while its only moving about 1/2"--3/4" before reversing direction it weights several ounces, and at that rat of acceleration it requires hundreds of labs of valve spring resistance to force it to maintain constant contact with the cam lobe

notice the more aggressive cam lobe acceleration rate on the roller cam lobes than flat tappet cam lobes
as a general guide you want to get the valve open to well above the 1/4 of the valve diam. to maximize the potential flow as quickly after TDC as physically possible and hold it open as long as possible if you want to maximize the cylinder volumetric efficiency, but obviously factors like exhaust scavenging and compression and the cars gearing and the need to run well over a wide rpm range preclude, maximizing efficiency in a single narrow power band in most applications

when a manufacturer posts a cams designed cruise or power and rpm range, hes obviously not able to know the application,youll be using it in.
so they generally assume a standard and more common displacement and that youll use parts that will commonly be selected for the application, or they will post some info, stating the cams designed for , lets say 11:1 compression or it will require a 5000rpm stall or other useful info to help you narrow your search, they will generally start with a small block chevy, assume its to be used in a 350-383 displacement, and assume its to be used with a single 4 barrel carb as thats the more common range.
obviously if your building a 427- sbc, or a 302 sbc the displacement and heads and rear gearing etc. needs to be factored into the cam selection process.
in most cases a discussion with the cam manufacturer will help clear things up, but remember some cam manufacturers tend to be focused more on long term engine durability and high rpm valve train stability,rather than looking at MOSTLY at peak power, potential, some concentrate more on maximizing power and pushing the extreme edge of the physical limits on the valve train,stress levels, under the assumption that making a few extra hp, is more important than making the components last longer under the idea that any race engines going to be inspected and refreshed far more frequently.
the more conservative designers figure you need to Finnish a race to win a race and most builders and owners don,t want to constantly be replacing components.
as your engines displacement, compression ratio, port flow rates and other factors, change the objects usually to increase the air/fuel mix volume thats flowing thru the engine and increase the number of power strokes per second, thus its assumed the average rpm range will need to be increased and the low rpm volumetric efficiency is sacrificed, to increase the upper rpm power.
now it should be obvious that a roller cam can be used to provide more lift under the valve lift curve than a flat tappet design, due to simple limitations due to the cam lobe clearance and base circle limitations in most engines,but keep in mind the port design and valve size have a big effect on flow rates
Isky claims that the Comp XE cams violate the 47.5% rule. The 47.5% rule applies to flat tappet cams for SBCs with 1.5 rockers but the concept is still the same for other configurations where the designs are "on the edge" or "over the edge" for lobe intensity. For 1.5 ratio SBCs, the duration at .50 must exceed 47.5% of the total valve lift or your asking valve train problems. For example, take a Comp Cams Magnum 280H, with 230 duration and, 480 lift...230/.480 = 47.9% which exceeds 47.5% therefore would not pose a threat to components. We do not regularly hear about the older, safer HE and Magnum designs rounding off lobes anywhere near as often as the XE cam designs. Unfortunately, some of the Comp Cams XE dual pattern lobes break this 47.5% rule on the intake side so they are likely to be problematic. The design has "steeper" ramps that are too quick for durability and reliability according to other cam manufacturers. They will wipe lobes in a heart beat especially if you have not followed the proper break-in procedure. Other designs are more forgiving during break-in and less likely to fail.

viewtopic.php?f=52&t=126&p=35159&hilit=lobe+acceleration#p35159

viewtopic.php?f=52&t=3809&p=10227&hilit=lobe+acceleration#p10227

viewtopic.php?f=52&t=3729&p=9689&hilit=lobe+acceleration#p9689

 

[grumpyvette]

If your thinking of building a street/strip combo with an auto transmission and want it to be drivable on long trips Id suggest keeping the cam durration reasonably low.
I think youll find a CROWER 00471 cam or crane 119841 will be very similar in duration to what your looking for if your pushing for max power and some hint of drivability on the street, but it requires a 3.73 -4.11:1 rear gear and a 3000rpm-3300rom stall converter or a manual trans, and a 10.5:1 cpr to work correctly,and I know from experiance they make excellent power, but Im running a crane 119661 because its easier to drive in traffic, and still makes good hp, after running all three and about a dozen others I settled on the crane 119661 and a serious nitrous system for my 383

http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00471&x=47&y=12

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=119841&lvl=2&prt=5

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=119661&lvl=2&prt=5

this might interest you, its my current 383 combo

viewtopic.php?f=69&t=263