stroker tips By Len Emanuelson


Staff member
Stroker Tips from the Pros

Some great advice from the folks who build big strokers for a living

By Len Emanuelson

Engine Builders Stroker Motor Resource Guide has become an annual feature. Last year this publication ran an introductory story about increasing your business with the growing demand for stroker engines. It was focused on popular O.E. and aftermarket-based engine combinations, and covered the basic dos and donts of building a stroker motor.

We are fully aware that the bread and butter stroker business in your area may be the 383 cid small-block Chevys and the 347 cid small-block Fords, but the growing trend is for really big stroker engines like the 550-630 cid Chevys and the 420-450 cid small-blocks. Getting there with O.E.-based components is just not practical in most cases, and simply impossible in others.

In this installment on strokers we will take the bigger perspective consulting several pro engine builders who build 600-900 cid engines for a living. Much of what they have to say will apply to building any stroker engine, regardless of make or size.

We have a stellar lineup of professional race engine builders including Sonny Leonard of Sonnys Racing Engines, well known for building 700-900 cid IHRA Mountain Motor Pro Stock and Pro Mod engines; Jon Kaase of Jon Kaase Racing Engines, also known for his prowess in the IHRA Pro Stock wars and winner of the 2003 and 2004 JEGs Engine Masters Challenge; and Scott Shafiroff of Shafiroff Race Engines who probably builds and sells more stroker engines and stroker kits than anyone else in the country. Scott also fields Vinny Budanos NMCA three-time championship winning race team out of his shop. And finally, Tony Bischoff of Bischoff Engine Service (BES) who won the 2006 and 2007 JEG’s Engine Master Challenge and was the 07 NMRA Diablosport Pro 5.0 champion in his own racecar. Besides all of his racing accomplishments it is interesting to note that BES started out as a small engine rebuilder like many of our readers and has made the transition to focus on high performance and racing almost exclusively.

Aftermarket Blocks
A key bit of advice provided by the experts in last years Stroker Guide was to start with a good aftermarket block because they solve a lot of problems encountered with building the larger displacement motors. First, there is more room for the rotating assembly. Many aftermarket blocks have wider pan rails, eliminating a bunch of grinding for rod and counterweight clearance for medium stroke applications.

You can purchase several blocks with raised cam locations so that you can run a standard base circle or even a larger cam core. Another great feature available in some aftermarket blocks is a taller deck height that enables you to run a decent length connecting rod without having the piston pin ending up in the oil ring.

Thicker cylinder walls, allow for even more displacement and can handle the higher thrust loads created by greater rod angularity. Granted, youre not going to be able to start with a $150 core, but your engine build wont be compromised at every step of the way, and the end product will make more power and be a better value for your customer.

Getting Started
This years esteemed panel of pros had some good advice about managing your customers and their expectations at the beginning of the project. According to Scott Shafiroff, it is extremely important to consider the total engine combination because frictional losses from the longer stroke and higher piston speeds drastically increase with a stroker engine.

“Some of your customers may want to build their engines in stages,says Shafiroff, doing a really big shortblock now with plans on purchasing the correct cylinder heads later. Many times that never happens. Scotts advice is that, if you are definitely limited to your present cylinder heads, build a motor appropriate for those heads, because it will make more power and be much more efficient. Another recommendation is to call your suppliers and get advice on what combination will work best.

Brian Adams of BES claims that one of any shops biggest problems is having a customer wanting to build an engine around the parts he already has. This always causes problems, he warns, and ends up costing the customer more money in the long run. BES recommends that when available, start out with a pre-engineered stroker kit that you know fits together.

Weve had good results with companies like Eagle says Adams. Their kits are almost a bolt-together deal The real high-end race engines usually require piecing together.

Block Notching
Due to both Sonny Leonards and Jon Kaases high-end racer clientele, the O.E. parts issues posed by Scott and Brian simply dont come up, however, the same assembly problems confront them too. When asked what the number one problem is in prepping a stroker engine the conversation always turned to notching the block for connecting rod clearance.

Scott said that the biggest problem he sees in block prep is that people over-notch the bottom of the bore for rod clearance. This allows the piston to pull out of the bore and rock, losing ring seal and power.

Jon Kaase concurred, stating that they maintain at least .500˝ of piston skirt below the oil ring in the block at bottom dead center. He also said that when prepping an aluminum block for a really large (5.750˝) stroke crank, it is very tempting to throw the block on a mill and make the needed cuts. Jon cautions against doing this because two things can happen: first, the notches will be larger than they need to be reducing piston stability, and second, the end mill will probably grab the sleeve and crumple it up like a beer can. At Kaase™s they tediously grind these notches by hand.

A neat tip that Jon shared with us is that he cuts the top off of a piston so he can look down through the bore to see any clearance problems. You can see things from the top that you just cant see from the bottom side.
Sonny mentioned the cylinder notching issue as a big problem too, and he also brought up the point that when you run these large 5.5˝-5.75˝ stroke motors, crankshaft flex is a big problem, even with a high quality billet crank. He allows .080˝ of clearance all around the counterweights and for rod-to-cam and rod-to-cylinder clearance. BES still does quite a few strokers based on production blocks and Brian mentioned that its not uncommon to hit water when grinding the bores for rod clearance. He also added that the widened pan rails on aftermarket blocks save a bunch of time and money.

Rod Ratios
Theres been a lot written over the years about rod length-to-stroke ratios, and some experts consider a 2.0-rod ratio optimum for best power. With a big stroker motor you can forget all that. You simply put the longest rod you can physically fit in the motor.

Shafiroff warns that rod ratio is a dangerous way to judge an engine intake manifold design has more importance on how an engine will run than rod ratio Kaase said,dont ever do the math on rod ratio or piston speed, itll scare you Sonny Leonard stated that some of his larger drag race engines have a 1.34-rod ratio, but he likes to stay in the 1.43-1.52 range for his marine engines that require a lot of endurance. Lower rod ratios load the cylinder walls extremely hard requiring more frequent rebuilds.

Tony Bischoff the owner of Bischoff Engine Service slightly disagreed on this point telling us that he builds a large number of short deck 598 cid engines that are very popular for bracket racing, and his customers get up to 400 runs on an engine. Tony recommends that they get freshened up every 250 runs, but its up to the customer and some extend the rebuild intervals without catastrophic results.

Camshaft Timing
Scott Shafiroff statedœstroke and cam lobe centers are connected more stoke generally requires wider centers. He also recommends as much lift as possible with shorter duration. Sonny was more specific saying that in general his 4.5˝ stoke motors use 116-117-degree lobe center cams, and his 5.5˝ stroke motors get 121-degree lobe center cams. (That of course depends upon application.) Sonny also stated that he runs more duration or rocker ratio on the exhaust to broaden the horsepower curve with the wider lobe centers. Kaase also subscribes to the wider lobe center school of thought stating that the piston acceleration is so high in a stroker that the power stroke is probably over when the piston is halfway down the bore.

Cylinder Heads
Like rod length, stroker cylinder heads defy traditional logic. As a general rule they cant be too big. In fact, Sonny builds his own heads for his 800cid-plus engines. He has both Hemi and wedge versions to meet the demands of 800 cubes at 8,000rpm. According to Scott, you can never have enough cylinder head, especially when you are dealing with the 430cid-plus small-blocks. On the cylinder head topic Brian concurs with Scott, aftermarket is the only way to go, its silly to use an production head on any serious stroker motor. Weve had good results on our big-inch small-blocks using CNC ported heads that have 230cc and larger runners.” The good news is that the aftermarket cylinder head manufacturers have realized what the stroker market needs and is doing a good job of filling it for the more popular engines.

Parting Shots
We asked our panel if they had any other advice about stroker engines. The following are some of their parting thoughts on the subject. Jon Kaase volunteered some information on crankcase vacuum. He said that in his wet sump motors he likes to see at least 10˝ of crankcase vacuum, and for his dry sump engines he looks for 20˝. Jon left off with,When the pistons are going up and down, theres a lot of air trying to swap places at 8,000rpm!

Sonny Leonard reminds us that stroke isnt everything use as much bore as possible too. It will allow you run bigger valves and un-shroud the valves in the combustion chamber. He also mentioned clearances. Sonny adds .001-inches of piston-to-wall clearance to the manufacturers recommendations because the piston speeds are so high that it produces more heat and expansion. Piston speeds in 800 cid Mountain Motors is approaching those of an F1 engine at 19,000 rpm. He also advises a little more deck clearance due to the heavy pistons in these big motors. About .070˝-.075˝ is the minimum that you can safely get away with for one of these motors at 8,000 rpm.

Scott Shafiroff made the point about how important it is to calculate the compression ratio before doing any machine work – “it’s easy to get stupid compression in one of these motors!

Brian also added that BES tries to steer its customers to EFI because the driveability is so much better and EFI is easier to tune. Like cylinder heads its difficult to get big enough carburetors that will perform on the top end and still be responsive on the bottom end. With EFI its possible to tune for the full power band. Tony Bischoff made the excellent point that when selecting individual stroker components, check to see what the shortest rod length is that will clear the crankshaft counterweight in the piston pin boss area. This is often a problem area that can be easily avoided with a little planning.

There you have it from a team of engine builders that have won more championships and races with stroker engines than just about anybody on the planet. Their advice is straightforward, specific and easy to follow.
When asked about what else they do differently when screwing together a stroker the answer was nothing. Just assemble it like any other race engine.

So the next time a customer comes by wanting a 632cid Chevy street motor, have no fear, order up the parts and follow the few simple tips provided here.


Staff member
Re: stroker tips a good deal more info
IF your going to build a big block Chevy it usually helps to know your options and longer strokes and rods help.
Id also point out that doing the math before you purchase parts will save you a great deal of wasted cash,
and if that engine your contemplating is intended to exceed about 4200 feet per minute in piston speed or 6200rpm,
you might want too think seriously about 4340 forged steel crank, forged pistons, and rods with 7/16" ARP rod bolts
youll generally want to build a tall deck, engine with longer connecting rods to take full advantage of the tall deck architecture
the deck heights .400 taller so youll generally want connecting rods that are longer on the 4.25", stroke , stroker crank
IVE GENERALLY USED SCAT CRANK ROTATING ASSEMBLIES WITH 7/16" ARP ROD BOLTS and 6.385" 0r 6.535" rods as they are longer to compensate for the .400 taller deck height, a call to SCAT will get you the correct part number for a kit forged and internally balanced rotating assembly kit
Phone: 310 370 5501

I takes time to learn the skills and you need to do research any time you are not 100% sure you know whats required, if your a first time engine builder that will damn near be everything you touch,by the time you buy the minimum tools required and a few books for research, and total up the local machine shop labor charges , youll most likely find the price of a crate engine looks much more reasonable, to think you know everything you need to know on the first few engine builds is absurd, thats about like If I offered to charge someone $3000 to build them an engine.
allowing them to watch , so they see how its done,
and then expecting them to have identical skill,
and have the tools collected over a lifetime , and the knowledge, of how the tools are used and why its required,
even if that particular engine I build never needed them!
at the end of a couple weeks!
easily 70% of the skill involved, is in knowing what to look for,
and recognizing what needs to be corrected ,
what components are ok as they are,
and what needs major machine work,to function correctly,
what should be pitched in the trash and replaced ,
and what can be modified and used!
and because that varies with every engine,
it takes experience and time to gain those skills, and know what to look for ,
some thing you gain over time making mistakes and being forced to do research,
that you would not gain in a couple weeks time,
and something requiring you to spend a few years getting your hands dirty in the process of learning.
be sure that FLYWHEEL,you select matches the intended application
and it is SFI certified, IDEALLY billet, your feet will thank you,
and ideally, you use a blow proof bell housing, thats a good idea

and I would select a 28 lb-36 lb flywheel,for street use.
if its the newer sbc single rear seal block.
be sure its for a single rear seal crank,
and they make 153 and 168 tooth gear designs,
you need to match your application, and your bell housing and starter
also be aware there are internal and externally balanced 383 SBC kits and 5.7" and 6" rod kits,
and some that require a neutrally balanced damper and an externally balanced flywheel

as usual, there's a ton of related info in the links and sub links

common BB CHEVY piston compression heights are
remember the blocks deck height, minus the piston pin height minus 1/2 the crank stroke will equal the required connecting rod length
the blocks deck height, minus the connecting rod length, minus 1/2 the crank stroke. will equal the required piston pin height
yes its common for a combo to have the piston deck height located .010-.015 above or below the deck of the block so you'll need to select a head gasket thickness that compensates, too allow your engine to get a .038-.044 piston deck to cylinder head QUENCH DISTANCE.

YES, youll really want to read thru these LINKS BELOW ALSO, as it will save you a great deal of time and money
When having a machine shop do any work, always ALWAYS get everything in detailed writing before you start,
specifying all machine work, to be done in detail,list parts and labor costs, mandate a delivery due dates and have every single part you supply ID stamped, and photographed, have all the work too be done and parts individually listed and a value assigned, with both YOU and the machine shop having identical signed copys
listing the cost and dates and work details

Ive been building engines for over 40 years now, eventually even my hard head learned
rule one
read the manufacturers instructions carefully and call the tech guys if ANYTHINGS not 110% clear
RULE two
IF something won,t fit or function....STOP, call the the tech guys after you re-read the manufacturers instructions carefully and measure carefully so you sound at least 1/2 way like you know what talking about, then call the tech guys if ANYTHINGS not 110% clear

milling stroker clearance on 350/383 ... ock-chevy/

RULE three
STOP AND DO THE REQUIRED RESEARCH if youve got questions
I never mind sounding dumb as long as I get the correct answers, so I won,t LOOK dumb by doing something wrong
use a good 7-8 quart baffled oil pan
canton2.jpg ... ch-part-1/ ... ch-part-2/

IF this is your first engine rebuild Id suggest you buy these three books, and actually read thru them and post questions ... 793&sr=1-1"]How to Build Max Performance Chevy Small Blocks on a Budget (S-a Design): David Vizard: 9781884089343: Books ... 724&sr=1-1"]Smokey Yunick's Power Secrets: Smokey Yunick: 9780931472060: Books

read thru these threads and sub linked info

and your going to need a cheap but sturdy engine stand






viewtopic.php?f=52&t=399 ... sGuide.pdf ... c_oil.html ... ewall.html

viewtopic.php?f=44&t=38&p=46#p46 ... index.html ... 383_cu.htm






viewtopic.php?f=52&t=399 ... 010_10.pdf ... index.html ... index.html

viewtopic.php?f=44&t=700&p=973#p973 ... index.html

viewtopic.php?f=50&t=770 ... index.html ... 7&mode=cat ... index.html ... index.html
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Staff member

"I'm so glad that I took your advise and looked around for stroker tips! One of the sites showed a guy that had ground his rod bolts (for cam clearance) like 2 of mine were. It showed how he had gone too far (as I also had), and it had failed upon torque down. I went out to the garage to look at the bolts but couldn't see well enough. A quick trip to the Harbor (Freight) and a extendable mirrror later, I was witness to the failure of the rod bolts after torqueing in my engine that would've spelled disaster for sure!
The rods are out now, being checked for useability, or replacement.
The new Lunati is here, and it has a base circle of only 1.181". This will give ample room for clearance.
Thanks for all the great info on this site! It saved me from a waste of more time, and money than I want to think about! Time to get the rod bolt stretch gauge back out insted of the trash bin.



Staff member
BTW I only learned to start checking things during the engine assembly carefully after screwing things up just like most of you gentlemen, IM certainly not immune to screw ups, but I DO TAKE NOTES AND TRY NOT TO REPEAT MISTAKES
yes it tends to take a little more effort to do things correctly, sometimes some research, sometimes new tools, are needed, but you may be surprised at the satisfaction you get from knowing its been done correctly

read thru these threads, its well worth the effort















viewtopic.php?f=44&t=392&p=5415#p5415 ... sGuide.pdf


viewtopic.php?f=50&t=1249 ... index.html ... 383_cu.htm ... 010_10.pdf







its really refreshing to see someone take the effort to do those clearance checks that are so critical to long term durability

for those just starting on their 383 build ups heres some very useful linked info ... to_07.html ... index.html ... index.html






this book includes a CD you can watch with a great deal of useful tips and info
the book and CD are one of the best basic sources of info IVE found for new guys

I was asked to repost this info for the newer guys

Ive built dozens of 383 and 396 sbc engines and the clearancing can be done BY YOUR OWN HANDS with a standard HAND HELD drill and a few CARBIDE BURRS OR GRIND STONES in that drill in well under two hours if you take your time and total expense even if you need to buy that drill and burrs will be well under $50 total ... _1-4_Shank

buy a 1/2" burr and a cheap drill ... 82476&rd=1

The subject of heads to use always comes up and the current craze seems to be vortec heads, vortecs are great heads for a 383 build if the object is good low and mid rpm torque,and a responsive street engine build for transportation.
youll have a great combo if its matched with the correct cam and compression ratio, provided of course the transmission, gearing, converter stall speed and rear gear ratio are matched to the 1300rpm-4500rpm power band that the heads will effectively flow at.
Id suggest a good dual plane intake design to maximize the torque curve ,vortec heads easily flow enough air to support 450 hp and good torque, but they will prove to be very restrictive if maximum peak hp is the goal, if your looking to make over about 470hp ID strongly suggest the better aftermarket heads that flow a minimum of 250cfm at .500 lift.
a decent 383 combo thats designed to produce good peak hp will require a larger better flowing cylinder head and cam selection, and will need to match a generally higher average power band , EXAMPLE
3000rpm-6500rpm,if peak hp is the goal theres several good 195cc-210cc port heads that will work. naturally that will also effect the cam and drive train components selected

place you old bearings in the block an place the crank in those bearings after coating them with axle grease
slowly rotate the crank and grind a minimum of .060 clearance anywhere the counter weights might touch the block and try NOT to grind more than about .070 any place it touches the block (use a JUMBO size paper clip as a gauge if you don,t have feeler gauges)
next assemble two connecting rods and pistons, one connecting rod and piston for the left one connecting rod and piston for the right, use old bearings coated with axle grease and no rings on the pistons, assemble them to the crank and grind anyplace the rods touch the block, grind minimum of .060 clearance and try NOT to grind more than about .070 any place the rods touche the block (use a LARGE size paper clip as a gauge if you don,t have feeler gauges)move them to the next journal and repeat until all 4 journals and 8 connecting rods clear. now assemble all eight rods and pistons without rings and install them in their correct locations and recheck everything carefully.
next install the cam and index it correctly with the timing chain/gears, rotate the engine slowly and look for clearance issues, between the cam and rods/rod bolts ,you'll need to use a small base cam if there are major clearance issues and thats almost always a good idea when building a stroker combo but in most cases if your cams lift and duration is under about 230 at .05 and .500 lift there should be minor if any clearance issues, usually the outside edge of a rod bolt head is the only area needing a touch up.

once everything clears, wash all the parts VERY CAREFULLY ,TWICE and re-oil then send out to be balanced now you might ask why do that! well, first you'll know its done correctly, and that a correctly built 383 will have a very significant hp and torque advantage over any similar 327 or 350
be aware that a small base diam. cam might be required in some cases,it will depend on the rods and the cam combo you chose ... 383_cu.htm

use the correct tool to install the balancer

need a few pictures?
this may help
yes the cam lobes can very easily contact the connecting rods when the cam index is out of its proper timing, on almost any chevy engine the cam lobe center lines will be spaced at between 103 and 116 degrees, with the piston at TDC theres SUPPOSED to be about .060 MINIMUM clearance between the connecting rod bolts and cam lobes, this is a mandatory clearance check point and a plastic cable tie can be used to gauge clearance, its best done on each individual connecting rod to cam lobe clearance point AFTER the cams been degreed into the block as each connecting rods being installed but Ive generally done it during the several trial assembly points where I check other clearances like block to connecting rod clearance.
if you think about it the cam lobes will pointing basically up in the 180 degrees of rotation and be lifting the valves when the pistons are on the way up the cylinders, and point down toward the crank mostly when the crank throws pulling the rods downward,away from the top of the engine




thats why on some stroker crank engines a SMALL BASE CIRCLE cam is used to MAXIMIZE CLEARANCE,between the two moving parts.
a cams lobe lift is the difference the lifter moves off the cams base circle between its base circle and its max lobe lift, thus a cam with a 1.1" diam base circle and a .400 lobe lift would have a , .400 lobe lift and if you had 1.5:1 ratio rockers a .600 valve lift, but if you wanted more clearance you could use a smaller base circle at .900, and a 400 lobe lift this would allow the connecting rod, to sweep by with an additional amount of cam lobe to connecting rod bolt clearance, the change in diameter generally requires a swap to a stronger cam billet core . vs cheaper cast core,to maintain cam strength

removing the rod caps during clearance checks while building your 383 ,does seem to allow you to see the clearance issues a bit easier





rods that use bolts with nuts like pictured below will be weakened if excessively clearance ground

stroker profile rods offer more clearance to cam lobes, and yes the stroker clearanced profile rods are available in both (h) and (I ) beam designs


generally its a minor easily done clearance job





the cam rotates while indexed by the timing chain at 1/2 crank shaft speed , there are connecting rods designed to provide additional clearance.






IF your installing a longer stroke crank in a SBC, the first step is test fitting and carefully marking the connecting rods and block after carefully checking which rods need clearance, in most cases only two or four cylinders will require cam/rod clearance work, and the amount that is normally required too be removed is small enough that the difference in weight is so minimal it won,t have any significance in the engine balance, so grind the rod only in the potential area of cam to rod interference, only on one side, just at that one location, try hard to allow a .060 rod/cam clearance and no more, and do it in a shallow rounded depression so you don,t create stress risers, with any and all the grind mark lines only parallel to the rods long axis and then polish, the grind marks until the areas smooth with 500 grit sand paper, then clean carefully to remove metallic dust
on many blocks all the block rails will need minor clearance work for the rods to clear the oil pan rails, and don,t forget to verify the counter weight to lower cylinder clearance, cap-screw rod designs , designed for stroker use,tend to have less clearance issues

keep in mind the problem is easy to totally avoid simply by selecting rods designed for stroker engines,EXAMPLE
SCAT and LUNATI both make 7/16" rod bolt rods with far stronger than stock forgings, that have cap screw rods designed for much greater clearance

theres a great deal of useful info in the links so read and take advantage of it ... roker.html ... index.html






both these pictures show a rod that was probably over or excessively ground & clearanced for most engines, careful rechecking as you rough grind,the rod, helps, take off as little material as you can to get the required clearance.


don,t forget to verify these areas also




the common areas are the area near the block oil pan rail where the rod bolts touch
and the lower inner cylinder walls and where the cam lobes touch the rod bolts upper shoulder on some types of rods, now you can,t grind on the cam, but you can grind the edge of the rod bolt and you can use a small base circle cam to give greater clearances
cap-screw rod designs , designed for stroker use,tend to have less clearance issues ... roject.htm

your basic 383 short block can be built on a tight budget, but read thru these links,and sub links for info and tips ... index.html ... t-kit.aspx ... index.html







"What do you think about hard blocking the bottom inch of the block?"
hard block poured in the cylinder base area up to the level of the bottom of the freeze plugs has little effect on the cooling and adds significantly to cylinder strength on thin bore walls, so yeah! any time you exceed about a ..040 overbore its a good idea.
GOOD ... &x=19&y=11
MUCH BETTER, because it gets into the fine cracks and pores in the cast block surface, as its a liquid epoxy and holds far better than the basically structural concrete that moroso sells ... =PDEVCON05





thoughts guys?
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Staff member
I was asked what threads to read to get the basics of engine building,
well the whole darn site was my first thought,
but heres a list to get you started and don,t forget the SUB LINKS and THEIR sub links
as theres a great deal of info to read, comprehend and absorb
when you build an engine you generally have some idea as to its intended operational rpm range and the octane level of the fuel you want to use.
normal quality blended gasoline tends to produce its best power at about a 12.5:1 fuel/air ratio, and lowest exhaust emissions at about a 14.7:1 f/a ratio
the higher the effective compression ratio (up to about 13:1) the more torque you can expect to produce from an engine,if you use, high octane gas or race fuels, but the octane of the fuel currently available from pump gas drops the max effective dynamic compression ratio to about 8:1
obviously the components selected must work in the desired rpm and intended power range.
you need to select a cam duration and LSA , and static compression that BOTH matches the static compression ratio and your cars gearing so the effective dynamic compression ratio falls in that range, and intended rpm/power band
obviously if your willing to run race octane fuel and operate the engine at higher average rpms you can increase the cam duration and static compression ratio








as you get questions, use the search feature then post questions


















if your building a big block Chevy start by researching the subject with these books ... 345&sr=1-4 ... 345&sr=1-3 ... 345&sr=1-7 ... 345&sr=1-5 ... 345&sr=1-2

if your building a small block Chevy start by researching the subject with these books ... 929&sr=1-1 ... 929&sr=1-3 ... 046&sr=1-2 ... 123&sr=1-2 ... 23&sr=1-11