How the Summit Racing Cam Timing Calculator Works

[Music] everyone its Carl have you ever wondered why one cam makes more power than another would you like to compare the behaviors of multiple cams without actually performing any cam swaps written descriptions referencing Idol quality power range compression gear and converter requirements let me go so far when the same cam fits both a 283 and 460 cubic-inch engine fortunately understanding cam specs and how they relate to specific valve events is a great way to benchmark an engines performance let's take a quick stroll down memory lane back in the 50s cams were called three-quarter race or full race etc in the 70s cam companies began using advertised duration this was a step forward except the companies used different measurement standards one companies 292 could be smaller than another companies 288 by the 80s and 90s most cam manufacturers were publishing duration at 50 thousands lyft numbers customers could compare seat 50 thousandths and 200 thousands lyft numbers to compare lobe intensity all these old methods gave us these generally accepted truths wider lobe separation and less overlap idles better than a narrow lobe separation with more overlap advancing the cam makes more low-end torque retarding increases power up top longer duration cams make more power up top but suffer from a rough idle and lack of low-end torque nitrous and blower cams have wider lobe separation numbers unfortunately this led to generalities such as always install a cam four degrees advanced or never run less than 110 degrees of lobe separation on the street nothing could be further from the truth your engine only cares about individual timing events this is because these valve timing events create duration lobe separation cam advance and overlap numbers not the other way around what are these four events they are exhaust valve opening intake valve opening exhaust valve closing and intake valve closing by choosing these events independently we have more control over the engine's behavior what's the easiest way to do this check out the Summit Racing cam timing calculator by using the search bar on our site or click on the calculators and tools link on our site and it will pop right up by using it you can compare each cams advantages and disadvantages directly so if you want something a little more dialed in than a 3/4 race camshaft for your engine and keep watching Summit Racing's cam timing calculator does two things first it turns duration lobe separation in advance into the four individual valve timing events it also works the opposite way you can tweak any of the four events to see what the resulting duration lobe separation or advance would be let's look at a few common camshafts and see what's going on the cam used in a 2001 and later LS one and the lq9 motors had one hundred and ninety six degrees of duration on the intake and two hundred and one degrees on the exhaust lobe separation was 116 degrees and it was ground with one degree of advance the bigger ls7 cam had two hundred and eleven degrees of intake duration and two hundred and thirty degrees on the exhaust it had a hundred and twenty point five degrees of lobe separation and it's ground with three degrees of first let's enter the LS one cam specs into the calculator we entered the numbers in and see the cam has negative thirty three degrees of overlap this is pretty common for a factory camshaft the exhaust blows down at thirty seven and a half degrees before bottom dead center and closes at sixteen and a half degrees before top dead center the intake opens seventeen degrees after top dead center and closes it thirty three degrees after bottom dead center next let's enter the LS seven cam specs into the calculator GM has decided to crack the exhaust valve open at 52 and a half degrees before bottom dead center and hold it open until two and a half degrees before top dead center what has GM done here they're releasing the exhaust earlier and keeping the exhaust valve open longer the extra flow will make more power and the exhaust note will be a little louder as well the intake valve is opening 18 degrees after top dead center and it's closing 49 degrees after bottom dead center notice the LS 1 and LS 7 intake valves are opening within the degree of each other an idle will be similar between the two the LS sevens intake valve closes much later to shift the power band upward this is why the LS 7 cam can produce 70 more horsepower in some applications also notice the overlap number has dropped from negative 33 degrees to negative 20 and a half degrees so what's the lesson here these two cams have wildly different durations and lobe separations plus their cam advances nearly 5 degrees different what does that resolve in one of the four events lands in roughly the same place and three other events have been set to achieve a certain behavior next up let's hot rod this cam a little bit let's say you don't mind a rowdy or idle will open the intake valve earlier to seven degrees before top dead center the piston is briefly pushing air back into the intake port which lowers idle vacuum but we net more airflow on the intake stroke we have to be careful though the LS one has true flat top Pistons which limits how soon we can open the intake valve and still have enough piston to valve clearance next let's say you have deeper gears or a bigger stall converter we can trade bottom in torque for top-end horsepower by closing the intake valve a little later we're taking advantage of the intake runner length and velocity to maximize how much air we can trap at high rpm in this case we'll close the intake at 50 degrees after bottom dead centre now we're going to change the exhaust events a bit let's open the exhaust earlier at 59 degrees before bottom dead center and close it's seven degrees after top dead center so now is the moment you've all been waiting for you hit the Update button and here are the results with these events we're looking for a cam with 237 degrees of intake duration two hundred and forty six degrees of exhaust duration a hundred and thirteen degrees of lobe separation and three degrees of advance based on this we'd pick a Summit Racing pro LS stage four cam part number sm99251 or perhaps a marine or circle track application check out some new cam specs on Summit Racing calm and compare them to specs four popular cams you've had experience with you can quickly compare what makes them run like they do thanks to the Summit Racing cam timing calculator you can compare specs between the obliterator stage 3 and the wreckingball stage 4 no longer will you be confused when one person says the cam is too big and another person says the exact same cam is too mild the calculator gives you the ability to dial in your cam choices more easily and get the results you're looking for so how do you buy that perfect cam stick around now that you have an idea of what you want your duration lobe separation and advance numbers to be what's the easiest way to find a suitable camp type camshafts in the search field on summitracing.com enter engine make an engine family information and hit the blue get results button when looking for cams it's best to leave out displacement to get the widest variety of offerings enter the cam style you want such as flat tappet hydraulic rollers solid roll or etc you'll have a choice of what filter to use next go to duration at 50 thousandths lift tab and click on up to 5 Kim's that have the intake duration you want an exhaust eration numbers that are close then hit the get results button next you'll find a selection of cams to the right hand side you can pick by brand lift lobe separation etc click on the compare boxes on the cams that are closest to fitting your needs up to 10 and hit the blue view compare button next you will see the cams in table format this makes it easy to find the one closest to your needs most times being a degree off here there isn't critical remember the order of importance of the events the intake closing event is the most important to power band and take opening effects Idol quality you can make small adjustments by degreeing the cam in if you don't see exactly what you're looking for just give us a call we'll help you find the right cam and supply you with matching valve train parts to ensure your engine runs at its peak

Channel: Summit Racing

Views: 84,130

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Id: i3KqEhq2zGo

Length: 10min 6sec (606 seconds)

Published: Fri Oct 12 2018