Popular Post BobbyBreeze Posted March 20, 2014 Popular Post Share Posted March 20, 2014 Hello OS! So I thought I would start this thread to answer any questions I can on camshafts. I am hoping I can help educate you guys as much as possible & also get asked some tricky questions that helps further my own knowledge on the topic too. I might also throw some updates / photos in here of interesting & relevant stuff I am up to at the moment. It is a bit of a mystery subject and not very well documented (even most engine builders have no idea) so ask away! I am by no means an expert but have been designing and grinding performance cams for 3 years now at Kelford cams so have a good grasp on the basics. Happy to give advice on specific cam recommendations, run in procedures, profile design, cam timing, how cams are ground/manufactured etc Cheers, Robbie 11 Quote Link to comment Share on other sites More sharing options...
Brock-Lee Posted March 20, 2014 Share Posted March 20, 2014 Can you grind me a cam so that my car pulses like my friends lumpy cam 13b? 1 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted March 20, 2014 Share Posted March 20, 2014 Can you grind the cam in his friends lumpy cam 13 so that it idles like a corolla? I'm keen to know why na cars can run huge cams compared to turbo cars Quote Link to comment Share on other sites More sharing options...
SOHC Posted March 20, 2014 Share Posted March 20, 2014 I'm keen to know why na cars can run huge cams compared to turbo cars so you don't turbo all your fuel air mix out the other end 1 Quote Link to comment Share on other sites More sharing options...
cubastreet Posted March 20, 2014 Share Posted March 20, 2014 on a pushrod engine, if I shave the heads 0.5mm, can I get the can reground with the base circle 1mm smaller dia and everything's hunky dory? Quote Link to comment Share on other sites More sharing options...
Maru-So Posted March 20, 2014 Share Posted March 20, 2014 Hey Rob, Have you ever heard of cars running aggressive cams using an air flow meter rather than a MAP sensor? On kelfords site they list a regrind service for B18c engines, it also says theses can be run with stock ECU how is this possible? Do you re-harden the cams surface after a re grind? What are the implications to the power curve? ThanksGrant Quote Link to comment Share on other sites More sharing options...
BobbyBreeze Posted March 20, 2014 Author Share Posted March 20, 2014 Can you grind me a cam so that my car pulses like my friends lumpy cam 13b? Yep. Can you grind the cam in his friends lumpy cam 13 so that it idles like a corolla?I'm keen to know why na cars can run huge cams compared to turbo cars In most modern engines with a decent exhaust port they don't really have *hugely* different cams in terms of duration/lift for a similar power band, the main difference is in the timing. Turbo cams run an advanced exhaust and retarded intake relative to NA cams. This does a couple of things: -reduces overlap (you need this because generally the exhaust manifold pressure is greater than the intake manifold pressure on a turbocharged engine) -opens the exhaust earlier (to help blow down the high cylinder pressure due to boost) -closes the intake later (to make the most from the boost filling the cylinder) Quote Link to comment Share on other sites More sharing options...
BobbyBreeze Posted March 20, 2014 Author Share Posted March 20, 2014 on a pushrod engine, if I shave the heads 0.5mm, can I get the can reground with the base circle 1mm smaller dia and everything's hunky dory? Yes, as long as it is the standard cam. Depends on the cam profile if its a performance grind. Hey Rob, Have you ever heard of cars running aggressive cams using an air flow meter rather than a MAP sensor? On kelfords site they list a regrind service for B18c engines, it also says theses can be run with stock ECU how is this possible? Do you re-harden the cams surface after a re grind? What are the implications to the power curve? Thanks Grant Nope. Generally run TPS / Alpha-N tuning for big cams. Hondas are a bit different due to vtec. We can leave the low lobes still mild to use with the stock ecu. Only reharden on steel cams that have been ground down a lot! Chilled cast iron is fine. Quote Link to comment Share on other sites More sharing options...
camo_78 Posted March 20, 2014 Share Posted March 20, 2014 Hey Robbie,is there an easy way to tell if a cam has been altered from stock??reason I ask is I have a mystery engine,its based on a Cortina 2 litre but it will rev past 8000 rpm quite happily.i got it with a BHG,measured the bores and it has been bored out to a 2.1,but apart from that its a total mystery. Quote Link to comment Share on other sites More sharing options...
BobbyBreeze Posted March 20, 2014 Author Share Posted March 20, 2014 Hey Robbie,is there an easy way to tell if a cam has been altered from stock??reason I ask is I have a mystery engine,its based on a Cortina 2 litre but it will rev past 8000 rpm quite happily.i got it with a BHG,measured the bores and it has been bored out to a 2.1,but apart from that its a total mystery. Yeah man. Set a dti up to measure valve lift off the top of one of the retainers. Stick a degree wheel on the crank and turn the motor over, noting the crank angle at different lifts (the 0.050" or 1mm duration is the most useful number). Can also measure peak lift too. Quote Link to comment Share on other sites More sharing options...
smokin'joe Posted March 20, 2014 Share Posted March 20, 2014 Hey Robbie,is there an easy way to tell if a cam has been altered from stock??reason I ask is I have a mystery engine,its based on a Cortina 2 litre but it will rev past 8000 rpm quite happily.i got it with a BHG,measured the bores and it has been bored out to a 2.1,but apart from that its a total mystery. where did it come from ? we built an Escort rally car about 8 years ago with a similar spec engine. blew HG due to head bolts being too long for milled head , thus bottoming out before they clamped head properly. Quote Link to comment Share on other sites More sharing options...
camo_78 Posted March 20, 2014 Share Posted March 20, 2014 it came out of an auto mk5 Cortina ghia,I bought the car to save it going to the scrappy.can you remember what the specs of your cam were?? Quote Link to comment Share on other sites More sharing options...
Roman Posted March 20, 2014 Share Posted March 20, 2014 Nope. Generally run TPS / Alpha-N tuning for big cams. Hondas are a bit different due to vtec. We can leave the low lobes still mild to use with the stock ecu. Disagree with this bit, for an AFM car. Tuning via TPS or Alpha-N for big cams is your best option if you previously ran a map sensor. As with big cams you're not necessarily generating useful variations in vaccum anymore. However an airflow meter is placed ahead of vaccum, so it doesnt care what's downstream of it, it just measures the airflow coming into the engine. Which may be why some cams list as being fine for use with an aftermarket ECU. More air = more air measured, more fuel dumped in and less ignition advance. A map sensor runs calculations where the known VE of the motor with stock cams is part of the equation to ascertain the volume of air coming through, so changing cams can mess things up to a larger extent. Tuning by TPS / Alpha-N is a last resort if there arent any other options (like open quads) Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted March 20, 2014 Share Posted March 20, 2014 Is there a rule of thumb regarding Ramp rate vs lifter diameter? Why can you run a faster ramp with a solid lifter? Quote Link to comment Share on other sites More sharing options...
yetchh Posted March 20, 2014 Share Posted March 20, 2014 so you don't turbo all your fuel air mix out the other end Thats what I always thought but if that was the case how can some of those big hp, blown 8's run lumpy as fuck cams? Quote Link to comment Share on other sites More sharing options...
yetchh Posted March 20, 2014 Share Posted March 20, 2014 Is there a rule of thumb regarding Ramp rate vs lifter diameter? Why can you run a faster ramp with a solid lifter? couldn't be that high surely, I wouldv'e thought you'd have to go roller for max ramp Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted March 20, 2014 Share Posted March 20, 2014 Yes but if you're getting Rob to dream up a cam, you'd want as much ramp as the lifter can take. SBM's can run faster ramps that the other guys on a flat tappet cam, as they run a larger diameter lifter. Quote Link to comment Share on other sites More sharing options...
BobbyBreeze Posted March 20, 2014 Author Share Posted March 20, 2014 Disagree with this bit, for an AFM car. Tuning via TPS or Alpha-N for big cams is your best option if you previously ran a map sensor. As with big cams you're not necessarily generating useful variations in vaccum anymore. However an airflow meter is placed ahead of vaccum, so it doesnt care what's downstream of it, it just measures the airflow coming into the engine. Which may be why some cams list as being fine for use with an aftermarket ECU. More air = more air measured, more fuel dumped in and less ignition advance. A map sensor runs calculations where the known VE of the motor with stock cams is part of the equation to ascertain the volume of air coming through, so changing cams can mess things up to a larger extent. Tuning by TPS / Alpha-N is a last resort if there arent any other options (like open quads) I always thought the choppy idle screws with afm's and causes idle & part throttle issues? Is there a rule of thumb regarding Ramp rate vs lifter diameter? Why can you run a faster ramp with a solid lifter? When you say ramp rate, are you referring to the speed the valve is lifted from its seat, or the maximum speed of the valve during the entire lift profile? Thats what I always thought but if that was the case how can some of those big hp, blown 8's run lumpy as fuck cams? Overlap is generally what causes rough idle quality. Supercharged motors run decent overlap so the boost scavenges the cylinder, turbo's don't (unless we are talking pro built drag motors). Quote Link to comment Share on other sites More sharing options...
sr1600 Posted March 20, 2014 Share Posted March 20, 2014 Sir voldo Been thinking about throwing some mild cams, say 264's in my sr20det with the new headgasket. What impact will this have on spooling the hairdryer? Assuming it breathes better would help my cause in the mid/upper range? Quote Link to comment Share on other sites More sharing options...
BobbyBreeze Posted March 20, 2014 Author Share Posted March 20, 2014 Sir voldo Been thinking about throwing some mild cams, say 264's in my sr20det with the new headgasket. What impact will this have on spooling the hairdryer? Assuming it breathes better would help my cause in the mid/upper range? Depends on the cams, but if they are a decent modern design they should help spool. More lobe area with short duration at the seat means you're getting the extra breathing without sacrificing driveability. Quote Link to comment Share on other sites More sharing options...
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