Big cam durability
08-21-2008, 12:54 PM
#1
Big cam durability I've searched this and talked to a lot of people but cannot seem to get a decent answer.
I realize that in high performance nothing lasts forever and the faster you go the more it breaks but I'm wondering is there a certain point in cam lift relative to duration where it just gets very unreliable.
I've had reputable builders tell me to stay away from bigger than .600 lift and 240ish duration if I want the motor to be trouble free longer than 10,000 miles. They reason that the ramps will be so steep and spring rates so high that the valvetrain just won't last.
I'm in the research stage of putting together a budget max effort street strip 346. I don't care about idle quality, "driveability", bucking, or anything like that. I don't mind loose converters and bad gas mileage. My goal is to go as quick/fast as possible with a mid weight f-body with a stock shortblock (upgraded bolts, rods, pistons) and ported factory heads.
My only criteria for streetable is 93 pump gas, not tossing rockers and breaking springs, and shooting for 50,000mi or better with many strip passes and very good maintenance.
I realize that in high performance nothing lasts forever and the faster you go the more it breaks but I'm wondering is there a certain point in cam lift relative to duration where it just gets very unreliable.
I've had reputable builders tell me to stay away from bigger than .600 lift and 240ish duration if I want the motor to be trouble free longer than 10,000 miles. They reason that the ramps will be so steep and spring rates so high that the valvetrain just won't last.
I'm in the research stage of putting together a budget max effort street strip 346. I don't care about idle quality, "driveability", bucking, or anything like that. I don't mind loose converters and bad gas mileage. My goal is to go as quick/fast as possible with a mid weight f-body with a stock shortblock (upgraded bolts, rods, pistons) and ported factory heads.
My only criteria for streetable is 93 pump gas, not tossing rockers and breaking springs, and shooting for 50,000mi or better with many strip passes and very good maintenance.
08-21-2008, 01:06 PM
#3
stock is .500
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Mirek Again (08-25-2019)
08-21-2008, 02:40 PM
#4
it comes down to the ramp rate of the specific cam. Even the 220 cams can be hell on drivetrain depending on the lobe. If you have a 224 cam with over .600 lift, thats going to be a pretty steep ramp, where as a 230's cam with the same lift wouldnt be as harsh. Like the cheater cam, that thing is like less than 220 duration and over .600 lift if I remember correctly. I think you are a little confused on your goals. The words "budget", "max effort", and reliable arent going to go hand in hand. I would go with a decent set of ported heads, and a 230's cam with around .600 lift. That should put you in the 420-450 RWHP range, not be too bad on the valve springs, and should easily land you in the 11's with a good stall and weight reduction.
08-21-2008, 02:52 PM
#5
i don't understand the question you are asking. will a huge cam with violent ramp rates last very long? haha that shouldn't be hard to figure out.
race motors can last, but the parts required to do so will cost considerably more. so your "budget", "max effort" engine that is "reliable" is quite the oxymoron.
you have the same goals as every man modding his car. he wants to go fast all the time for minimal investment. it won't happen, it has been proven time and time again.
race motors can last, but the parts required to do so will cost considerably more. so your "budget", "max effort" engine that is "reliable" is quite the oxymoron.
you have the same goals as every man modding his car. he wants to go fast all the time for minimal investment. it won't happen, it has been proven time and time again.
08-21-2008, 03:00 PM
#6
Your question really is hard to give a blanket answer to. It really depends on the cam lobe profile. Just because it is 240 duration or .600 lift doesn't really mean that it will be rough on the valvetrain. Talk to one of the sponsors and find a camshaft with lobe profiles that are not too extreme.
08-21-2008, 07:12 PM
#7
I plan on changing my springs every 10-15k or so with my LSK lobes and .651 lift. I broke a dual spring ony my z06 in the first 3k miles of the new heads i had put on with only a .600 lift cam so i mean anything can break at anytime. Same as anything can last no matter how unsafe it may seem. Pick what you want and just be prepared to pay for what you dont.
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08-22-2008, 10:10 AM
#9
Some of y'all are misunderstanding my question. I don't....edit...I do want my cake and eat it too, but I realize the reality of going fast.
My question is: Is there a generally accepted range of cam size to stay under for a motor reasonably expected to make it 50,000 mi or so without pulling a valvecover? I mean LS6's have what like .550 lift and low duration and pretty much runforever. I'm not looking for a magic number not to exceed, just an accepted ballpark.
Based on that, I am deciding how much headache I am willing to live with to reach my goals.
In other words I'm deciding between 224dur/.570 lift that runs say 11.65 and can drive to africa and back vs 245dur/.640lift that goes 10.9 but always is on the ragged edge of self imposed destruction. I'm just wondering is there a blurry line in the sand between the two and if so where is that line?
Do none of you ever think this way? Maybe I need a vacation.
My question is: Is there a generally accepted range of cam size to stay under for a motor reasonably expected to make it 50,000 mi or so without pulling a valvecover? I mean LS6's have what like .550 lift and low duration and pretty much runforever. I'm not looking for a magic number not to exceed, just an accepted ballpark.
Based on that, I am deciding how much headache I am willing to live with to reach my goals.
In other words I'm deciding between 224dur/.570 lift that runs say 11.65 and can drive to africa and back vs 245dur/.640lift that goes 10.9 but always is on the ragged edge of self imposed destruction. I'm just wondering is there a blurry line in the sand between the two and if so where is that line?
Do none of you ever think this way? Maybe I need a vacation.
08-22-2008, 10:21 AM
#10
rules:
must run on 93 octane, race weight of car will be right about 3400-3500lbs, converter and gearing to be determined by cam and heads, car will see maybe 5000-6000 street miles per year, maybe 75-100 strip passes per year, I don't give a **** about having enough torque to pull down trees or enjoy off Idle acceleration.
08-22-2008, 10:27 AM
#11
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Ok, for example a ms4 is 239/242, dual valve springs will last about 20k miles
while a 233/239 will go for around 30-40k with duals, you can look up the lift on tsp's site!
while a 233/239 will go for around 30-40k with duals, you can look up the lift on tsp's site!
Where did you get this info?
08-22-2008, 11:07 AM
#13
I don't think it's an oxymoron. Let me put it this way:You got roughly $6000 to spend on a motor top to bottom. The #1 priority of this motor is to go as fast in the quarter n/a as $6000 will let it go. #2 priority is to NOT need rebuilt every 8000 miles since that would have to be factored into the $6000.
rules:
must run on 93 octane, race weight of car will be right about 3400-3500lbs, converter and gearing to be determined by cam and heads, car will see maybe 5000-6000 street miles per year, maybe 75-100 strip passes per year, I don't give a **** about having enough torque to pull down trees or enjoy off Idle acceleration.
rules:
must run on 93 octane, race weight of car will be right about 3400-3500lbs, converter and gearing to be determined by cam and heads, car will see maybe 5000-6000 street miles per year, maybe 75-100 strip passes per year, I don't give a **** about having enough torque to pull down trees or enjoy off Idle acceleration.
At least you are willing to forego driveability but still...the only way I can see being close to "fast, reliable and cheap" is to lose lots of weight.
08-22-2008, 11:26 AM
#15
his ***. just because one cam has .030 less lift doesn't mean the valvesprings will last twice as long. measure .030 and tell me if you think it *really makes a difference. i don't know that i've seen too many cars built as a strip car first, street car second that even last 30k miles.
i'd go with a small(er) cam and vic jr intake for starters. determine what shiftpoint you want and go from there, as the shiftpoint will most likely determine longevity of the engine. custom grind all the way, then you can determine lobes, lift, duration, lsa, advance, etc etc. the single plane will let you see the true colors of a cam. meaning you won't need as much cam to equal or surpass the performance of a larger cam on the crossover style intake. just my thoughts.
i'd go with a small(er) cam and vic jr intake for starters. determine what shiftpoint you want and go from there, as the shiftpoint will most likely determine longevity of the engine. custom grind all the way, then you can determine lobes, lift, duration, lsa, advance, etc etc. the single plane will let you see the true colors of a cam. meaning you won't need as much cam to equal or surpass the performance of a larger cam on the crossover style intake. just my thoughts.
11-08-2008, 05:55 AM
#20
Your builder was giving you good/safe advice. Big cams with agressive lobes beat up valve trains. Dont confuse expectancy with reality either. It just there as a guide not a line in the sand. It isnt just the spring that gets beat up, the lifters are taking that abuse as well. Builders see the reality of it when they get broken engines in for repair so your builder I'm sure was speaking from experience and was trying to help you.