Roller cam

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aaronk785 said:
Thinking of going roller cam in my drag car this winter. I'm looking at 2 cams. One is 263at .050int. and 269 at .050 ex. Lift is .675 in. and .650 ex. Other is 270 at .050in. and 275 at .050 ex. Lift is .670 in. and .635 ex. My question is what is the purpose of less exhaust lift. Most cams have more on the exhaust.
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Im pretty sure it has something to do with the heads if they flow 70% of the intake flow then it's not necessary to run longer duration or higher lift on the exhaust.
 
Finally got my cam in. Ended up 265-265 at .050 and .650 lift on both, on a 108 Lsa in at 103. Sound way more responsive and idles much better. The sound is different to. It’s really raspy now. TNT tonight we’ll see if it improves or not. It is 7 smaller at .050 but sounds way milder.
 
I’ve gotten good results from single pattern cams in stock stroke 440’s for bracket race type applications.
 
B3422w5 said:
i have cam swapped before and found that a wide LSA cam(112-114) is a dog in a typical N/A bracket type car unless you have lots of compression and convertor.
It will effectively kill 60 foot.
If you have lots of compression, real good heads and vert, they CAN shine. Especially at the big end.
As an example, you wont find Stock/ Superstock type stuff running usually anything but narrower cams
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to the guy who “ disagreed” with me…
Its pretty hard to disagree with on track testing i did on a known combo. Have you also done cam swaps and noted the differences? I doubt it
If you read the link about the cam tests in this thread, they pretty much verify what i said as well.
 
Pre Internet days, swapping cams was the only way to know. Sooooo many cams I have changed.
 
Exhaust opens at about 100 psi pressure, intake , less. A ratio of .35 of valve diameter provides max flow. So a 2.00 intake maxes out at .700 lift, an exhaust of 1.6 maxes out at .560. Plus the huge pressure difference comes into play as well as when the best time is to have the best exhaust pulse and how long it should be.
 
B3422w5 said:
to the guy who “ disagreed” with me…
Its pretty hard to disagree with on track testing i did on a known combo. Have you also done cam swaps and noted the differences? I doubt it
If you read the link about the cam tests in this thread, they pretty much verify what i said as well.
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I'm not the only guy who disagreed with you. I agree with some of it. There are far too many generalizations in your response, and some is subjective as well.
 
roccodart440 said:
I'm not the only guy who disagreed with you. I agree with some of it. There are far too many generalizations in your response, and some is subjective as well.
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i had a 260/266 flat tappet cam( on a 107, in at 104) with 620 lift that PRH on the board here specced years ago.
Car went 10.38 best, typically 10.45/ 10.48. I raced it a lot, pretty much weekly. 128/129 mph.
A friend of mine, Scott Brown who knew my combo extremely well, suggested one of his cams( he owns a business that sells custom cams, still does)
He told me, let me design a cam for you, your car will pick up with it..
It was 258/269 620 lift on a 112. Installed per his instructions at 108.
Fastest the car ever went with that cam was 10.55. When you launched the car it felt like it had been given a shot of novacaine. Just numb, and lazy. Looking at the incrementals, it was off everywhere, but i will say the MPH was almost identical.
I changed nothing, except the camshaft and lifters.
This was a 416, 11.5 compression, W5 heads, 3350 pounds.
Nothing is 100% this or 100% that, but GENERALLY, a wide lsa cam shines with a power adder, also with real good heads, lots of compression, and or convertor.
As i mentioned earlier, class cars like stockers and super stockers most always run narrow LSA cams, because they are generally head limited by class rules..
Pro stock cars, on the other hand, have great heads, and shine with wider lsa stuff. Huge compression is used.
Always will find exceptions, but i stand by the above.
 
aaronk785 said:
This combo has always ran better with a single pattern cam. Don’t know why it just does.
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Most likely great exhaust flow that allows a great overlap cycle. I should look up the cam specs for a 3valve 4.6 Furd. I bet the exhaust will be same as intake or shorter.
 
I'm guessing that's why my custom roller has a split pattern. Full ported headed with 2.20 intake valves probably makes the exhaust side limited in comparison
 
aaronk785 said:
This combo has always ran better with a single pattern cam. Don’t know why it just does.
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Most engines run better with a single pattern cam. Unless you need 800 rpm of overrev. If that’s the case you can use a dual pattern cam. Most people don’t want to shift 800 rpm over peak.
 
aaronk785 said:
Thinking of going roller cam in my drag car this winter. I'm looking at 2 cams. One is 263at .050int. and 269 at .050 ex. Lift is .675 in. and .650 ex. Other is 270 at .050in. and 275 at .050 ex. Lift is .670 in. and .635 ex. My question is what is the purpose of less exhaust lift. Most cams have more on the exhaust.
Click to expand...
I would go with the 263@.050, it has lower lift but more exh. duration to compensate. It has enough duration for your RPM range. It will make more torque down low due to less duration.
 
Many cam grinders will grind less exhaust lift depending on the cylinder head. Less lift will generally have less exhaust reversion. If looking at shelf cams the ones with more exhaust lift generally are Chevy grinds. Got that info from Chet Herbert many moons ago.

You also want a cam ground on a Mopar core designed for a .904 lifter. Otherwise you will get a Chevy grind with less performance. There is a reason many GM guys use the .904 lifter...
 
B3422w5 said:
if you read my post i didnt say it effects it other than to say its worse.
A bracket car is about consistency, nothing else. I know that.
What i said was( reread my post) is that in a typical N/A bracket car the wide LSA cam will be a dog compared to a narrower LSA cam. The 60 foot will be doggier too. Maybe you like doggier, i dont.
My goal is to get my car to run as good as its capable of, then try and make it consistent. Some guy make them consistent by putting big tires on, others having a good suspension, etc.
Everybody is different. But i would never put something in my car knowing it will slow the car down.
I also said “ typical”
Now if you have lots of compression, real good heads, lighter car, dont mind spinning it....a wider LSA cam “might” work better.
Pro stock guys run wide lsa cams. Stock/ superstock guys dont.
Do you have any ideas why that is?
See what i said just about for a clue[/QUOTE
Wide LSA = more vacumm
Less bottom end grunt & more up top
makes since !!
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aaronk785 said:
Thinking of going roller cam in my drag car this winter. I'm looking at 2 cams. One is 263at .050int. and 269 at .050 ex. Lift is .675 in. and .650 ex. Other is 270 at .050in. and 275 at .050 ex. Lift is .670 in. and .635 ex. My question is what is the purpose of less exhaust lift. Most cams have more on the exhaust.
Click to expand...

Look on utube [Engine Masters] covered this subject using a N/A RB Mopar engine and results were very interesting !!!
[engine personality test] Camshaft LSA explained
 
Krooser said:
Many cam grinders will grind less exhaust lift depending on the cylinder head. Less lift will generally have less exhaust reversion. If looking at shelf cams the ones with more exhaust lift generally are Chevy grinds. Got that info from Chet Herbert many moons ago.

You also want a cam ground on a Mopar core designed for a .904 lifter. Otherwise you will get a Chevy grind with less performance. There is a reason many GM guys use the .904 lifter...
Click to expand...
How do you determine which cams are Mopar grinds?
 
He determines by the cam companies description of “904 lifter use only.”
 
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