Camshaft duration question - Ford Bronco Forum
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post #1 of 26 (permalink) Old 03-11-2017, 03:32 PM Thread Starter
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Question Camshaft duration question

Ok so I have a question about duartion. I know what duration is and how the numbers are derived, but how exactly does it affect the performance of a vehicle? Will a higher duration cam create more power higher up on RPMs compared to a cam that has smaller duration? less duartion = lower rpm power?

Solve my example?

Cam 1 : Duration 284/292, Lift .536/.536 (Same lobe seperation and lift)

Cam 2 : Duration 276/286, Lift .536/.536

How will the cams behave compared to each other?

I look forward to hearing from you guys! thank you!

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post #2 of 26 (permalink) Old 03-11-2017, 05:23 PM
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.050 durations are better to compare, but you won't physically notice (from the driver's seat) much difference between those two. Amount of power will be comparable, but the longer duration will make the peak power point a couple hundred rpm higher. Again, you won't notice this in your application and usage.
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post #3 of 26 (permalink) Old 03-11-2017, 05:43 PM
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As a comparison, here is the difference between a 274 and a 256 by the same manufacturer, in the same product line. That's more than 2x the cam difference you asked about. The main difference between these two is over 4500 rpm, which you won't use (based on your otherwise-stated usage and purpose):
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post #4 of 26 (permalink) Old 03-11-2017, 07:45 PM Thread Starter
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Originally Posted by the Son View Post
As a comparison, here is the difference between a 274 and a 256 by the same manufacturer, in the same product line. That's more than 2x the cam difference you asked about. The main difference between these two is over 4500 rpm, which you won't use (based on your otherwise-stated usage and purpose):
Those are advertised duraions, anyways would you think this would be a good cam for my bronco or would suggest I go to a lower operating rpm range cam?

This is the cam I picked now : https://www.summitracing.com/parts/l...view/make/ford

Its also ecu compatiable.

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post #5 of 26 (permalink) Old 03-11-2017, 09:17 PM
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Well here is what I have found, as displacement increases a cam gets more tamed. So if say you have a 650 @ .5 lift ( .5 is the standard mesurement by the industry to show like specs) 292 / 300 duration with a 110 seperation the cam will act like a thumpity drag cam with a 302 but an RV cam on a 450 cube engine. This is not because of the actual grind but because the engine is drawing more fuel and air which lowers the usable RPM rang on a cam of the same spec. The base configuration would start with displacement, then desired RPM then the effieciency of the engine itself. A cam with a big lift and long duration might start pulling at 3500 RPM on a 289 but would be a grocery getter in a 600 cube BB.
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post #6 of 26 (permalink) Old 03-11-2017, 10:46 PM Thread Starter
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Originally Posted by 445 FE Bronco View Post
Well here is what I have found, as displacement increases a cam gets more tamed. So if say you have a 650 @ .5 lift ( .5 is the standard mesurement by the industry to show like specs) 292 / 300 duration with a 110 seperation the cam will act like a thumpity drag cam with a 302 but an RV cam on a 450 cube engine. This is not because of the actual grind but because the engine is drawing more fuel and air which lowers the usable RPM rang on a cam of the same spec. The base configuration would start with displacement, then desired RPM then the effieciency of the engine itself. A cam with a big lift and long duration might start pulling at 3500 RPM on a 289 but would be a grocery getter in a 600 cube BB.
Ok, do you think this is a good cam for my bronco? It is one out of 6 that are ecu compatiable from summit.

https://www.summitracing.com/parts/l...view/make/ford

UPC: 788120719698
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,500-6,200
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 228
Duration at 050 inch Lift: 218 int./228 exh.
Advertised Intake Duration: 276
Advertised Exhaust Duration: 286
Advertised Duration: 276 int./286 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.536 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.536 in.
Valve Lift with Factory Rocker Arm Ratio: 0.536 int./0.536 exh.
Lobe Separation (degrees): 112
Computer-Controlled Compatible: No
Valve Springs Required: Yes
Quantity: Sold individually.

P.S Ok I actually have another question here. There are two cams, one has an operating range of 1,500 - to 5,200 the other has 2,500 - to 6,200. Does that mean the lower operating cam motor will have better acceleration or better low end power?

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post #7 of 26 (permalink) Old 03-12-2017, 09:16 AM
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The lower RPM cam will produce torque and HP at a lower RPM in general, but will peak sooner. A 2500 - 6500 base RPM cam you might find a little hot for off the line and crawling unless you have a sick with a creepy first or a modified auto with still and valve body.
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post #8 of 26 (permalink) Old 03-12-2017, 12:28 PM
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It all comes down to what Operating RPM range your Bronco's Engine will be running at 90% of the time. The Bigger Cam shaft, needs a Lower gear ratio, Stall Converter (for an Automatic) as stated by @445 FE Bronco "a modified auto with still and valve body." . Then if you add Taller tires, you'll need a even lower gear ratios in the axles because of the added height of the tires, to keep the engine in it's new operating RPM range. What I'm trying to tell you, is: you have to consider all the aspects of the whole package. (Driving style, usage, and find a happy Medium.)
The Shorter the Duration of the Camshaft again in "General" means a Lower RPM Range.
The Longer duration of the Camshaft again in "General" means the Higher RPM range.
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post #9 of 26 (permalink) Old 03-12-2017, 04:17 PM Thread Starter
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Originally Posted by 445 FE Bronco View Post
The lower RPM cam will produce torque and HP at a lower RPM in general, but will peak sooner. A 2500 - 6500 base RPM cam you might find a little hot for off the line and crawling unless you have a sick with a creepy first or a modified auto with still and valve body.
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Originally Posted by Fast Floyd View Post
It all comes down to what Operating RPM range your Bronco's Engine will be running at 90% of the time. The Bigger Cam shaft, needs a Lower gear ratio, Stall Converter (for an Automatic) as stated by @445 FE Bronco "a modified auto with still and valve body." . Then if you add Taller tires, you'll need a even lower gear ratios in the axles because of the added height of the tires, to keep the engine in it's new operating RPM range. What I'm trying to tell you, is: you have to consider all the aspects of the whole package. (Driving style, usage, and find a happy Medium.)
The Shorter the Duration of the Camshaft again in "General" means a Lower RPM Range.
The Longer duration of the Camshaft again in "General" means the Higher RPM range.
So whould you guys suggest I go with the higher rpm cam, my plans for my Bronco are to have it as a weekend toy, such as bring it to the strip and sand dunes. And I do plan on re-gearing it and putting maybe like 33's on it, but those will be the last things to be done.

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post #10 of 26 (permalink) Old 03-12-2017, 04:59 PM
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I'm glad you guys are dealing with this guy and not me anymore. I tried to explain in all his other posts but...... Good luck.
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post #11 of 26 (permalink) Old 03-13-2017, 08:29 AM
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Originally Posted by RLVBronco View Post
So whould you guys suggest I go with the higher rpm cam, my plans for my Bronco are to have it as a weekend toy, such as bring it to the strip and sand dunes. And I do plan on re-gearing it and putting maybe like 33's on it, but those will be the last things to be done.
No I do not recommend You step up to the Higher RPM Camshaft, (Reason #1 you have a used/Stock, lower end. (Reason #2 you don't have a Modified Automatic Transmission with a Stall Converter, and/or Modified Valve body. (Reason #3 you do not have the lower gear ratio Axles. (Reason # 4 The higher Camshaft will probably Freak out your computer...................

But you will get whatever you want, and learn things the hard way, Because We have given you all the necessary information to try to guide you in the right direction, but you just Keep asking the same questions worded differently.
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post #12 of 26 (permalink) Old 03-13-2017, 02:37 PM Thread Starter
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Originally Posted by Fast Floyd View Post
No I do not recommend You step up to the Higher RPM Camshaft, (Reason #1 you have a used/Stock, lower end. (Reason #2 you don't have a Modified Automatic Transmission with a Stall Converter, and/or Modified Valve body. (Reason #3 you do not have the lower gear ratio Axles. (Reason # 4 The higher Camshaft will probably Freak out your computer...................

But you will get whatever you want, and learn things the hard way, Because We have given you all the necessary information to try to guide you in the right direction, but you just Keep asking the same questions worded differently.
I've actually decided to go with the 1,000 to - 5,200 rpm range cam, it's lift is a little less, but its duration is more. Althought what do you mean modified valve body?

Summit Racing Part Number:LUN-20350612

UPC: 788120719742
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,000-5,200
Intake Duration at 050 inch Lift: 210
Exhaust Duration at 050 inch Lift: 218
Duration at 050 inch Lift: 210 int./218 exh.
Advertised Intake Duration: 276
Advertised Exhaust Duration: 284
Advertised Duration: 276 int./284 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.525 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.525 in.
Valve Lift with Factory Rocker Arm Ratio: 0.525 int./0.525 exh.
Lobe Separation (degrees): 112
Computer-Controlled Compatible: Yes
Grind Number: 10-HR7-HR8-12-A01
Valve Springs Required: Yes
Quantity: Sold individually.
In-Store Pickup:Choose In-store pick-up (OH, GA, NV) on our web site.

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post #13 of 26 (permalink) Old 03-13-2017, 04:18 PM
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Originally Posted by RLVBronco View Post
Intake Duration at 050 inch Lift: 210
Exhaust Duration at 050 inch Lift: 218
Duration at 050 inch Lift: 210 int./218 exh.
Advertised Intake Duration: 276
Advertised Exhaust Duration: 284
Advertised Duration: 276 int./284 exh.
This is why I mentioned .050 duration.
To compare this 276 cam to my "smaller" 268 cam, this .050 intake duration is 210. The .050 intake duration on my advertised smaller cam is 218. That's 8 degrees more.

This 276/284 cam is not a bad choice.
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post #14 of 26 (permalink) Old 03-13-2017, 04:31 PM Thread Starter
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Originally Posted by the Son View Post
This is why I mentioned .050 duration.
To compare this 276 cam to my "smaller" 268 cam, this .050 intake duration is 210. The .050 intake duration on my advertised smaller cam is 218. That's 8 degrees more.

This 276/284 cam is not a bad choice.
Now what about this cam Would I be able to run it with stock gears, trans, and stall without having any problems you think?

UPC: 788120719667
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,000-6,000
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 226
Duration at 050 inch Lift: 218 int./226 exh.
Advertised Intake Duration: 284
Advertised Exhaust Duration: 292
Advertised Duration: 284 int./292 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.500 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.510 in.
Valve Lift with Factory Rocker Arm Ratio: 0.500 int./0.510 exh.
Lobe Separation (degrees): 112
Computer-Controlled Compatible: Yes
Grind Number: RRN1-284-292
Valve Springs Required: Yes

P.S can anyone tell me the stall converter ranges for a stock 351w?

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post #15 of 26 (permalink) Old 03-13-2017, 04:52 PM
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I would suggest you stay with a cam with rpm range from idle to 5,000 with stock 351w or 302 they will not last long hitting above 5,000 regularly. Can you do it yes how long will it last who knows but you have to remember these trucks are heavy these isn't a mustang or drag car. but then again that is my .02....... I've built many mustangs stoked, blown, and N/A.... If you want to order from summit they have a good tech line. At the end of the day just be honest with yourself as to what you are going to be doing with this rig and what you expect.
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Originally Posted by natedawgg94 View Post
I would suggest you stay with a cam with rpm range from idle to 5,000 with stock 351w or 302 they will not last long hitting above 5,000 regularly. Can you do it yes how long will it last who knows but you have to remember these trucks are heavy these isn't a mustang or drag car. but then again that is my .02....... I've built many mustangs stoked, blown, and N/A.... If you want to order from summit they have a good tech line. At the end of the day just be honest with yourself as to what you are going to be doing with this rig and what you expect.
Well it's not really going to be stock anymore... I'm changing the heads, all the valve train, intake, all of the exhaust, and the cam.

The best cam will probably be the operating range of 1,000 - to 5,200. But I want to know if I can use the 2,000 to 6,000 cam with a stock stall converter.

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post #17 of 26 (permalink) Old 03-13-2017, 05:55 PM
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Open discussion on engines I can do all day NP, theory, flow charts and cam design is a constantly changing thing. What was true a few years back is not so much anymore, advances in technology have with new head design and camshaft options have changed everything. As a base line I always go one step less than what a would generally want for the same displacement on an engine for off road. For street middle of the road and track go big. In the end there is many variables in a like family of Cams like say a computer controlled roller family. So if say you do a 400 cube stroker out of a 351 block, Cams from a 302 would physically fit but act different. Add heads like some Edelbrock aluminum Yates ports with raised exhaust runners and I would step up. If you run stock heads and stock Speed Density you would get more gains from a milder cam due to optimized cam profile for the displacement and projected HP. REALLY YOU NEED TO CALCULATE THE CAMSHAFT TO THE PARIMITERS OF YOUR ENGINE. Kinda simply put but there it is, the manufacturers have web sites and pages for cam recommendations, I call Comp Cams or plug in my numbers and send them an email for recommendations as they have tested and run the product so it isn't a crap shoot. The camshaft is my last stop on my shopping list after the heads, block and static compression is calculated. The compression has a drastic affect on the camshaft design also so this needs to be considered. Most of my Cams I buy are custom grinds anyhow as a generic cam many times does not fit the bill for what I am trying to accomplish.
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post #18 of 26 (permalink) Old 03-13-2017, 08:50 PM
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Quote:
Originally Posted by RLVBronco View Post
Well it's not really going to be stock anymore... I'm changing the heads, all the valve train, intake, all of the exhaust, and the cam.

The best cam will probably be the operating range of 1,000 - to 5,200. But I want to know if I can use the 2,000 to 6,000 cam with a stock stall converter.
What about your stock pistons, stock rods with stock bolts, stock crank and stock torque converter? None of these parts were intended to rev over 5000 RPMs. In clear english, you will have a stock engine with big exhaust, and an aftermarket intake. Aftermarket heads, will increase RPM, but won't make your engine withstand RPMs over 5000.
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post #19 of 26 (permalink) Old 03-13-2017, 09:52 PM
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Quote:
Originally Posted by wyatt earp View Post
What about your stock pistons, stock rods with stock bolts, stock crank and stock torque converter? None of these parts were intended to rev over 5000 RPMs. In clear english, you will have a stock engine with big exhaust, and an aftermarket intake. Aftermarket heads, will increase RPM, but won't make your engine withstand RPMs over 5000.
Say what?

If they couldn't handle over 5k ford would have out a rev limiter on them to stop them from exceeding that.
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post #20 of 26 (permalink) Old 03-13-2017, 10:06 PM
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Yep start at the bottom and work your way up, pan, pump, baffles, scraper, rotating assembly pre balanced ( scatt ), some heads with 180-190 CC intakes with tulip valves and roller cam.
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