Which Cam should I Purchase

Ken Adams

Member
I'm in the process of purchasing performance parts for a Buick production 4.1. I have so far purchased a Scat 4340 3.400" stroke crank, CP pistons,5.960" h-beam rods and Harland Sharp 1.6 roller rocker . At this point, I need your input as to what camshaft kit should be considered. Should I go roller cam kit or a flat tappet kit? Lift? Duration? Once this engine is completed, it will go into my 86 turbo GN. Car will be used 99% of time on the street.
 
I'm in the process of purchasing performance parts for a Buick production 4.1. I have so far purchased a Scat 4340 3.400" stroke crank, CP pistons,5.960" h-beam rods and Harland Sharp 1.6 roller rocker . At this point, I need your input as to what camshaft kit should be considered. Should I go roller cam kit or a flat tappet kit? Lift? Duration? Once this engine is completed, it will go into my 86 turbo GN. Car will be used 99% of time on the street.


what fuel will you be running ?
 
I'm in the process of purchasing performance parts for a Buick production 4.1. I have so far purchased a Scat 4340 3.400" stroke crank, CP pistons,5.960" h-beam rods and Harland Sharp 1.6 roller rocker . At this point, I need your input as to what camshaft kit should be considered. Should I go roller cam kit or a flat tappet kit? Lift? Duration? Once this engine is completed, it will go into my 86 turbo GN. Car will be used 99% of time on the street.

We need some more information from you in order to better help with a cam profile suggestion.

If you could please provide the following information, it would help everyone who is trying to aid you in your cam profile selection;

1) What fuel will you be running?

2) What type of cylinder heads do you have?

3) What RPM range are you looking to have your car operate at? (What redline are you shooting for? Do you want more low-end power? More mid-range power? More top-end power?)

4) What size turbo are you running?

5) What type of exhaust/downpipe do you have?

6) Is your transmission already built to handle the power?

7) Have you already purchased a new torque converter, or plan to purchase a new one to go along with your camshaft selection?

8) Do you have any issues going with a hydraulic roller camshaft?


Based on the information you provide us, that will help us with a recommendation.

If you go with a hydraulic roller camshaft, I would highly recommend going with Johnson short-travel (NOT the reduced travel, those are different than the short-travel lifters) lifters. These can be purchased from TA Performance for around $460 or $480, which is a good $75 less than what I have seen them listed for at other vendors' websites. These lifters compress very little, which means you lose much less valve lift as the motor revs. As your motor revs normal hydraulic lifters will compress a few thousandths, which means now the lifter is effectively shorter, which means it doesn't push up on the rocker as high, causing the valve to not open as much since it is not being pushed on as much. A poor analogy would be like saying regular hydraulic lifters would make your 1.60 ratio roller rockers more like 1.56 ratio rockers, and short-travel lifters would be more like 1.58-1.59 ratio roller rockers, so you can see that you'll be getting much more lift out of the cam with the short-travel lifters. (Those numbers are completely made up and explicitly to illustrate the point of the difference in valve lift between short-travel lifters and regular lifters.)

IMO, any current grind that I have seen in a cam kit wouldn't give you as much gain in performance as if you went with a custom grind that had a much more aggressive ramp rate profile.

The ramp rate of a camshaft profile is the speed at which the camshaft lobe reaches max lift. A higher ramp rate means that the valve opens much sooner and much farther than a camshaft with a less-aggressive ramp rate. I would look at some cams that have some pretty aggressive profiles, like cam lobe #3188 in the Comp catalog, which has a duration @.050 of 206 degrees and @.200 lift it has 132degrees duration. For 1.6 ratio rockers the total lift would be .538"

But when you respond with that info, we'll know much better how to answer your question :)
 
Here’s a copy and paste from my fb page on camshafts:

Here’s the most common based on overlap @ .050” as a reference point and rpm range for indicated performance levels:

-20 stock/close to stock 4000-5000rpm
-18 to -12 stock to low 11’s with a 57mm turbine 4400-5600rpm
-12 to -8 low 11 to high 9 with 62 compressor and 62 turbine and larger 4800-5800rpm
-8 to -4 9 sec with 64mm compressor and larger. 66mm or larger turbines 5200-6200rpm
-4 to 0 66mm turbine

0-4 mid 8 sec

These will cover 99% of peoples needs.

I’ve used reduced travel and short travel Johnson lifters. Most of the gain comes on the closing side. Neither design bleeds down more on opening. There is more rpm potential on a short travel. Most people aren’t technical enough or have the no how to install short travel lifters. Excessive preload will make the valves stay open and or cause engine damage. I have these lifters on the shelf most of the time. Spring requirements vary for different cams. The less degrees of crank rotation between two events the more aggressive the lobe is. Usually the more aggressive the more lobe lift because the lobe needs to decelerate the lifter to give the springs a chance to maintain control. Often the lift is a product of the lobe aggressiveness. Running very aggressive lobes isn’t practical for most and definitely not practical if cost is any concern.


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Here’s a copy and paste from my fb page on camshafts:

Here’s the most common based on overlap @ .050” as a reference point and rpm range for indicated performance levels:

-20 stock/close to stock 4000-5000rpm
-18 to -12 stock to low 11’s with a 57mm turbine 4400-5600rpm
-12 to -8 low 11 to high 9 with 62 compressor and 62 turbine and larger 4800-5800rpm
-8 to -4 9 sec with 64mm compressor and larger. 66mm or larger turbines 5200-6200rpm
-4 to 0 66mm turbine

0-4 mid 8 sec

These will cover 99% of peoples needs.

I’ve used reduced travel and short travel Johnson lifters. Most of the gain comes on the closing side. Neither design bleeds down more on opening. There is more rpm potential on a short travel. Most people aren’t technical enough or have the no how to install short travel lifters. Excessive preload will make the valves stay open and or cause engine damage. I have these lifters on the shelf most of the time. Spring requirements vary for different cams. The less degrees of crank rotation between two events the more aggressive the lobe is. Usually the more aggressive the more lobe lift because the lobe needs to decelerate the lifter to give the springs a chance to maintain control. Often the lift is a product of the lobe aggressiveness. Running very aggressive lobes isn’t practical for most and definitely not practical if cost is any concern.


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Great info right there!
 
What is the travel distance difference between the short travel and reduced travel lifters?

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