66 tri power cam - Pontiac GTO Forum
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post #1 of 14 (permalink) Old 01-31-2011, 07:15 AM Thread Starter
 
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66 tri power cam

Im looking to kick my 66 Tri-power up a few notches. The engine is a stock tri-power with headers and pertronix ignition. Currently no other mod's. Looking for some input on a good cam shaft for the motor. It is a street car so Im not looking for anything to radical. Would just like to bring it up to date with a good flowing cam. Thanks!
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post #2 of 14 (permalink) Old 01-31-2011, 10:35 AM
 
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I put a hydaulic roller cam in my car. I never have to worry about oil additives any more. Another great thing about them is there is no beakin procedure for them. Start it and go.
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post #3 of 14 (permalink) Old 01-31-2011, 10:52 AM
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The Tri-Power cam is very aggressive and Pontiac did alot of research to get it right so it has alot of power but still have some idle quality.
Does your car have power brakes??
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post #4 of 14 (permalink) Old 01-31-2011, 11:12 AM Thread Starter
 
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Yes it is a power brake car.
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post #5 of 14 (permalink) Old 01-31-2011, 11:15 AM
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Yes it is a power brake car.
Then if you go bigger then the factory Tri-Power cam you will start to lose vacuum to the booster at an idle (making stopping the car difficult). If you went with a hydro boost booster (uses power steering pressure) you could go way bigger on the cam without worrying about the vacuum issue.
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post #6 of 14 (permalink) Old 01-31-2011, 11:40 AM
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Then if you go bigger then the factory Tri-Power cam you will start to lose vacuum to the booster at an idle (making stopping the car difficult). If you went with a hydro boost booster (uses power steering pressure) you could go way bigger on the cam without worrying about the vacuum issue.
Also, it's very important to pay attention to things like transmission (auto or manual?) rear gearing, torque converter (if auto), cylinder heads, and generally how you plan to use the car. For example, if the car has an auto, a "tight" converter, and high ratio (highway friendly) rear gear you can very easily "kill" it with too much cam. What a "bigger" (longer duration) cam actually does is move the engine's point of peak volumetric efficiency (where it makes peak torque) up to a higher RPM range. The down side is that torque at lower RPM will actually be less, sometimes significantly. This can turn a street car with the "wrong" gearing and converter into a real dog.

Budget ought to go into the mix too.

There are solutions out there to preserve or even improve the operation of power brakes, and other vacuum operated accessories (like A/C) even with a radical cam, but be aware those concerns will add to your overall expense.

With all that in mind, what are you trying to accomplish?

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post #7 of 14 (permalink) Old 01-31-2011, 12:05 PM Thread Starter
 
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M20 4 speed, stock 3:55 posi rear.

Was looking for some more kick. I did not know the original cam was still a very popular choice so maybe staying the same is the way to go.
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post #8 of 14 (permalink) Old 01-31-2011, 12:16 PM
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M20 4 speed, stock 3:55 posi rear.

Was looking for some more kick. I did not know the original cam was still a very popular choice so maybe staying the same is the way to go.
That's the same set up as mine, (sept for the center carb) try filling the tank with race fuel, add 5* timing and hang on!!
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post #9 of 14 (permalink) Old 01-31-2011, 12:32 PM
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M20 4 speed, stock 3:55 posi rear.

Was looking for some more kick. I did not know the original cam was still a very popular choice so maybe staying the same is the way to go.
Well all-righty then Which heads do you have, and are your pistons/rotating assembly factory stock?

Having a manual and those gears does open up your possibilities quite a bit. I suspect Mr. P-Body will be along directly and will have some good recommendations. If your budget can stand it, a mild solid roller can net you quite a bit more effective duration while still keeping overlap reasonable enough so as not to affect your idle vacuum too much. The cam I have in my 69 has intake/exhaust duration of 236/242 @ .050 and it still makes 13 to 14 inches of vacuum. That's borderline for brakes so I went ahead and put a hyrdoboost on my car. You could probably run something in the high 220's/low 230's at .050 and still be able to operate your brakes. That'd be on a 110 degree LSA. A little wider LSA to kill some overlap would get you even more vacuum at the expense of a little power. You've got options.

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post #10 of 14 (permalink) Old 01-31-2011, 12:36 PM
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Unless your comfortable messing with the valve adjustment every/other weekend, I would not opt for a solid lifter cam.
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