# 66 tri power cam



## 66TRI (Jan 6, 2011)

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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## dimitri (Feb 13, 2009)

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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## Rukee (Feb 8, 2007)

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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## 66TRI (Jan 6, 2011)

Yes it is a power brake car.


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## Rukee (Feb 8, 2007)

66TRI said:


> 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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## BearGFR (Aug 25, 2008)

Rukee said:


> 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.


:agree 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?

Bear


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## 66TRI (Jan 6, 2011)

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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## Rukee (Feb 8, 2007)

66TRI said:


> 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!!  :cheers


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## BearGFR (Aug 25, 2008)

66TRI said:


> 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.

Bear


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## Rukee (Feb 8, 2007)

Unless your comfortable messing with the valve adjustment every/other weekend, I would not opt for a solid lifter cam.


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## BearGFR (Aug 25, 2008)

Rukee said:


> Unless your comfortable messing with the valve adjustment every/other weekend, I would not opt for a solid lifter cam.


That's the way it "used to be". With today's profiles, spring pressures, and most importantly the lifters that have positive oiling for the roller bearings, plan on adjusting them only a couple of times a year unless you're running a huge, aggressive "race only" cam with associated high spring pressures.

Bear


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## geeteeohguy (Feb 2, 2008)

I installed a Sig Erson High Flow I in my '65 389 when I built the engine in '81. It's a primitive, single profile, high lift, big duration hydraulic cam with a ton of lope. It stings your eyes, and pulls about 12" vacuum. My car has a 4 speed and manual brakes. I did the best I could at the time with old school technology. I added tubing headers and good valve springs. That said, I got lucky. The engine ran like a scalded cat and was (and is) trouble free. Still runs super strong today. I have never had to re-adjust the valves and have never had any issues (press in stud, stock #77 heads....lucky as heck). Today, 30 years older and maybe a little bit wiser, I wish the car had a little less cam....it's pretty obnoxious, but the 20-somethings think I'm cool. I have to run boosted fuel in this engine, as the compression ratio is 10.75-11 to 1 (milled heads). If you are going to drive your car a lot, an "068" grind camshaft is a pretty safe all around choice. Doing it over as an "old guy', I would run less compression with better heads and a modern cam to make my power.


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## 66TRI (Jan 6, 2011)

My rotating assembly is factory stock. Thanks for all the good advice!


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## Mr. P-Body (Jan 20, 2011)

66tri,

Bear has nailed it (as usual...). And no, solids DON'T require "constant" maintainence, that's a myth "left over" from the 327s of the '60s. 

068 is HARDLY a "max-effort" cam. It's a "compromise" as are most factory grinds (not restricted to the Pontiac factory). While not a BAD performer, it has been eclipsed LONG AGO. 

Your compression ratio is too high for 93 octane fuel if your internals are indeed "stock". Inaudible detonation has ruined MANY a 389. I would take "steps" to lower the static ratio if that hasn't already been done. If it has been done, I would recommend a Comp XE262H cam. It will "wake up" that 389!

If ratio is still "high", and you use "race gas" (at least as a "mix"), the XE grinds are not as well suited. They build cylinder pressure rapidly at lower engine speeds, which can induce detonation. I would recommend an 041 (Ram Air IV) cam, installed at 4 degrees "advance". By advancing the cam timing, you take a little of the "lump" (lope) out and build cylinder pressure at about 500 RPM lower than "straight up". Your 3.55s and the wide-ratio Muncie will LOVE this. My '70 "400 Ram Air III" GTO ran low 13s in 1973 with this combo. Today, a similar build will get you into the low 12s. Vacuum may or may not be an issue. A storage canister or as Bear said, "hydro-boost" are good remedies IF vacuum drops below 12". Your booster should work fine at 13". 

FWIW

Jim


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