Street build question/opinions
 

I am building a 461 stroker for my 66 gto convertible, 4 speed, 3.23 rear. I have a set of 6x-4 heads that I have cleaned up at home. No major work done, just cleaned the sharp edges in the bowls and rounded the short radius and smoothed any casting flaws in the ports and finished with 80 grit rolls. My goal is a nice sounding, fast, reliable street car. I contacted Butler and they said that I need to work with a machinist to figure out a plan before ordering parts. They did say to go to 1.77 valves instead of 1.66. I also want to get bronze guides installed. I have no idea what cam/ rockers/ lifter choice/ valve length, etc., to use.

So I guess I am looking for real world opinions on what to use for a streetable motor that I would like to see at least 400hp/500tq from. As far as budget, I would like to stay on the more "affordable" end of things. I plan on assembling the motor myself.

Thanks
Drew

Pretty good combo. Helpful thoughts: 1-piece Ferea valves. Pypes Aluminized Exhaust with the Super-Turbo Mufflers. Q-JET or known-good carb for break-in.
Cam shown below in 12.2 ET Signature is on the edge of "Too Big" for 9.0:1

I forgot, i have the original tripower that I plan on using. But I can't rebuild that until I know the engine specs to know jetting, etc...

Car is no power brakes and no power steering.

And I can't order the pistons until I know the CC's of the heads, which I won't know until I get them back from the shop, which won't happen until I know what to tell him to do with the heads....So many decisions are dependent upon other decisions...paraylsis by analysis maybe.

You should be able to get 9.5 to 9.7 compress out of those heads on 461 cubes. So, I would pick a mid 230`s to 240 at 050 cam, on 112 sep, with a 6 to 8 degree spread on the exhaust.

Your 400 to 430 hp should be there.

This should help you out a bunch.

Sorry but today I don’t have time to type a in-depth reply back.

You don’t need 1.77” exh valves unless your planing on buzzing the motor over 5500 and with a what might be a hotter cam the you can live with on long drives.

Note that your cam pick lift wise may dictate what length valves you need.

Also be double sure that any valves you do get have chrome plated stems, as I have seen a few companies/ sellers cheaping out on this important detail.

My 9.4 compression 461 came in at 429.2hp and 531.4 trq with Butler kit and 16 heads with mild port.

282/288, 230/236 .561/.573 112 LS with 1.65 ratio rockers

Butler/Comp Pontiac Custom Grind Billet Hydraulic Roller Cam/Lifter Kit BPI-CL-BP8022SP

Id be thrilled with those numbers.

What where your average power numbers out of your 461?

If you are asking me, I dont have any numbers yet because this is a new build and it is also my first build in about 30 years. I was just commenting that Roys numbers looked great to me and I would be thrilled if whatever I put together ended up like that.

461
 

I by no means know how to read a dyno sheet. I'm pretty ignorant to these numbers as I just followed the engine builders and Butlers lead. I was just looking for a nice streetable engine. I'm assuming there is more to be had with head and carb upgrades. Has forged rods and pistons. I too will be adding a 66 tripower when it comes back from Mr. Boeneske

Roy the average numbers are not on your dyno sheet so I figured them out.

Between 3700 and 5200 your motor did 489 ft lbs. and hp wise made 411.

What advantages would a 1.65 rocker give me over a 1.5? And should I look at hydraulic rollers or stick to flat tappet?

461
 

Thanks Steve, that cam was recommended by Butler. The car has turbo 400 with 3.23 gears. Has Dougs headers and I plan on a 2.5 exhaust. Not to hijack the OP thread but any other cam recommendations to get a little more out of the engine?
Also, that's a typo on the dyno sheet that says 462.

Thanks in advance, Sorry if I don't respond I'm heading out for the evening.

I'd got with 1.65 s on the Intake, 1.5s on the exhaust.

When working on a build, what is the first thing someone should think about once a decision is made on what you want from the motor? Cam? And then build out from the cam? From there, springs, rockers, valves, lifters, etc? Then rotating assembly? Just want to make sure I am thinking about things in an order that makes sense.

I would suggest going easy on the cam so you don’t have to mod the Tri-Power carbs too heavily.

I know Dick Boneske runs a fairly mild cam in the Tri-Power 428s powering both his and his wife’s 1964 GTOs, something around the Summit 2802 or a tad bigger like the Crower 60243:
https://crower.com/camshafts/pontiac...amshaft-7.html

A quiet exhaust system is a big plus when you’re cruising along with the top down. Exhaust noise with convertible cars is much more apparent, you hear a lot of road and exhaust noise whether the top is up or down.

That makes sense. I would like a little lope to the idle but I dont need anything ridiculous. Im not sure where that falls as far as lobe separation? Will 112-ish have a nice idle?

112 would have a nice idle as in smoother than a 110 or 108.

I’m just more in favor of having a more comfortable car rather than one that annoys me nowadays. If I was 18 years old I’d think differently I’m sure.

The Crower cam would have a nice powerful rumble. A nasty sounding cam has its downsides, you’re stuck listening to that racket and it’s going to get poor fuel economy.

You have to decide if you want a race car sound or not. In a convertible cruiser quieter is better for me at least.

If it sounds nasty it better run as fast as it sounds.

The advantage of running higher ratio rockers are greater lift and about 4 degrees more duration over the nose of the cam lobe.

A motor with a longer / bigger stroke then it’s bore size gets starved for air faster as the rpm’s go up then a motor who’s bore is bigger then it’s stroke, even when where taking about lightly reworked iron heads.

With a motor like above its best in terms of max power ( both torque and Hp ) to run valve lift greater then where peak air flow takes place into and out of the heads.

Most post 1967 stock iron d ports attain peak flow at .550” lift.

If you run a cam of .500” lift rates with 1.5 rockers and replace them with 1.65 rockers you will then have .549” lift.

Getting back to added 4 degrees of over the nose duration produced from going to 1.65 rockers, the great thing about that is this added duration does not really have much effect on the idle quality of the motor, nor degrade low speed torque.

The only question left then with a 4.210” stroke motor is weather or not to run 1.65 rockers on the exh side also since this can help or hurt power.

In general if your running iron heads With 1.66” exh valves with no decent level of porting work and you have added 1.65s to the intake side then you should also run the 1.65 rockers on the exh side of the motor also.

Many times even if your heads have 1.77” exh valves there are so many other interrelated factors taking place ( cam, headers or not, compression, running open headers or not, that the only way to nail down what the motor responds to in a positive way is by empirical testing, as in doing a A vs B test.

Did you port them yourself or increase valve size at all? Kind of curious on the cost/benefit of putting money into iron heads vs buying new aluminum. My application would be a street motor for a Catalina wagon...I'd think the iron 6x heads would be good enough to create a good torque motor (461 stroker plan).