Thread: Brodix IK Heads.

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Originally Posted by Scooting

Object is to street drive, coast to coast, have the most usable torque curve that is huge and flat as a board, and be able to jump on Junior and his new muscle car when desired. The motor will be backed by a bowtie overdrive built 200r, 2500 stall, 3.70 rear gears, 31 inch tires, car weight is 3900,, aerodynamics of a brick . I would like for you to take a shot at recommendations for me.
4.03 bore
3.75 stroke
Ross forged pistons -12cc
6.0 rods
pistons are even with deck - zero
I would like to use the pro-filer heads - 185 or 195 what chamber size?
head gasket .041
performer rpm manifold
780cc Holley 3310 with vacuum secondaries.
Retro fit what roller cam?
Premium gas - mile high altitude for home base
Thanks, I am trying to figure this out before getting too far.

You know, hot rodding is fun....until you add an overdrive transmission....and vary the elevation between 5000' and sea level.
That's what the factory engineers have to do every time they design a new vehicle, but they have mega-computers to aid them in their choices.
The best I have to work with is some basic math and a modicum of common sense, but I'll do what I can to contribute to the project.

The first thing that must be considered is the gears in relation to cam timing. Your 3.70 rear gear with a 0.67 OD transmission gear and a 31" tire is the same as using a 3.20 rear gear, 0.67 trans gear and 27" tire, so the cam will have to be pretty short to work with that at cruise speed (65 mph @1750 rpm's). I have encountered many fellows who failed to take that into consideration, using a cam that has an operating range of 2500-6000 for instance, when they actually need a cam that has a low operating rpm of ~1500-1600 up to a high range of ~5000. Question is, how do you drive around Henry Hotrod with a short cam? The obvious answer is to use a turbocharger or a blower. Before we go any farther, are you up for that?

The other variable is elevation. If you jet the carb for running good at 5000', the motor will go real lean at sea level, with a very real possibility of holing some pistons. If you jet it for running good at sea level, it will be hog-fat at 5000'. The obvious answer is programmable electronic fuel injection with O2 sensors in the header collectors and using a cam with a 114-116 lobe separation angle, like the OEM's do. Again, are you up for that?

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Originally Posted by techinspector1

You know, hot rodding is fun....until you add an overdrive transmission....and vary the elevation between 5000' and sea level.... The other variable is elevation. If you jet the carb for running good at 5000', the motor will go real lean at sea level, with a very real possibility of holing some pistons. If you jet it for running good at sea level, it will be hog-fat at 5000'. The obvious answer is programmable electronic fuel injection with O2 sensors in the header collectors and using a cam with a 114-116 lobe separation angle, like the OEM's do. Again, are you up for that?

Not trying to hijack, but I remember a sign at one of the real "service stations" (the kind with mechanics on duty...) back in the early '60's as we drove the road approaching Pike's Peak in Colorado, "Get Your Carburetor Adjusted Here". We were from south Missouri, elevation about 1000' ASL driving at about 6000'ASL and getting ready to be pushing 14,000'. I remember that I couldn't tell the car was running at idle at the top, as it was only turning about 250rpm, and pressing on the gas got a sloooooow ramp in rpm's, zero "snap" to the throttle. I wondered at the time how many people paid a few bucks for smaller jets to drive in the mountains, then wondered why their car ran like crap when they got back home.... We didn't stop, but I expect the mechanic told his customers to stop back in before they headed home, and he'd re-tune them back to flatland specs using the jets he removed a few days before....for another few bucks, of course.