'71 429 thunderjet

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Oct 29, 2004 | 10:27 AM

notyettoday

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From: Nashville

'71 429 thunderjet

i have the opportunity to get my hands on this motor,and i would like to get some suggestions on how i can get some useable power for towing and just driving, without making my gas milage terrible. i'm pretty sure its supposed to be putting out ~365/500 stock, and i'd like to bring that up a bit. torque over horsepower, but whatever i can do to make this thing a monster that gets decent milage.

Oct 29, 2004 | 01:51 PM

Brad Johnson

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Begin by reading through the threads on this forum, a great number of which deal with what you are asking.

Brad

Oct 29, 2004 | 02:16 PM

68torino

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From: South Dakota

Will depend on what you mean by good mileage. With that motor you will see around 14-18 on the highway in good tune, depending on what you put it in. Light car will get a little better mileage than a heavy truck. Other factors are final drive ratio and aero. Also a '71 is not set up for the low octane we have now and may need hardened exhuast seats installed. As for making more torque vs horsepower you can go with a stroker kit, tri-y headers and a 'truck/rv' cam. When choosing a cam I was told the best way is to call the cam manufacturer, tell them what your motor is, bore-stroke, trans you're running, final drive, what it is in and how you will be driving it. They will be able to steer you to the right cam.

Nov 2, 2004 | 09:05 PM

fast_barry_racing

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actual stock power numbers for a standard thunderjet will be closer to 270hp 450tq

Nov 3, 2004 | 03:53 AM

BigRed350

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From: Las Vegas, Nevada

Quote:

Originally Posted by fast_barry_racing

actual stock power numbers for a standard thunderjet will be closer to 270hp 450tq

No 429 made in 1971 was rated at 270 hp. There were actually 4 different 429's made that year. First there was the "base" engine which had a 2 barrel Autolite carb. This engine was rated at 320 hp @ 4400 rpm and 460 ft. lbs. torque at 2200 rpm. It had 10.75 "approx.) compression. Next in line was the "Thunderjet" which was rated at 360 hp @ 4600 rpm and 480 ft. lbs. torque @ 2800 rpm. Compression was the same 10.75. Next in line was the Cobra Jet and Police engines which were rated at 370 hp @ 5400 rpm and 450 ft. lbs. torque @ 3400 rpm. The compression was 11.45 (pretty high). Last in line in '71 was the Super Cobra Jet which had 375 hp @ 5600 rpm and 450 ft. lbs. torque @ 3400 rpm. It also had the 11.45 compression ratio. Note that the Cobra Jet and Super Cobra Jet had lower torqe than the "plain Jane" engines because they had bigger ports in the heads and manifold which allowed for greater top end breathing but killed the low end torqe to a degree. Lower velocity of the air/fuel mixture. Ford switched over to using the "net" ratings which were much lower in 1972.

Last edited by BigRed350; Nov 3, 2004 at 03:55 AM. Reason: typo