low end troubles

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low end troubles

Post  1971tjet on June 30th 2012, 6:09 pm

i have a 1971 429 thunderjet with stock dove c heads, electronic ignition,edelbrock performer 460 intake an 750 double pumper holley on it an it runs down the road fair but it seems not to have the low end or raw torque it should have an i dont know if its the carb or the timings off but something not rite it will barely turn over the tires from a dead stop the stock thunderjet i had before felt alot stronger any ideas where to start to look ? thanks

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Re: low end troubles

Post  LivermoreDave on June 30th 2012, 7:27 pm

A 429 doesn't have a lot of stroke to begin with although a properly tuned 429 should spin the tires a little, assuming it's not wore out! Areas to search for performance is timing, rate and amount, carburetor secondary function and opening rate. Any ticking in the valve train?

Dave.

Oh, I just realized you are using a "double pumper" ! That may not be the best choice if your engine is stock or near stock and the vehicle is heavy.

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Re: low end troubles

Post  466cj on June 30th 2012, 11:26 pm

That year engine should have a staight up timing chain gear, but over all these years could have been swapped out for the retarded set. That will kill low end. Make sure the distributor advance is working and that the advance curve is set up for performace. A slow advance and not enough timing can make the engine soggy. Also make sure the vac. adv. is set up correctly and working. No vac. adv. can effect part throttle response. A VS carb be better than a DP, but if you get it set up right should work ok.

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Re: low end troubles

Post  dfree383 on July 1st 2012, 12:07 am

whats it in and how much gear is in it?
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Re: low end troubles

Post  1971tjet on July 2nd 2012, 9:51 pm

dfree383 wrote:whats it in and how much gear is in it?
its in a 4000lb 71 thunderbird with a 270 rear automatic c6 transmission, my first one would break loose at 45mph, this one runs like a 351 windsor 2v . thanks

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Re: low end troubles

Post  jasonf on July 2nd 2012, 10:28 pm

What is the initial timing set at? That will make a huge difference if it is at 6* for ex.
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Re: low end troubles

Post  dfree383 on July 2nd 2012, 10:43 pm

A little gear would help immensely........ And like said above a little tuning.
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Re: low end troubles

Post  1971tjet on July 4th 2012, 2:56 am

LivermoreDave wrote:A 429 doesn't have a lot of stroke to begin with although a properly tuned 429 should spin the tires a little, assuming it's not wore out! Areas to search for performance is timing, rate and amount, carburetor secondary function and opening rate. Any ticking in the valve train?

Dave.

Oh, I just realized you are using a "double pumper" ! That may not be the best choice if your engine is stock or near stock and the vehicle is heavy.
it doesnt smoke or no ticking in the valvetrain has good compession its a 10.5 to 1 , 360hp/480tq engine seems to have been takin care of im hoping its just timming an the carb. thanks for the help

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