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71 blazer rebuild questions (speedo calibration and transmission question)

68MUDSTUD

68MUDSTUD

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Howdy fellas, been a while. I'm rebuilding my 71 k5, and thinking about going with 17" wheels and 35x12.50s. I need to know what width rim and offset to order. I'm running about 6.5-7" lift in the back, 4" in front.

Currently sitting on stock 15s and 35x12.50s.

Thanks in advance!

PXL_20240320_133015615.jpg
 
Pretty sure mine are 4.5, but had to order using communist measurements
 
Ok, another question... How do I calibrate my speedometer? Count teeth in rearend, then what? I'm running the stock np205. engine will be a blueprint 383, and a TCI maximizer th350. Had a 350/th350 before.

also, when I go to install new engine and trans, that maximizer should drop right in, correct?
 
also thinking about acessory brackets... I'm going to stay with a short water pump, but would like to move my alternator to the pass. side. No AC.
 
68MUDSTUD said:
Ok, another question... How do I calibrate my speedometer? Count teeth in rearend, then what? I'm running the stock np205. engine will be a blueprint 383, and a TCI maximizer th350. Had a 350/th350 before.

also, when I go to install new engine and trans, that maximizer should drop right in, correct?
Click to expand...
You don't drive off of the tach? hmm

THere's an inline correction that goes onto the tcase end to correct the speedo
 
Bent77 said:
You don't drive off of the tach? hmm

THere's an inline correction that goes onto the tcase end to correct the speedo
Click to expand...
I understand that you can buy different blocks that screw into the tcase, that the speedo cable hooks up to, but how do I figure out which one i need? And yes, I used to just use the tach. lol
 
Well I never changed it when I put the 35s on it, so I know it's quite a ways off.
 
68MUDSTUD said:
Well I never changed it when I put the 35s on it, so I know it's quite a ways off.
Click to expand...
You will need to find the amount that the speedometer is off, change that number into a percentage. This will let you know the amount of percentage of correction needed.
Say that it's 10% slow, you would need a correction box with a 1.10 ratio to speed it up.

On the alternator mounting, I would first ask why, because the factory bracket works.
But I don't know of any factory brackets to move it to the passenger side, so aftermarket is the only option that I know of, besides fab it yourself. You could make a lower bracket that flips the configuration of the stock bracket.
 
As for your question about the trans dropping right in place that will depend on what tail shaft you ordered it with.
Most 2WD & passenger car TH350’s will come with a variety of longer tail shafts than what a TH350/205 combo uses - did you give the supplier the dimension and application of it being a 4WD ?
 
There are adapters made by Stewart Warner with little gears in them to compensate for different rear end gear ratio's and tire sizes. Mine broke a couple of months ago on a trip back through Montana at -30. I found several good sites on the web with charts to assist in selecting the correct adapter ratio for your rig, then found one on ebay. These adapters were made for several different truck manufacturers. Mine was a correct part number and was used on an IH truck.
 
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