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Discussion Starter · #1 ·
I just took a 1000 mile trip in my 71 El Camino 402, 350 at with 3.73 posi, 29" rear tires. ran a average of 3400 rpms at around 66-70 mph and got about 10 mpg, any one know what the difference would be if i put a 2004r trans in place of the 350 ?? rpms and mpg
 

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You would lose about 1000 rpm`s. Can`t help with the mileage but it should go up.
 

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The 88 montes ss i had with 373 gear and 200r4 got approx 21.5-22mpg in bone stock form .

Then i kept the block stock & installed world product 305 trq heads,a mild crane compucam specifically designed for the monte ss 305 computor controlled q-jet motor.

I also installed and edel req intake but retained the q-jet and panted it blk to match rest of the motor. That combo woke up the little 305 mouse so it would get out of its own way but it still got the same mpg on the road which was still 21.5-22mpg.

I believe it was turning approx 2150-2200rpm at 60mph (stock tire size/was shorter then your 29" tall tires),going to the 200r4 would definatley help alot esp if you hook up the converter lockup system. They make kits to get the lockup working in an older application that never had it but without lockup the trans will run hotter due to increased converter slippage when in the higehr 4th gear and you will definately need a trans cooler in that case not to mention the 2-3mpg loss without lockup too so hook it up.

That swap would help your mpg,thats for sure and it will work fine with your 373 gear but you may need to drop down some from your current 29" tires.

I am assuing your not running a wild cam & if thats the case then that you should be fine with your current gear for the 200r4 swap and it would improve you mpg,just how much depends on your setup,driving habbits,and it you utilize the lockup fearture in 4th gear which not all people do.

Scott
 

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Discussion Starter · #4 ·
The 88 montes ss i had with 373 gear and 200r4 got approx 21.5-22mpg in bone stock form .

Then i kept the block stock & installed world product 305 trq heads,a mild crane compucam specifically designed for the monte ss 305 computor controlled q-jet motor.

I also installed and edel req intake but retained the q-jet and panted it blk to match rest of the motor. That combo woke up the little 305 mouse so it would get out of its own way but it still got the same mpg on the road which was still 21.5-22mpg.

I believe it was turning approx 2150-2200rpm at 60mph (stock tire size/was shorter then your 29" tall tires),going to the 200r4 would definatley help alot esp if you hook up the converter lockup system. They make kits to get the lockup working in an older application that never had it but without lockup the trans will run hotter due to increased converter slippage when in the higehr 4th gear and you will definately need a trans cooler in that case not to mention the 2-3mpg loss without lockup too so hook it up.

That swap would help your mpg,thats for sure and it will work fine with your 373 gear but you may need to drop down some from your current 29" tires.

I am assuing your not running a wild cam & if thats the case then that you should be fine with your current gear for the 200r4 swap and it would improve you mpg,just how much depends on your setup,driving habbits,and it you utilize the lockup fearture in 4th gear which not all people do.

Scott
I have a Huges 2500 stall , mild cam
 
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