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71 vs 72 351c.


Capn_Morgan
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I’m sure this has been discussed multiple times over on this board but I’m restoring my 1972 Mach and I’ve been looking at numbers for the motors from 71-72. I know 72 was the start of the emissions crack down but how did they derate the motors from 240 to 177 on the 351 2v? I know the compression was lowered from 9:1 to 8.6:1 but what else? I have a hard time believing that was it. Did they just pull vacuum? Or lie about numbers? Any incite would be golden.

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The cam timing was also changed.

 

However, what made the biggest difference was when they changed from brake horsepower rating to SAE net horsepower rating in 1972. Brake horsepower was measured at the crankshaft without any accessories (water pump, alternator, exhaust, etc.) connected, SAE net horsepower is measured at the crankshaft with the accessories attached.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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Cam timing in 72 was retarded 4* across the line for most engines. Changing from SAE gross to net was the biggest reason. We all know the pain of the difference between our gross and net take home pay.... :/

 

 

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Cam timing in 72 was retarded 4* across the line for most engines. Changing from SAE gross to net was the biggest reason. We all know the pain of the difference between our gross and net take home pay....  :/

 

So true lol. So with an electronic ignition, 4v carb, and open header on a 72 would it regain me a bit of power? At this point I’m not sure how much I’m gonna be looking at. Keeping the car 90% original aside from the bolt ons.

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Cam timing in 72 was retarded 4* across the line for most engines. Changing from SAE gross to net was the biggest reason. We all know the pain of the difference between our gross and net take home pay....  :/

 

So true lol. So with an electronic ignition, 4v carb, and open header on a 72 would it regain me a bit of power? At this point I’m not sure how much I’m gonna be looking at. Keeping the car 90% original aside from the bolt ons.

 

A simple 4V carb swap and a set of header with duals is a great way to wake up a 2V engine. I think you'll be very happy with the power increase.

 

 

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