Looking for 400 performance tips
New User
Joined: Apr 2014
Posts: 12
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piston questions??
from what im hearing pistons are the challenge. correct? why couldnt you just take 351M pistons, that have a taller pin to top of piston measurement @1.9xxx and machine them down to the 1.6xxx of the 400 pistons? Essentially being able to cut out the dish and taylor making your cr to what you want?? if this is a stupid question fell free to flame away 
Posting Guru
Joined: Jul 2007
Posts: 1,355
Likes: 1
I made the same exact question years ago in this forum, you will need to mill them down to 1.710, make valve reliefs for the intake valves and that would make them brittle and expose the top compression ring to excessive heat overheating it... If you wanna keep it cheap use your stockers, the worst part of these engines is not really compression..
Laughing Gas
Joined: Dec 2012
Posts: 801
Likes: 7
From: Toledo, Ohio
. The static compression ratio in a '78 400 is prolly actually down in the 7's and the dynamic compression ratio down in the 6's... which is how they avoid spark knock/pinging with crappy quench...
. The better pistons not only give a higher, more efficient compression ratio, but also improve 'engine quench' effect... producing an engine more like a 2014 engine...
http://www.crankshaftcoalition.com/wiki/Quench
Moparts on the Web - Main Index
. BTW, the stock valves in a 2 bbl. 351M or 400 are actually bigger than the vaunted "big fuely valves" used in fuel injection SBC engines that the Chevy guys like to use for past 50 years to make 500 HP...
. DiMora on here had his 400 engine rebuilt the usual, typical (wrong) way and hated it, couldn't get it to run right, stop pinging, disappointing power, so built it again the right way himself... and loves it... some interesting reading and some good lessons...:
https://www.ford-trucks.com/forums/1...part-deux.html
.
. The better pistons not only give a higher, more efficient compression ratio, but also improve 'engine quench' effect... producing an engine more like a 2014 engine...
http://www.crankshaftcoalition.com/wiki/Quench
Moparts on the Web - Main Index
. BTW, the stock valves in a 2 bbl. 351M or 400 are actually bigger than the vaunted "big fuely valves" used in fuel injection SBC engines that the Chevy guys like to use for past 50 years to make 500 HP...
. DiMora on here had his 400 engine rebuilt the usual, typical (wrong) way and hated it, couldn't get it to run right, stop pinging, disappointing power, so built it again the right way himself... and loves it... some interesting reading and some good lessons...:
https://www.ford-trucks.com/forums/1...part-deux.html
.
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