Increased Compression 400m
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5th Wheeling
Joined: May 2020
Posts: 37
Likes: 3
From: Massachusetts
Increased Compression 400m
Hello,
I have a 1979 F150 Supercab with a 400m motor, and I'm looking to increase the factory compression without emptying my wallet. Ive read that the 400m's have negative deck high, so I want to do something that will raise the piston at top dead center. Ive been thinking about either longer connecting rods, or taller pistons. Does anyone have suggestions for parts? Ive seen some thing that 351m pistons could be used, but have a smaller wrist pin. Could I then use 351 Rods? Just thinking out loud so to say, what do other people think?
Thank you in Advance!
I have a 1979 F150 Supercab with a 400m motor, and I'm looking to increase the factory compression without emptying my wallet. Ive read that the 400m's have negative deck high, so I want to do something that will raise the piston at top dead center. Ive been thinking about either longer connecting rods, or taller pistons. Does anyone have suggestions for parts? Ive seen some thing that 351m pistons could be used, but have a smaller wrist pin. Could I then use 351 Rods? Just thinking out loud so to say, what do other people think?
Thank you in Advance!
More Turbo
Joined: Nov 2018
Posts: 563
Likes: 143
From: CA
Tmeyer and Dss have off the shelf pistons at correct pin height. 1.710 for zero deck.
351c pistons have a different size pin and still an incorrect height for zero deck. 351m have the same pin size, it’s a destroked 400.
351m rods are the same. 351c rods won’t fit the crank.
351c pistons have a different size pin and still an incorrect height for zero deck. 351m have the same pin size, it’s a destroked 400.
351m rods are the same. 351c rods won’t fit the crank.
Laughing Gas
Joined: Dec 2020
Posts: 869
Likes: 186
From: Near my truck
''Negative deck height'' is when the piston head protrudes above the deck.
Why do you want to increase the compression ?
The pistons mentioned in the above posts would work fine.
But you may or may not have to change the cam also.
Why do you want to increase the compression ?
The pistons mentioned in the above posts would work fine.
But you may or may not have to change the cam also.
Hotshot
Joined: Feb 2004
Posts: 10,743
Likes: 2,587
From: The Shenandoah Valley
I had a coworker ask about boosting compression once. I told him to drill holes in the piston tops and put bolts in the holes and lock-nuts underneath, the bolt heads would act like compression building bumps. He thought I was serious. Don't do that.
Tuned
Joined: Nov 2015
Posts: 365
Likes: 13
You could have your block decked to the correct height for your stroke, rod, piston stack height. The block probably isn't square anyway.. That way you could use stock dimension parts too.
Jess
Jess
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More Turbo
Joined: Nov 2018
Posts: 563
Likes: 143
From: CA
yup but cutting about .060 off isn’t going to let you use an intake with stock dimensions.
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