compression differences on a 302 vs a 351
Thread Starter
|
Elder User
Joined: May 2007
Posts: 548
Likes: 0
From: Sparks, NV
compression differences on a 302 vs a 351
so ive been pondering about this for a good while... lets say a 460 with 62cc heads makes an alarming compression, but a 302 with 62cc heads yeilds a faily low compression. If the 302/351W heads were symmetrical from 87+ did the 351 have a slightly higher compression? or did ford realize this and put a mild dish on the 351 to lower the said compression?
just a thought
just a thought
Thread Starter
|
Elder User
Joined: May 2007
Posts: 548
Likes: 0
From: Sparks, NV
oh i get it, it would yeild a lower compression if the pin and the top are closer than the previous 351... gotcha
Trending Topics
Super Moderator
Joined: Apr 2004
Posts: 34,481
Likes: 2,801
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Thread Starter
|
Elder User
Joined: May 2007
Posts: 548
Likes: 0
From: Sparks, NV
its only a question man... chill out, im not about to tear apart any engines... yet.
im jus saying, since the 351 pistons are dished, then add flat-top/flycut pistons (302) you would increase compresion ratio slightly... thats all, and thank you guys for answering my question
im jus saying, since the 351 pistons are dished, then add flat-top/flycut pistons (302) you would increase compresion ratio slightly... thats all, and thank you guys for answering my question
Super Moderator
Joined: Apr 2004
Posts: 34,481
Likes: 2,801
Since I started all this trouble:
Ross Pistons Ford High Performance Forged Racing V8 Flathead FE Pistons
Compression heights vary, but the most basic list seems to indicate a significant difference between the two. In addition, they list the pistons specifically for 302 or 351, not both as far as I can see.
So yes, flat tops will bump up the CR, but there is a flat top specifically for whatever iron you're running.
Ross Pistons Ford High Performance Forged Racing V8 Flathead FE Pistons
Compression heights vary, but the most basic list seems to indicate a significant difference between the two. In addition, they list the pistons specifically for 302 or 351, not both as far as I can see.
So yes, flat tops will bump up the CR, but there is a flat top specifically for whatever iron you're running.
Posting Guru
Joined: Mar 2007
Posts: 1,649
Likes: 2
Compression height is what makes a 302 piston a 302 piston and a 351w piston a 351W piston. Compression ratio is determined by head volume, cylinder volume and piston dome /dish cc. Boring a 4" hole oversize will raise the compression slightly. The difference in CH between the 302 is great enough that a piston swap would drive the piston into the head with a stock rod. When the stroke of the crank is increased to 3.85, a 302 piston will then fit with a higher CR. A 302 piston could theoretically be used in a 351w with the stock 3.50 stroke, but the rod length would then have to be shortened by the difference in CH between the 302 and the 351W pistons, but then most likely the pistons would hit the counterweights. Nice try, but there really isn't any parts swaps that work out like that. Bottom line- a 351W with stock stroke needs 351W pistons. A swap to 351W flat top pistons would give an appreciable boost in CR.
Thread
Thread Starter
Forum
Replies
Last Post
351Cleveland C4
Performance & General Engine Building
13
Mar 7, 2014 06:59 PM
ford5.8
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
3
Oct 10, 2010 10:41 PM
smallblock351w
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
7
Feb 28, 2007 06:44 PM
Billy Freeman
335 Series- 5.8/351M, 6.6/400, 351 Cleveland
2
Jan 14, 2003 03:23 PM