351M 9.1/1 Compression question
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Trailering
Joined: Jan 2022
Posts: 21
Likes: 0
351M 9.1/1 Compression question
Hey everyone Im halfway through the rebuild on my 79’ 351M and my machine shop has told me I need .030 over bore on my block intern in need the matching pistons and I’d like to bump my CR around 8.5 to 9 only ones I can find around that are 9.1 to 1 and I’m dead set on keeping my boat anchor factory head because of price and my 2bbl Sniper efi ( don’t mention Aussie heads)
In some forums I hear that 9.1 on a factory head will ping / blow a head and I’m wondering if those suspicions are correct , if so what options do I have with stock heads? I checked Tmeyer and the lowest they go is 9.3
I’m doing a mild build to pair with a Np435
I have a mild cam and straight up timing kit and 1 under rod and main bearings from Tmeyer (links below)
heres my cam kit I already bought
https://www.compcams.com/xtreme-energy-218-224-hydraulic-flat-cam-k-kit-for-ford-351c-351m-400m.html
Here’s my pistons I am thinking about buying
https://cnc-motorsports.com/auto-tec-pistons-1000772-forged-351m-flat-top-4-030-bore-sb-ford-357.html
THANKS
any insight is appreciated
In some forums I hear that 9.1 on a factory head will ping / blow a head and I’m wondering if those suspicions are correct , if so what options do I have with stock heads? I checked Tmeyer and the lowest they go is 9.3
I’m doing a mild build to pair with a Np435
I have a mild cam and straight up timing kit and 1 under rod and main bearings from Tmeyer (links below)
heres my cam kit I already bought
https://www.compcams.com/xtreme-energy-218-224-hydraulic-flat-cam-k-kit-for-ford-351c-351m-400m.html
Here’s my pistons I am thinking about buying
https://cnc-motorsports.com/auto-tec-pistons-1000772-forged-351m-flat-top-4-030-bore-sb-ford-357.html
THANKS
any insight is appreciated
Laughing Gas
Joined: Jul 2009
Posts: 1,032
Likes: 424
From: NE Ohio
Shiiii... Hold my beer...
My wife's (her car before we were married 37 years ago) is a '70 M-code 351C-4V, coming in at around 11:1cr. Yes, we almost are forced to mix 110 octane leaded racing gas 1-part with 2-parts of pump Unleaded fuel.
My two '73 (slightly modified) Q-code 351C-4V Cougars come in at around 10.2-10.4:1. One is using the stock '73 dish pistons in the earlier closed chamber 4V heads, and the other has 'Boss 351' replacement domed pistons in the '73 open chamber heads. Neither combination is optimum, but that's what options we had 35-40 years ago, LOL! Again, these also run on a mixture of Racing fuel and pump Unleaded...
35-40 years ago, I used to recommend the Crane Econopower 260 cam (.493/.510 lift, 260/272adv dur, 204/216 at .050) because it closely resembled the 351C-4V Q-code cam which ws obsolete at the time - BUT it was not ground retarded for emissions . I STILL have that cam in my closed chamber/dish piston 10.2:1 351C-4V!
My wife's (her car before we were married 37 years ago) is a '70 M-code 351C-4V, coming in at around 11:1cr. Yes, we almost are forced to mix 110 octane leaded racing gas 1-part with 2-parts of pump Unleaded fuel.
My two '73 (slightly modified) Q-code 351C-4V Cougars come in at around 10.2-10.4:1. One is using the stock '73 dish pistons in the earlier closed chamber 4V heads, and the other has 'Boss 351' replacement domed pistons in the '73 open chamber heads. Neither combination is optimum, but that's what options we had 35-40 years ago, LOL! Again, these also run on a mixture of Racing fuel and pump Unleaded...
35-40 years ago, I used to recommend the Crane Econopower 260 cam (.493/.510 lift, 260/272adv dur, 204/216 at .050) because it closely resembled the 351C-4V Q-code cam which ws obsolete at the time - BUT it was not ground retarded for emissions . I STILL have that cam in my closed chamber/dish piston 10.2:1 351C-4V!
Logistics Pro
Joined: May 2015
Posts: 4,478
Likes: 978
From: Tri Cities, TN
Read thru this thread it deals with dynamic compression and some other stuff. 400 Project for my 77 F100 - Ford Truck Enthusiasts Forums (ford-trucks.com)
I run my Cleveland's at 10.5-1 and burn pump gas you just have to pick a cam that keeps the dynamic compression at 8-1 or so. Picking the cam before you know your static compression puts you in a box, you will have to find a combination that gets the stars lined up.
I run my Cleveland's at 10.5-1 and burn pump gas you just have to pick a cam that keeps the dynamic compression at 8-1 or so. Picking the cam before you know your static compression puts you in a box, you will have to find a combination that gets the stars lined up.
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