Drivetrain Safe power on stock bottom end [fox body]

91 Fox

New Member
Nov 17, 2020
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Hello I want to do some bolt ons to my fox I was looking at the upper end kits. So heads, upper and lower intake, cam, and probably headers. I was wondering how much power I can have while still be some what reliable on a stock bottom end? Would it be safe to install all those bolt ons without changing rods piston crank?
 
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MustangIIMatt

I need something stupid to play with
Mod Dude
Mar 7, 2002
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In all reality 450rwhp or so seems to be the magic number to break stuff.
 

7991LXnSHO

Now I want a 10 year badge
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Sep 1, 2010
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From a power standpoint, no problem.
You still need to make sure the cam lift and top intended rpm match the springs. Also that the valves do not hit and that the cam gear and distributor gear are compatible.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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Many people install top end kits on the stock bottom end. Really, the biggest issue, like said, is ensuring the cam lift agrees with the pistons, as some of those kits require special pistons. Custom grind cams can be a work-around as well.

My cam is 0.565" of lift on the intake side, but it clears my stock pistons due to a custom grind.
 

91 Fox

New Member
Nov 17, 2020
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Fort worth
Many people install top end kits on the stock bottom end. Really, the biggest issue, like said, is ensuring the cam lift agrees with the pistons, as some of those kits require special pistons. Custom grind cams can be a work-around as well.

My cam is 0.565" of lift on the intake side, but it clears my stock pistons due to a custom grind.
bought my car with a different cam already in it. So what do I do to make Shure It works?
 

2000xp8

SN Certified Technician
Aug 8, 2003
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You either need to find out what the cam is, or get a new one.
If the heads and intake are stock, i'd say the chances are low you have an aftermarket cam or the last owner wasn't the most informed.
 

7991LXnSHO

Now I want a 10 year badge
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A dial gauge can be used to check cam lift.
you can use silly putty or modeling clay to check piston to valve clearance with a mock up assembly and hand rotating the engine. Google and YouTube will have how to’s on these steps.
 
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Haste347

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Oct 6, 2020
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HCI on stock bottom end is completely fine, power adders are completely fine as well. Just don't run them both at the same time and expect it to hold together. I have seen 'stangs with stock engines that had aftermarket cams just to get "that sound". Modeling clay is the route I would take if I were in your situation.