what cam do you recommend? - Page 2 - MustangForums.com

Go Back   MustangForums.com > Ford Mustang Tech > 5.0L (1979-1995) Mustang

5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

what cam do you recommend?

Thread Tools Search this Thread
Old 08-24-2007, 05:58 PM   #11
5th Gear Member
Joel5.0's Avatar
Join Date: Jan 2006
Vehicle: 1986 Ford Mustang GT
Location: Puerto Rico
Posts: 3,926
Default RE: what cam do you recommend?


What Is Piston-to-Valve Clearance And How Does It Affect Me?

Piston-To-Valve clearance is just what it says ... the minimum distance between the engine exhaust and intake valves and the top of the piston at the closest given position of the reciprocating cycle. Piston to valve contact is probably one of the most common causes of damage to a racing engine. Piston to valve interference can be caused by many items, including: Cam Lift, Cam Timing, Piston Design, Timing Chain/Drive Failures, Deck Height, Cylinder Head Modifications, Valve Diameter, Broken Valvetrain Parts (valve locks, springs, retainers, lifters, pushrods and cam lobe failures), Valve Diameter, Connecting Rod Stretch, etc. In this article I will simply be addressing cam timing, cam lift, and basically anything that has to do specifically with the valvetrain.
Anytime you make a change to your engine in relation to the cam lift, cam timing, pistons, cylinder heads, rockers arms, or anything else that can change, even so slightly, the position of the valve in relation to the piston, you MUST verify that you have the minimum clearances safely met. This procedure consists of setting up your engine and measuring the clearance at the valves closest point to the piston and validating a "safety margin" clearance. This is typically .080" on Intake valves and .100" on Exhaust valves when using steel connecting rods. With aluminum connecting rods this dimension changes to .100" on Intake and .120" on Exhaust. The exhaust always needs more clearance because of the added COE (Coefficient of Expansion) of the hotter exhaust valve. These are standard numbers, in some cases you have to look at your entire combo and make your own decision as to the minimum clearance values.

back to top
I agree that ptv issues are not always a result and or deciding factor in ptv problems....and I know duration plays a major factor in ptv issues......but come on....were dealing with a bone stock block and stock pistons ...you won't get 600 lift with 1.72 rockers to not have ptv issues even if your duration was on the light side.....I seriously doubt the guy is going to degree in the cam and or advance it or retard it to achieve maximum valve timing and efficiency.....most people install their cams straight up to be safe so this is why I reccommended what I did.......I agree with you Joel 5.0 that irregardless of cam choice ptv should always be checked....
Cam lift during the overlap cycle (when both valves are open at the same time and the piston is @TDC)..... YES.......total valve lift ....NOPE....and yes, you can have a .600" total lift cam with 1.72 rockers and not have PtV issues on a stock block/pistons......not that you need it, but I'm simply trying to explain this.

How can total valve lift be a factor, if it happens when the piston is down the cylinder >1.5" ? .......

LUK=Let Us Know, GL=Good Luck, LMK=Let Me Know, JIC=Just In Case, BTSTDTRT=Been There Seen That Done That Repaired That, YCYDYP=Your Car Your Dough Your Prerogative and the classic... DILLIGAS=Do I Look Like I Give A S***

1986 GT-X303-289 heads-1.72 rockers-RG 4+1 Trans.
Originally Posted by Joel5.0
Great thoughts will overwhelm a feeble mind.
There is never money to do it right, but there's always money to do it over.
The proof of understanding is the ability to explain it. (H. Torruella)
Joel5.0 is offline   Reply With Quote


Similar Threads
Thread Thread Starter Forum Replies Last Post
Vintage AC shop referral - frontrunner serpentine system bradleyb Classic Mustangs (Tech) 3 Yesterday 08:50 PM
The "I Just Watched A Great Movie" Thread HRnB Off Topic 55 10-28-2015 11:03 PM
Any tuner available 95 3.8 ?? patchshaffer Tuner Central 3 10-05-2015 03:24 PM
So who wins uedlose The Racers Bench 4 10-01-2015 09:31 PM
Vintage AC shop referral in los angeles bradleyb California Regional Chapter 0 10-01-2015 02:02 AM

17, 91, cam, converter, ford, gt, recommend, rockers, stall, x303

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT -5. The time now is 06:49 PM.

This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. FordŽ is a registered trademark of the Ford Motor Company