What are 4.6 DOHC compression amounts

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DMALEMODEL

New Member

Apr 24, 2001

39

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0

THE WOODLANDz TX.

May 12, 2009

#1

• May 12, 2009

• #1

I am about to put a vortech on my 96 w/ 86k miles. I wanted to make sure my rings and valves etc. are good so I did a dry compression test. They ranged from 175-180 w/ the exception of one cylinder ( second cylinder from the firewall on the drivers side) that I tested twice and it only made 165 PSI. What does this mean? Should I be worried? Should I still put the vortech on or is there some other tests?
Thanks

 

SVT32VDOHC

waiting for the next hack atta

Founding Member

Nov 22, 2001

3,501

28

119

Motor City

May 15, 2009

#2

• May 15, 2009

• #2

Put the Vortech on there and call it a day. It will be fine. One cylinder is always lower than the rest. I've seen 100's of threads on here where that is the case. If it was down to like 100psi or 125psi and the others were 175-185, then I would worry.

 

slayr281

The poster formerly known as slayr420

Founding Member

Jun 15, 1999

7,591

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98

San Diego, California

May 15, 2009

#3

• May 15, 2009

• #3

That doesn't sound too bad, actually.

The acceptable tolerance is about 10%, so 175-185 and 165 isn't bad.

If you check later and find out that one cylinder has gotten even further away from the others, it could be a valve not fully sealing, but you're still fine. When you have two bad numbers next to each other, it could be a head gasket, and if all of them are low, then it's things like the rings or pistons telling you that it's time for an overhaul.

 

P

postalbunny

Member

Oct 26, 2005

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Aug 15, 2009

#4

• Aug 15, 2009

• #4

Run leakdown test to rule it out... Sometimes an exhaust or intake leak won't show up as bad on just a compression test.

 

jeremy canter

Member

Dec 2, 2008

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Orange County , NY

Aug 16, 2009

#5

• Aug 16, 2009

• #5

96 to 98 cobra have a 9.85 compresstion ratio stock so 160 is nothing to wory about on a dry test > go for it with the supercharger > I'm at 107,000 miles on mine and just now starting to mod the he!! out of it > I SMELL NITROUS >