Compression issue- Help

S

sdviper700

New member
Joined
Sep 16, 2015
Messages
37
Age
39
Location
Dell Rapids sd
So my 04 Viper runs great but I pulled a compression test on it just to check. I have 105 on PTO 110 on both the others. I know compression is staggered on Vipers so I'm not concerned about the difference, However it seems low across the board on it. I ran a leak down test and had about a 2%-4% drop on all cylinders so I'm thinking rings are good. I rebuilt the top end about 1000 miles ago with SPI pistons and rings but compression has never been good since then, most I've ever got is 110 and 115 on other 2. My question is what's causing my low compression? I did test my other 03 Viper to make sure it wasnt my tester and that one came out at 115 PTO and 125 on other 2 so guage is reading right. Could a leaking head gasket cause this? Wouldn't a leaking head gasket show up on the leak down? Hoping for some input. Thanks

Sent from my SM-G960U using Tapatalk
 
What head gasket you running? With leakdown that good rings are not issue. I don’t know if spi pistons can effect compression. This numbers are lower to other one but within reason. My o4 ran the Sam with opticool head gasket.
 
It was a windrosa gasket kit that I used when top end was done. So I'm sure a windrosa brand head gasket

Sent from my SM-G960U using Tapatalk
 
likely the headgasket thickness. easy way to tell if its that is simply check the squish with lead solder. Take solder that's .080-.090" thick and bend it in a "L" shape, remove a spark plug, and bend the solder so you can feel the side of the cylinder wall while holding onto it thru the spark plug hole. grab the primary clutch with other hand and rotate engine till is squeezes the solder, remove and check thickness where its squished. do the same on your other viper. one with lower compression should read thicker solder, thus lower compression.
 
I have the same sled with almost 4000 miles on it. Same compression numbers and i thought it was low as well. I have rings and an opticool head gasket on the way. I can let you know what i get after the rebuild
 
Pulled the head to inspect everything, looks in tip top shape with no scoring. Piston wash was good also. Question is can I peel a layer of head gasket off on a Viper to try to gain a fee lbs of compression? Is this stupid? I remember doing it on an old 600 mm I had. My gasket is 3 layers 1 of which (middle) is metal.

Sent from my SM-G960U using Tapatalk
 
sdviper700 said:
Pulled the head to inspect everything, looks in tip top shape with no scoring. Piston wash was good also. Question is can I peel a layer of head gasket off on a Viper to try to gain a fee lbs of compression? Is this stupid? I remember doing it on an old 600 mm I had. My gasket is 3 layers 1 of which (middle) is metal.

Sent from my SM-G960U using Tapatalk
Click to expand...

Yes, unless you plan to run a very high octane fuel, every single time, you will be asking for trouble on a Viper.
Thinning head gasket works well on twins, redhead triples, and even cutting the head on a SRX. But a Viper in my opinion, is a no no.
 
You must log in or register to reply here.


Back
Top