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View Full Version : Wedge Rover 3.5 (TR8) compression numbers



Cheapsnake
01-13-2007, 08:04 PM
I'm about to do some headwork on my TR8 (Rover 3.5) and prior to pulling the heads I checked compression on each cylinder and got dry readings ranging from 119 to 123, except for a 108, on a cylinder that I know has a bad valve seat. Just for kicks, I squirt oil in the cylinders and ran the check again. I was a bit surprised to get readings 10-15 psi higher. The cylinder walls aren't scored or scuffed and the engine seems to run strong so I'm not sure if I'm looking at bad rings or not. BTW, there's only about 6k on a rebuild.

Are these typical numbers for a 3.5, especially the substantial increase with oil? Thanks a bunch!

Tom

gjh2007
01-13-2007, 08:10 PM
Talk to Woody at the wedge shop, he's the expert on these motors.


https://www.thewedgeshop.com/about.html


I'm about to do some headwork on my TR8 (Rover 3.5) and prior to pulling the heads I checked compression on each cylinder and got dry readings ranging from 119 to 123, except for a 108, on a cylinder that I know has a bad valve seat. Just for kicks, I squirt oil in the cylinders and ran the check again. I was a bit surprised to get readings 10-15 psi higher. The cylinder walls aren't scored or scuffed and the engine seems to run strong so I'm not sure if I'm looking at bad rings or not. BTW, there's only about 6k on a rebuild.

Are these typical numbers for a 3.5, especially the substantial increase with oil? Thanks a bunch!

Tom

tr8todd
01-14-2007, 09:01 AM
120 psi sounds about right for a bone stock motor with 8 to 1 comp. You will get a little noticeable leakdown on a cold motor spinning at low RPM's. Rover V8's seem to develope a bit more crankcase pressure than other motors. It's typical to set up a larger breather on the bigger motors. I think Woody sells one that was designed for a 351 Cleveland. On a side note, I bought a 75 BMW 2002 at an auction the other day for $55. 50 for the car and 5 for buyers premium. It had twin 45 DCOE weber carbs, so I knew it had something special for a motor. That's alot of carb for 2.0 liters. I did a compression test when I got it home and saw around 180PSI in all four cylinders. We got it running and pulled it out. I'll send it to my engine builder to freshen it up and find out exactly what's in it. It should make a good spare for the BMW race car I have.

Cheapsnake
01-14-2007, 02:20 PM
Thanks for the feedback Todd. Now that I think about it, how much pressure can you build with 8.15:1 CR?

Finding that 2oo2 has gotta be fun, especially for $55. Give you 60 and you got a quick $5 profit...OK?

Tom