How much power loss do you guys think I would have if I dropped my compression from 10.3 to 9.8? I am kind of worried about cylinder pressure.

 

Several tests have shown that there is roughly a 3% loss with each point of compression drop. These numbers are probably good when talking about changes in the range from 8:1 to 12:1. At the extremes of CR this generalization may not hold, say down to 6:1 or way up high like 14:1.

That being said, you will probably lose about 1.5% of your power output.

 

We put one together in an F350 with 44s and 5.13 gears with a comp 268. It's a perfect cam for this combo, nice idle with lots of low end power .

 

Alright I am going to revive this thread. I posted a while back and figure I might as well give an update on what I have done. Comp replaced the 'flattened' cam for free so I put the new one in followed the instructions and I will be danged if it didn't happen again. One thing that I was told by a rep from Crane was to watch pushrod rotation, he said if the pushrod isn't rotating your lifter isn't either and it's going to fail...I wish that was in the Comp instructions...the Crane rep said BBC's are notorious for this. My first question for you all is: Although not much of the two lobes lost much metal, the lifters did, therefore I realize I need to get as much of the loose metal out as possible. The engine is fresh and it was enough of a pain rebuilding it the first time so I do not want to take the engine out again, so my plans are to drop the pan clean it out and whatever other parts of the internals I can get to. I will then run some engine flush through, drain the oil and then change the oil every 300 miles or so for the first thousand, I will also install a magnetic drain plug. Do you guys think this will be enough? Also in lieu of my bad luck with the flat tappet cams, I have bought and plan to install a Crane roller conversion cam (CRN-359341), how much of a power increase will this give me over the Comp 4x4 239-4? Will the idle quality be much different? I am very impressed with how much longer the roller will hold the valves open, when comparing the cams side to side it's rather impressive. I can't wait to get it installed!!!!

Tony

 

you might try putting a big magnet on the outside of the oilpan, then put some flush in and run the oilpump drive with a drill for a while, this should get most of it if not all out, you might turn the crank with a breaker bar while doing this to help flush it better.....use a large magnet to ensure that your getting all the metal particals out of the oil......just a thought......