compression #s

[bad V6]

At a recent outing to the track, the Scan Master showed 15.9 degrees knock retard, this was at 24#, timing at 21/19, with Sunoco 116 in the tank. This was at the topend of the track, running about 110 mph. When this event occured the exhaust came loose under the car and was hitting the floor pan, so I think this was what the knock sensor picked up. Following this I made a WOT blast down the highway for a split second and watched the boost gauge swing to 30#, blowed an intercooler hose. I have since fixed the swingarm on the downpipe. I've been a little leary that I may have hurt the car since then, but haven't had any signs of a blown headgasket or other damage.

So I decided to do a compression check on the motor, here are the results:

#1 170
#2 170
#3 170
#4 165
#5 167
#6 167

How do these #s look? Should I be concerned or check anything else?

I have since drove the car and not had any knock retard or other issues while going WOT. I guess that I'm lucky for having the 116 in it.

Thanks

 

[boostingbuick]

The numbers are not showing anything out of the normal. I'd say your ok.

 

[2QUIK6]

Those numbers look great to me. Mine only has about 150# on a stock factory long block with 50k miles. Those numebrs are near what my 12.8:1 LT1 car has, course thats SCR so cam profile has alot to do with that and what the real DCR is.
The exhaust banging will definitely cause some knock. If you had 116 in the tank and hit 30# with only 19-20 degrees of timing you are fine. Theres' folks on here that run that kind of boost and alot more timing than that, as long as its not knocking you should be good to go.

 

[bison]

I doubt the knock was detonation if you were running c16. If you have further doubt drop the pan and inspect the rod bearings. That will tell you if it was detonation or not. Id get it going and run the timing up next time out. Go up a degree at a time and watch for KR.

 

[84BuickGNYorkPA]

I wish I had #'s that good, I'm currently between 140-150, soon time for a fresh lower end for me.

Chuck

 

[bison]

I wish I had #'s that good, I'm currently between 140-150, soon time for a fresh lower end for me.

Chuck

Those look good for an 8.0:1 stock bottom end engine. I wouldnt go with a fresh one unless you plan on running over 125mph all the time.

 

[bad V6]

Thanks for the response, it made me feel a lot more comfortable that I had not hurt the motor. Since the incident I hadn't noticed any symptoms of anything being wrong, but hadn't really leaned into it either.

The numbers from the compression check surprised me, for 78k miles, I wouldn't have thought they wouldn't be that high. I guess the previous owners had not abused the car.

Well, I bumped the timing up to 23/21, boost still at 22#. I got the car out and took it for a spin up the road and back. No knock shown on the Scan Master or the knock gauge. The increase in timing really woke the car up.

Thanks again for enlightening me into what I needed to be looking for.
Pat

 

[1baad6]

Those numbers are awesome,same thing happened to me a while back did a comp check on all cyl, high 160s across the board,those engines are tougher than you think, gm did a good job with the engine managment on those cars,when that happened to me I had pump gas in the tank with octane boost but the has since had nothing but race gas in it,I was worried for a minute but everything checked out ok...