Posted By: W5Duster436
340 bent valve and still have good compression? - 10/04/08 03:02 PM
Anybody ever have a very slightly bent valve and still have good compression? My engine doesn't seem to run as well as I think it should and it sounds strange when idling and snapping the throttle. Under a load it seems like it may be just slightly kicking back through the carb. Idles fine but also the vacuum gauge will flutter about 2-3" back and forth. When the engine ran last it would hit 7K almost instantly and it just doesn't seem to do this anymore even though I have the limiter set at 6K for now.
All cylinders are reading 170-180 on a compression test and I have set the lash multiple times. Cam is 310/310 .585 solid and compression is 11.5:1.
When I first put the rockers on I had left them how they were previously when the engine was first built 20 years ago. As I was turning it over to adjust the valves the crank deadheaded and I layed into it a bit trying to figure out what was keeping it from moving. I am thinking that I may have just slightly bent a few valves. I finally figured it was the rockers and backed them off and then got through adjusting them. Should have taken the darn heads off and had them checked at the time but several people assured me that my cranking on the balancer would not have enough strength to bend a valve. Now I think otherwise.
Gotta find someone with a leakdown gauge to test but just wondered if anyone else has had this happen where you have good compression but still have a bent valve even if it is just slight enough to blow back up the carb?
All cylinders are reading 170-180 on a compression test and I have set the lash multiple times. Cam is 310/310 .585 solid and compression is 11.5:1.
When I first put the rockers on I had left them how they were previously when the engine was first built 20 years ago. As I was turning it over to adjust the valves the crank deadheaded and I layed into it a bit trying to figure out what was keeping it from moving. I am thinking that I may have just slightly bent a few valves. I finally figured it was the rockers and backed them off and then got through adjusting them. Should have taken the darn heads off and had them checked at the time but several people assured me that my cranking on the balancer would not have enough strength to bend a valve. Now I think otherwise.
Gotta find someone with a leakdown gauge to test but just wondered if anyone else has had this happen where you have good compression but still have a bent valve even if it is just slight enough to blow back up the carb?
Much more likely that this is the problem, than a bent valve.