MikeM

I don't believe this is your problem. I would still check the condition of the spark plugs. If they're wet, they're no good and can cause a backfire.

Backfire defined as a loud "bang"out the tailpipe!

1snake

I'm still amazed how many people don't know that and install the distributor 180 degrees out. Thanks for posting it.

Jim

MikeM

It won't start/run that way so it's not usually a problem,

OG VETTE

What brand of cam did you use, comp cams always grind 4 degrees advance in them, call the manufacture and check on it.

waltonb123

Well...it looks like I have a major problem. I was working on my engine today trying to iron out the issues when...I checked for TDC first, (finger over #1) checked to make sure distributor was in correctly, and it was. Next readjusted the valves, everything looked right here. Was adjusting the carb and all of a sudden white smoke started pouring out of exhaust. Looking back I don't know if it was both sides or not. When I ppulled the plugs 2 looked brand new, a few were tan and a couple looked sooty. Then I got to # 8...when I pulled the plug oil was soaked all over it! So with that I did a compression test, here is what I found: #1-170, #2-180, #3-137, #4-65, #5-75, #6-165, #7-180, #8-10. This was a dry test, I ran out of time and didn't get to the wet test but just the fact that #8 was soaked with oil and only 10 lbs means I've got some serious issues here. The rocker and valve seems to be going up and down without a problem. Any advice or opinions are welcome.
Bob

OG VETTE

Sounds like a blown head gasket to me, check below the heads for water leak or air bubbles in the radiator check for water in the oil these are symptoms of a blown head gasket, and of course low compression, what type of lifters do you have and what did you set the back lash at and the ratio of the rockers and the lift on the cam I hope you did not push your valves Thu the pistons. when was this engine built. Sorry to hear this, hope it is the gasket and not the other. Keep me informed hope you get it straiten out
later OG

MikeM

I would start by pulling the engine and do a teardown and inspection.

plaidside

I don't think it is a head gasket. They normally go in between two adjacent cylinders.
I would back off the rocker arm adjustments on the cylinders with low compression and redo test.
You stated the engine ran worse with the new cam so I suspect it could be valve adjustment.
Joe

waltonb123

After I got it started I adjusted the hydraulics while running, loosened till they were clicking then tighted 1/2 turn so I don't think its the valve adjustment, plus it was running pretty good at that time. All backfiring had stopped, I was adjusting carb when it started to spew white smoke. Like I said, when pulled #8 plug oil was dripping off of it. I think Mike M may be right and I'll start with the heads first.

Muncher

Like Kienan said, in order for it to blow as low as 10, one of 3 things has happened. A piston has a serious hole/crack, a valve is SERIOUSLY bent, or the valve isn't being allowed to close. Even a blown headgasket, or a cracked cylinder would blow higher than 10, assuming everything else is ok. If the lash is to tight, it would prevent the valve from closing. Now comes the oil issue. If the valve wasn't closed as the piston came up on its compression stroke then the pressure could force a valve seal/guide out. This is just his over-the-phone analysis though. Nothing is certain without him seeing it.

If it's possible I would get some head gaskets, re-torque the heads and do a leak down. Still waiting to hear back from Seth though.

Muncher

Kienan and I were talkin again last night and he asked a question I couldn't answer. Are you sure everything was fully pumped up before you set the lash? Because if the valve train wasn't pumped up when you set the lash it'll go way outa wack when it does pump up.

Westlotorn

How old is the fuel in the gas tank, old fuel will gum up the valves and they stick in the valve guides. I see you just replaced the cam but I did not see time frames.
The plugs would smell like old bad gas when pulled in this case.

waltonb123

We'll I thought they were, it was running for awhile right after we put the cam in and then again a few days later when I adjusted the valves while running. Oil was pumping really well. I also did a vacuum test before it started blowing smoke. It was fluctuating rapidly between 15 to 20. From what I read, this is a sign of bad seals or guides, which could also be the source of smoke. Now as far as the no/low compression who knows. Maybe the lifters weren't pumped up, and if that was the case I still think I need to have the valve guides and seals checked before I put the heads back on and retest the compression.

Muncher

Yeah, that's not a bad idea. Kienan talked to Seth (machine guy). I'll call you tomorrow about it if that's ok.

Westlotorn

If your heads are still on, a recheck of your valve adjustment is in order. Back off one at a time till it starts to clack, wait a few moments to see if it adjusts and the clack stops by itself, doing this allows the lifter to pump up, if it does quiet all on its own loosen another 1/2 turn and wait. When it won't self adjust the noise out after you back off 1/2 turn or so you have backed the lifter off all the way. Now take it slowly down till the clacking stops, then give it another 1/2 turn tight. Do all the cylinders this way and you will have the lifters adjusted correctly and eliminated lifter adjustment as a possible cause of your issues. Good Luck.