what are some signs of a cracked head or valve issues?

[Swims350]

I got a question for all of you out there... what are some signs of a head with a crack in it or maybe burnt valve, bent valve, too tight, too loose. I ask because I see alot of ppl talk about tbi heads cracking and such, and can be missed by the eye and such. I don't have collant lose or oil in the rad or anything. It kinda scares me though wondering lol.

I get a miss or pop out the ps exhaust, I got duals so I know it's that side ONLY, ds is fine. It's done it since the motor has been put back in, runs and drive fine, just has a cold start miss and pop and warm too I think still does it. I'm thinking of hopeing maybe wires? I got new dist. completely new one, new coil, they are accel wires and new plugs, new motor, well rebuilt and the valves got cleaned up with a wire brush on a drill and some valve grind compound put on them and spun in the drill, my old man did it, he's done it that way fr years. Is there a for sure way to know if it's valve? Like leakdown or compression test? I don't have a cylinder leak down tester but I do have a compression gauge. I also plan to do a running valve adjustment on it. I've had it in the truck for about a year and half now, and only drove it for less then a year, probably not even 500 miles on it.

I'm really hoping it's not valve or head related because if so it's gotta come apart and it'll be parked for awhile and not on the road or put together forever cuz of my tight budget.

I'm gonna try the valve adjustment and yank some wires off another 305 or 350 motor and try them. I can yank em off my brother in laws monte carlo(my old one) since it's here at my place and I'm working on it for him. I guess afterwards maybe do a compression test.

The valves were spotless though, but I guess anything can happen. it's a stock replacement flat tappet cam too from northern. Brand new lifters as well as everything else in side minus rods, pistons and crank.

New 02 as well and has headers, shorties that do not leak anywhere, AIR pump and lines have been removed and cats were gone before I got it.

Every other motor I built and did heads the same way and reused them never had this happen, but this is my first computer controlled build the rest were all carbd motors and still run great.

 

[71 cuda man]

Doesn't sound like a cracked head.You need to find which cylinder is missing.The way i do it is get a pair of long needle nose put some vac line over them then pull 1 wire at a time till you find the one that has no impact on how engine is running.Get an old plug put it in the wire & ground it,if it fires then your ignition should be fine take out plug from cylinder & see if that fires Then inspect the lash with feeler gauge.Also check the springs.good luck

 

[Swims350]

Thanks for the reply and good idea. Now if one wasn't firing the plug would look different right? When I changed the manifolds for headers the plugs looked the same all 8.

I also read or seen something about the egr passage in the head plugged up with carbon, that wouldn't cause this would it? I didn't notice mine when it was off being plugged up, but it's a possibility esp. in the intake itself.

 

[Swims350]

anyone? like I had mentioned if it were a plug or wire there would be a difference in plug appearance right? like ones black and fouled?

 

[barebones 1500]

i would think it would look different but i have never had this problem so i could be wrong

 

[Swims350]

me too because anytime a plug isn't working fuel is just laying in there not getting burnt, so I'd think the plug would be fouled and black, they were fine but might have to recheck.

 

[71 cuda man]

I don't think the plug will look that much different if the engine has low miles on it.By the way I had the same problem with a miss at idle.That ***** drove me nuts for 2 weeks.took it to my buddies shop hooked it into the scanner,did the leak down & compression check everything came out fine,thought a plug was bad check um they were fine,ohmed the wires,cleaned IAC valve,you name it I either checked or replaced the part.As it turned out the distributor rotor was multi sparking.The place of crap was brand new also.Don't ask me how I missed something so obvious.Must of looked at it 5 times & it looked good.I'd just start from the beginning & check timing,valve lash,& egr valve.It's probably sometime stupid that when you find out what it was you'll what to kick yourself in the ass.That's just Gods way of keeping you humble.I hope this helps & good luck.let me know what you find.

 

[Swims350]

yea I'm gonna mess around with it and see what I can come up with, if nothing else pull a wire off at a time or just yank it, fire it, shut it down, hook it up, try another, and repeat til it's all done on that side.

 

[Swims350]

haven't done much but I noticed if you put your hand right near the end of the pipe it'll kind of blow it off then suck it back towards the pipe and repeat over and over the other just keeps it blown off all the time.

 

[71 cuda man]

If your hand is getting sucked toward the tailpipe your exhaust valve is staying open to long.If only 1 side of engine is doing this then you can rule out timing & spark.Pull valve cover & readjust valves but when you re-tighten just go 1/4 turn not 1/2-3/4 like the book says.That might fix the problem.pay close attention to springs you should be able to see which one is staying open.If readjusting doesn't work then you probably have a broken or binding spring.You might what to do a leak down test just to make sure valves are seated correctly.Good luck