small block heads?

[HotRodPC]

yea air works if you can do it, like you said, place to do it and tools or if it'll hold air. I had one that wouldn't hold the air, had to jerk the heads off.

So true. If you have severly worn engine with tired rings or burnt valves, the cylinder won't hold the air. It'll just escape into the crankcase or the come out the vavle port, so in that case, you have no choice but to do the rope. Honestly though, if its that bad, valve seals aren't even a quick fix and its just no worth doing. Yank the motor and start a new build or find a decent used motor.

 

[Swims350]

exactly, had bad valves or something, mine was coming out the exhaust, had to had a valve grind job done.

 

[HotRodPC]

Probably had burnt exhaust valves on those cylinders, or depending on the year of the truck, maybe it has recessed valves from running unleaded fuel on a leaded head. Some people say that is a myth and it doesn't happen. I am here to tell you, it happens. I have a set of heads that it happened to. Every single exhaust valve was recessed at least an 1/8 inch and some up to a 1/4 inch. I am not even sure those heads can be saved with a new set of hardened valve seats the valves were recessed so deep, and I am amazed it didn't drop a valve. It would have, had the recess got any deeper and allowed the valve stem to come up higher and lose the valve keepers.

 

[HotRodPC]

I found the pic of those recessed valves. This was taken after the heads had laid out in the yard a few months, but you can still clearly see how the exhaust valves were recessing and eating away at the valve seats.

 

[Swims350]

wow never seen that before. Mine weren't sunk or sucked in, but might have been warped or burnt or something. I had to have them redone. it happened after it got hot once and blew the upper hose off, it wasn't in a truck then, but was built for a truck and is in a truck now lol. I noticed it smoking a little on start up and revs sometimes, mostly start up and went to put seals in it, wouldn't hold air pressure on no. 2, can't remember if we tried 4 or not, but we had started on that side.

 

[HotRodPC]

This one was still running too, it just had a slight miss that I could never get rid of, and seemed to lack power. I knew the motor couldn't have had many miles on it, so I did a compression test and 2 cylinders on one bank we like 45 lbs differant, so I decided to pull that head, and thats what I found. Then the pulled the other head, and same thing. So when someone tells you, you don't need hardened exhaust seats in an older leaded head to burn unleaded fuel, you can tell them they are full of **** that you seen pics of it happening. If it were just one valve, I'd suspect something else, but no, it was all 8 exhaust valves did this, just that a couple were worse than others. In that photo, its actually not showing the worst 2, I just wanted a pic of 2 valves together in the same shot. I'm wanting to say valves on cyl #1 and #8 were the worst, and probably why I noticed the miss since firing order is 1 then 8, 2 weak cylinders right in a row of the firing order.

 

[Irishman999]

This sucks, I have always had a driveway or some sort of area to work on a car until now, now that I have a piece of junk to keep up with haha.

 

[HotRodPC]

I know the feeling and your right it does suck. I lived with a gf in an apt for about 8 months. The only time of my life I ever lived in apt I might add, and I had to pull a trans in the parking lot, rebuild it under the stairs in my breezeway, then reinstall it. Sucked Royally.

 

[GreaseDog]

So true. If you have severly worn engine with tired rings or burnt valves, the cylinder won't hold the air. It'll just escape into the crankcase or the come out the vavle port, so in that case, you have no choice but to do the rope. Honestly though, if its that bad, valve seals aren't even a quick fix and its just no worth doing. Yank the motor and start a new build or find a decent used motor.

if it won't hold the air, putting valve seals on it is like putting a bandaid on an amputated limb.

and no, just because it won't hold the air doesn't mean its time to yank the engine. you need to do some more research... so back to the leakdown tester.

and if you don't have the tools or the facility to do the job, take it to someone who does.

 

[HotRodPC]

if it won't hold the air, putting valve seals on it is like putting a bandaid on an amputated limb.

and no, just because it won't hold the air doesn't mean its time to yank the engine. you need to do some more research... so back to the leakdown tester.

and if you don't have the tools or the facility to do the job, take it to someone who does.

Exaxctly my point. If its that bad, its just not worth doing. But, at least the heads have to come off, and if you don't see any obvious burnt valves or stuck valves, then I'd say its safe to assume the rings are in very bad shape. Of course leak down tester would be the ultimate test, If you happen to have one.

 

[Irishman999]

I wish the guy that posted earlier with the heads off his race car would message back! Any day now I will spring into action and try this rope trick, right after I fix the transmission and give it a good rattle can paint job.

 

[HotRodPC]

To add another note to this valve seal process, be sure the use the more expensive Umbrealla type valve seals. Don't go with the cheap O rings style. Those are the type that really dry out and harden quicker, and the umbrella type provide a much better seal anyway, espeically when you are likely dealing with a motor that has some valve guide wear, and the umbrella type will help compensate for that. Not saying it'll fix them, but they will work better and outlast the O rings, and be more functional to squeeze a few more miles with less burnt oil before its time to yank it for a rebuild.

 

[GreaseDog]

Exaxctly my point. If its that bad, its just not worth doing. But, at least the heads have to come off, and if you don't see any obvious burnt valves or stuck valves, then I'd say its safe to assume the rings are in very bad shape. Of course leak down tester would be the ultimate test, If you happen to have one.

assume nothing. fix it right, or find a new hobby. tearing an engine apart without KNOWING what is wrong with it is the best way to throw away money.

as for the availability of a leakdown tester... everyone has one... you just have to go to your local chain auto parts store and ask for it. its in their loan a tool lineup, and costs you nothing to use.

 

[82chevy350]

To add another note to this valve seal process, be sure the use the more expensive Umbrealla type valve seals. Don't go with the cheap O rings style. Those are the type that really dry out and harden quicker, and the umbrella type provide a much better seal anyway, espeically when you are likely dealing with a motor that has some valve guide wear, and the umbrella type will help compensate for that. Not saying it'll fix them, but they will work better and outlast the O rings, and be more functional to squeeze a few more miles with less burnt oil before its time to yank it for a rebuild.

i use both

 

[GreaseDog]

I was searching about it and learned they do match but it lowers the compression a ton. Im going for mileage here so maybe I will just stick with stockers.

that depends on what 305 you have. many truck 305s used 76cc heads, just like the 350s.