can bad gas/nasty tank cause valve problems?

[rogergodding]

my truck hasn't been driven much the past year and the tank has been bad for a while. I just bolted up a new edlebrock 600 and am running gas from the new tank to it. the idle is rough. timing has not been adjusted. there is a slight tick, I've needed to do a valve adjustment for a while. I'm just wondering if there is some damage to my valvetrain..... any thoughts appreciated.....

rg

[68gmsee]

Originally Posted by rogergodding

my truck hasn't been driven much the past year and the tank has been bad for a while. I just bolted up a new edlebrock 600 and am running gas from the new tank to it...

Can you explain re: tank has been bad for a while? Does this mean that you replaced the bad tank and now have a new tank with fresh gas?

Bad gas makes a difference in the way it runs but you'd have to run some real bad gas for a long time before it would do damage to your valve train.

I imagine you'd get pretty tired of rough idle, sputtering and misfiring fairly quickly...

[rogergodding]

Originally Posted by 68gmsee

Can you explain re: tank has been bad for a while? Does this mean that you replaced the bad tank and now have a new tank with fresh gas?

Bad gas makes a difference in the way it runs but you'd have to run some real bad gas for a long time before it would do damage to your valve train.

I imagine you'd get pretty tired of rough idle, sputtering and misfiring fairly quickly...

the tank had that smell, rust on the inside of the gas cap etc.
it just recently started running rough, (I'd run it every day or so), it got bad enough that it wouldn't idle and would backfire.... so I changed the carb.....

my new tank has fresh gas

[cdowns]

i'd look more at a timeing chain or distributor points problem

[rogergodding]

accell blueprint hei.... entire engine has only 2500 miles on it....

[68gmsee]

I'm still missing something. You mentioned that it started acting up, wouldn't idle and it would backfire and then you changed the carb.

Question I have is did you run some bad gas through before you changed the tank?

Also, did it run okay after you changed the carb? Could be the carb may also have a problem?

I'd check for vacuum leaks first. Sometimes you can't see them, but, old rubber will crack and can sure screw you up.

Then go down the list. Check timing, to make sure its okay.

Spark plugs to insure they didn't get messed up by the bad gas.

Loose wires in ignition.

Fuel filters to make sure they're not clogged up.

[OhioDan]

Did ya change fuel filters when ya installed the new tank? Might help?

[68gmsee]

Forgot to add... If it's backfiring through the exhaust, that's an indication of unburned gas igniting as it's going into the hot exhaust. A rich adjustment may cause this as well as plugs, wires, etc..

I've had bad valves, but for the most part, I've had them sputter and miss occasionaly. Usually get better at higher rpms. I guess if they are bad enough they can backfire through the carb and exhaust also.

Only other thing that comes to mind is a bent push rod or valve caused by the backfiring...

[rogergodding]

Originally Posted by 68gmsee

I'm still missing something. You mentioned that it started acting up, wouldn't idle and it would backfire and then you changed the carb.

Question I have is did you run some bad gas through before you changed the tank?

Also, did it run okay after you changed the carb? Could be the carb may also have a problem?

I'd check for vacuum leaks first. Sometimes you can't see them, but, old rubber will crack and can sure screw you up.

Then go down the list. Check timing, to make sure its okay.

Spark plugs to insure they didn't get messed up by the bad gas.

Loose wires in ignition.

Fuel filters to make sure they're not clogged up.

no bad gas was run through the new carb

since new carb was installed, it will now idle, but is rough

only vacuum leak would be on the dist. advance hose or the pcv, the brake booster vac is plugged currently

new inline filter

[rogergodding]

Originally Posted by 68gmsee

Forgot to add... If it's backfiring through the exhaust, that's an indication of unburned gas igniting as it's going into the hot exhaust. A rich adjustment may cause this as well as plugs, wires, etc..

I've had bad valves, but for the most part, I've had them sputter and miss occasionaly. Usually get better at higher rpms. I guess if they are bad enough they can backfire through the carb and exhaust also.

Only other thing that comes to mind is a bent push rod or valve caused by the backfiring...

with the old carb it was backfiring really bad through the exhaust.... no backfire now just a rough idle and I guess I forgot to mention, that roughness continues through the entire rpm range.....

[rogergodding]

thanks for all the feedback. will be checking for leaks and inspect the wires and maybe do that valve adjustment tomorrow.......

[68gmsee]

Originally Posted by rogergodding

with the old carb it was backfiring really bad through the exhaust.... no backfire now just a rough idle and I guess I forgot to mention, that roughness continues through the entire rpm range.....

If running rough is missing and/or sputtering out the exhaust, it may be caused by carb adjustments, bad valves, ignition and or electrical problems.

Some years ago I bought a rebuilt carb from a local auto parts store. It ran rough the same way and I took it back for a replacement. The replacement didn't give me any problems.

Let us know what you find.

[rogergodding]

well it seems as if the problem was these little thingys I've never had plugs this bad.......

[68gmsee]

Man, them's some nasty looking plugs... Hope that fixes your problem.

Thanks for update.

[rogergodding]

yeah that fixed it! now to actually install the new gas tank!

[68gmsee]

Okay, now you got my interest... That tank looks like the one on my old '96Tahoe. What is it out of and how are you going to install it?

I've got a 68 GMC but I'm staying with the stock location on it. However, I'm seriously thinking of removing the one on my 69 chevy and getting a rear mounted one.

[rogergodding]

I just got that from LMC, it is going under the bed as soon as I have my exhaust altered and the remnants of an old "donkey dick" hitch removed......