Two Issues

Blackwaterforge · Post by **Blackwaterforge** » August 31, 2009, 12:50 pm

Have a 300 engine from parts truck. Truck is a 66. Engine is a 75 Fred Jones long block. Engine had dead miss #2 cylinder. Rocker studs had pushed up so valves were not opening. Replaced rocker studs with treaded type. Rebuilt carb (Carter YF). Engine runs much better but still has a miss. Replaced lifters (Clevite) and adjusted valves. Issues are that 7 rockers are oiling properly (steady stream at idle) 5 rockers are oiling but not a steady stream. Engine still has intermittent miss. Dwell is 37 degrees, idle is 500 rpm, timing is 8 degrees btdc. PO installed new plug wires but they are graphite. Am I correct that you are not supposed to use graphite wires with a point based ignition system? Engine holds 30 lps of oil pressure after warm up. Compression is 150-155 across all cylinders. Miss is worse after it warms up. Should I check the coil?
Thank you for all your help!

Post by **Greg D** » August 31, 2009, 5:13 pm

Likely in the ignition yes. Other possibilties, you are sure none of the other studs moved but not as much right?, bent pushrod, bad lifter, rich mixture - the way the intakes are on the I 6's if it's flooding, it will flood worse to the center cylinders.

Tech · Post by **Tech** » August 31, 2009, 5:55 pm

old points distributors can cause the miss at idle. The bushings get sloppy and it allows the shaft to wobble around This either causes the points to fail to close or fail to open depending on how the gap was set. If you can grab the rotor and cause the points to open and close it's time for an upgrade. As for graphite wires I generally despise them, too fragile for anything that actually gets worked on. The stainless wrapped graphite core wires are much tougher.
Tech

Blackwaterforge · Post by **Blackwaterforge** » August 31, 2009, 6:04 pm

Thank you for your replies. Replaced all studs with treaded ones. All lifters new (Clevite). If there was wear on the distributor would the dwell angle remain stable at 37 degrees? Vacuum is 18lbs. Drops to 15lbs when it misses. :help:

Tech · Post by **Tech** » August 31, 2009, 11:40 pm

If you can find an old engine scope you can easily see the spark timing jumping around. I think your right the dwell should also be hard to get stable if the bushings are worn.
Tech

oldtrucks · Post by **oldtrucks** » September 1, 2009, 3:03 am

Blackwaterforge

You are experencing a valve sticking in the guide. To fix it you will have to pull the head and have the valve guides reconditioned.

There was a practice some time back of using steel valve guides and they don't expand and contract with heat the same as cast guides and machinists being what they are like to have close clearences and with steel valve guides when the engine warmed up the valve stems would stick to the valve guides and hold a valve open to long or not let it close at all. I have experenced this problem and my machinest is one of the best but we figured it out and he hasn't used steel replacement valve guides since. This wasn't something that happened a lot but it was enough that he changed his practices.

This may or may not be your problem but I am betting it is in the valves.

Blackwaterforge · Post by **Blackwaterforge** » September 1, 2009, 7:38 am

Thank you for your replies! I had wondered about a stuck valve. How can I confirm valves sticking?

slick4x4 · Post by **slick4x4** » September 1, 2009, 7:57 am

if it is a sticky valve , you might try this before you tear it down

i have had good luck with marvel oil
have used it in lawnmowers to tractors.... seems to work good for lubricating valves

Blackwaterforge · Post by **Blackwaterforge** » September 1, 2009, 8:09 am

Would you add it to the fuel?

64 f100 · Post by **64 f100** » September 1, 2009, 8:11 am

One thing you can try besides mystery oil, is set the idle way up, and run mystery oil down the intake. Don't let the engine die while doing this.
However, one other problem occurs to me with the 6 cylinder engines. The flapper ( heat riser ) in the exhaust manifold may be loose and or not opening right causing a problem. Will cause engine to not run right and be eratic when it does run.

Rich

Thunderboy · Post by **Thunderboy** » September 1, 2009, 8:24 am

I think Oldtrucks has it.
If the engine was recently rebuilt, the valve guides may be too tight. If the head has a lot of miles, then the guides wouldn't be tight, but you could have a slightly bent valve instead (unlikely).

I don't think one can do a good job of confirming this without removing the head and checking for lateral movement of the valve with the springs removed. If guide replacement is in order, bronze guides are the way to go. They last forever, and are much less likely to cause any further problems if fitted properly.

Your rockers studs likely wouldn't have pulled out if the guides were sized properly (unless you have a giant cam and racing valvesprings). That is why I think this is where I would look. Good Luck - Let us know what you find...
Drew

slick4x4 · Post by **slick4x4** » September 1, 2009, 8:25 am

pour it down the carb while running at first , like Rich said
also mix it with the gas for added lubrication

Blackwaterforge · Post by **Blackwaterforge** » September 7, 2009, 7:36 am

Thanks for all y'alls help! After much tinkering I found that I had two bad (brand new) Spark Plugs. I moved plugs from cylinder to cylinder and the miss followed the plugs. Engine would run fine then miss. Bought six new plugs and engine now sounds great.
Thanks again for all y'all help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

deviant1 · Post by **deviant1** » September 7, 2009, 7:56 am

It is good to hear that it was a simple fix.

Two Issues

Two Issues

Thanks guys!

Thanks guys!

Thank You!