Alright... In this post is an explanation of the last big problem I had, but since then I have been having nothing but trouble. The fan/pump/alternator belt slipped off when I was coming home from work last week, and by the time I noticed, it died a mile from my house. I had it towed, and replaced the burnt oil and restored the coolant levels.

When I got everything back together, I took it out for a test drive. Under moderate acceleration, I noticed a knocking sound coming from the engine that sounded similar to the sound it made for the last few seconds before it died when it overheated. It always sounds suspiciously similar to valves tapping. When idling, I can rev the enginewithout noticing any sound change. When I did a manifold vacuum test, the needle sweeps back and forth over about 3 hg (which could have to do with valves), and is a bit lower than normal (which could mean late timing).

There is another some problem that might be connected. Oil has been coming up the dipstick tube. I guess this is what is meant by "backpressure," but my knowledge of this is limited to the term.

The one thing I don't understand is the fact that this only happens on the road, and not in park. To me, it would seem that it would be a problem with the transmission or suspension, but the symptoms go against this thought.

Does anyone have any ideas?

 

If the engine is overheating, the sound you're hearing is 'spark knock', which sounds more metallic than that to tapping lifters....

Mainly because the engine is cool.

If you'e testing vacuum without a load, it's definitely not late timing. The valves are probably too tight, or you have a vacuum leak at either the base of the CARB (BTW, double check that you're CARB gasket is not on backwards).... or by the manifold bolts.

Backpressure usually refers to a blown head gasket, or loose head bolts. In which antifreeze is kept from entering the block to cool it off.

Mainly because the engine has a load

It's definitely engine related. Overheating can cause major headaches, accompanied with so many different scenario's.

First, check for air pockets in the cooling system. Disconnect the radiator cap, and let the engine run til she's warm (do this a number of times if you don't have the proper tool to pump out any existing air).

Second, make sure you're thermostat isn't sticking or binding.

Third, you're distributor (which won't cause a spiking vacuum gauge, but will cause overheating though) might be too advanced. Retard (Turn) it clockwise a drop to see if this helps any....

Fourth, if the car idles fine.... then you're valves are seated good. If she idles roughly, then they might be set too tight. With the engine running, re-seat them down until the tapping stops.... then go only 1/2 a turn more).

 

Sorry.... I meant 'blow-back', and not 'back pressure', which keeps the antifreeze from entering the engine.

 

Well... I haven't had any more problems with overheating since I put the belt back on. Also, even when warmed up, it idles perfectly fine.

Another thing is that the vacuum was solid when I got the new cylinder heads, but was sweeping before when I had the blown pushrod. Now it stays about 5 notches lower, and sweeps.

I guess the next step is to pull the spark plugs and check under the valve covers. I might be able to borrow a compression tester and check all the cylinders while I'm at it.

 

Ran a compression test, and all signs point to blown head gaskets, with a possibility of over-advanced timing.

By the way... Can I adjust advance by looking at a vacuum gauge for the highest result?

 

If it's running too advanced, just turn the distributor (a drop) clockwise. If she's still running hot, and the cooling system is okay, double check for any air pockets in the system (allow the engine to run with the radiator cap off til she's warm)....

As for adjusting the timing with a vacuum gauge.... you could do this during idle, but it's impossible to get it dialed in with the addition of a load. Just use the ole trial and error method;

Retard the timing.... drive the car hard, if spark knock is prevalent, then retard it some more. Do this continually until desired timing is reached. But if she's still running hot, you probably have an air pocket, or a faulty thermostat.

 

Well... me and my buddy spent 5 days tearing everything apart, cleaning everything up, and putting it back in. Had a bit of trouble with timing (without the timing mark), but I got everything straithened away.

After idling for about 3 minutes in my driveway, the alternator belt snapped, taking a power-steering belt with it. The belts are Goodyear Gatorbacks. Anyone that is reading this, never buy these belts. The belt slipping off is what caused this whole problem to begin with.

I got a set of decent quality belts from Advance, so all I have to do is go throw them in.