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I have a knocking sound on my 1800CC that seems to come from #1 cyl. I also notice that this spark plug is black. When I start the engine and hold my hand to the exhaust, it feel normal. When I rev the engine, it hesitates. I have also pulled the #1 plug wire and the sound disappears, when put back, sound is back. There is a serious loss of power when I attempt to pull it out of my garage.

I think I did somethig stupid - I adjusted the valves to .006 shortly after running the engine, and the sound became appearent. Perhaps I should have left these at .008.

I am currently going to purchase new plugs (the originals were new also), a Bosch blue coil ( I have some chrome POS for a coil that came with the vehicle), and some Kendal 20-50 oil.

When adjusting the valves and turning the engine manually, all rockers do operate.correctly from what I can tell.

My stats:

'73 bus with rebuilt 1800CC
dual webber ICT 34's
Bosch 009

UPDATE:

Changed oil (20W50), plugs (Bosch .070) , adjusted valves (to .008 (new engine break in?? Should I be setting this to .006 already?)) loud knock is gone. I get louder then normal sound in my valve areas on both sides (Like a loud tick).

I spent some time adjusting the mixture on my jets, and my power is much better. Now I get sputtering like mad at about 2500 RPM and the bus backfires alot, I think, through exhaust, but might be through carbs, but I am leaning to exhaust.

Popping and loss of power are both possabilities with a vacume leak. Check everything related to your weak cylinder such as intake manifold top and bottom for a vac leak. Check balance bar fittings too though that will effect both cylinders on the side. Good luck. Bob

OK, will do. I have the paper gaskets on the bottom of the manifolds (Bugpack) and remember coating them with a thin layer of grease to keep them steady (could this affect my seal?). My engine also came with thick, plexiglass gaskets (like 1/4 inch if I had to guess) with paper on either side, which I opted to install the paper ones instead. Would there be an advantage with the thicker ones? Would it seal correctly?

BTW - I played with my carb mixture and got more power.

Those are probably insulator gaskets to keep heat soaking down. You should never apply grease to gaskets. yes..That will make them leak. Oil...maybe lightly...but even that will cause leaks. Ray

Copper Kote or permatex #3 is all I'll use...
Have (sucessfully) used Ultra-(copper or blue) silicone on Progressive manifolds that wont stay flat..

Goose grease is for chevys with big solid manifolds with tons of surface area... that you would almost NEVER get off if attached with Permatex.

It's an old racers trick. Leave it for that app.

Take a look at your valve adjuster screws... They may be beaten to death.

Then use search, I have a trick that works for ME, but other knowledgeable folks somewhat disagree.

The screw tips get a flat... When you make the next adjustment, you end up on an edge, and the adjustment goes south within a few miles, or minutes.

They are supposed to have a small radius. I reradius mine and polish them... Haven't needed to touch them in nearly 50K miles once I replaced a few and had a good set.

Used is better than new...

The (REAL) Porsche 911 adjusters work best... if you have 8mm screws... just take off ~60 thousandths (1.5mm) off the rocker towards the valve for clearance.
(Where the screw goes thru)

And .006 in is CORRECT unless you have hydraulic lifters, and then it's between 1/4 and 2 turns past contact, YMMV.

First things first - this forum is totally AWSOME!!! This site has helped me more then any other source of information have tried. Thanks to everbody...

The sound happened to be a heat exchanger working itself loose. Tighted this up, and the engine sounds somewhat normal. I still get it a little, and I have an additional pair of exchangers. 1 pair is in mid-condition, with a nice coat of light rust (which are installed). The other pair are cleaner, but have rust holes in various spots. None of these are new, and I don't feel comfortable paying out big $$$ for new ones.

Also, my timing was off, and still might be off a little. Instead of trying to time 7 degrees (009) and adjusting my carbs to that, I turned the distributer until the motor sounded real healthy, then adjusted my carbs down to this. My idle is fast, and the idle speed screw is not touching the throttle body (no linkage hooked up). I have played with the mixture screws, but still run idle at 13 degrees(ish). I will rev the bus up and time it at 30 degrees next. Any advise here?

The above two fixed my backfire issues.

Piece of mind tells me to replace the gaskets without grease this time. Should I go with the bigger? Should I stay with the same?

Your right on the valves - These are new heads, and my screws are definitly not worn, but I do a valve adjustment almost every morning, being as paranoid as I am. How thight should the lock nuts be on these? Enought where I have to really reef on them to loosen them or just tight enough? I cannot find clear documentation on this.

UPDATE - My timing is a little over 30 degrees when engine is reved. I do get a little backfire still, but not as bad (BTW, olny occures when de-accelerating). One of my carbs - I cannot get the mixture screw to misfire, could this be a leak? Vaccume or Exhaust?

On exhaust - I just put the metal gaskets in on the head to exchanger, should there be more?

Backfire(actually popping) on letting off is classic exhaust leak symptom. It is exactly backward of popping on acceleration caused by intake leak.
32 Degs is fine as max total advance with an 09.
In the future use the term backfire to describe firing back through the carb is indicative of firing into open valve when out of time or with crossed plug wires. Best of luck. Bob

Thanks Bob,

I notice a hissing sound from the left side carb, and assume this is a leak. Will replace gaskets ASAP...

The HX units are hard to get sealed sometimes, a little "adjustment" with a rubber mallet, heavy//shot filled type, is frequently called for.

They should just slide in place. They never do.

Another thing is the ends that hit those copper rings might need a touch up with a file occasionally... take a straightedge to it... should be flat and parrallel.

RTV is sorta OK to keep the copper rings in place. A little rubber band can work on squareports, I usually use super glue.

(don't laugh. It works fine)

To get it all "right" one usually needs to take the exhaust system apart, straighten out the HX units, then put everything back together loose/snug, then start tightening at the HX units.

Usually if a idle fuel needle is nonresponsive, ie does nothing to the idle when closed, the jet feeding it is plugged...

What kind of carbs? 32 degrees total is too much for a Bus BTW, probably OK for a T4-in-a-bug setup.

The hissing is either a carb balance issue or you have stock carbs, one side has the idle circuit in it... feeds both sides thru a ~1/2" tube.

Thanks for the HX advise, I assume I can do this w/o dropping the engine (right?).

I have dual Webber 34 ICTs (hey, I'm cheap). I took the hissing carb off and found my gasket to be rough. Replaced the gasket, hissing is gone, and my power is great, I am very pleased. This took alot of tin work and injurys to get at the area, and plenty of gasket cleaner w/scraper to get that guy off. Of course I stuffed paper towel down the head intake holes to ensure no junk or hardware got down there (that would really suck).

My carb is now responsive to mixture settings, and is running strong. Now on to the exhaust leak!!

Popping on decelleration can be caused by several things. Yes, the gasket is one. Running lean is another, having an exhaust leak is another. Add to this, the high advance rate you get on overrun/decelleration with the mechanical advance distributor...and you may need to keep your eyes open. Ray

Right on.

I definitley have an exhaust leak. It is on #1, as I have listend closley and notice carbon/burn marks on my shiney new pushrod tubes.

I was just going over your previous thread, and have another tidbit or so of advice---

If the original distributor is in reasonably good shape, pull the 009 and save it for a dire emergency spare...
The people who push 009s like that should be beaten, then shot.

Search for "float test" on these forums.

Hook up your vac advance, if IS a vac advance port, it should NOT suck at idle, just when the butterflys are open a bit, as at light throttle.
(use a "T" if both carbs have the port, should...)

This can be worth 5MPG, and will GREATLY improve your light throttle performance.

Set your max MECHANICAL advance to 28 degrees @~3500, vac hose disconnected, this is not "just a good idea" in a Bus.

Search will also find info on how to make those shiney new pushrod tubes never leak...