Weird low rpm problem

[Ivan]

Valves either seal or they don't. So yes they are usually a sudden onset. They typically act like your bike is acting. Runs fine until the head heats up then the expansion of the valve stem hold it open just a hair. This is enough to cause a miss at idle, but during the early stages, not enough to keep it from firing at speed. This is because the mixture cant flow past the gap fast enough so there is just enough compression to fire, but it isn't a very powerful burst. Expanded over time, some engines longer than others, the valve will melt at the edge and ruin both the valve and seat. In extreme cases the head can "Fire slot" between valve seats.

As I said before, the only thing it will cost to check is time and some silicone for the gasket.

As far as oil leaking around the generator, I might say it would be a problem if it was a brushed alternator and the carbon in the used oil shorted out the armature. But on a brushless one, probably not. It too is easy to check. The battery should have more than battery voltage while charging. Also, use your DVOM's AC volts setting across the battery terminals and look for AC voltage of more than a couple volts. This is called a "ripple" check. If one leg of the alternator (in all actuality a 3 phase AC Generator which is rectified and regulated) has failed, you will see somewhere arount 3-5v AC. Normally this is a failed diode in the rectifier, but could be a short in the stator windings.

I realize I am not there, so I can't be 100% sure on this, but your reports keep leading me to valve issues. I have been wrong before, but sometimess with free advice, you get what you pay for... (shrug)

[dbeardslee]

Ivan - I found the cause of the oil leak - that f*****g banjo fitting on the bottom of the oil delivery tube. I took the carbs and adjusted them all 1.5 turns out on the mixture with no appreciable change in the problem. I respect your mechanical abilities, so I'm going to pull the valve cover and see what's what with the clearances. I hope your right - crow doesn't taste that bad . Let me ask you this before I get started - wouldn't valve problems be apparent at higher rpms also? It runs great once it's over 3k.

[Ivan]

Ahh, Banjo fittings. One of the great mysteries of the world. Mysteroius why they ever even made them....

Most people don't know that oxygen tends to embrittle and harden brass. The brass washers, when hard dont seal very well. The answer to this is to anneal them. The process is exactly the same as hardening steel or iron. Heat to glowing and quench. Use water for brass. this will soften the washers so they will conform and seal again.

Most people scoff at the idea, since they are normally on brake lines. They'd rather replace them with new washers. The problem with this is that the old timers and most any decent technical reference will tell you to anneal even new washers before use.

Personally, I never buy new washers unless the old ones show cracks around the edge. That is the sign to replace them.

[dbeardslee]

Ivan - You may have nailed it. I ran it a little this morning, but it had been sitting for several hours, and the header pipes were stone cold. I could still feel a tiny bit of warmth in the engine, so I hope that's cold enough to qualify as cold. I just got finished checking the clearances which are as follows:

Intakes - #1-.15, #2-.11, #3-.06, #4-.15

Exhausts - #1-.24, #2-.21, #3-.23, #4-.25

#3 was the worst in the bunch, and that's also the cylinder that the synch gauge was really acting up on. The intakes are all below spec, but the exhausts all look good. I think it's interesting that the inner cylinders (the ones that get hotter) are farther off than the outer cylinders. And the problem gets worse as the engine gets warm. Hmmmmmm, says I.

That crows kind of chewy, but not too terrible .

[Ivan]

Hey, Im just glad you found the problem. Lapping valves usually needs an adjustment after a few thousand miles. +1 for hydraulic lifters :rollseyes:

as far as cold engine, if you can work on it painlessly, thats good enough. Idealy, you want 0 lash at operating temp, but that is never going to happen in a less than perfect world.

Now if you get this all adjusted out, and still have trouble, we'll both be scratching our heads.

[dbeardslee]

Let the head scratching begin...

Just got through with a test ride, and after adjusting the intakes it's better, but she's still got issues. As I watch the vacuum gauge on #3 it rises to about 23" and I hear a little poot, and it drops to about 18". Then it rises back up to 23, poot, back down to 18. Does it just like a valve opening and closing. I'm thinking the #3 boot is still leaking, and it will only seal up to 23" of vacuum. When I was putting it back on I could feel that top bolt trying to strip, so I didn't get it as tight as I would have liked to. Tomorrow I'm going to get a permacoil and some of those 2.3L ford thermostat gaskets, pull the carbs, and make for difinitely sure the boots aren't leaking. If that doesn't do it, I'm at a loss for where to look next.

Ray - You wouldn't happen to know what kind of 2.3L ford would you? 4 cylinder? 6?

[DGXSER]

Hey Doug, Quoteth the Gospel of John....."An inexpensive way to aquire intake boot-to-head-gaskets is to go to your local auto parts store and get 4 thermostat housing gaskets for an old Ford Pinto engine, 2.3 Liter. They have the correct offset bolt pattern, and require just a little trimming. I have done this to my/our 81 SH and Succubus has done it to his bike also. The cost should be around $4."

As I watch the vacuum gauge on #3 it rises to about 23" and I hear a little poot, and it drops to about 18". Then it rises back up to 23, poot, back down to 18.

Is it doing this on every cycle? OR does it build up to this vacuum level through several cycles of the cylinder?

[dbeardslee]

It's pumping it up, and then releasing it. I would say it's maybe a 3 to 5 second cycle. Thanks for the info on the 2.3L gasket - and for one of my beloved Pinto's no less - I had three, and one even had the 2.3L (that was the jumping pinto ). Could be a sign from God...or not. One way to find out. Right now I'm going to break out the ben gay and hit the La-Z-Boy - bending over that thing all day took it's toll.

[John]

Any good parts guy will know that the 2.3L is a four cylinder. It was used in Pintos, Escorts, Mustangs, Rangers...It was the workhorse four cylinder engine for Ford.

[dbeardslee]

John - Thanks for the verification. All this talk about 2.3L's and Pinto's is bringing back memories. The '76 I owned had the 2.3 liter with a standard 4 speed. The speedometer went to 110, and that little sucker would pin it and keep going. I had a Cutlass Supreme with a rocket 350 and a turbohydramatic at the same time, and that Pinto would outrun the Cutlass. Great little motor. I'll get a big kick out of it if a little piece of one lives on in Betsy .

[John]

I used to own a 76 Gutlass also. 350 cubic inches... Q-jet 4bbl..155 net HP
What a slug! Beautiful car, but no nuts. My folks had a 73 Cutlass, 350...2bbl carb...ran like a scalded ass ape!. What a difference a few years can make.

[dbeardslee]

Mine was a '71, rocket 350 with a 4bbl. rochester, if I remember correctly. I called it the brown monster. That Pinto called it lunch .

[Crazcnuk]

Too bad you didn't realize you could have added 100+hp for about $100.

This would have also imporved the mileage...

[dbeardslee]

OK, I'll bite...

Craz - I can think of a lot of things that could have been done to the Cutlass - dual-plenum intake and headers (with the appropriate jetting), holley double pumper, hotter coils, etc. - but the only one I can think of that would have been in the $100 range that could possibly have supplied that much horse power is a 1/4 cam. You've got me curious - what's the answer?

I'm getting ready to pull the carbs (for the umpteenth time) and then it's off to the autoparts store. With a little luck I should know by around lunch time if sealing the boots will be the final chapter on this issue. I've got my fingers crossed - It makes it hard to turn bolts, but I'm not taking any chances .

[Crazcnuk]

They came with Dual plane intakes stock, but your guess on the cam is correct although the 1/4 (3/4?) race cam thing is meaningless. There are a bazillion cam combos out there that would get that engine up another 100hp (or more) but for more you would have to do a few other things.

We put one in a 91 Dodge 318 a few years back. Just a 4x4 econo torque cam, and it adds 100hp.

You talk about 3/4 race cams, my beast back then was a '71 Pontiac LeMans Station Wagon (shades of the Vista Cruiser!) with the 350cuin Pontiac engine. The cam I put in it was the biggest hydraulic cam I could find from Crane. With a Holley Street Dominator manifold, Carter thermoquad 780 VS, RAM Air MkIV exhaust (headers woudn't fit) it was rated about 380hp.

I found out Powerglides are a tough tranny, except in reverse...