new rebuild idling rough

[martyk]

I'm putting a '46 chief back on the road after many years. A builder in Sacramento (about 2 hr.s away) did the engine for me and put 80" wheels and bonniville cams in it.

In its previous incarnation (74" - std. cams) I could get it to lope along at a good steady idle. Now I just can't get it to idle like that.

When I retard the spark, the idle evens out just fine, but with the spark advanced, it misses about every 5th beat or so.

I've rechecked the timing 5-6 times, reset the carb a similar number of times. Before I start digging deeper, I want to find out if this is characteristic of the bonniville cams? Do they idle a bit rougher than standard?

[T. Cotten]

MartyK!

Many tuning confusions originate at the manifold.
You can eliminate this variable,.. or at least locate problems and assess them,.. by pressuretesting your installed manifold as per http://virtualindian.org/11techleaktest.html

No bubbles is good: Don't fix it.

But even the tiniest of leaks affect performance, so inspect carefully.

Good luck,

...Cotten

[indianut]

It has been my experience that 80's don't idle as smoothly @ full advance as 74's. Just one of a few reasons I will not stroke any more of my Indians and will someday de-stroke my '37.

[martyk]

Thanks Cotten! My next thought was that the intake manifold might be leaking (even though everthing seems tight). I wanted to eliminate other possibilities before spraying 3-in-1 all over the place. I like your test much more. I'd never thought of using pressure and soapy water to test the manifold. I'll see if I can mock-up an air fixture for the manifold and give that a try. If I don't find any leaks... well I'll cross that bridge when I get there.

[brian_groff]

My experience has been that newly rebuilt Chief engines typically idle rough for the first couple thousand miles. My 80" that I built VERY tight idled rough for the first 2500 miles and then it did fine.

That said, it also had one of the newer style oil filters on it, and I think it would have 'broke-in' quicker had I not run the oil filter. Lesson learned.

I built a 74" Bonne once and it only took about 500 miles to calm down on the idle.

All of my engines had the intake manifold pressure tested with the heads off and lifters completely loose to make sure all valves were fully seated.

[T. Cotten]

Your intakes can leak without affecting a bubble test. It seems like Chief's overlap every time, as I can hear it.

Just adjust your regulator to give 12 to 15 psi. It's the differential that makes bubbles . A constant air source is manditory even if the valves are welded shut.

....Cotten

[brian_groff]

Gee. Wow. You are sooo right. Who cares about a good valve seat when you're really testing for *differential* pressure bubbles! Who wudda thunk it!



Let's not forget them stellite valve seat inserts have been known to come loose ... if he's got 'em. A loose valve seat always makes for a nice idle

It's nothing to free the lifters for a leak test. Time well spent. (No need to pull the heads ... it's just convenient during an engine build).

[martyk]

Can you tell me more about those valve seat inserts?

I see new valves and guides on the work order for the engine, but not seats.

This engine has seemed a bit more noisy since its been back together, but then it was apart for 15 years, so I don't know how good my memory is - and I've thought that this might be from the Bonniville cams that were put in.

(BTW, I've made a test fitting for my compressor to the intake and will probably check for intake leaks this week-end. Its just been too hot to work in the garage lately!)

[brian_groff]

This reply will probably generate a slew of opinions ...

The original cylinders had their valve seats machined as part of the cylinder casting. Valve seats wear. If you wear the valve seat too much and go to grind it back out, the seat edge gets too close to the cylinder wall. It's cheaper to install a 'sacrificial' valve seat than to replace the cylinders. Many people opt for stellite. It's a modern material common for this application that seems to hold up well. It's also a last resort because the cylinders can expand enough on a hot day to risk a seat coming loose.

Regarding engine noise, the Indian flatheads all sound somewhat like a sewing machine. Their valve train noise has always been an identifying characteristic. Every engine I've heard sounds a little bit different. It would be very premature to say that there's anything wrong with your engine ... it's very likely you have the original valve seat as this is something that the builder would have charged $$$ for.

Go ahead and ride it like you stole it

[T. Cotten]

I have a tin of vintage soft castiron seats that I hold close to my heart.

How strange that what was once the most common of replacement seats are now
unobtanium.

...Cotten

[brian_groff]

I wasn't aware Indian had replacement seats for the Chiefs. Did the soft iron seats that you're talking about have the same risks we're seeing today with the modern materials? (I say risk because most of the time, the replacement seats work fine).

I've also heard of people "spray welding" the seats back up and machining them down, but I've not heard if this really works or not. My guess is they're using some sort of welding material with cobalt in it?

[T. Cotten]

Brian!

I doubt the Wigwam ever offered seats.

Seats were offered by the companies that made them, (like K.O. Lee, Martin-Wells, etc.) in nominal sizes. Any automotive machine shop would have a wide selection in stock, and would lathe-trim as needed.
My small stash survived from an implement garage.

If indeed extra hardness is necessary, then spraywelding would be the ticket. But I know of no one who has resorted to it upon a castiron cylinder. Yet.

....Cotten

[brian_groff]

I have a friend who's trying the spray welding approach. Will post its effectiveness after he's got some miles on it.

Just got my newly sleeved jugs back today! New stellite valve seat, new ductile iron sleeves, nitrated & domed exhaust valves, Total Seal Rings and T-Slot Pistons. Can you spell OVERKILL!?!? No chances baby!

Burt Munro, eat your heart out!

[martyk]

OK, it took me a while to mock-up a fitting to pressure test the intake manifold, but, yup, its leaking.

I've got bubbles coming out from under the edge of the nut, between the nut and the manifold (not between the nut and the cylinder), on the rear jug. That's the "back" side of the nut, away from the cylinder.

So I guess that means that the nipple is OK and the chamfer is leaking back through to the back side of that nut.

I'm in the process of pulling the manifold. Those nuts are on tight! I've got the 1 13/16 open-end tool from Greer, but I'm having to hammer on that thing to break those nuts loose. More later...

Thanks much,
Marty

[martyk]

When I removed the manifold. I could see that the brass manifold cone on the leaking side had not seated evenly. I replaced it, to be safe, reinstalled the mainfold and tightend everything down untill I had no pressure leaks.

I didn't think the leak was significant, but what a difference! Now, it not only idles right, but acceleration/deceleration, throttle, rideability, are all improved.

I have one minor issue left, that I'll throw out on this thread... When running at a sustained speed, under constant throttle, I'll sometimes feel a slight miss. Just about two beats, and then everything is fine, until it happens again. I'm thinking electrics, probably the coil, but if anyone has any other insights, please let me know.

Thanks much,
Marty