The Stovebolt Site Forums The Shop Area Engine Shop Got it running - now to set it up.

The day's battle goes mostly well.

I got it running and brought it up to temperature - but something's not right.

Initially I got it going with a fairly smooth (but too high) idle and 20 inches of vacuum, but I'm having a bit of trouble 'reading' the results of my adjustments. When it idles the best it's blackening the plugs, and I can't seem to get a steady idle at 750 where it should be.

I've got the choke full off.
Engine up to temperature.
I've set static timing to 12 BTDC (vacuum plugged)- although it idles best at 15 BTDC.
Both vacuum and flyweight advance are working. (can tell by the movement of the mark)
Set the idle speed as low as it would go, and started backing out the idle bleed for the highest idle speed.

Sounds nice - but the vac guage is down to a jittery 12-15 inHG.

Absolutely everything is new except the carb which is a correct monojet that I picked up and "half" rebuilt. (The kit was pretty barren - accelerator pump, disharge ball and spring, gaskets, and float needle).

Probably just out of practice, but any suggestions on what order to set things up?

I also noted that it ran best just before the bleed screw backed entirely out (where it stalled). does "more out" lean or richen the mixture?

Here's a youtube clip on the first start. Oddly enough, it ran decent on the "guess it's likely to start" settings I dialed in before cranking - and I've made it worse with the procedures above.



As always, thanks for any help.

Don't worry to much about actual timing setting, put it where it idles best, starts ok, and doesn't ping under decent load. Numbers are just starting point. Once set, hook vacuum advance up and readjust carb to set idle speed.

Idle screw (mixture screw) is out for lean, in for rich. 1 to 1 1/2 out is normal.

Vacuum reading should settle down with more timing, 18 to 21 inches of vacuum is pretty good for stock engine.

Do you have a PCV? The Monojet is designed to accept (tolerate) extra clean air from the PCV, which will lean out idle mixture.

Yes PCV.

So backing the screw out to the last thread - the screw wobbles, and I figure is likely to full out with normal driving - is where she runs best, but the plugs still carbon up. it's almost as if i had another couple of turns everything would be right.

As I have an extra mixture screw, I'm tempted to file it back a bit and see what happens.

But - Joe has me thinking I might have missed something.

As the mixture and idle affect each other, where the mixture might be about correct, the initial setting for the idle is already too low perhaps.

So maybe start with a higher idle setting then bring it down after ballparking the mixture 1-1/2 turns out.

A bit uncomfortable playing around with extended idle periods on a brand new engine.

If you have zinc additive in the oil, and a stock camshaft, the pressure on the lcam & lifters is pretty small. You should still break it in with a 15 minute high rpm run if you haven't done so yet if the cam is new.

Does it smell like it's rich? or are the plugs just black?

What jet is in the carburetor and what number of carburetor are you using?
I can look in my Rochester book to see what should be in it.

Idle at 750? That seems high to me, but whadda I know! Sounded nice on initial start.

Things to check: 1, Valve lash. I do this the old way. Turn to the BB. #1 should have both rockers loose(both valves closed)I know this is "advanced" just a bit, but both valves should be closed. There is a very good Tech Tip for this. It will let you adjust 1/2 the valves in this position. Turn to the BB again(one turn on the crankshaft) and the #6 should be loose(both valves open) The other 1/2 of the valves can be checked at this time. At this time a little valve noise would be OK.
2, Check the vacuum advance for leaking, not hard just suck on the line, slap your tongue over the tube and see if it holds. Leaks? Need a new one. Holds? Good to go. Most set ups use "ported" vacuum so no need to undo it. No vacuum at idle.
3, set the timing with a vacuum gauge, after it starts, set to max vacuum. That will be good for now.
4, Set idle speed to about 500(if you can) Turn in the idle mix screw until it stumbles(slowly) Back out about 1/2 to 3/4 turn and it should idle.
5, Get a Dwell meter and see if the dwell is about 25-30 degrees(point gap is the check here)
6, Verify the firing order(153624) it is the same for all inline 6 engines.
These should get you running and then after the "break in" you can tune it.
Opinion: Most crappy vacuum readings, are from valves set too tight. A little valve noise at initial start up won't hurt. The Dwell Angle matters, the coil needs to saturate(field must build, then collapse for a good spark). Let us know what you find.

Interesting .. No, it doesn't smell rich at all. My previous engine did the same carbon plug thing on idle (except smooth with a solid 20 inches)but ran perfectly for decades. However, it was pretty 'hacked' together and I had always assumed it was running "wrong". Having hit 50 with finally the means, I vowed to get it as the factory intended correct this time around.

Part of the to get done list this time around is a passive O2 sensor - the exhaust is currently elbows and arseholes clamped together sufficient for initial starting. Once I've got the brakes on I'll take her down and have a full proper exhaust (with O2 bung) made up, and I'll know exactly what that particular score is.

Joe - it'll take a few days for an answer. Work week now . But if I'm not mistaken the main metering rod size, or adjustment - shouldn't affect the idle, no?

Steve - She is running reasonably well for 15 minutes of mucking about 20 years after forgetting how, so we're not suspecting firing order, assembly, etc. (Although 5 years on a stand makes me paranoid about such things as a weak spring, toasting a cylinder wall, etc.) As well, the ignition is HEI - no points. Plugs at .035 - which in my experience will make just about anything American start and run.

I do recall the factory specs calling for .060, but that anything much over .040 and change didn't like a firm pedal in real life.

Lol, was trying to recall myself whether it was supposed to be 500 or 750. Dumbest thing I ever did was get rid of my old school "Motor" manual, which unlike the Chilton/Haynes (okay, they can come in handy for trim info) was chock full of useful information.

So, what we have here is 292, HEI ignition, hydraulic cam and lifters, .035" gap plugs, 500 or so idle rpm, and has been setting for 5 + years on stand after a rebuild.

Is that about right?

Carburetor meter should not effect idle, float level will. My concern was about the size of the carb. 250's use a smaller bore and rebuilders tend to swap parts not caring if its right or not.

Yep, about right. Can't get a nice idle below 7-800 though.

Quote - Carburetor meter should not effect idle, float level will.

This might be something I should revisit too then. Roughly set to 3/8, but the kit had a vastly different needle and seat (lower ovearll with a side discharge port) as well as two different thickness of seat seals (ring gasket). I used the thinnest which was closest to what came out.

Carb number btw is 17058374.

Finally got a hold of the ovesized caliper retainers (Bendix type) I needed - so weather and time permitting tonight she should be able to move under her own power.

Aw man, I need to read the labels a bit more closely.

My Hy-per lube zinc additive - which has ZINC! not once, but twice on the bottle, contains absolutely none as it turns out in the fine print.

It's a ZDDP "replacement" additive made from an "exclusive polymer ester formula".

Soo.. Unless it whitens my teeth and makes me an animal in the bedroom - it's pretty well useless as far as it's intended purpose?

My Rochester books must not cover Canadian carburetors, the number wasn't listed. All of the US built 292's seemed to have the same metering, #091 jet & #122 metering rod.

Joe

Thanks Joe.

Actually I just bought it from CA!

The spec sheet with the rebuild kit calls for 11/32" of float on 80-84 trucks - I've got mine at 3/8, so I'll change that tonight. May be that simple. Fingers crossed.

After tinkering for a few evenings things seem to have gotten worse - she'll barely pull herself around the lot, and the vac needle is swinging wildly.

Couldn't get a torque wrench on the manifold bolts, but I did 'em up snug and a half turn with a short combo wrench. There's a bit of soot from the inner exhaust ports (2/3 & 4/5)coming upon the rocker cover (I've seen this before) but I don't think the intake is too loose or over-tightened.

I'm going to try to eliminate a few possibilities: Although I'm not suspecting ignition I picked up a new cap and rotor because it's not going to hurt.

My old carb which was a bit of a bastard made from several and missing several bits - nonetheless did run well until the day I pulled it off. I'll stick it on just to see if anything improves - which would point to the new carb.

Also, if the idle tube, seat, or metering rod is incorrect - the old carb should have the correct (or more correct) one.

Update.

Turned out the cap had a bit of wet under the coil - which presumably was even wetter last night and might account for the horrific run.

At the moment the plugs blacken on idle but at 1500 RPM or more for a few seconds clean up nicely.

It's not running horrible - but I still recall my other truck running a lot better. Solid 20 inches and rock steady idle.

I find myself wondering tonight if I'm simply remembering it wrong, and after 8 years of modern EFI cars it just sounds rough because it's supposed to.

The low gauge (17inHG)and needle jitter - maybe 2 inches worth - possibly because I'm reading from the large (5/16") port right at the carb base instead of the smaller nipple on the old carb that went to the vac advance?

The main jet seat is definately larger in this carb, and the metering rod more tapered - and swapping them caused starvation at throttle.

The 1/32" of float made no difference, but I've brought it up to 13/32" seems to have helped.

Quite interestingly - the other carb which ran wonderfully from 1994-2003 as a daily was entirely missing the idle tube. Whether I lost it when I was 28 years old, or some carbs just didn't have it - dunno.

Think I'll hold off tinkering around any more as i haven't managed to stumble upon some magical setting, and focus on getting it out for a real world test drive for now.

Sounds like a good plan. With 20" of vacuum, it can't be to far off!

Joe

With respect to the idle tube, I have three model B carburetors and only one has an idle tube. The other two do not even have a provision for one.

Chad

Oh boy!

Since my last visit I've re plumbed the brakes stem to stern (found a crusty line), lost hair over a fuel starvation problem (crack in the hose from the tank), new power steering pump, and got the electrics done.

Tomorrow an oil & filter change (get the metallic sheen from the initial run, ring seat, cam break in out of the oil), swap the water for a proper coolant mix, and a quick walk around to see if I've forgotten anything.

She's not "done" - but she should run okay.

With a proper fuel supply it's running much better, but still that odd miss and a few inches of wobbly vacuum.

At the moment I'm still only running enough exhaust (about 3' of 2" with a glass pack) to sort things out. It occoured to me this evening .. Wondering if another couple of feet of pipe might smooth the vacuum gauge out?