292 Questions

[May70]

I have a 292 I6 manual 4 speed with the rochester monojet carb, as far as I know its all stock. I bought the truck a few months ago, seemed to run fine when I got it but had barely been driven in years. Not sure if running a lot after years caused some issues.

Ill recap first....
Motor had been leaking oil a long time before I got it, so I was cleaning it up and putting new valve cover/manifold/side cover gaskets in. I also bought a reproduction exhaust manifold and installed it. When I installed it it really did not seem to seal up with just one gasket, the manifold was flat, I checked it with a straight edge. I ended up using two manifold gaskets just to convince myself (not sure if that's a no no). I pulled the distributor and reinstalled it, without checking what the timing was before doing so. The manual I have suggests timing for the 292 manual tranny at 0 degrees. So that's where I put it at and I am 100% sure im not 180 off. I did plug the vacuum line on the distributor while doing so. I also changed the oil and put in conventional 10w-40 as the manual suggested for my temperature range (Coastal Virginia) and I wont drive when its super cold here (coldest is around 10F, maybe a little less in dead winter).

Its idling okay but serious hesitation when you give it some gas. It also has started putting some white smoke out when I hit the gas. I have probably driven it 50 miles in the last couple months, I assume that's more than its been driven in years. Maybe 25 miles since I did all the above and the issues have appeared and got worse. I have good oil pressure and it has never over heated while ive had it.

It hasn't had any maintenance in many years so I am contemplating just pulling the whole thing and rebuilding it with a friend's help, if I can convince him.

My questions are; What are your thoughts on the timing and on the situation?

Thanks

[Steeveedee]

With the engine off, look down the carburetor and pump the throttle to check for a stream of fuel out of the accelerator pump jet. No squirt, your carb needs work. You could bump the timing up a little, but I'd personally check the carb first. It's an easy check.

[dflarsen77]

Honestly not being a smart Alec, but I really though this was a post asking a total of 292 questions. I was ready to see some interesting info about our trucks! Like, why are those tow hooks so expensive? And how bad is rust on rockers before I should just replace the whole rocker?

[jfnar]

I don't think timing at TDC is correct. I think my 292 is at 11 deg.

[Steeveedee]

Book says 4º BTDC for auto, TDC for manual. But if it runs without detonation, basic timing aids in mileage if it is more advanced.

[May70]

If it stops pouring rain for 5 minutes I am going to go check what you said about the carb Steeveedee. I ordered a carb kit for it yesterday so I should have that next week. I figured it needs one anyway. My neighbor is gunna put it in his ultrasonic cleaner.

I assume the manual calling for TDC (manual trans) is at idle, not total timing. I do not know how to determine what total timing should be. Its my understanding if you have a motor rebuilt at a machine shop they would calculate the curve and tell you what total timing @ XXXX rpm should be.

I also have a question on the carb, in the picture attached what is this vacuum line for? Mine is plugged off (plug removed in pic). Talked to the guys at the carb website and they didnt know.

[Steeveedee]

It's below the throttle plate so is constant vacuum. Couldn't tell you off the top of my head, and it won't help to look at my truck, since it has a 402.

[Bonestock3ott]

On my 71 with a monojet that vacuum port is connected to a flapper valve in the stock air cleaner snorkel.

[geezer#99]

That port is manifold vacuum. Likely used for your vac advance.
With zero timing and no vac advance it’s no wonder it has serious hesitation.
Machinist doesn’t determine your timing. You do. They might make a suggestion, though. You need at least 10 initial or more.
Getting your timing fixed first then think about a carb rebuild. Likely won’t need to then.

['68OrangeSunshine]

I run the initial timing of my 292 L6 at 12 degrees.
If we could still buy the kinda gas we could in the last century, with no alcohol, you could use the factory-specified timing of 0* or 4*, but fuel available now is no longer formulated for performance.
'68 C/10, SM465, 3.73 12-Bolt Corp rear.
My engine, although original, has been rebuilt -- bored .030 over, Crane 260H cam, larger [1.84''] exhaust valves, Clifford headers, Offenhauser intake, Edelbrock 1404 500 CFM 4Bbl Carb, HEI. I haven't run a Monojet carb in 41 years, so I can't help there.

[May70]

With the air cleaner off, I can look into the carb and give it throttle and gas does shoot out into the carb.

There is another vacuum port currently connected to the distributor (see pics). So I am not certain what the open vacuum port on my carb is for. There was also a hole on the manifold with nothing connected to it (see pics). Even on the original manifold it was open so I wasnt sure what was supposed to go there.

Sorry I dont know how to prevent the forum from turning my pictures sideways.

[geezer#99]

I guess that means your vac pot is hooked to ported vac.
I think that hole is for the throttle bracket For a different carb linkag
Do you have a breather on your valve cover or just a solid cap?

[May70]

I have the solid cap and the two hoses go to manifold and air cleaner. Ill post a pic

[Ziegelsteinfaust]

I like my timing at 13-15* btdc.

Also check your timing chain since they can get a lot of slack, and not work the way you want them.

Other then that. I would do a compression test, and leak down. Before you commit to either a rebuild or rehab of this engine.

[geezer#99]

Your pcv and hose to the air cleaner are good.
Pic of the other type throttle linkage here.

https://www.autabuy.com/Vehicles/Det...evrolet&Model=

[Steeveedee]

The hole in the manifold is tapped, right? Probably not a vacuum leak. Geezer#99 pointed out that the one open vacuum port is probably for your air cleaner. If you don't have that flapper on the snout, just plug that nipple.

[geezer#99]

Originally Posted by Ziegelsteinfaust

I like my timing at 13-15* btdc.

Also check your timing chain since they can get a lot of slack, and not work the way you want them.

Other then that. I would do a compression test, and leak down. Before you commit to either a rebuild or rehab of this engine.

No timing chain!
Just gears.
Timing is close to what I run though.

[Ziegelsteinfaust]

Originally Posted by geezer#99

No timing chain!
Just gears.
Timing is close to what I run though.

I am not big on the 6's. I thought they had chains too.

Are you using coolant when you drive?

White smoke can also be excessive condensation in the exhaust too. Does it go away as you drive.

This Obama gas we have is hydroscopic. Or at least I believe is the right term. It absorbs water, and can make engines run horrid till you flush out the old gas. Plus it can clog the passages in your carbs like nothing I have seen before. Besides marine motors. So if your only go to putt around in your truck I would not fill it up. Just hit the has station up to put in what you need or plan to use in the next month. This way your always freshening up the gas.

Maybe someone has experience with sta-bil, but I have not used it.

You may need to do what has been called a Italian tune up. Get it good, and hot. Drive it hard so it blows out the carbon, and everything frees back up. My mom's old cars would respond very well to this since she has always drove slow.

Then do like I said with the leak down, and compression test. Then you can decide if you want to freshen up this engine, and save money by now. Or rebuild it to what ever standards you want.

['68OrangeSunshine]

I use Sta-Bil all the time. I get a 10-cents-off-per-gallon deal from a supermarket chain. The discount can add up to a dollar off a gallon. At the end of the month, I tank up and can fill as many as 7 jerry cans. Since I will need to stash these cans until needed, I use the stabilizer. The imporoved formula can keep gas good for 24 months now. Two ounces per 5 gallons.
While the manufacturer claims it's a performance booster, I haven't noticed that, only that my stored gas is still good after a year. I try to rotate before that, though.
There will be a pink stain on the porcelain of your spark plugs. The color does not affect performance, but it can throw off tuners who aren't familar with it.
I usually add 5 or 10 gallons to my tank, when low, then top off with fresh pump gas.
If you have a hangar queen and must leave it parked for months, you can also put a bottle of Sta-Bil in the fuel tank, and the fuel will not break down.

[BCOWANWHEELS]

like all chevy 6,s the front 2 cylinders are worn out. bet even .060 ob wont bring em back in spec..................

[Grumpy old man]

I have an extra 292 and some .040 pistons , also a fresh 292 sitting here if you need another 292 to build ? I know they are getting harder to find around here .Also a spare 250 and an extra L6 head .

[BCOWANWHEELS]

I also have a stash of I-6 stuff. run em for 40 plus yrs

[Steeveedee]

If taper is a problem, a sleeve could fix it cheaper than another block.

[BCOWANWHEELS]

yep sleeve 1st 2 holes, use thick sleeves. but its pricey. sbc is best route for many reasons IMO

[May70]

Based on what most of you said, I set the initial timing at 12 degrees of advance with vac on distributor plugged @ idle rpm 600-700. Hesitation with gas seems to be gone. Smoke is definitely still there. Small steady amount at idle, smoke cloud with a good pedal. So much so that I didn't drive it around block. White smoke maybe a slight amount of blue tint. Even after engine warmed up revving/idling 20 mins.

Another thing i noticed, I covered the intake on the breather with my hand and it didn't impact it at all. Strange??

Dwell is reading 39.
15.4V @ idle

Checked compression with about 3-4 seconds of turn over, cyl wall best i could and plugs.

Cyl 1: 110, black deposit with some visible wear on cyl wall, black plug
Cyl 2: 110, black deposit with some visible wear on cyl wall, plug very bad
Cyl 3: 120, black deposit, plug slightly brown not bad
Cyl 4: 135, black deposit, plug slightly brown not bad
Cyl 5: 120, black deposit, plug slightly brown not bad
Cyl 6: 110, less black deposit than others, plug slightly brown not bad

My scope is not very good but i could see what looked like some visible scratches on cyl 1/2. I could barely see them on the camera so pics are bad. (pic of cyl 6, smoke and video on next page)