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292 Questions
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 |
Re: 292 Questions
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.
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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?
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I don't think timing at TDC is correct. I think my 292 is at 11 deg.
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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.
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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. |
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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.
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On my 71 with a monojet that vacuum port is connected to a flapper valve in the stock air cleaner snorkel.
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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. |
Re: 292 Questions
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. |
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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. |
Re: 292 Questions
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? |
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I have the solid cap and the two hoses go to manifold and air cleaner. Ill post a pic
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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. |
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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= |
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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.
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Just gears. Timing is close to what I run though. |
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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. |
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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. |
Re: 292 Questions
like all chevy 6,s the front 2 cylinders are worn out. bet even .060 ob wont bring em back in spec..................
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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 .
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Re: 292 Questions
I also have a stash of I-6 stuff. run em for 40 plus yrs
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If taper is a problem, a sleeve could fix it cheaper than another block.
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yep sleeve 1st 2 holes, use thick sleeves. but its pricey. sbc is best route for many reasons IMO
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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) |
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And cyl 6....
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I'm not an expert but have you looked for vacuum leaks?
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Hand over the snorkel doesn't change anything because the air will then go in through the choke stove port further back. It looks like your pistons are pretty coked up. That engine is really noisy, too. In any event, if you take it out and put a load on it, that will burn all the crap off the pistons. I think that that is where most of the smoke is coming from. Those compression numbers aren't stellar, but they're good enough. Those scratches on the cylinder walls only have one solution, though, and that's bore and/or sleeve.
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Re: 292 Questions
Apparently the PO put a lot of miles on your 292. Or the long vacation allowed gum and varnish to harden up in your valve train.
I used a valve-cleaning spraycan of foamy stuff -- shot thru the carb -- on a sluggish 350 V8 in my '71 GMC. Can't recall the product name or maker, but it worked pretty good - followed by a long drive. I would try that first before getting down to a rebuild. Or try any other shadetree magic: Marvel Mystery Oil, Rislone, warm diet CocaCola? If your rings are somewhat worn, you can try getting better compression by increasing the viscosity of your engine oil. I use straight 30 weight Valvoline Racing oil [VR1 p/n223] in a normally good 292. As mileage racks up, I run 40 weight, then SAE 50. [But before I get to filling the crankcase with SAE 90 gear oil, I rebuild. ] So maybe 10W-30 is too light for you. Try 20W-50 or SAE 40, and see if it runs better. I once got a 25 year run out of a 292 L6 I built in 1977. Only variance from stock was a .030 overbore. It went for 250,000 miles in my little Orange Stepside. Towards the end it was blowing blue smoke rings of pure 50 weight, but it still started right up and ran. In 2002, I started rebuilding the original L6, that I had put up in a crate, and rebuilt that with a more aggressive profile. That's the L6 that's in there now. |
Re: 292 Questions
I have had a hard time deciding where to start.
>>Dwell is reading 39. 15.4V @ idle << Dwell should be 31*, which is to say your point gap is way too small. FIX. NOW. 15.4 volts @ idle ? That's a real problem. An original 10Dn externally regulated Alt will seldom generate more than 13.0 V at 600 rpm idle. You have a bad voltage regulator or bad volt regulator ground. That is a noisy video. Either use a stethoscope or a long wood dowel and listen to the water pump and the alternator bearings. The high Alt voltage will contribute to alternator noise. You could also just remove that single fan belt and run the engine, to see if some of that noise goes away. With engine off, spin the water pump and Alt by hand. While you have the belt off, remove that ridiculous fan spacer. Without a full fan shroud, the only thing that fan spacer could ever do is reduce the life of the water pump bearing. You are right about using two manifold-to-head gaskets as being a bad idea. You should have listened to yourself. Loosen the intake-to-exhaust bolts to just snug. Then with 1 manifold-to-head gasket installed, tighten those nuts/bolts first. Then tighten up the intake-to-exhaust bolts. Has the coolant level been going down? Has the engine oil level been going up? |
Re: 292 Questions
The 15.4V could be from the battery being low and getting brought back up. If I read this thread right, he's been doing a bit of cranking which could lower the battery voltage. I was taught that minimum charging system voltage is 13.5V to overcome system resistance with enough voltage to charge the battery.
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Re: 292 Questions
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Apparently I went with my first thought and didn't put two gaskets on there. Checked it earlier and was scratching my head, definitely just one gasket there.
I cranked on it a lot just before checking voltage, I was doing the compression test. However I did check the ground on the voltage regulator and it needed some cleaning up. Will check that again once I get things back together. Carb is apart and in the ultrasonic cleaner now, it had a thick layer of gunk in it. I have a kit, new float and in-line filter ready to go. The barrel filter and spring weren't in the carb so gonna have to order those. Do these years use the paper or the bronze/ceramic (?) filter in the carb? The alternator was caked inside and out with oil gunk, bearings were going on it that's what most of the noise was. Decided to just go grab a refurb. By the time I ordered bearings and took the time to clean it out im money ahead. Water pump/fan spins freely no issues and no noise. I need a new belt so I will pick one of those up tomorrow, wow they are proud of that little belt.... Napa B151 premium xl 25-10035 with notches on the inside is what was on there. Not sure if I need the notches, I dont see one on napas website with the notches but the one i see is about 45$... Anyone have advise on that? New plugs are in. Used some seafoam in oil/gas. Will check to make sure all goes well with carb before adding too many variables at once. I have a feeling the smoke is coming from the valve seals but we will see. Once I get this all back together and it runs I will put new points/condenser and probably a cap on it. Recheck dwell after that. Once all that is done I am going to attempt to get 75-100 miles driven over a few days. Then see where we are at. Probably at night so they will think im a mosquito truck haha. I was told that a few squirts of oil and another compression test will show drastic increase if the rings are bad (made sense to me) but not really sure what would be drastic vs rings are good. Will probably try that after the drive. Once the seafoam has run its course ill probably bump it up from 10w-40 to 20w-50 as mentioned before. And re-evaluate from there. Thanks for the inputs. This forum is invaluable. |
Re: 292 Questions
Either the short paper filter or the sintered bronze filter will work. The sintered bronze filter stops water, but once it's clogged the spring lets whatever is in the fuel system by, anyway.
Take the cap off and see what the points look like. You can do that without upsetting the timing, since there is an indexing lump on the cap that fits the slot in the distributor. If the points are all pitted, it'll be obvious. That belt price is ridiculous! Check around. They should be about 1/4th that price. |
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I did a carb kit and put it all back together. When I went to clean the old gasket on the intake manifold I saw there was oil sitting in the bottom of the intake manifold.
The pcv on the valve cover appeared to be letting oil past it. Im not sure if that amount of oil could have passed up through the hose and into the manifold via the nipple. Anyone have that experience? I picked up a new pcv today. Belt was a special order for 30$ at Advance so I wont get that for a few days. Im not too confident that failed pcv is 100% source of the oil. |
Re: 292 Questions
Temporarily replace the black pcv hose with a clear hose to see if that’s the oil source.
Clear hose is available at Home Depot plumbing section. |
Re: 292 Questions
That's probably the source of all your smoke. Take a look into the valve cover and make sure that the baffle is in there. If it has that much blow-by it needs rebuilding.
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Re: 292 Questions
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As for the baffles in the valve cover I am not sure what you are talking about, do you have a picture? Mine doesn't have one of those breather things it has the regular fill cap (if thats what youre talking about). |
Re: 292 Questions
I'm referring to the oil in the manifold. Looking into the valve cover where the PCV valve goes, there should be some sheet metal that interferes with the splashing oil to keep it out of the PCV system. You should not be able to see valves or push rods when looking in. I don't have a pic, sorry.
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Re: 292 Questions
Oh ok I follow you.. I dont believe my valve cover has that. I had it off and cleaned/painted it and am not recalling. Will check tomorrow. Thanks
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