The Stovebolt Site Forums The Shop Area Engine Shop Adjusting valves on 283...again??

Hey guys,

I have a 61 1/2 ton with a 283. Shortly after bringing it home, I adjusted the valves, and it sounded a whole lot better, no more tap tap tap. Now, only 2 months later, it sounds like it needs to be done again. The motor has a distinct tapping sound, especially after it's been warmed up pretty good. This is what it sounded like before. Do these old engines really have to be tuned that frequently? Or maybe there's something worn in there that I will need to replace?

Hy Adam61, the only things i can think of which cause the lifters to make onise are, a lack of oil to them, loose adjustment, and part wear [cam lobes, lifter bottoms, rocker arm pivots], sometimes the rocker arm adjusting nuts don't hold their adjustment, they become too loose. Are you sure it's a lifter noise? Check your harmonic balancer, they can wear their key way and hunt back and forth, most 283 balancers were not retained by a bolt and can work loose, hope that helps.

Well, I do know that when I adjusted the valves before, there were a few of them that had bolts that seemed really loose, and although I adjusted the valves to get rid of the tapping, the bolts never really tightened up. Maybe they came loose again. How would I fix that id that was the problem? Would I have to rebuild the heads? Oh, and some of it could be the harmonic balancer. It also has a slight thumping noise when it runs too, but that never really concerned me much, I just wrote it off as the engine being 48 years old.

Oh, and the oil is full, so it isn't that:)

Look at the threads on the rocker studs and make sure they are good. Then put a straight edge across the top of studs and make sure they are all the same height. If that is good then replace the locking nuts. The studs are replaceable with out pulling the heads.

LG

Replace the adjustment nuts and that should cure the problem with coming loose assuming the studs are OK.

Don't get excited, and don't deviate from your original thoughts just yet, but if that doesn't cure the problem.....Sometimes the tapping noise could come from excessive piston clearance. Piston slap is what I call it. Another thing you say about it happening when it gets warmed up (and thumping) is a connecting rod could have excessive clearance or rod bearing going out.
What weight oil are you running? And how many mile engine is it?

The fuel pump can also make a noise similar to a rocker arm tapping noise.

What oil are you using? I'm not much of a 283 expert but if it's a flat tappet engine and you're using API-SM oil you could be experiencing excessive wear on the cam lobes. As they wear the lash increases. Just a thought.

The thumping noise happens upon startup, and goes away pretty quick. The tapping gets worse as the engine warms up. Unfortunately I have very little history on the truck, so I dont know how many miles the engine has on it. But I do know that it's original. It wouldn't really suprise me if I have a rod bearing going out on it, but I hope not, as I am not in a position at the moment to have the engine pulled and rebuilt. I have 10W30 oil in it right now. Maybe I should go with something thicker?

I would assume the engine has hydralic lifters. A heavy oil may help with some noise if it is lifters, but won't cure the problem. I know some will hate me for the suggestion, but you could try some STP oil treatment to help thicken up the oil. If you change the oil you might try a straight weight oil (30W), but that won't help much in cold weather.

Does the engine burn much oil, or burn blue out the exhaust?

Also get a cheap diagnostic stethiscope. It may help pinpoint the area that the noise is coming from.

If you have a oil pressure guage that displays actual PSI, does the oil pressure drop off real low after it warms up? It may indicate a rod bearing problem. What are the oil PSI's when cold idle, warm idle, cold when driving, warm when driving?

Thumping on start up could be the crank bearings. What you describe is the way my Dad described it.

Builder is right get a oil pressure gauge on it. I have a mechanical that I bought at a motorcycle shop, and use to check oil pressure. I keep it in the tool box to check pressure when there is no oil pressure gauge or I doubt the gauge.

LG

There is an oil pressure gauge hooked up and mounted under the dash. I don't know how accurate it is, and I can't quite remember the readings on it. But I do know that it stays roughly the same when it's warmed up as to when it's cold. It goes up a little higher when the engine is revved high, which is to be expected, obviously. I'll go and run it for a while and see what it reads out.
I don't have a stethoscope, but the noise definitely sounds like it's coming from the valve covers. And no, it uses absolutely zero oil. I changed it 2 months ago, hasnt gone through a drop, and it still looks pretty clear. And I drive the truck typically about 5 times a week. No blue out the exhaust at all. Oh, and yes, it has hydraulic lifters.

A long screwdriver held to your ear will work as a stethoscope.

Ok, I adjusted the valves again today, it's sounding great now. I did notice that two of the nuts have been replaced at one time. They are 5/8, while all the rest are 9/16. There were a few of the other ones (9/16) that seemed looser than the rest. And they were the ones that were out the most. So I think some more nuts need to be replaced, or some studs. The threads looked fine, but then again, i didnt take the nuts off. I'll run it for now and see how things turn out. Oddly today, I heard no "thumping" really at all. I think that's pretty much only right on startup.

Got some oil pressure readings too. I very highly doubt that these are accurate. They seem way too low.

Upon startup, 10 psi.

Revving high, 15 psi.

Warmed up, about 9 psi.

Oh, and thanks so much to all of you for your input:)

I drove a Austin Healy six for a few days that had oil pressure like that. A friend let me use if I dropped the oil pan and checked the bearings. I dropped the pan and the bearings were well worn. I don't remember what they micrometer readings were, but was surprised that it sounded as good as it did, there was plenty of movement to the rods. Nice car definitely on my wish list.

I would definitely not push it too hard. IIRC the healy was driven for another 6 months, not regularly, before it was sold to be restored.

LG

Like I said, I dont know how exact this guage is. It's an aftermarket one that is hanging under the dash, hooked up to a tiny hose that has oil in it, which goes to the engine. This hose is full of air bubbles though, and they don't really work their way out of there. Why would the engine having worn bearings affect the oil pressure? I don't really get it. I thought a drop in oil pressure only meant two things...it's low on oil, or the oil pump isn't working right. I need to be enlightened, lol....thanks

I should maybe drop that oil pan soon too, and have a look at the bearings. Maybe clean the oil pump?

I've wondered about air in the oil line to the pressure gauge myself. Then the oil pressure on that particular engine was reading around 30 which is about normal. I've just assumed that the air compresses and there is some small error.

Worn bearings have more clearance for the oil to squeeze by so you loose oil more quickly. Another way to look at is if you hold a garden hose flat against a wall. The closer it is to the wall the more pressure you will feel.

You should be able to bleed the air out. Disconnect the line from the gauge, pull the coil wire or,,, then turn the motor over with the starter till the air is pumped out. Reconnect everything and see if there is a difference in oil pressure.

It wouldn't hurt to drop the pan and check things out. Then again you might not like what you find. I'd baby it along and look for a replacement.

LG

LG

I don't think that an oil pressure gauge line should have necessarily have oil in it. I know on my 216, the line does not have oil in it. It is all about pressure and not about being full of oil.

If your oil pressure is that low, something is very marginal. There is nothing to clean on the oil pump except maybe the sump and the relief valve.

Does anyone know what the proper oil pressure for a 283 V8 is? I've been looking all over the net and can't find it anywhere.

"proper" depends on the condition of the engine and it's specific equipment - mine [rebuilt about 10,000mi ago, high pressure pump] will peg the stock gauge cold [over 60] and run about 30-40 at an idle when hot [185* thermostat], 50 at higher rpm

Bill

For a 283 those oil pressures seem pretty low to me. When it is warmed up real good, what is the oil pressure at idle?

I don't really know. I think I'll make sure the oil is full, and take it out for a good drive today to find out. I Do have intentions of rebuilding the engine, just not now. Was hoping to drive it as is, but not very often, for about a year, before parking it and ripping it apart.

I think that you are going to find that answers will vary. IMO for an OEM motor that has been cared for and less than 70-80k miles. I would like to see 30# warmed up and at idle. If it shows around 20# it's showing signs of wear and thoughts of rebuilding should be considered. I'd also consider what my compression is and balance that off against the oil pressure. When the motor is showing less than 10# warmed up and at idle I'd consider it very marginal.

As an example the 327 that was in my 68 C20 had been taken care of. It had 120k on the motor and showed a little under 30# warmed up and at idle. It was replaced because it decided to crack a head.

LG

Drove it today, runs at 12ish while I'm driving, unless I let off the gas, then it'll shoot up to 20, then come back down. Idling at lights, it was at about 9 or 10. So yeah, even though it sounds pretty good now and still has alot of get-up-and-go, I will have to rebuild it. Kinda sucks, but I guess that's to be expected.

You've got a good lookin truck, it runs and sounds good, and it's original. You've done everything right so far, and seem to be pretty level headed. There's no way of saying for sure, but you could drive it for another year on weekends. Put 40W oil in it, high viscosity, what ever. Just DON'T try and blow off any F*rds, nows not the time.

I don't know what your plans are, but if you are going to restore it to original, and a 3 spd back in it. I'd look for a 3 spd with an overdrive. Keeping the rpm down would help a bunch.

Start looking for a used motor. I found a 350 out of a 72 for $200 from someone I knew. He said the motor ran good and it does. I did replace the cam since it was going and I had almost new cam in the 327. The oil pressure is a little under 30# at idle when warm. It will last till I finish my 63.

Your still lookin good and have sometime to work things out.

LG

Thanks LG, I was thinking about rebuilding the 283. But, seeing how I'm new to this hobby, any suggestions are welcome. Would you recommend I just find another motor for it that's in good shape? Likely loads cheaper than rebuilding the 283, eh? I do plan to restore the truck, but not necessarily to original. I'll probably leave the existing transmission in it (4 speed manual, granny gear 1st) but I'd like to swap out the rear end gearing to get the rpms down a bit. I think it has 3.90s in it now but I don't know for sure. Original rear end though. If I do happen to stumble across a 3 speed with overdrive, I may consider it. The steering column still has the linkage in it, but they removed the shifter.
Really wish I could start tearing it down, but I need to buy a house with a garage first.

I think you have two choices.

The easiest would be to find another motor. I'm not sure what the cost or what might be available in your area though that might be a factor. If you can't get a warranty on it. Then I would want to hear it run and know what the oil pressure is. If you do go this route you can then take your time rebuilding the 283.

The other option would be to change the rear axle. There is a problem with changing the rear axle and that is the lower gears are going to put additional load on the engine. It looks like you have an SM465 which does have a granny gear. I swapped out the 4.56 in my 68 for a 3.73. Second went from about 15 mph to about 25 mph at my shift point. Perhaps some else has an idea.

LG

LG, I've heard from several people that it's possible to change out the gearset in these rear ends without having to swap out the whole axle/rear end. Someone once told me (actually it was the previous owner) that the truck would work well with 3.73 gears. The yoke on the rear end (the part that connects to the shaft) is worn and vibrates a bit under higher speeds, so I think I may have this done pretty soon, to get the rpms down a little. The engine has to rev pretty high on highways....don't know how high...I dont have a tach, unfortunately.

3.90 to 3.73 is not a significant change. I would suggest you find an RPM calculator on the internet and play with it. First you will need to know what tire size your going to be running. Then I'd find a rear axle ratio that would keep the RPM under 2500 and above 2000. I use 2.5k as the limit because that's about where the secondaries kick in on a Quadrajet, and gas mileage drops. Quadrajets are my preference for carbs. The 2k bottom is because the I think with the 283 you should be a little more into the torque curve than a larger sbc.

With the 4spd your options drop a bit for and OD. An OD would drop your rpm by 20-30%.

here's a link to the "Tech Tips" an a rpm calculator;

http://www.stovebolt.com/techtips/calculate_rpm_tire_axle.htm

LG

IMHO
Buying another engine vs rebuilding your 283 is a wash if you are building a stock engine. The costs of a different engine makes up the difference in the extra costs of rebuilding the 283.

So your suggestion is to rebuild the 283? That's what I want to do anyway. I was told that it is the original; engine, but don't really know how to verify that. There is no "V" in the hood where the emblem is, which makes me question the originality. But regardless, for some reason I like the 283 and would rather yank it out and rebuild it than put something else in there.

I'd rebuild it - in fact I've done so, more than once, they're the best V8 GM ever made - the 58 has a rebuilt 283, 060 over, runs like a stuck pig and if they're sound, they don't mind the revs at all, with the stock 3.90 rear I've cruised at 70 for extended periods [3000rpm?] .... bit noisey, but won't hurt the engine

you're right that no V means it was a 6 from the factory, but of course anyone could have chosen the V8 after the fact, being the optional engine - could have even happened at the dealer when the original owner wanted that truck 'right now' but with a V8

the OD trans is a good option for lower revs on the open road, and might be easier to find - certainly easier to install than new gears and would drop the rpm from 3000 to about 2200, the 4 speed is only useful if you plan on crawling around the farm fields in the mud, otherwise it's a 3 speed with an xtra useless gear

Bill

Without reading all the posts, I might be tempted to ask if the 283 has a solid cam. The other thing it could be is loose exhaust, which also gives a very similar tapping sound.

If your gauge is accurate, I think you are due to replace the bearings at a minimum. If you have 12# driving and it increases to 20# when you let up on it, your main bearings are loose. Those little Chevies very rarely give any crankshaft trouble, but anything is possible. You probably could get by with just new bearings. Of course, you won't know until you tear it down.

Also, on the loose nuts on the valve train, you can simply take the nut off and strike it with a hammer to make it tight again.

A 3 speed with over drive is easy to find? Like a 3 in the tree? If that's so, I have the correct steering column, just have to hook it all back up ha ha

Crabbyappleton, do you mean strike the nut itself with a hammer? What does that do, compress the threads just enough?

Yes, it will compress the nut enough that the nut is tight again. I have done this in the past several times.