How to tell intake and exhaust valve with the intake manifold on?

You normally don't have to adjust hydraulic lifter valve lash after the initial adjustment. Try some Sea Foam or something else made to free stuck lifters before you horse around with this. You could have a bad lifter(s) or flattened cam lobe(s). I put cams and new lifters in a Ford 352 and a Chevy 350. Used the method below, and never adjusted rockers with the engine running. No problems. Start at TDC #1 and work around the valves in firing order per the instructions below. Zero lash means when the pushrod stops turning freely in your fingers as you tighten down the rocker. You should be able to find a picture to sort out intake from exhaust. I think the exhaust is on the left as you face the head, but find a picture. Think hard about what you're doing, and what the actual problem is. I've got the feeling you're wasting your time.

"Hold the phone!! Everyone cover their toes cause I am about to start stomping...... We have covered this many times. Chiltons is a piss poor way to set lash as is the method with the engine running. The only proper way to set lash is one cylinder at a time when the engine is on the stand before it is fired. You set the exhaust valve when the intake valve opens and has about half closed and the intake valve as the exhaust starts to open. What this does is insure that the valve is on the back side of the lobe opposite the ramp. Using chiltons method you have some valves that are actually starting to open. This is especially true for engines with agressive cam profiles. Using the running method you either beat the piss out of the BRAND NEW cam while it is breaking or you let it idle while you set the valves....either is bad.

If you set the valves properly one cylinder at a time you can go

1/4-1/4 turn past zero lash and you are set from now on. I never take the valve covers off of an engine once I have cranked it unless something is wrong and have never had an issue with not having the valves set properly. Chris"

--Vic

With the valve cover off this is VERY easy. Take a look at the exhaust manifold. Notice how there are three sections that bolt to the head? They are almost exactly in line with the exhaust valves. One on each end and two in the middle.

A bad lifter can collapse and cause the rocker to become very loose. It also will NOT repair itself. You need to actually open the engine up and replace/repair the bad lifter. It could also mean that the cam lobe has ground down. The way to check that is with a dial indicator. You place it on a good rocker for the same valve (intake for intake and exhaust for exhaust) and see how far it travels then put it on the ? one and see how far that one moves, it should move almost exactly the same amount (almost because you will have some differences depending on the lifter/lobe wear) Another item on SBCs is that on the older engines with press in rocker studs they can pull out of the head over time, causing a loose rocker and then you need to reinstall it and pin it OR use a screw in stud conversion kit.

What generation is this engine? Or, what year was it made?

You may have a bad camshaft. What year is the engine?

-jim

Hi - all this great info has given me food for thought.

When I tightened the other rockers - it was only a smidgen - like maybe 1/8 turn at most just take a bit of slop out - some I actually loosened a tad. Just to get them sounding quite similar with just a 'little' noise on each thru a garden hose. (I know - I can hear the purists and experts cringing... lol, but I did not know any better)

That one noisy one though I had to turn a bit and now you have me worried. lol.

I think I'll get some Sea Foam and run it through - it may loosen that one and then I can re-adjust. All I can say is that from the limited bit that I drove it - it was a lot smoother for sure....

It is a 1976 corvette l-48 350 smogger - with about 125K miles on it. Never been opened up. FWIW, I usually do my own oil changes and I have never seen any metal grounds or debris in it.....

I'll try the loosening route first with Sea Foam (it sounds like a highly recommended product from what I read on the web) - if no go, then I guess I will have to gird my loins and pull the intake manifold. I am just a weekend mechanic and have never done any heavy duty engine work, so let's try the obvious first - that seems to make the most sense.

Thanks for all the great info - REALLY helpful!

BSA

Bad cams were common in that era - although you would think the bad ones would have been weeded out by now. If it is the cam lobe worn down you should be able to see that valve not moving as much as the others. And if it is a bad cam the clacking will be back fairly soon - they wear pretty fast once they start.

Changing the cam is not that hard and they should still be some available in junk yards.

-jim

LMAO. You are kidding, right?!?! You do not get a cam from a junk yard! Get a new one. Plenty around. If it comes to that, get an RV cam or one above the stock cam. 125K, you should change the timing chain anyway.

Someone that can't dsitinguish an intake from an exhaust valve sure as hell shouldn't attempt changing a camshaft.

Those cams tended to fail because of manufacturing defects. The ones that didn't have the defective hard facing would outlast the rest of the engine.

Any cam you find in the junk yard for this engine will be either like new or junk. It's pretty easy to spot the difference.

-jim

Just because he doesn't know the layout of the valves is not a reason for him to not tackle putting a cam in. Sorry the rest of us didn't come out of the womb as a rocket scientist, like you evidently did.

Your telling me it makes sense to take the time to pull cams in yards in hopes of finding a good one? Your telling me a yard is gona let you take apart a good engine? Your telling me you would buy a good engine from a yard, take it home and rip the cam out of it to put in another engine? All that work and what do you have? You still have a used cam and lifters when your done. And speaking of lifters, you gotta keep them matched up with each lope. Guess your gona tell him to use the timing chain that came out of the yard also?!?! Cam and lifters for small blocks are not expensive. For christ sakes use your head!

What does knowing the year of the engine have to do with diagnosing a bad cam?!?! I have a 300hp 350. It doesn't run right. It's a 1969. Can you tell me whats wrong with it? lol

What does knowing the year of the engine have to do with diagnosing a bad cam?!?! I have a 300hp 350. It doesn't run right. It's a 1969. Can you tell me whats wrong with it? lol

****** I think what he was getting to was that some years and models of engine have known problems with cam wear, lifter stud slippage, etc.

The OP's symptoms COULD come from a bad cam lobe, but that is not the only thing that would cause his problem.

At least, that was the way I interpreted his post.

You are guessing it would be difficult. I've stuck several bone yard cams in small block chevys.

He can buy a new cam and lifters if he wants to spend the money, but the engine isn't likely to last any longer.

-jim

Well - I have been reading the updates here.

Where I am now is that I took the most logical route and that was to stuff some Sea Foam in it. I also cleaned up the ignition to see if it would cure some of the roughness.

I have only done a few miles in it. There is a still valve noise, but it "seems" a little less severe. I will drive it for a bit and then pop off that valve cover again and check to see how far down the nut is WRT to the others and touch up the adjustments as best I can based on the info here and see where we are then. I think the nut travel was much the same from recollection, so it may be at the end of the day that It will only need adjusting after the Sea Foam does it's work. Time will tell I guess. That's the best, at the worst new cam, etc. Moderate would be new lifters... but one step at a time.

I note the dissertation about cam shafts. Always an unpleasant possibility, but it actually runs a little better now, so I have my fingers crossed.

If I do have to go to the trouble, I certainly would not put in a used cam, lifters, or timing chain - I mean what's the point of that? The differential in the cost of those parts (used vs new) is far offset by the time and effort involved. AFAIK those parts are readily available new.

Keep you posted.

BSA

PS. "someone that can't dsitinguish an intake from an exhaust valve sure as hell shouldn't attempt changing a camshaft. " - You could very well be right, and I probably would not tackle it because of time and equipment. But please don't mistake unfamiliarity with stupidity. (at least I am not afraid to ask, and I do know how to spell "distinguish"). lol.

On Fri, 08 Apr 2011 21:20:35 -0500, jim wrote:

New cams and lifters were pretty cheap when I did mine. I wouldn't buy any worn mechanical part from a boneyard unless I could mike it to new specs. Besides, this stuff has a tendency to snowball. On an old engine if you replace a cam, you start thinking about the cam bearings. Then the mains and crank seals. On my 352 I decided to do it all at the beginning, because I had the desire and energy, Big job if you DIY unless you're half machinist and have a good shop. I had my garage floor and rented an engine hoist. I took the crankcase, crank, rods and pistons to what they used to call a "speed shop" around here. They tanked the crankcase, polished the crank, miked everything, installed the cam bearings, and sold me the cam and bearings that fit their miking. Think the cam had a bit more lift. About 30 bucks IR. But that's 1975 dollars. Mains were different than original because of crank wear and polishing. Rings were different than original due to bore wear. I did the ridge reaming and bore polishing myself. Heads were reworked at another shop. It all came together fine except the head shop screwed up the guides or seals so I was sucking some oil. Not too bad and I lived with that. Just pissed me off. Probably had $12-1500 hundred in parts and shop work. And a whole lot of labor by me. It's a serious endeavor unless you really enjoy doing it. I don't regret it, but once was enough. My 350 had the about the same miles as the OP, maybe less. Hard to say since it was a rebuilt. Found the sticker on the crankcase. A major rebuilder but I can't remember the name. This was about 1990. A valve went bad so I pulled the heads, took them to a shop. The shop told me one of the heads was a 305 and recommended they get a boneyard 350 head and work that. Anyway that all went okay. I put new lifters in. Cost maybe $500 total and a lot of labor from me. Three months later a rod started knocking and I junked it. Rust was overcoming it anyway. My bottom line now for valve train or lower end issues is either junk it or buy a crate engine if you want to keep the car. But I don't really trust rebuilts either, since I had a bad one. I had my mech put a Targetmaster 307 crate engine in my son's car about then years ago, but that's a new engine with a good warranty. As soon as you start pulling heads for anything but a gasket you've got a good chance of going backwards moneywise. That's just my view. Usually rust has almost destroyed a car here before an engine becomes an issue. A fiberglass Vette is a different issue. Should be answers on a Vette forum. I hope that Sea Foam works for the OP. I've freed up sticky lifters on old V-8's before. Think I used "Engine Flush" products. Those were beaters, and I'm not recommending that. Not even sure about the Sea Foam. Think I used it for injectors once, Didn't work. I needed new injectors. You can find all kind of stories on the internet.

--Vic.

Don't recall how you located the noise and whether this applies. But one time I was *sure* I heard a bad or stuck lifter. When I examined the sound up close I found it was a leaking exhaust donut gasket.

--Vic

There wasn't the slightest implication of stupidity, although after reading your latest complaint (quite apparently you're also wholly unable to recognize the incorrectly sequenced letters in an obvious typo), in addition to your original plea for help (and advising a novice not to tackle a camshaft replacement on an SBC without available, onsite, experienced assistance, IS in fact help of the first order), I can readily understand how and why you might very justifiably and understandably be senstive. about an issue of competence.

But if in fact your otherwise empty, miserable existence is so conspicuously impoverished, wanting and devoid of actual meaning that for it to afford you any value whatsoever you desperately resort to cruising newsgroups (while solciting assistance, no less) for perceived errors in spelling, grammar, diction or punctuation (therewith providing your sole raison d'etre), in a pathetically feeble attempt at mocking those that would strongly discourage you from making a likely critical error, far be it from me to deny you that crucial perquisite ;^)

Best of luck to you, given your approach and personality, you're going to sorely require all you can possibly muster.

The point would be to save some money and frankly I suspect that unless you are willing to pay somebody who is competent to rebuild this engine you are probably not going to end up with a nice running engine no matter what you do. So I suggest not spending too much money on this 'learning experience'. Since either way you will likely end up with more or less the same result. I Personally put 200k additional miles on a cam pulled from a SBC engine. The donor engine was said to be worn out (burned oil).

Using aggressive solvents dumped into the crankcase will often do more harm than good. If you want to clean out a sludged-up engine just change the oil and filter every 100 miles until it is clean.

-jim