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Old 08-28-2011, 08:40 AM
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5.7L vortec knocking? need help with stethoscope

Recently I replaced a 305 with a 1998 350 (880 block and 906 heads) in a boat because I didnt realize it had a cracked block when I bought the boat. (yes this has been a nightmare)

The 350 I bought was a long block that never was started up, I received all the receipts for the machine work and parts. Well the guy put a .550 lift cam in the motor so after start up I had valve seal material on top of the heads and a couple Damper springs broken. I replaced the seals and springs and put a ramjet 350 cam that has I believe .450 - .462 lift. This is a roller cam - Hydraulic roller lifters - roller 1.6 rockers

I examined lifters and they seemed fine but I didnt try to push the bore down

end result is I have a small knock and I am curious if the lifters were damaged. I have a stethoscope and if i put it on the rocker arm studs it seems to be the loudest. I don't really get much noise from freeze plugs but I am a novice with the stethoscope and was looking for help??

Thanks for the help
Steve

Here is a video of the motor making the noise
350 engine noise

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Old 08-28-2011, 09:59 AM
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I hear piston slap.
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Old 08-28-2011, 10:54 AM
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I hate to say it, but typically Vortec heads need valve guide mods(machined shorter) for cams with over about .450 lift w/stock 1.5 ratio rockers, much less 1.6 ratio rockers as evident by the valve seal debris you found. The bottom of the spring retainers were probably crashing into the top of the valve guides pretty hard if not catastrophically.
You may have bent all of your pushrods and thats what you hear hitting in the slots in the head or trying to move the rockers sideways? Definitely possible if the previous owner didn't have the guides machined. I'd pull the pushrods and roll them on a glass tabletop to check if their straight. Someone else chime in on this please as I may be full of it!
Did you replace all of the valve stem seals? I'd have a good look at the retainers and locks while I was at it.
Do the heads have self guiding rockers or guide plates. Not both.
Hope he checked valve to piston clearance as well. I would think a compression check would tell if a valve was bent. I'm probably just too paranoid about stuff like that, but after seeing seal debris???
Good luck!
ssmonty
PS I never listened to the video.
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Old 08-28-2011, 11:24 AM
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Quote:
Originally Posted by ssmonty
I hate to say it, but typically Vortec heads need valve guide mods(machined shorter) for cams with over about .450 lift w/stock 1.5 ratio rockers, much less 1.6 ratio rockers as evident by the valve seal debris you found. The bottom of the spring retainers were probably crashing into the top of the valve guides pretty hard if not catastrophically.
You may have bent all of your pushrods and thats what you hear hitting in the slots in the head or trying to move the rockers sideways? Definitely possible if the previous owner didn't have the guides machined. I'd pull the pushrods and roll them on a glass tabletop to check if their straight. Someone else chime in on this please as I may be full of it!
Did you replace all of the valve stem seals? I'd have a good look at the retainers and locks while I was at it.
Do the heads have self guiding rockers or guide plates. Not both.
Hope he checked valve to piston clearance as well. I would think a compression check would tell if a valve was bent. I'm probably just too paranoid about stuff like that, but after seeing seal debris???
Good luck!
ssmonty
PS I never listened to the video.
When I put the lower lift cam in I checked for retainer to seal clearance - coil bind, bent push rods etc.. I also replaced all the valve seals. I just did not really know how to check lifters but they seemed fine?

As far as piston slap or a crank bearing it is possible I dont have any faith that the guy knew what he was doing.

I just pulled a plug wire one at a time with no change in the way this engine sounds. I read that it will determine if it is a rod knock or piston slap but This is my first rodeo.

Last edited by Steveon91; 08-28-2011 at 11:47 AM.
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Old 08-28-2011, 11:58 AM
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I watched the video and could'nt help but notice the vacuum gauge fluctuating at idle or so I thought. I would have though with that small a cam it would have been more steady. Kinda looks like a valve sticking or out of adj. if I'm not mistaken. They make a noise kinda like that when they have too much slack in their adjustment. Did you use polylocks w/set screws? Sometimes(often) they come loose. You did say it seemed loudest at the stud.
I also thought I heard a growling noise kinda like a cam/distributor gear under load. Could the distributor be bottoming out in the oil pump? Do you have a melonized gear on the distributor? I don't know what other accessories you have on a boat that may make that kind of noise?
ssmonty
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Old 08-28-2011, 12:20 PM
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Quote:
Originally Posted by ssmonty
I watched the video and could'nt help but notice the vacuum gauge fluctuating at idle or so I thought. I would have though with that small a cam it would have been more steady. Kinda looks like a valve sticking or out of adj. if I'm not mistaken. They make a noise kinda like that when they have too much slack in their adjustment. Did you use polylocks w/set screws? Sometimes(often) they come loose. You did say it seemed loudest at the stud.
I also thought I heard a growling noise kinda like a cam/distributor gear under load. Could the distributor be bottoming out in the oil pump? Do you have a melonized gear on the distributor? I don't know what other accessories you have on a boat that may make that kind of noise?
ssmonty
I took off the belts so I know that it is not the water pump, alternator or power steering pump. I also pulled the drive.

And yes the vacuum gauge does fluctuate a little bit at Idle

I am not sure about the distributor gear it is a stock GM Steel gear and GM cam. The distributor did come off a 305 and is a thunderbolt 4 ignition if that tells you anything? I did check the coil primary resistance and got 1.9 ohms and suppost to be .6 - .8 but I am using a fluke digital so I am not sure if that is accurate.

When i put the new cam in I thought to my self there was allot of cam walk until I put the cam gear on and that took the slack up is this normal on a roller cam? there is no cam button just a plate that holds cam in

Last edited by Steveon91; 08-28-2011 at 12:26 PM.
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Old 08-28-2011, 01:16 PM
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After installing the cam retaining plate and timing chain cam gear there should be almost no cam walk that you can feel.
Did you use a stock timing chain set? A double roller may be grinding the front of the block if not clearanced. You would see evidence when you change the oil, but it would be too late by then, at least for the chain. I should shut up now.
I wouldn't think you had piston slap on a new build if you have receipts for the machine work. Every time I've had a block bored, they ask for the pistons so they can bore them to fit.
I know its messy, cramped, and awkward, but you ought to try to adjust the valves with the engine running. Get an old valve cover from the salvage yard, cut the very top out of it with a cutoff wheel and be-burr the edge good. Install it in place of yours on one side after the engines been warmed up a bit(easier said than done I know). Start the engine and backoff the 1st rocker slowly (say #1 exhaust) until you hear it clacking, slowly tighten it until it quits clacking. Do it a couple of times until you know just where the sweet spot it quits clacking is. Then slowly give it 1/4-3/4 turn more CW.(I prefer 1/2). The lifter may not bleed down enough for 1/2 turn and hold the valve just off the seat and the engine will run rough, it may smooth out in a few moments time, if not, you may have to settle for 1/4 turn preload.
Then do the #1 intake and so on until you have the drivers side done. Obviously do the otherside. Shouldn't have to worry about adj. the valves again.
ssmonty
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Old 08-28-2011, 01:33 PM
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Quote:
Originally Posted by ssmonty
After installing the cam retaining plate and timing chain cam gear there should be almost no cam walk that you can feel.
Did you use a stock timing chain set? A double roller may be grinding the front of the block if not clearanced. You would see evidence when you change the oil, but it would be too late by then, at least for the chain. I should shut up now.
I wouldn't think you had piston slap on a new build if you have receipts for the machine work. Every time I've had a block bored, they ask for the pistons so they can bore them to fit.
I know its messy, cramped, and awkward, but you ought to try to adjust the valves with the engine running. Get an old valve cover from the salvage yard, cut the very top out of it with a cutoff wheel and be-burr the edge good. Install it in place of yours on one side after the engines been warmed up a bit(easier said than done I know). Start the engine and backoff the 1st rocker slowly (say #1 exhaust) until you hear it clacking, slowly tighten it until it quits clacking. Do it a couple of times until you know just where the sweet spot it quits clacking is. Then slowly give it 1/4-3/4 turn more CW.(I prefer 1/2). The lifter may not bleed down enough for 1/2 turn and hold the valve just off the seat and the engine will run rough, it may smooth out in a few moments time, if not, you may have to settle for 1/4 turn preload.
Then do the #1 intake and so on until you have the drivers side done. Obviously do the otherside. Shouldn't have to worry about adj. the valves again.
ssmonty
OK i will try it I have an extra set of valve covers, and also I did a compression check on each cylinder and basicly they are all between 130 - 150 pounds biggest gap was #1 was about 130 and #6 was about 150

I did research on piston slap and I guess alot of engines have it and it can just be one of those things?

I can get a mechanic that has a Custom engine shop to come out for 50 bux to diagnose the problem. He told me he is really good at it over the phone? Should i spend the 50 dollars?

Yes i did use a stock timing chain and after installing it I was curious if it had a little to much slack in it
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Old 08-28-2011, 02:26 PM
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valve cover

Hi,take that chevy valve cover,and make 1 long cut(lengthwise)then a shorter cut on both ends,then bend up the uncut part of the cover,and it will catch MOST of the oil when youre adjusting the valves.have fun.
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Old 08-28-2011, 02:40 PM
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I would adj. the valves 1st if you had already decided to do it, and see what your results are before calling the mechanic. IMO. You may get rid of your knock.
As far as the growling noise, did you notice if the distributor seemed to sit flush with the manifold before you tighten down the distributor hold-down clamp? It should have come with a gasket. A good check is to try to install it without the gasket 1st to see if it will set flush with the manifold. If it wasn't quite flush you need a/some spacers to lift it up a bit so that its not pushing down on the oil pump drive shaft/oil pump assy.
Was the 305 it came out of a roller cam engine? If it was it was probably the right type of gear, but I think you should always install a new gear with a new cam.IMO
By the way, I'm no pro mechanic. Just a shade tree.
FWIW
ssmonty
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Old 08-28-2011, 03:41 PM
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Quote:
Originally Posted by ssmonty
I would adj. the valves 1st if you had already decided to do it, and see what your results are before calling the mechanic. IMO. You may get rid of your knock.
As far as the growling noise, did you notice if the distributor seemed to sit flush with the manifold before you tighten down the distributor hold-down clamp? It should have come with a gasket. A good check is to try to install it without the gasket 1st to see if it will set flush with the manifold. If it wasn't quite flush you need a/some spacers to lift it up a bit so that its not pushing down on the oil pump drive shaft/oil pump assy.
Was the 305 it came out of a roller cam engine? If it was it was probably the right type of gear, but I think you should always install a new gear with a new cam.IMO
By the way, I'm no pro mechanic. Just a shade tree.
FWIW
ssmonty


Shoot I appreciate whatever you have to suggest Shade tree or ASE certified

The 305 had a flat tappet cam. I just pulled it and took the gasket off and it sits pretty flush with intake , I may put 2 gaskets next time to have some clearance.

Check out this Distributor gear it looks pretty bad and when I take the rotor and move it back and forth there is considerable clanking going on down there! I would say by guess it will move back and forth 3/16 or so.

I happen to have a brass distributor gear for this motor but I thought brass was for billet Cam?

here is a pic
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Old 08-28-2011, 05:55 PM
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Here is my take on the vortec, Vortec motors use a different timing chain then the older motors, so a standard double roller won't fit (http://www.fullsizechevy.com/forum/general-discussion/technical-maintenance/327568-correct-timing-chain-set-96-350-vortec.html} may rub on block or cover. Also are you running a roller cam? Vortec were all roller cam, so if you went flat tappet, did you change push rods or check length? If you didn't and just adjusted valves normally, the angle of push rods will rub the hole in the heads. First mod or vortecs is drill out to 3/8 push rod holes. Also check all the rocker studs, lay a straight edge across, check if any are starting to pull out.

As some noted about cam walk, did the cam and lifter bore get checked? a cam thats off, will limit oil to bearings. Also your compression, back off 1 turn on the rockers and retest, if they come up in number then your bottom end is probably good.

I built a 383 vortec, broke studs, the stock 3/8 studs are weak, ran into the timing chain issue. Also the dist gear was designed for the cam, roller cams are different. The vortec marine had a different distrubuter with gear, so you might have make changes. As long as the motor is not reverse rotation, get a good marine/rv cam, lifters and push rod checker. you will get it going.
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Old 08-28-2011, 06:06 PM
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If you got it to sit flush without a gasket, you should be fine using just one, and it will hold its adjustment better.
With 3/16" of play I would think your timing would be very erratic. Besides it is supposed to be a melonized(hardened) gear for a roller cam. The cam is steel vrs cast iron for flat tappet. Not necessarily billet. I wouldn't use the bronze gear unless it was a billet. They don't last and end up in the oil pan as shavings.
Pace Performance sells GM melonized gears PN 10456413 for old style HEI distributors with .491" shafts for $36.95. Its a slip fit after you remove the roll pin with a punch. If you order one from them you might also ask for a new roll pin to install it. While your at it check the end play(feeler gauge between the gear and the distributor body bushing.) I'm not sure on the spec. I want to say .015"-.020". Maybe someone else will chime in? Hopefully its not too late to put on a new gear to save the cam dizzy drive gear? Should be ok.
You didn't say if you were using polylocks on the rocker arm studs(allen set screws in the middle)? Probably are. I should have mentioned that when I adjust them, I will get the outer body almost where it needs to be, tighten the set screw, then turn both at the same time, just a little, to make it stay tight. I've had them loosen up by themselves too many times unless I do it like that.
FWIW
ssmonty
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Old 08-28-2011, 06:19 PM
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Quote:
Originally Posted by ssmonty
If you got it to sit flush without a gasket, you should be fine using just one, and it will hold its adjustment better.
With 3/16" of play I would think your timing would be very erratic. Besides it is supposed to be a melonized(hardened) gear for a roller cam. The cam is steel vrs cast iron for flat tappet. Not necessarily billet. I wouldn't use the bronze gear unless it was a billet. They don't last and end up in the oil pan as shavings.
Pace Performance sells GM melonized gears PN 10456413 for old style HEI distributors with .491" shafts for $36.95. Its a slip fit after you remove the roll pin with a punch. If you order one from them you might also ask for a new roll pin to install it. While your at it check the end play(feeler gauge between the gear and the distributor body bushing.) I'm not sure on the spec. I want to say .015"-.020". Maybe someone else will chime in? Hopefully its not too late to put on a new gear to save the cam dizzy drive gear? Should be ok.
You didn't say if you were using polylocks on the rocker arm studs(allen set screws in the middle)? Probably are. I should have mentioned that when I adjust them, I will get the outer body almost where it needs to be, tighten the set screw, then turn both at the same time, just a little, to make it stay tight. I've had them loosen up by themselves too many times unless I do it like that.
FWIW
ssmonty
The nuts to adjust rockers are standard lock nuts

I think i need to replace the timing set. after I changed the Dist. gear and started the motor I noticed the knock seemed better ( i made a video) but I also noticed the motor was more responsive. I checked timing with a light and it was advanced quite a bit when i set it at about 8 BTDC is was sluggish again
I am wondering if the timing chain stretched when the .550 lift cam was binding against the valve seals. and also making some noise

After changing dist gear
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Old 08-29-2011, 02:52 AM
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Very possible the Chain stretched. It's suprising that none of the Pushrods were bent.
The RamJet Cam is Billet Steel which is much softer than Cast Iron & uses the Melonized, Composite/Plastic or Brass distributor gear.
Melonizing is kind of like a soft Powder coating over a hardened steel gear.
Brass gear isn't good for a street engine, it wears too quickly and needs to be changed frequently.
Flat Tappet Cast Iron cams use a hardened steel gear which is equal in hardness to the Cam.
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