Rattling noisr 502

[jstwkd]

I have a gen 6 502.When i let off WOT I get this rattling noise from motor any ideas?

[gnarley]

To give idea's we need more info, but from your explaination I bet top end is suspect. You need to post before (cold) & after (warm) info plus different running range data. I see from your profile your in my backyard & a mechanic. If your a mechanic you should know all the trouble shooting methods and what you've done & then share that with the rest of us to get your input. How many hours on the motor? what oil? what hull? weight? drive? oil cooler? stock or modified engine & by who? EFI or carbed?

[Backtanner]

jstwkd:
When i let off WOT I get this rattling noise from motor any ideas?Yeah, don't let off WOT!!
Seriously I would start at the easy stuff. Timing, valve play, etc.

[Liberator TJ1984]

Could be worn timing chain , piston slap...? how many hours on the motor ??? and RPM's when you let off??

[jstwkd]

Gnarley,
Cold warm does'nt make a diff.approx. 2 full hours on motor.vavoline 10/30,89 caribbean,1800pounds,12jg approx. 2 hours on it as well.Some slight modes to pump.
Gen 6 502 hyd. roller,edelbrock 6045 oval ports alum,weind tunnel ram,single hp 950,msd marine system complete,9.6 -1 comp 502 gm specs on short block.
Spinning this set up 5100 rpm AA alum. Imp.Droop and deverter.Played with timing sounds like pinging timing makes no diff.Oil press at WOT is 40 psi no fluctuation,Motor temp is 160 deg.
I have personally never herd anything like it kinda of throwing me for a loop.
My best guess is piston slap or lifters not staying pumped up.
I have checked timing chain.It looks good.I checked for a loose loader its tight.the flex plate has no cracks and is also tight.I have even pulled the intake off and looked at the lifters wile pumping oil thru the motor dint see anything.I was just hopping some one else would have came across this noise before I tear down.
Gnarley where are you located?

[gnarley]

OK now your talkin spec's! Do you know what the lower end clearences are set at? You said 2 hours on it, so is it new or rebuilt? and by who? I would like to know what the piston clearences are what type of pistons, expected expansion on them from the mfg & rods & main clearence if your using 10 weight oil. Do your heads have the rocker bolts on them? I'm in NW SR near Piner HS
[ November 04, 2002, 03:36 PM: Message edited by: gnarley ]

[jstwkd]

OK,Originally I used a crate 502 short block.Wasted three pistons due to lean mixture.Learned something about the correct size fuel line and a Gm fuel switch.Fixed all of that with - 8 fuel line a Huge frikin fuel filter and a manual fuel switch.And a rebiuld to motor.Honestly I didnt think I was running that much power.
The reason I'm leaning towards an oil problem is My cam had these really strange looking wear marks on some of the lobes.Sent it back to comp. cams and they replaced the lifters and polished the cam.Said my lifters were not pumping up.
The motor was rebiult back to stock specs for a gm gen 6 502.Part Number: 12360893
Displacement: 8.2L or 502 cubic inches
Bore/Stroke: 4.446 in./4.00 in.
Engine Block: GEN 6 design with 4-bolt mains and siamesed cylinder bores
Crankshaft: Forged 1053 steel, one-piece rear main seal
Connecting Rods: Forged 4340 steel with 7/16" rod bits
Pistons: Forged aluminum with mini-dome
Compression Ratio: 8.75:1
Camshaft: L29 hydraulic roller P/N 12552296
Valve Lift (Inlet/Exhaust): 0.480"/0.483"
Duration at 0.050" cam lift (Inlet/Exhaust): 204/209 degrees
Cylinder Heads: Cast iron round port with 2.07"/1.72" valves and 118 cc open combustion chamger
Gross Horsepower: 320 at 4400 rpm
Gross Torque: 515 lb. ft. at 2800 rpm
This is what I started with then added the rest.I'm not sure what the clearances were set to I can find out.The heads are studed with comp. cams roller rocker,springs.locks,retainers,stud girdles.etcThe valves are still edelbrock.
The shop is R&R mach.in napa and the pistons are by JE semi closed chamber flat tops.

[gnarley]

OK Now I have a way better picture, but you still need to find out what those clearances are! If its on the loose side with that 10 weight oil it may not be getting enough up top with the stock pump. Also I didn't see what oil pump. Did you assemble it or them? Does it have restrictors in the galley? I'm thinking not, but since you have studded heads with rollers instead of the bolt rockers you should be able to divert some of the oil to the lower end. If my suspicions are correct I think you need the high volume pump & I suspect the bearings are on the loose side hence 10W/30 won't do. I use 50W racing in mine (Mark V 454) & an oil cooler. Prior to the better oil & a cooler it rattled up top after it got warm. How big is the oil pan or capacity?

[jstwkd]

10 qrt oil pan. Ordered a cooler should be here soon.I went with the 10/30 because of the year motor.Stock pump that came with motor. They assembled and no restrictors.should I try a straight 50 before dissasemble?

[powerplay230]

Two things, not answers but questions-
Isn't that kinda light weight oil?
Isn't 40lbs pressure at full throttle low at that temperature?
My carb' 502 runs about 60lbs pressure when 160-170 degrees at higher rpms, but with straight 30 weight. I am in warm water here if that makes a difference with oil weight.
Rick

[gnarley]

I think before I did a tear-down I would try 40 or 50 weight racing But make sure its warmed up good & has temp in the oil before you get into the throttle. The OP just sounds a bit low with the 10 W oil. If you need I might be willing to lend my Mac 6 channel listening aide, it's amplified so you can really zero in on noises :D . I think if you check you'll find that (and I might be wrong) Merc runs a 40 weight oil in it's big engines. I run heaver grade oil in all my big blocks. You might even do a search here to see what others are doing. But if the lower end was assembled a bit loose that 10 weight isn't enough. JMO

[Blown 472]

Are you using a windage tray? did you pull the dipstick right away after you heard the noise to see if the oil is foamed, maybe you are pumping the pan dry and filling the valve covers full of oil???

[Tinkerer]

It sounds to me like colapsed hyd lifters -caused by TOO light weight of oil and low oil pressure. If you arn't running an oil cooler now than that is a big problem. Does the noise go away after you idle down say within 1 or 2 minutes??

[jstwkd]

I do have a windage tray but no restrictors.The noise is only thier at letting off of WOT.Sounds great at idle and while spnning the motor up to rpm even holding rpm no noise until I let off throttle.

[jstwkd]

Also I can not get it to make the noise on the trailer with no load.

[gnarley]

jstwkd:
Also I can not get it to make the noise on the trailer with no load.Because you can't get hot enough??? And what else would the heat affect? I think you might know whats going on.... So What are you going to do to fix it ???

[DUCKY]

40 psi at 5100rpm? OUCH!!!! What is it at idle, 10? I still say you should not run a multi-grade in marine engine. You should run at least straight 30wt in that motor, but in a jet application (under load all the time) I would run 50wt. I use 50wt Valvoline in all my marine engines. You should have at least 10psi per 1000rpm as a bare minimum. 15 per 1000 is better.
if you don't have at least 55-60 psi at wot after changing to thicker oil, I would pull the motor and drop the pan and consider shimming the spring on the oil pumps' relief valve.

[paradigm shift]

jstwkd any new news on what the problem is / was.
gnarley what are you thinking?

[jstwkd]

I have'nt had a chance to look at it yet.Been raining like crazy up here.I'm planing on measuring my pick up hight.I must be pulling air from some where in the system. Also want to recheck my dip stick,make sure it is corect reading.Alos switching to a diff oil

[Blown 472]

If you have the pan off make sure it takes ten quarts and is not over filling and the crank getting into the oil and foaming it, might say ten but eight works and keeps the oil out of the crank.

[gnarley]

paradigm shift:
jstwkd any new news on what the problem is / was.
gnarley what are you thinking?I suspect crank clearence on the big size of .std & with light weight oil & no cooler the oil is overheating & not able to keep the lifters pumped up & causing the racket on the valve train. I could be way off here but I bet heavier single vis oil & a cooler take care of it. I think he did say it ran & sounded fine until it was run at WOT which under load heats the oil a lot!

[jstwkd]

Hey Gnarley, Actually runs fine at WOT its as soon as you let off WOT that the noise shows up.It doesnt sound like a lifter noise to me.Its too deep but I may be wrong.I'm going to check those things.And try to get the oil cooler in.The only other thing I found strange was the clearance of the connecting bar for the lifters.But last time I pulled them out.I found no marks on them.They have .003 clearance from the bar to deck.I may switch back to stock set up to see if it makes a differance.

[gnarley]

Yeah I under stand it runs good at WOT but I wonder do you know how much more the oil heats up as RPM increases to the point of WOT? Drag increases as speed & RPM increase which puts the strain on the motor which in turn heats the oil more & more. Maybe it is deeper inside, and I don't think it's piston slap, I would think you'd hear the pistons specially when cold, thats when expansion is just starting & the slugs are the loosest. I still feel its oil related in valve train or lower end due to the 10wt oil. Before you test I would swap the stock rockers back on install the cooler & put in 40wt oil minimum.

[jstwkd]

Ya I relize the oil is getting hot.You dont think I should look for an air leak.Or check my pick up for the pressure drop in the system first?I didnt realize until recently how hot the oil was getting .I asked questions before but I was told I wasnt running enough power.Or spinnig this thing that high.Plus the motor is exposed so I didnt worry about it.I preety new to boat applications.They're seems to be quite a few differeces between automotive and marine.Thanks for all the help.I will be changing the oil this week I beleive its going to be dry for a couple of days.Which brand oil do you recommend?

[gnarley]

I don't think I'd want to pull it apart & check if I didn't have to. It is possible you could suck air but unlikely, you rarely hear of it happening to anyone. But if the sump & pickup were not checked for heights the pickup may not be low enough in the sump, again possible but not likely. I think the key is the oil cooler & higher vis oil, that I can attest to. I wouldn't even bother taking it out for a test until I had the cooler in it to. For oil I like Valvoline Racing, I use the 50wt in my 94 Mark V 7.4 & it should not be much different in clearance to yours. I just reread this from your 2nd post "Cold warm doesn’t make a diff." maybe it is piston slap if you hear it cold? So let me ask again, you hear it cold? What do you mean by cold? Do you go WOT cold? And for how long? I would say let me hear it but you can only get it to happen on the water right? Will it make the noise at idle after the WOT test? If so I'd pull plug wires 1 at a time while running to see if you could isolate a cylinder or cylinders that might be suspect.

[JEThro]

Travis,This might sound stupid. Are you sure all of the bolts in the coupler between the motor and pump are tight? Jethro

[canuck1]

jstwkd
[QB]Hey Gnarley, Actually runs fine at WOT its as soon as you let off WOT that the noise shows up.It doesnt sound like a lifter noise to me.Its too deep but I may be wrong.Sounds like pump to me. over pressure on the intake side

[powerplay230]

jstwkd,
Did you ever figure out what the problem was??

[jstwkd]

No not yet Been working on house.And garage seems to be getting filled with more crap.
Also spent two days purchasing a new truck to tow other boat.Not fun!I will reply with some info soon.wkd