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Unread 07-02-2014, 08:21 PM   #1
gpcl16
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1988 FSJ Wagoneer 
 
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Clattering when hot

Just recently finished a rebuild for my '88. It runs okay, but I'm getting a clattering noise when the engine is fully warmed up, i.e. run for at least 15 minutes. It does not sound like lifter ticking, more of a bad clattering noise that follows RPM and gets worse at higher RPMs. It seems to be coming from the passenger side valve cover but I honestly can't tell for sure. Seems like maybe the valves have too much clearance when they warm up??? Doesn't valve clearance usually go down as the engine warms up???

I thought perhaps the 10w-30 I was using was thinning out and not getting enough oil to the lifters so I changed to 20w-50 with a bottle of Lucas oil stabilizer and not much of a change. I'm also running a bottle of lucas break in additive.

The engine had 191,000 miles and had never been apart. It was surprisingly clean inside. I did find a flat cam though. I went .030" over and went for a pretty stock rebuild besides using a Melling Torque Cam. The valve seats and valves cleaned up nicely and easily so I only took about .008" off the valve stems. The cam and lifters specified an installed height, which was right on the money when I assembled the heads. I don't have too much experience with checking the lifter preload but it seemed like the pushrods were about in the middle of the lifter.

I torqued all of the rocker arm bridges to spec. Does that need to be done with the valve on the base circle of the cam, because I just torqued them all down with the engine in one position.

Anyways, any advice is appreciated. Thanks!

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Unread 07-02-2014, 10:33 PM   #2
super98lsc
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1999 WJ 
 
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Sounds like ignition timing. Back off the total timing a few degrees. 3-4 and test. As the engine heat soaks over advanced timing will cause detonation and destroy the engine. What's your base timing and total timing at? A short duration cam will (typical for a torque cam) will bleed off less cylinder pressure making the dynamic compression ratio higher. That combined with the .030 overbore, any milling of the deck and heads and or thinner head gaskets can add static compression which of course also adds to the DCR. Might also dump a bottle of octane booster and top it off with 93 octane and see how it runs. I would keep total timing at no more than 32 degrees until you have it all sorted then experiment with more depending on your altitude and jetting. A lean mix will detonate easier than a rich mix etc.
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Unread 07-02-2014, 10:48 PM   #3
XJTexas
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Quote:
Originally Posted by super98lsc
Sounds like ignition timing. Back off the total timing a few degrees. 3-4 and test. As the engine heat soaks over advanced timing will cause detonation and destroy the engine. What's your base timing and total timing at? A short duration cam will (typical for a torque cam) will bleed off less cylinder pressure making the dynamic compression ratio higher. That combined with the .030 overbore, any milling of the deck and heads and or thinner head gaskets can add static compression which of course also adds to the DCR. Might also dump a bottle of octane booster and top it off with 93 octane and see how it runs. I would keep total timing at no more than 32 degrees until you have it all sorted then experiment with more depending on your altitude and jetting. A lean mix will detonate easier than a rich mix etc.
All very good advice!!!
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Unread 07-04-2014, 10:59 PM   #4
gpcl16
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I seriously doubt that it's a spark related knock. The noise happens at all times, regardless of load. It even happens in park when revving the engine. My timing is set at 12 degrees with vac disconnected. The noise seems to be running at crankshaft speed. I'm thinking piston slapping???
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Unread 07-04-2014, 11:45 PM   #5
super98lsc
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Piston clatter will be worse cold until the piston expands to the bore then it will quiet down or go away completely. If it's and exhaust leak use a piece of 1/2 diameter hose as a stethoscope and run it along the header gasket. May be one cylinder leaking clacking away. Pull a rocker and check the lifters. Fire it up for a second with the cover off you will know which one it is in seconds if it's a lifter/rocker/cam lobe wiped out. (Hopefully not)
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06-Corvette z51-6spd,b&b,K&N low miles.
77-Corvette Stingray 496 BBC/TH400 built 667hp+
===================================
00 WJ 4x4, 4.7 stroker, turbocharged,..lots more..
01 WJ 4x2 4.7v8 Limited (needs valve job)
90 Grand Wagoneer 401 Edelbrock Heads, Lunati .510/.527 FT Cam, Edelbrock RPM Air Gap, Holley HP 750, Thorley Headers, HEI, Electric Fan w Digital controller,4" lift 31x10.50 Goodyear Duratrac's on Pro-Comp Wheels,new interior, seats,seals,Alpine and JL full system, Remote HEI, Clifford 2 way with remote start,windows,tailgate.
96 Cherokee Country 4dr/2x2 White/Tan 3" Lift Sahara 18" Wheels 32.5"'s 99up head and intake- for sale soon!
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Unread 07-05-2014, 01:40 PM   #6
XJTexas
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Might want to check your flex plate bolts also!!! These get loose and can sound similar to a piston slap or rod knock. Pull the lower bell housing cover/access plate and see if they are loose. Normally sounds like it is coming from behind the starter. Hope this helps & you find your problem soon.
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Unread 07-05-2014, 08:26 PM   #7
carnuck
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^This. You'd be surprised how many "blown motors" were just the cover being hit by converter bolts!
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Unread 07-05-2014, 08:28 PM   #8
XJTexas
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BTW:

I always set valves on TDC for each cylinder to ensure the valve train is on the base circle of the cam lobe for that cylinder. Might want to recheck your valve settings also.
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Unread 07-05-2014, 10:19 PM   #9
super98lsc
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Flex plate bolts good call. Been there man that is a sick feeling then you find the flex plate cracked or the loose bolts and rejoice rofl.
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===================================
00 WJ 4x4, 4.7 stroker, turbocharged,..lots more..
01 WJ 4x2 4.7v8 Limited (needs valve job)
90 Grand Wagoneer 401 Edelbrock Heads, Lunati .510/.527 FT Cam, Edelbrock RPM Air Gap, Holley HP 750, Thorley Headers, HEI, Electric Fan w Digital controller,4" lift 31x10.50 Goodyear Duratrac's on Pro-Comp Wheels,new interior, seats,seals,Alpine and JL full system, Remote HEI, Clifford 2 way with remote start,windows,tailgate.
96 Cherokee Country 4dr/2x2 White/Tan 3" Lift Sahara 18" Wheels 32.5"'s 99up head and intake- for sale soon!
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Unread 07-06-2014, 04:00 PM   #10
XJTexas
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Quote:
Originally Posted by super98lsc
Flex plate bolts good call. Been there man that is a sick feeling then you find the flex plate cracked or the loose bolts and rejoice rofl.
I wasn't so lucky on my 2001 XJ ;-(

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Unread 07-07-2014, 11:51 AM   #11
gpcl16
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Thanks for the advice. I'll check out those things. Will probably be a few days before I have time for it though.
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Unread 07-23-2014, 07:04 PM   #12
gpcl16
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Sorry have been slow to update. I took my jeep in the other day to have a more experienced pro diagnose the noise. First of all, the noise seems to be crankshaft speed, bottom end, and coming from the front end of the engine (which likely rules out a cracked flex plate or torque converter bolts). We did a power balance test and determined that cutting cylinders made no difference to the noise, so a rod bearing, piston pin, etc are unlikely as well. His professional opinion is that the front main bearing got wiped out somehow. Next step is to pull the oil pan and remove the main bearing cap to inspect and plastigauge the front mains, and the others as well. I will definitely pull the inspection cover and check the bolts as well though before pulling the oil pan.

If the only problem is indeed the front main bearing, I'm considering buying a bearing set and replacing it in the jeep. I know it's generally best to just pull the engine and do it right but the engine only has about 75 miles on it since the rebuild, and otherwise runs great. I had the crank ground 10 under while it was apart. And I'm honestly not very interested in pulling/reinstalling that engine again... Has anyone attempted to replace main bearings without removing the engine before. I've been told that it can be done. Can you just loosen the main and rod bearings and fish the bearings out? Does the timing set/ torque converter need to be disconnected?
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