I've got my carb adjusted and engine (350 SBC) timed at 12* initial and it seemed to run great, good vacuum etc. After running it its developed a ticking/knocking that almost sounds like a spun bearing. I disconnected each plug wire individually while the engine is running to see if the sound dies down hoping to rule out rod knock. The sound persists. I then was wondering if the engine was detonating so I hooked the timing light up and the timing is bouncing all over the place. I checked the timing chain for stretch by pulling the distributor cap and watching how many degrees the crank would rotate before the rotor would move. The crank rotates about 5-6 degrees. Could this be a source if the problem? I have a new chain, I just don't want to tear things apart in vain. It's only a cheapo motor that I got until I can afford to rebuild the engine that I really want to install. I don't want to spend a lot of money or chase my tail fixing this thing but its been a great learning experience so I'm willing to do the work that needs to be done. I'm getting closer, but this engine keeps fighting me lol! Posted from the TJJ App for iPhone & iPad
I should add that the oil still looks clean. The oil pressure seems to be between 30-45# regardless of rpm. Posted from the TJJ App for iPhone & iPad
Is the ticking possibly in the distributor locations? any chance something broke off inside the dist?
I reciently bought a truck that has a 454 chev. the timing was flucuating so much is sheared the teeth off the starter drive. I wiggled the bottom pully back and forth. lots of slop. I pulled the timing cover and it was clean inside no sludge . the timing chain was one of those cheap roller chains looked like new but had plenty of slack. I replaced it with a stock link belt timing set and it runs like a champ. My youngest son everytime he gets a chevy V8 in a vehicle that he is going to drive will put a new timing chain, fuel pump.,thermostat and water pump on it. If the timing chain is one of those nylon gears and it is coming apart he will pull the oil pan and replace the oil pump too. if he finds any metal shavings in the pan he changes the rod & main bearings. OldWolf
You need an oscilloscope! That sucker would be on my Counsellor II scope right now. Are the noises lighter/higher ( like valve noise) in engine or heavy/lower in the engine (not good)? 5 or 6 degree slack in chain sounds ok to me. Did you check correct way? Rotate crank c/w until pointer is at end of timing scale. With dist off turn crank c/cw until rotor moves. Sometimes takes two people. Brand new chain has slack in it. Somewhere around 10 or 12 degrees you worry. Do the noises change with load? Are the plug wires on correctly? 18436572? Pull one or two plugs, deposits on plugs that would glow and fire mix prematurely?
It doesn't sound like its coming from distributor. I've had the dizzy in and out and all the gears etc. look good Posted from the TJJ App for iPhone & iPad
The noise sounds like its coming from mid crank case. Almost a ticking sound but more pronounced. I've gone over the plug wires everlasting times. Checked lifter preload a couple times. I checked stretch in the manner you described. Plugs are new and look ok. Could open lakes headers replicate an exhaust leak sound? Thanks for the advice so far Posted from the TJJ App for iPhone & iPad
HEI BIG CAP Dist? Or what ignition sytem? Points or what? Vacuum advance? With cap off, grab rotor turn the only way it will turn and release? That's mechanical advance. Does it turn a few degrees and snap back(good). Or does it not turn or turn hard and not snap back?(bad). If it has vacuum advance try disc temporarily and see if noise or timing scatter changes.
Stock vacuum advance with pert tonic. I took it all apart and cleaned and lubed everything. No play and advance weights seem to snap back Posted from the TJJ App for iPhone & iPad
Does the timing bounce around or is it more like the rolling picture on an old tube TV? Had a Pertronix go bad, I suspect from grounding each plug in search of a bad cylinder. Ended up being a bad valve and reinstalled distributor in new motor, then noticed the erratic timing when I hooked up the light. Also had solid core wires but worked fine till I started shorting plugs.
Difference hot or cold? Once in awhile I'll see bad ground through dist. It's supposed to ground through the base. The Pertronix unit grounds like that. You can temporarily add a redundant ground (I use jumper cables) from dist housing to bty ground. Another possibility is low voltage to coil/ Pertronix. Time to go back to basics. What IS the vacuum reading at idle? Should be 17"hg or better unless you have big cam. Is the needle steady? Slow hunting is OK but FLICKING needle means you've got bigger problems in valve train/ head gasket. Check timing like this. With vacuum advance dis. What is timing at idle and what is it at say 2500 RPMS? Should show advance around 10 or a liitle more degrees plus initial advance. Reconnect vacuum advance and at 2500 rpm what is total advance? Around 35-40 ish? If all timing works should have three numbers. Initial. Initial plus mech. And initial, mech plus vac advance. What is charging system voltage? Should be around 14v on 12 v system. Wrong voltage can cause erratic ignition. Compression check can never hurt. If you use your ears you can hear the starter working against compression on each cylinder. If one grunt is missing you've got a low hole. Deposits on pistons and valves can cause uneven cranking hot and pinging when you drive. You can only do so much at home without diagnostic tools. Once you run out of ideas and no willing outside help it's time for a professional. I'd charge $90.00 for "the works" on diagnosis--scope, infrared, electronic compression check, vacuum guage check,timing set, smoke check intake for leaks, boroscope in cylinders for a closer look. Test drives, etc. There's gotta be someone there near you that's qualified that you can trust.
I'm getting about 20" vacuum at idle. Timing is set at 12* idle and I think in getting 34 ish all in but it's hard to read. I will try grounding. My old SW volt meter is reading about 12.5 volts. Thanks Posted from the TJJ App for iPhone & iPad
In my experience, if a timing chain is ticking, you can put the broomstick (or screwdriver) on the front cover and hear the chain hitting the front cover.....if it is a loose chain, it can wear a hole thru the cover OR jump the timing gear....if the ticking isnt on the front cover, it is something else.
Cranked it back to take out slack then marked the location and cranked clockwise. Posted from the TJJ App for iPhone & iPad
^^^^^ I see I'm too late, but F it, I'll leave it posted. X2 on this reply. You need to rotate engine one direction (normal rotation) till rotor turn's, then rotate the crank the other direction. Please note !!!!!!!! this is done manually and with no power to the ignition system.
Does anyone think its worthwhile changing the chain and gears at this point? Posted from the TJJ App for iPhone & iPad
Sounds like an exhaust leak rather than a bearing. Check the manifolds for black soot marks and bolts for tightness.
Yeah, those old scopes are worthless. British used them to quickly diagnose WWII Spitfires and defeated the Luftwaffe. You know better...
I've read and even commented already but this comment I quoted stand's out and 5 to 6 of chain slap should not being doing this. How old is your Cap on the distributor? You may have a carbon track or tracks causing a detonation that sound like a knock.
New cap, rotor, coil, wires and plugs. Another thought; could the harmonic balancer be slipping dramatically? I redid the timing marks on the balancer with a piston stop and a new timing tape. Posted from the TJJ App for iPhone & iPad
Well listening for engine noises with open headers is pretty difficult at best. You say your noises seem to be mid block just afew inches away from the open headers ???? Chain slap can be heard thru a screwdriver or broomstick on the cover. Almost any noise can be hunted this way. 5-6 degrees or crank vs rotor rotation isn't a whole lot, but I supposed theoretically that can lead to timing bounce of 5-6 degrees although I've never seen it. What I have seen be responsible for timing bounce absent pnvious chain stretch is worn distributor parts. Bushings on the shaft, weights with oval holes, pins with grooves, a flakey vacuum can, poor quality brand new caps and rotors. And on the obscure, worn oil pumps that load and unload the drag. ( ps on chain stretch, from the very first revolution of a new chain, it begins stretching and continues until it is replaced of fails.)
If you had this problem ,, Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” What might your timing light show ?
Engine is pretty stock with bolt ons. No crazy cam or anything. Vacuum is around 20" at idle Posted from the TJJ App for iPhone & iPad
Your comment about the oil pump is intriguing, my oil pressure seems to stay within 30-40 psi regardless of rpm. Posted from the TJJ App for iPhone & iPad
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