Vibration: L18: Annoying: Clutch / Pressure Plate / Flywheel?

[datzenmike]

So  SOLVED.

20 posts ago... :lol:

[KoHeartsGPA]

:lol:

 

 

Well....it's solved nonetheless :thumbup:

[Cardinal Grammeter]

UPDATE:  It's sort of solved.  Vibration level varies.  Definitely more vibration when it's cold.  Which leads me back to a weird observation that there was more vibration when I had the upper inner aft control arm bushing that was creaking/stiff/frozen - I don't think that is the case any more but possibly a piece of the puzzle.

 

Won't be looking into this one but might stumble onto something.  What I did stumble onto was my radiator core is leaking like a sieve.  Time to get that L20B radiator...

[datzenmike]

Well, all I can say is engines vibrate. Carburetor engines run roughest when cold and smoothest when warmed.

[KoHeartsGPA]

I'll shoot video of mine at start up and post it here so you can compare.

[Cardinal Grammeter]

The alternator is resonating with a peak-to-peak amplitude of over 1/8" (forward to aft direction, perpendicular to the belt) at the pulley - it could possibly crack something eventually.  I confess I replaced the water pump and I thought I tightened the pivot bolts, but I'll have to check...  However, loose bolts of not, getting an alternator to vibrate like that is no small matter especially when a belt acts like a dampener.

 

It's going to take me a while to get to this since I've got my daily driver all tore apart welding up floorboards for state inspection...  The 620 is now fulfilling it's mission - backup DD (!)

 

EDIT:  Checked and aft pivot bolt is GONE.  My Bad.

[KoHeartsGPA]

Please post a video....

[flatcat19]

SMH. This guy.

[KoHeartsGPA]

[datzenmike]

'74 is an L18. I think the L16/18s only used two bolts to hold the block alternator mount. The bolts sometimes shake loose. My 521 came loose and broke the bolts off in the block. L20B and up engines use a much more stable three bolt set up.

[Cardinal Grammeter]

That's a nice looking engine!

 

I guess I'm being shamed into posting a video.  But there won't be anything to see - only  hear.  Again, shaking is not what I'm talking about - it feels like some rotating part is out of balance.  You can feel various resonances in the body, dash, etc. as you run up the rpm.

[bilzbobaggins]

http://community.ratsun.net/topic/64703-vibratey-little-motors/   Knew I remembered a post similar to this one

[banzai510(hainz)]

motor looks good

[Cardinal Grammeter]

Wow about the alternator bolts coming loose - that didn't happen to me.  A couple days ago I noticed a bolt w/nut and washers beside the kitchen sink.  I couldn't remember what it was from.  What it was, was the rear alternator bolt that was US threads - I was going to get a proper metric bolt.  But I evidently forgot.

 

Or not.

 

Now that the alternator is bolted down tight, I'm back to where I thought I was with the SOLVED reply.  Maybe I did put the aft bolt in and when it fell out, that was when I thought the vibration came back.

 

I will say my alternator front bolt goes directly into a threaded cast bracket - no nut involved.

 

The fact that bolts come loose on the L engines suggests there may be an actual vibration.  When I say vibration, you won't realize it until you put a hand on the engine and it feels like you are touching a concrete vibrator.  (I put the concrete in there to spare the replies (!)  haha - oh snap, I should have said this....)

[flatcat19]

Every one of us have had the alt bolts shake loose...L motors are shaky.

[KoHeartsGPA]

I check just about every bolt and nut in my datto every couple of weeks and the day prior to long drives, some come loose like other people are saying...L series.

[Cardinal Grammeter]

A street racing buddy of mine who recently passed away (I'm 63), his son is in with a crowd of tuners.  They install custom TT's and the Whole 9 Yards. 

 

I mentioned the vibration and the fact that there is no harmonic balancer or balance shaft and he smiled - no wonder it vibrates.

 

I have a theory why I can feel vibration in the vertical direction on the front of the valve cover:  The back of the engine has the flywheel, clutch, and pressure plate.  When rotating, their mass would react any vibration since they will try to rotate around their CG.  This would constrain the rear of the engine.  So any vibration from the engine would present itself at the "free" end, i.e., the front.

 

I also found a thumb-sized hole on the back side, bottom of my radiator.  And while I'm pretty sure I had the alternator aft pivot bolt on my kitchen counter to take to Home Depot and get proper metric size, I maybe have used a temporary bolt for the aft pivot.   So when I said the vibration was back after I said it was gone when I isolated a muffler hanger, it maybe have been when the bolt felt out and someone made it to the fan which may have shot it into the radiator?   Too far-fetched?    NOTE:  Put a tablespoon of Flax Seed in the radiator - buddy found this is a great stop leak.  Fixed his leaky heater core and head gasket on his junky Chrysler mini van.

[datzenmike]

Millions of L series engines have been built and vibration is not a problem on them nor is vibration a known problem with them. So either there is something wrong with yours or you are overthinking a 'problem' that just isn't there. All engines vibrate to some degree. You may simply have a bad cylinder and this will show up as a missing power stroke (one in every four firing of the distributor) and idle will vibrate but it will 'smooth' out more as revved up.

[KoHeartsGPA]

NOTE: Put a tablespoon of Flax Seed in the radiator - buddy found this is a great stop leak. Fixed his leaky heater core and head gasket on his junky Chrysler mini van.

No disrespect....but...that's a terrible idea, anything that says "stop leak" means the product plugs openings....that includes radiator and smaller head water passages, you can actually see this if you look inside a radiator that has been treated with stop leaks and if you ever pull a head of that same vehicle, you will notice the crusty shit inside the water jackets oh the head and even some build-up in the engine block water jackets....

 

Bad bad bad all around.

[datzenmike]

I used 'stop leak' only once. Back flushed the heater core because there was no heat after and a half cup of what looked like dead flies in a coffee colored soup came out. Now I fix or replace when there's a leak.

[Cardinal Grammeter]

I just bit the bullet and put the new L20B radiator and shroud in it w/180* stat.  Not losing water like before, but system isn't pressurizing w/cap on.  Too soon to make any conclusions. 

[KoHeartsGPA]

Make sure to bleed the system...

[flatcat19]

Need cap.

[datzenmike]

Cannot see how air would ever be trapped in an L series head. The thermostat is at the highest point on the engine so air bubbles will rise or be pushed there by the flow from the pump. The thermostat sits flat, so the first time it opens any air immediately flows up and out the upper rad hose forming a void in the rad upper tank. This is why you check the rad after an initial warm up and top it up again. If you have a coolant recovery system probably not needed. Some thermostats are mounted sideways and have a jiggle valve at the top edge. (if installed correctly) This is a small opening that will allow air out.

[Stoffregen Motorsports]

I usually cut the jiggle valve out so the hole is unobstructed. Sometimes I even drill a couple more small holes in the t-stat. Just to keep things flowing even when the t-stat is closed.

 

Aluma-Seal or Silver-Seal are preferred types of stop leak, but only to get you back on the road or for an extended repair. If there's a hole in the radiator, bite the bullet and have it repaired.