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Engine Vibration High RPM
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taylorb1
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PostPosted: Mon Mar 03, 2014 9:12 am    Post subject: Engine Vibration High RPM Reply with quote

My quote "rebuilt" 1776 in my 72 bay window feels like its going to explode at higher rpm. The whole bus shakes and roars. Im not sure on exact rpm, but in 4 th gear it doesnt feel nice going over 57 mph. It still has power left but it feels and roars as if its going to explode.

The tires are 205's, and the trany is also quote "rebuilt" grinds going into 3rd but thats a rant for another time. First gear is like a granny gear and this engine has 0 problems starting in 2nd gear.

The engine is 100% fresh. Doest leak a drop of oil, and you can see the fresh seals. However it has a fair amount of enday, and what im asuming are cam and lifter flakes in the oil because they are magnetic. Here are my thoughts (the cam is on its way out, causing valves not to open all the way so the exhaust gasses cant exit at high rpm. Thus causing the shake and roar).

Please give me your oppinions. It has a single webber progressive with a 009 running regulat low grade gas.
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cbeck
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PostPosted: Mon Mar 03, 2014 9:33 am    Post subject: Reply with quote

Does the engine do the same thing at the same rpm while in any other gear
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VWporscheGT3
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PostPosted: Mon Mar 03, 2014 9:47 am    Post subject: Reply with quote

was the crank reground? it might have needed to be rebalance if it wasn't. any time material is taken away from the crank it can cause a imbalance. were the pistons new? were they weighed ? there are a lot of details engine wise that can cause this vibration. but if your only seeing it in 4th it may very well be vibration and imbalance magnified through that gear set...


all speculation on my part
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taylorb1
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PostPosted: Mon Mar 03, 2014 10:15 am    Post subject: Reply with quote

Its every gear. And yalls guess is better than mine on whats in this engine. The out of balance crank makes sense, and we can assume that has caused the endplay issue aswell. Idea
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Boolean
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PostPosted: Mon Mar 03, 2014 10:43 am    Post subject: Reply with quote

Sounds bad. Dont drive it until the fault is found.
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PostPosted: Mon Mar 03, 2014 3:39 pm    Post subject: Reply with quote

clutch,pp,flywheel,pully.loose, broken ,damaged,dead. cam,lifter,piston,carb issue.find out or pay for whatever it takes out
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PostPosted: Mon Mar 03, 2014 4:55 pm    Post subject: Reply with quote

mark i love ya brother but sometimes you make no sense what so ever. maybe a little bit more explanation on your post might help things
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vugbug68
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PostPosted: Mon Mar 03, 2014 5:22 pm    Post subject: Reply with quote

how much end play? I'd say that is a good place to start
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rockurob Premium Member
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PostPosted: Mon Mar 03, 2014 6:07 pm    Post subject: Re: Engine Vibration High RPM Reply with quote

Quote:
The engine is 100% fresh. Doest leak a drop of oil, and you can see the fresh seals. However it has a fair amount of enday, and what im asuming are cam and lifter flakes in the oil because they are magnetic. Here are my thoughts (the cam is on its way out, causing valves not to open all the way so the exhaust gasses cant exit at high rpm. Thus causing the shake and roar).


The excessive end play is not good...should of been corrected before the engine was installed....but you state you eng is 100% fresh....did it do this on the very first test drive?? or progressively getting worse ??....

I am sure you have already checked your fan for a grease rag ?

FYI, one can run an engine with out vibration with totally unacceptable amounts of crank end-play(needing a line bore w/thrust) and not have a vibration or leak oil....been there, done it....had to adjust the clutch free-play very loose....so not to push the crank too far when en-gauging the clutch.....so engine would not make knocking noise, Rolling Eyes .....drove to Dallas from Okla City and back...exceeding the speed limit....then to Denver and back....same speed limit issue....and then drove for about a year.....replaced with fresh engine....then sold the car.....still have the old engine in my core pile.....(what an engine and what a flywheel seal)
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taylorb1
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PostPosted: Mon Mar 03, 2014 6:21 pm    Post subject: Reply with quote

I think its done it the whole time. And ill try and measure the endplay, it makes a nice clunking sound when warm. When cold, its a faint clunk.

I got this particulat bus about 4 months ago. The tranny is a 3 rib. Should it have this low of gearing?
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rockurob Premium Member
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PostPosted: Mon Mar 03, 2014 8:51 pm    Post subject: Reply with quote

From reading your first post:
guess you purchased this about 4 months ago, but you did not do the rebuild....for you mentioned the fresh looking seals.....so you really do not know what? how this engine was rebuilt.......???

I speculate you are going to have to pull and tear down to determine'
what is wrong.....for knocking/clunking noises combined with the vibration and junk in the oil ?????
does not sound like it is going to get any better. When pulled, start at the flywheel first....then go from there

pending if you have the orig tranny.....here is a link to the gearing....which
is low:
http://www.thesamba.com/vw/archives/manuals/72bus/72II-83.jpg
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mark tucker
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PostPosted: Tue Mar 04, 2014 1:28 pm    Post subject: Reply with quote

possiability's.start with the easyest,I also forgot plug wires&cap and rag in fan.
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Quokka42
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PostPosted: Tue Mar 04, 2014 1:48 pm    Post subject: Reply with quote

I think you have nailed a couple of issues. Firstly, if you can detect the endplay easily on the assembled engine it has too much. From the sounds of things your bus is geared too highly for your driving requirements and an unbalanced engine with non-counterweight crank.

So, I'm afraid our little astronaut friend is right and you should pull the engine down and have a look. Check all the bearings and if it needs a line bore, as it sounds like it was assembled by a backyarder, Purchase a crank with counterweights - either welded onto a stocker, or a cheap way out is one of these little 74 or 76mm cranks. If the rest is OK have it all balanced, then re-assemble with new bearings. Be warned that one thing backyarders do is just assume the pistons and rods are all the same weight so this will add to your balancing costs.
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