Question about engine balancing?

[1BAD68]

I'm not sure if its just me being paranoid but when my engine is running it has a shake that doesn't seem right.
I had the entire rotating assembly balanced but I'm wondering if its just me or if something isn't right.
Its a very consistant "da da da da da da da da da" shake, it doesnt make noise and doesn't seem like the typical shake from a lumpy cam.
I can feel it in the steering wheel and its constant through the rpm's up until about 2500 when it goes away.
Is there a way I can determine if its a balance problem?

I'd post a video of it but its colder than you know what here and I dont want to fire it up until it gets above freezing.

[Musicman]

Just a small bit of clarification.... It does this all the time right?... Whether your Parked in the yard or out on the road.

[mally69]

 

[1BAD68]

I haven't driven it yet but it does it while idleing in park or neutral and in gear (automatic) and its steady as the rpm's change until about 2500 rpm then it seems to smooth out but I'm not positive, it may just be vibrating so fast that its unnoticeable.
It might be normal but it just seems like if you have a wheel out of balance and you feel that constant da da da da da da da, its like that.

If the crank is out of balance, wouldn't the vibration get worse at higher rpm's to the point of destruction?

[beedees]

Just to satisfy an old geezers' curiosity, what engine do you have? Lots of possibilities there.

[1BAD68]

its a 318 with a 390 stroker kit

[beedees]

Hmmm, you need to to start by eliminating possible external sources. Disconnect fan belts,  alternater etc. If you know, how was the engine balanced, with the harmonic balancer you have on there now and with a weighted flex plate or convertor.

[firefighter3931]

Does the torque converter have weights on it ? Is the Dampner for an internal balance engine ?


Ron

[Musicman]

  Yeah that...

[firefighter3931]

Yeah that...

Who ya callin stupid there musicman 

[Musicman]

Hey... a slap on the knot is one thing, but that kick in the ba**s really hurt   

[1BAD68]

Its internal balanced, I checked all the belts and they seem fine.
I'll have to start it up again and check for any misfiring but it seemed to be running fine.

[firefighter3931]

Its internal balanced, I checked all the belts and they seem fine.
I'll have to start it up again and check for any misfiring but it seemed to be running fine.

Ok, i'll ask again....what harmonic balancer is on this motor ? Stock ? aftermarket ?

What torque converter ? Does it have weights ?



Ron

[1BAD68]

oh sorry, its a stock damper and stock TQ (no weights)

[firefighter3931]

oh sorry, its a stock damper and stock TQ (no weights)

Assuming the stock balancer is still in balance then you will be looking elsewhere. 

Keep us updated. 



Ron

[1BAD68]

ok, I have video...
http://www.youtube.com/watch?v=H0_g9h3SL3Y

If you listen closely you can hear a strange sort of fluttering pop every once in a while, also you can see what I'm talking about with the shaking.

[1BAD68]

and this is what happens if I punch it...
http://www.youtube.com/watch?v=Jf3rmPwABR8

what is that, a timing issue?

[1BAD68]

here it is from the rear...
http://www.youtube.com/watch?v=fPxu2uxgHpE

you can hear that fluttering at high rpm through the exhaust.

[ChgrSteve67]

 

I would start with your timing.
What is your idle timing and timing at 2500 RPM?

Your carb could be running lean but I would start with timing.
IF you don't have a good advance timing light go buy or borrow one.

Steve (no expert but got done fighting a similar problem)

[NorwayCharger]

I would start with your timing.
What is your idle timing and timing at 2500 RPM?

Your carb could be running lean but I would start with timing.
IF you don't have a good advance timing light go buy or borrow one.

Steve (no expert but got done fighting a similar problem)

Let´s hope it´s not a wiped cam lobe
It sounds like its running on 7

[ChgrSteve67]

It could be a bad wire, plug or cap.
Those are easy enough to check but I would still start with timing.

[superduperbee]

I would start with your timing.
What is your idle timing and timing at 2500 RPM?

Your carb could be running lean but I would start with timing.
IF you don't have a good advance timing light go buy or borrow one.

Steve (no expert but got done fighting a similar problem)

Let´s hope it´s not a wiped cam lobe
It sounds like its running on 7

I agree, check the cam, also check the valve springs if the cam still looks good, could be a weakened/cracked spring[happened to me before]mine popped through the exhaust.  Ray

[1BAD68]

I checked the wires, I pulled each one and three of them made no difference when idleing.
I put the timing light on each wire and they all seem to be working so I ohmed them and they checked out ok, but why would three of them make no change in rpm when pulled?
So for now I'm just going to replace them and the dist. cap.
It does seem like its running on less than 8 cylinders though, it would make sense with the weird shaking.
Timing is set at 13 degrees at 1000rpm and 25 degrees at 2500rpm. I think that should be close to where it wants to be.
I haven't checked the cam, I'm going to try changing wires and cap first to see if that makes a difference.

[firefighter3931]

I checked the wires, I pulled each one and three of them made no difference when idleing.

That usually indicates that the cylinder is not firing for whatever reason.

Looking at the video it does sound like the engine is misfiring. It could be timing or something mechanical. I would start with a wet/dry compression check to rule out anything mechanical.


Ron

[l8rg8r]

ok three plug wires made no difference but they check out as fine sounds to me like fallty cap or fallty plugs I would say cap

[ChgrSteve67]

yep move on to plugs, cap and compression checks.

[Steve P.]

I checked the wires, I pulled each one and three of them made no difference when idleing.

I would start with a wet/dry compression check to rule out anything mechanical.


Ron

100%  Many things can cause a cylinder to NOT FIRE. a wet/dry compression test will answer the most questions. Biggest one being (are you making good compression).

[Rob R]

My first guess would be unhappy cam lobe but it could be really really lean with that E carb...how big is it 800 cfm I hope..

that plink plink plink has the sound of a rod nut hitting the edge of the tray or the rear counter weight hitting maybe the pump every once and a while...

[1BAD68]

did a compression check...
#1 - 159
#8 - 170
#4 - 172
#3 - 156      I would say these are good numbers right?
#6 - 160
#5 - 158
#7 - 158
#2 - 159
first I checked compression dry and then wet but numbers didn't change much at all.

I bought a new dist. cap and wires, changed cap first and started engine, total difference... shaking is gone and it runs good! I think the old wires were still good but i changed them anyway, the cap had carbon on the terminals causing too much resistance.
The only thing I noticed now is a popping through the exhaust, it pops from idle to 2500 rpm.
I tried advancing the timing and it goes away but only when timing is way too far advanced.
Tried playing with the mixture screws but that didn't make any difference.

[1BAD68]

My first guess would be unhappy cam lobe but it could be really really lean with that E carb...how big is it 800 cfm I hope..

that plink plink plink has the sound of a rod nut hitting the edge of the tray or the rear counter weight hitting maybe the pump every once and a while...

its a 600cfm

[firefighter3931]

did a compression check...
#1 - 159
#8 - 170
#4 - 172
#3 - 156      I would say these are good numbers right?
#6 - 160
#5 - 158
#7 - 158
#2 - 159
first I checked compression dry and then wet but numbers didn't change much at all.

I bought a new dist. cap and wires, changed cap first and started engine, total difference... shaking is gone and it runs good! I think the old wires were still good but i changed them anyway, the cap had carbon on the terminals causing too much resistance.
The only thing I noticed now is a popping through the exhaust, it pops from idle to 2500 rpm.
I tried advancing the timing and it goes away but only when timing is way too far advanced.
Tried playing with the mixture screws but that didn't make any difference.

Those compression numbers are fine.....it's safe to say that the cylinders are sealing up fine so this means it's a tuning issue. I noticed you said it has a 600cfm carb....that's way to small for a stroker of this type. I don't like Eddy carbs either....they tend to be all over the place on the fuel curve. Rich at idle, lean on the transition then rich again at wider open throttle positions.

My advice would be to ditch that carb and get yourself a holley double pumper and start tuning. That motor will want at least 16* timing at idle and 36* total all in by 2800 rpm.

If adjusting the mixture screws has no effect on the idle then you are running onthe carb's main circuit and not the idle circuit. This is usually what happens with bigger cams with more overlap and a mismatched carb....you have to idle the engine up to keep it running so the idle circuit is no longer functional.


Ron

[1BAD68]

I meant that when adjusting the mixture screws it didn't help the popping through exhaust, but it did change the smoothness of the idle and I was able to get a 600 rpm idle that sounded fine except for the popping.
Are you sure the carb is too small? This calculator says its ok...    http://www.4secondsflat.com/Carb_CFM_Calculator.html
What size carb would you recommend?
Thanks Ron