95 Mercruiser 4.3 LX Vibration Issue/Alignment?

[Bondo]

Do you think the harmonic balancer and flywheel could be weighted some weird way for a non-balance shaft engine vs a balance shaft engine? The marine motor was balance shaft and the donor motor was not, however I'm using the harmonic balancer and flywheel from the marine motor... Its just a thought I had.

Ayuh,.... This is what I'm talkin' 'bout in post 11,.... You've found yer vibration problem,....

 

[Mad Props]

It looks like all the 86 through 95 engines are balanced the same way, so my harmonic balancer and flywheel should not be an issue... Haven't had a chance to check spark or compression yet, that's next...

 

[third times the charm]

The vibration sounds more like a balance issue with your engine, the flywheel and harmonic balancer. I
I have been doing a ton of research on the 4.3 as i am going to be doing the same thing as you have done( automotive engine donor swapping to marine componets) there is a great many articles out there about the vibration. The 4.3 pre balance shaft block seemed noteble about the vibration, hence the balance shaft addition. I had an 87 four winns with a newer engine with the balance shaft. It ran like a top, with some vibration as your described in that rpm range.

 

[Rick Stephens]

I have a '95 (god knows what source) block w/o mechanical fuel pump shaft hole and no balance shaft. It has all the parts out of a '92 - flywheel, harmonic balancer, pan, timing cover and all the Mercruiser stuff. It was converted to Vortec heads using an Edelbrock intake.. My own personal morphodite bastard child. Runs pretty smooth though. I don't notice any particular RPM range that produces vibration. Smoother than the old 3.0L, that's for sure. So there is hope here that you can get this running smooth.

 

[chartersj]

I did the same with my original 4.3 lx, got a vortec out of 2001 s10, got a new intake intake manifold and used all the merc stuff off the 93 non-vortec balance shaft motor. I used the balancer off the old motor so i could use the v belt pulleys. Motor runs nice and smooth.

 

[Mad Props]

I took her out for the maiden voyage yesterday and am pleased to report no issues... The vibration didn't seem nearly as noticeable with the hull in the water, so I'm hoping that it just seemed worse than it really is on the trailer... From what I've been reading, I don't think there is really anything I can do to balance the motor any better other than have a machine shop do it, so I'm just gonna call it good for now...
Now that you brought that up, how do you like your vortec head setup? Did you notice a power increase after the change? And how did you handle adjusting the carb jets? Any size recommendation?

 

[Rick Stephens]

For me, I pulled a 3.0L, and built a 4.3L Vortec to replace it, so no comparison pre Vortec.

I purchased an Edelbrock 1409 to replace the Roc QJet that was on the motor. WIth the adapter plate the Roc wouldn't fit under my doghouse, and the Roc didn't have a choke. When I purchased the 1409 I also purchased the 1485 calibration kit for 4.3L. Total waste of money. That kit must have been made for a pre-Vortec engine, ,it is hugely lean. I ended up taking a WAG, buying a few jet sets and another calibration rod set and springs and worked my way up. Pulled spark plugs a few times after runs at low, middle and high throttle settings. I had no problem with the stock accelerator pump porting, which I believe is set to 5.0L V8 from the factory. IMHO, the stock calibration for a 5.0L is closer to what a Vortec will pull than the recommended kit from Edelbrock.

If you change to Vortec heads you engine will breath well enough that you will have to richen the mid and high range at the least.


Rick

 

[Mad Props]

Does the Edelbrock flow a lot better than the stock Merc carb? I was under the impression that the Rochester/Weber 4bbl carb was exactly the same as an Edelbrock performer... I planned on keeping my carb unless you think I could gain a decent bit more by upgrading... My plan for now as to get the new vortec heads, edelbrock performer intake, and keep my carb and rejet it. Should keep the cost under 300-400 bucks if I can find good heads at a junk yard for a decent price.

I'm also throwing around the idea of maybe leaving this motor alone and letting it run its course and just be happy with it for now, and if I have any issues down the road (since it was a truck motor with 100k on it) consider throwing a 350 in.

 

[Rick Stephens]

The Edelbrock is a Weber. Same same. In fact the Weber casting marks reside under the Edelbrock stickers.

You will most likely have to recalibrate. The Vortec heads move a lot more air.