I don't often drive in my son's 86 GN, but did recently and thought the engine seemed to run a bit rough compared to my V8. I've heard V6's run less smoothly, but was just wondering if this is normal. The car runs very strong with good boost (he runs 16-18lbs.) and no knock at all on 100 octane. He has poly motor mounts. Does this impact it? No codes or anything. It's just that to me you can kind of feel a roughness to it compared to my LT1. Is this normal? It is an original 30K mile engine. The plug wires and vacuum lines were replaced when he bought it a few years ago, but the ignition coil is original. Any thoughts?
How Smoothly should a Turbo Buick Run?
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DailyDrifter
The Slow and the Curious
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- Dec 5, 2007
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They should run fairly smooth. With the motor mounts you will feel the motor more, but it should be bad.
+1 car runs very smooth.....can't feel mine at idle....
As mentioned before the GN V6's are not as smooth as a V8 and you are feeling some of this due to the poly motor mounts. My friend's '87 T-type has stock style motor mounts in it and it feels silky smooth even when you see the engine under the hood shaking around a little as they all do.
turbo nasty
Turbo Dojo / MNTR
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- Jul 19, 2001
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My bud has 42.5 injecs, 5 angle valve job stock heads, 206/212 FT cam, .030 over and with the TT chip its is as smooth as a caddy at idle
+1 combo, +1 troubleshooting.
A v6 will never run as smooth as a v8 if you are just considering the basic design vs basic design.
More cylinders are firing for a given rpm. A V6 has 3 torsional stress peaks per revolution vs 4 for an 8 cylinder, furthermore, a v6 like ours by design cannot be as balanced as a v8 because for every torque peak that corresponds with a cyl firing, there is a valley that actually goes into negative torque on a V6 which does not happen on a V8. Couple this with the fact that buick V6's do not have a torsional absorber and most V8s (including LT1 ) do.
Buick engineers compensated for this by underbalancing the crank which moves the plane of imbalance to the horizontal which for some reason is absorbed by the engine mounts better than a standard balance.
Of course, in the real world, cam, tune, induction, etc etc etc, play a huge part in how "smooth" an engine feels. FWIW, my stock longblock setup wasn't super smooth at idle either.
More cylinders are firing for a given rpm. A V6 has 3 torsional stress peaks per revolution vs 4 for an 8 cylinder, furthermore, a v6 like ours by design cannot be as balanced as a v8 because for every torque peak that corresponds with a cyl firing, there is a valley that actually goes into negative torque on a V6 which does not happen on a V8. Couple this with the fact that buick V6's do not have a torsional absorber and most V8s (including LT1 ) do.
Buick engineers compensated for this by underbalancing the crank which moves the plane of imbalance to the horizontal which for some reason is absorbed by the engine mounts better than a standard balance.
Of course, in the real world, cam, tune, induction, etc etc etc, play a huge part in how "smooth" an engine feels. FWIW, my stock longblock setup wasn't super smooth at idle either.
I disagree that these engines are smooth. They are anything but smooth. They can not be balanced in both horizontal and vertical planes without a counter rotating balance shaft. Thats why they are under balanced from the factory. I believe they used 36.6% instead of the typical 50% for a V style engine. Therefore the factory rubber engine mounts are actually part of imbalance absorbtion. I noticed a lot more engine vibration when in the car when i switched to an HR mount. Polyurethane acts like a solid mount. Sit in a 3800 powered car with a balance shaft and sit in an earlier car like our TR's without a balance shaft. You will see for yourself. The difference is huge.
With a balance shaft they are as smooth. Balance shafts are standard these days in all v-6 designs
Underboost
Mr. Dull
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I have always found when these lil v6's run there best they're as smooth as silk.
