: Harmonic balancer choice
Mar 21st, 00, 11:26 AM
I have a 355, 10.5:1, crane solids, holley 700 double pumper, headers, Edelbrock Performer RPM intake. The motor has the stock balancer which probably isn't the best for my setup. What is the experience out there of the aftermarket?
Mar 21st, 00, 11:51 AM
Depends on RPM range of engine- stock unit not stable enough at over about 5500 RPM- if you're blasting into 6000-7000 range, definetly replace it with aftermarket unit, otherwise you should have no problem.
Mar 21st, 00, 11:52 AM
The ATI Superdamper works fine on mine. Have heard stories of the fluid-dampers breaking off the ends of the crank shaft, no personal experience, just heard that from a couple of the circle track boys.
Mar 21st, 00, 01:25 PM
Would just like to add my opinion...although the aftermarket (ATI, Fluiddamper etc) dampers are a must for drag strip use and very high rpm's, I would not count out the stock Chevy 8" damper for anything but an all out competition motor. I raced a 67 Camaro that went 10.70's for 13 years with a stock damper. Shifted at 7500 went through the traps at 7800. Never had a problem. Same with my 71 Chevelle that sees its share of 7000 rpm shifts but not as often as the race car. Guys ran the stock units for many years and to be honest with you, although I have heard of them coming apart once in a while, I have never seen a stock damper fail in close to 34 years of going to the drag strip almost every weekend. I am not suggesting that you cut corners, all the better engines that we build usually get an ATI damper on them, but in all reality most street motors will live just fine with the Chevy balancer. Once again, just my opinion.
Advanced Automotive Machine
Mar 22nd, 00, 02:37 AM
I would second BillK on this one. I spent approx. 350 dollars on a Fluid Damper for my big block and it didn't make ANY difference compared to the stock damper. Your money can be better spent elsewhere. I will admit though that the degree marks on the damper every 90 degrees has been helpful a time or two when adjusting valves.
Mar 22nd, 00, 05:11 AM
The purpose of a "harmonic balancer" (I can't stand that term...this device does not "balance" any harmonics. I prefer "vibration dampener" myself) is to reduce the amplitude of internal resonances of the crankshaft and connected components. These resonances become exponentially larger as the engine speed reaches really big RPMs. This increases fatigue on these parts, and can result in hairline cracks in the crankshaft and therefore can ultimately lead to engine failure. This supports why racing engines require something better than the stock dampener.
For the street, I agree that a good 8" stock dampener is adequate, simply because the average street engine rarely sees sustained (very) high RPMs. I personally opted for a reputable aftermarket dampener simply because I wanted some extra insurance on the engine that I just invested a bunch of money in, not because I expected any increase in power due to the dampener alone. And, yes, the timing marks are a bonus!
Mar 22nd, 00, 05:27 AM
Ok, since we are here. I bought a used 8" "vibration dampner". I bought it from a junkyard that a friend of mine has. He said it was for a 350. It was grooved out about 3 or 4 inches on the back. I asked if he was sure and he said yes. Do I have one from an externally balanced 400 sb?
Also my timing mark sits staight up (12 o'clock) when timing it. Is that normal? Will not run anywhere near the timing tab sitting about 2 o'clock.
67 ss/rs, MODIFIED
IM - sixtsevnss
Mar 22nd, 00, 05:46 AM
Perhaps I'm just too picky, and I don't want to come across as saying you're doing the wrong thing, but I wouldn't install that dampener if that were my engine.
Two reasons. First of all, you do not know what you have. Is it for an internally balanced or externally balanced engine? I don't know enough about the physical differences between the two to give you an accurate answer. The misalignment of the timing marks raise a red flag, too. Secondly, the rubber isolator between the two halves of the dampener tends to crack and deteriorate, which will adversely affects the dampening characteristics of the unit.
I recommend purchasing a new or rebuilt stock style (correct!) dampener for your 350. I believe Summit Racing sells them, and they are not very expensive.
Mar 22nd, 00, 08:37 AM
Based on my experience with Chevy engines you do have a balancer from a 400 and also from my experience it is from a newer year engine, say '76 up.
Hope this helps
Mar 22nd, 00, 01:26 PM
The balancer you bought must be off a 400. None of the internally balanced small blocks have the cut out that your's has, only the 400.
Advanced Automotive Machine
Mar 22nd, 00, 06:47 PM
Thats pretty much what I thought. I only have about 30 minutes on the engine with that balencer. Two quick trips down the road about a mile and the rest of the time just Idleing. Has the damage all ready been done? Am I going to have to change my mains or should I just chance it and go until something happens? With the new balencer installed of course.
67 ss/rs, MODIFIED
IM - sixtsevnss
Mar 22nd, 00, 08:54 PM
Your motor should be ok with that short amount of time on it with that 400 balancer.
When I built my 383 (350 with 400 crank) I
had it balanced. When I got it back, the machine shop forgot the alignment dowel in the crank and I put the flywheel 180 degrees
out. I drove the car for about 30 miles with a bad vibration. I just pulled the motor, rotated the flywheel and put it back in the car. That was 5000 miles ago and the motor tachs to 6000 rpm and is smooth.
Mar 23rd, 00, 04:45 AM
I agree with Bob- not a problem.
Jun 5th, 01, 09:41 PM
i agree that you have a 400 balancer. the groove in it is the clue . and i bet it is a little bigger . the timing marks vary from early to late model years for all small blocks . i try to match the timing cover to the damper . generally there are two different ones- straight up , and off to the right a little. you have to use the latter with the short water pump set up . you can make things simple by setting no.1 cyl to TDC. then CAREFULLY spot weld a new tab on in a convenient place . now place your timing tape (summit has it) in place with 0 at the pointer. problem solved!! and now you can check your total timing advance a lot easier and tune that mr. gasket advance kit! (haha) and while we are on the subject of vibrations . always check the casting #'s on your 350/305 cranks .the 305 crank has to be rebalanced for the 350 or the vibration gets real annoying. send it to a machinist you can trust . drop the extra bucks for a micro polish on any crank. it makes a big difference . good luck!!