well? do think i'd be fine using the 305 harmonic blancer on my 350? shift points should be in the 5800-6000rpm range.

 

same **** different pile

 

What timing cover will you be using?

 

the same cover from the 305 the balancer will be used from.

 

I've done it, and it works just fine

...I've never spun my 350 up that high, so I dont know how well it will hold up to that rpm, but I do know it will bolt up and fit/work just fine.

 

call up a company that makes it and ask.

 

No.

But then my opinion comes from being educated in vibration & control, and in understanding what a torsional damper does and why it works. The bore <s>stroke</s> on a 305 is different than on a 350, so the torsional vibrations modes (and the frequencies and rpms that they resonate at) will be different than on the 350 tahn on a 305, so the damper design is different for each engine. It might bolt-on fine, and the crank might not crack for however long you use it -- but do you want to take that chance?

Do a search on "torsional damper" -- I think there is a thread I contributed to that discusses it in more detail and provides links to other more useful web sites. HTH.

EDIT: the thread appeared within the father-son project pages on engine swap, starting near the bottom of page 2 and continuing onto page 3:

https://www.thirdgen.org/techbb2/sho...5&pagenumber=2

 

The'yre both 3.48" Unless you're thinking of a different 305 than me.

 

doH! My bad.

No, I wasn't thinking of a different 305. The 305 has smaller bore than the 350 (which I did know) but wrote stroke instead. The smaller bore means less weight so the assembly will resonate torsionally at a different (higher frequency, hence higher rpm) than on the 350.

Thx for the correction. I'll edit what I wrote to fix it.

 

run it just fine

run a 327 one, 283 one, 307 one, whatever, same deall it will work fine, make sure you use matching cover though

it is a dampner
not a balancer

good luck

 

Yes, exactly... they are all the same for the SBC, with the 400 being the obvious exception. Just match it with the timing cover, and its cake.

 

Even though the PN is the same, stoke and everything. Does it make a differance since the 305 and 350 cranks are balanced differently?

 

The only thing to make sure of is that the 350 crank you are using and the 305 crank are both either internally balanced or externally balanced. Otherwise you may have a problem.What size balacer is it,6"?

 

yep, both internally balanced...i believe it to be 6".

 

Well, we opened a can of worms with this thread. I agree, it is a damper. Could we call it a "harmonic damper"? (sure on the 400 it is a balancer also)
Anyone that has looked at 350 and smaller engines will notice that GM put a lot of different dampers on these engines.
For the sake of argument lets look only at dampers that GM put on two 350 engines (timing pointers aside), why they did and why they are different. If GM could put just one damper on their engines they would, to save money.
First is '80 1/2 ton pickup. It measures 7-3/4" x 1-3/4"
Envision this engine pulling a trailer up a hill at sustained WOT @ 5800 rpm.
Second is '88 TPI motor. It measures 6-3/4" x 1-1/8".
This engine will see WOT @ 5200 rpm only for short periods of time.
The amount of dampening needed in the first engine will be greater than the second so it is heavier.
I believe that high performance, high rpm engines need a heavier damper than stock engines. Putting on a lighter damper from a smaller engine or lower rpm engine would be a mistake. Sure it would "fit" and "work" to a degree, but would not be the best choice for high performance applications.

 

...and the '88 TPI 350:

 

Well GM offers timing tabs with thier crate engines for either. The smaller damper weights less and has been cosidered a "performance upgrade" in past car mags.

 

It is a performance upgrade like aluminum flywheels and 9" converters are. Less weight for the engine to accelerate to higher rpm, for dragracing at the track; where performance is more important than durability, and the occasional broken crank is just a part of life. For the street it is a different story...

 

Ok, I plan to install a GM crate engine and use the car as a daily driver. So which damper is best under these conditions? I read thru this thread and am now confused.

 

What matters in looking at pix of the different torsional dampers is the mass of the outer ring, and the thickness and cross-sectional area of the rubber.

The rubber provides the stiffness (or capacity for you EEs), the outer ring is the mass (inductance), and together they form a resonant system. They are designed to resonate at a specific frequency (which means rpm for an engine), and because they rubber is very lossy, the damper will absorb vibrations rather than enhance them (like a bell would).

Keep in mind that many older cars from the 1960s and earlier had solid pulleys instead of metal/rubber/metal pulley/dampers. That's because those older engines were never designed to rev over 4000 rpm... so the vibration damper wasn't needed. So how you drive, especially if you like to rev the engine on the street or track, will mean it becomes more important to use the damper that was designed for the engine you have.

IOW just because it bolts-on, doesn't mean that it's correct nor that it will do what it's supposed to do especially when you rev the engine (as many people here tend to do).

Here's a few links that discuss torsonal dampers:

http://www.chevyhiperformance.com/techarticles/4402/

http://www.enginehistory.org/
http://www.enginehistory.org/NoShortDays/TV.pdf

http://www.grapeaperacing.com/Grape...ngs/dampers.pdf

ATI has some useful info on their web page:

http://www.atiperformanceproducts.c...s/101/index.htm
especially the tech articles at the bottom of the page.

This one is probably the best one I found:
http://www.vibratechtvd.com/the_facts.htm

 

hmmm...well, what about using it just to get by (and NOT revving it) and save up the $300 to buy an ATI unit? already running two of their converters and 1 dampner...one converter and dampner have been around since 1988...they make GREAT stuff.

i just need to drive this car by Christmas.

 

Run it. You'll be fine.

 

That discussion last spring got me worried enough that I ended up getting the Pioneer unit myself (off eBay).

I still have my doubts about the factory reasons for differences, thinking none of them have anything to do with 305 vs. 350, but the aftermarket covers you in any case.

 

From

http://www.vibratechtvd.com/the_facts.htm

The key words are tuned to the vibration frequency of the crankshaft.

As someone reminded me before, the 305 and 350 have the same stroke, as well sharing other crank dimensions. The pistons on a 350 are larger than on a 305 so there is more weight hanging on each crank throw. That weight will alter the location (in frequency) of the torsional resonances.

 

...But should not alter the displacement of the hamonic activity.

 

The tech links all assumed high operating RPMs. If that's the case, you should be getting an SFI damper, anyway. For what's being asked here (and the Father/Son thread), you're still in production-range RPMs. And for that, the CHP Mag article says, in the "Production Dampers" paragraph: "An internally balanced damper ... will work on any small-block except the 400- or 383-style stroker engine." No discussion of tuning the production dampers to different displacements (although they did say the dampers tended to get bigger as displacements increased over the years). FWIW, the damper on my '71 GMC 3/4 ton 350 was no bigger than the original damper on the 283 that came in the '57. The damper on my current '84 Chevy van 350 is a different story, and it was originally on the 305 that came in the van - the 350 is a Goodwrench replacement that doesn't come with a damper.

For my Camaro 350, the part that convinced me not to use the 305 damper was the cast vs. steel crank discussion. I've got a steel crank.

However, the real reason not to re-use the 305 damper is age, not design.

 

I'd like to quote the paper written by the guy at GrapeApeRacing.com that sums up my view:
"When it comes to a stock damper, every test
I have seen shows that bigger is better. The big
ones used on the stock 302 Chevy engines show
power improvements over the lighter ones used on
other engines even though they are heavier and
may take more power to spin. This power gain is
from a reduction of vibration to the valvetrain. A
stable valvetrain will make more power. The bigger
is better thinking isn’t true with aftermarket dampers,
but I am a firm believer of it when it comes to stock
parts."
I spin my 350 with a cast crank to 6700 rpm and that big stoopid looking damper in picture #1 is probably part of the reason I'm not picking up pieces. I also think that the damper in high performance applications is probably one of the most overlooked and misunderstood parts.

 

ok, but it will work for just putting around town till i can get enough $$ up to buy an ATI unit?

 

Sure! Just don't forget about it a year from now when you find out how much power you can make with nitrous/boost above 6000 rpm.