I am looking at a car that supposedly has a 408 in it. Would it have an after market balancer for sure? He cant find paper work on engine, any other ways to tell what it is?

 

LS engines are normally internally balanced.

On a 408 LS a stock dampener (aka harmonic balancer) could be used, an aftermarket one or aftermarket one with underdrive. Some folks like to use a stock harmonic balancer since strokers usually aren't spinning quite as high rpm etc.

Have a 25% UD ASP on my 383 and 10%UD ATI on my 416.



Here one of many different examples

 

It could have a stock balancer on it.

As mentioned these engines are internally balanced. All the balancer does on these engines is absorb harmonics.

 

You could probably tell if it's underdriven by the length of the belt it's got if the markings are still visible or just by measuring the diameter of the pulley with a ruler. I think it's 7.5" stock, 6.78" for 10% underdrive and 5.5" for 25% underdrive.

 

OK thanks for info. It has prc heads on it, will it have prc cast into the head?

 

+2 on the ASP balancer. I have a 25% UD on mine. I will say that I don't recommend any 25% UD balancer if you live in/near frequent 100° daily temps, and/or do a lot of stop and go driving, especially with a stock radiator. I spend a lot of time in Florida, and they have a LOT of 3 minute red lights!! I also have a DeWitts radiator in my C5 Vette. If I ever do get another balancer, it'll probably be a 10% UD ASP. But 25% UD does give a marginal increase in power, and definitely must increase component life, because my 23 year old car still has the original A/C compressor, and alternator........

 

Grinder has a very good point. It would be best to use a ATI though.

 

I see the consensus here on Tech in balancer choice is always ...ATI....wonder why no ever mentions Fluidampner ?

 

I have Fluidampner on my SBC Dart 400. The engine builder said the Fluidampner was what was needed for the application and an ATI wasn't justified. I'd planned to do the more expensive ATI etc

Left me with the impression is in the serious professional engine builder world, ATI's products are regarded as superior at dampening harmonics to Fluidampr and that filtered down to the LS enthusiasts.

 

Just don't run an ATI 10% UD balancer if you've got an LS7. Hib Halverson kept throwing his A/C belt on his C6 Z06. The ATI 10% UD balancer does NOT have a lip at the back end of the balancer, towards the engine, to help keep the belt on like the OEM balancer!!! When he pointed out this obvious shortcoming to ATI, they apparently told him to buzz off, although I think they spelled buzz starting with an "F", and followed by a uck. They flat told him they had no intentions of changing the design. Arrogant attitude, in my opinion. I have run an ASP since 2005. No thrown belts, or any issues at all. I'll stick with them.......

 

Fuzz off?? That makes no sense...

 

Ive read the Hib deal…it’s weird. He’s had issues, along with a dozen other guys. Meanwhile hundreds, if not thousands of other 10% ud LS7 ATI guys have no issues with the ac belt. Tony Mamo is currently having ATI build a bunch of LS7 Dampers with a much bigger curb for the AC belt. I’ve spoken with Tony at length about this deal, and his consensus about this is that it’s a bandaid fix to an issue that is not the dampers fault. In my opinion, I think it’s the ac belt tensioner, being too weak to hold the belt. If a manual tensioner could be made for the ac belt, I think it would solve the problem. Same type of issue with the main drive belt being thrown by our high revving LS7 setups, and a manual tensioner corrected the problem. I threw a couple of main belts myself before I went manual tensioner. ATI is by far the most respected damper in the industry. Tunable and rebuildable.

 

I'm just going by the fact that their standard balancers have a lip, and I'm sure there's a reason for it. I agree they are of very high quality. What puzzles me is why ATI thinks the lip is beneficial on the standard balancer, but isn't of value on the UD? If the lip serves no purpose, ATI could save a bunch of money, and aluminum, by starting with a smaller diameter of aluminum round stock for the standard balancer, which would eliminate the lip. Food for thought; I once overreved my LS7, to at least 8,500+rpm. Never threw either belt, and this was with the original, 100,000+ miles OEM C5 Corvette tensioners. Just my experience and .02........

 

ATI 10% UD on the LSX and I was throwing the A/C belt until I replaced the tensioner. I bought the Gates tensioner and belt and I've hade no problems since.

 

Yes PRC will be on the heads. Look on the side front or back and you will see there logo.

 

Yes the outer “curb” is there. I’ve given this a lot of thought over the last year or so. In my mind, one could totally remove the outer lips because there are 4 grooves on the LS7 A/C dampener pulley that would keep the belt in place. I really don’t see why the outer curb is needed if the tensioner is doing it’s job. The belt would have to completely raise up off of the pulley surface to jump across the 4 grooves (which are plenty deep enough to keep a belt in line) and come off. That’s a tensioner issue. Harmonics will come into play somewhere in the rpm band, and cause the belt to shutter briefly under acceleration, (or deceleration) but again a tensioner doing its job properly would combat this, in my opinion. This is why Tony having ATI custom build a dampener with a taller curb is only a bandaid fix to the real issue at hand, but a fix is a fix, I suppose. The AC tensioner is very weak in comparison to a main belt tensioner, as I can almost pull them down by hand. Great discussion here.

 

I can see where you're coming from, and I pretty much agree with you. The Serpentine design should, in theory, keep the belt location in check. As we know, production tolerances can vary, and it could also be some of the stackup tolerances in a select group of cars align in all the wrong directions. I have no other explanation as to why this happens on a select few cars. My ASP does have the lip. I'm thinking back to the v-belt days, when deep "V" pulleys were available for higher revving cars, which is effectively a lip on both sides. This is a very good discussion, and I was under the impression that most everyone who had the ATI UD was having these issues. So, I think Tony is doing the right thing, even though, as you say, it may be band-aiding the actual problem. Like idiot-proofing machinery. Most have no issues, but a select few will unless you cover every angle......

 

Sometimes you use both a belt AND suspenders. Redundant, but it WORKS.