how many people are running them?
Pros/cons on an NA cammed car?
anyone actually have before/after dyno numbers with just the crank pully swap?

thanks in advance.

 

Although I dont use one, my buddy has one on his and swears by it. I believe it's an ASP. Not sure on HP gains though. You will need a new belt with this mod. From what I've been told the key is the design of the pulley, where belt rides, so you dont throw it off at high RPM's.

 

I am running one with no known con's. I didn't do a before and after with just the pulley. It went on with the cam. Thus, I have only a suspected pro of an additional 8-10 HP.

 

Do a search, I have read that they may be the cause of timing chain breakage in M6 cars. I did say may be.....

 

I have one, it came with my cam set up. I have a MN6 and have had no problems so far.

Like VetteNo2 states suspected pro of an additional 8-10 HP.

 

maybe 2 hp maybe..... when you make the pulley smaller it takes away some of the balancing effct, every probelm I have seen on this forum with timing chains have had a UD pulley

 

Not to mention electrical charging and cooling issues.

 

I have a 10% ASP under drive pulley with my cammed MN6 LS2. I also have a double roller timing chain. I don't have any cooling or electrical issues with the pulley. I seldom drive in city stop & go traffic, but even when I do, I have not had issues. I don't know what the pulley gave me, but I did pick up 60 rwhp with the cam, pulley, ported t.b. installation.

 

I have an SLP 25% pulley and have a Dyno pull from right before and right after install ( pulley was the ONLY thing that was changed), it was good for 10 rwhp and 10 rwtq on my Cammed MN6 LS2. I have a double roller timing chain, so I don't feel that breaking it is a concern.

 

Is the timing chain only an issue on the manuals?

 

I have heard of some chains breaking, but I have no idea why. Could have been bad chains. But I really don't know.

I have not had any issues with my set-up.

 

Chains have broken on stock cars.

Single row timing chains on 450-500rwhp cars is why they are breaking.

The exact same UD pullies where used on LS1's and LS6's for years with no issue but the average power made on those engines was 50hp less. Very few LS6's hit the 450rwhp mark until AFR's and the like became available. Most used double row timing chains at that point. The UD pullies didnt have a bad rap back then and they were used on the same exact crank. Connecting rods have remained unchanged since 1997 and Mahle 124 and 142 pistons all weighing 434 grams have been used since then. Now all the sudden harmonics from the UD pulley make a difference? I think a few people learned a new big word that cant be proven not to be the cause and it has been employed to cover up for a bad choice of chains for a given power level.

LS2's have been using single row chains because people doing installs know the timing cover now has the cam position sensor and fear of fitting a double row chain has been in place because of this. The truth is, they do fit and the bolts on the face of the oil pump can be shaved a bit and there is no interference with the sensor itself.

Manual cars have more chain slap when you decelerate. Autos are easier on the whiplash of the chain when you come off the gas.

 

When using a UD pulley with a cam, cams use higher rpm idle speeds that overcome the loss in RPM of the accessories. A 600rpm idle is replaced with a 800rpm idle and thats the same 25% lost to the alternator and water pump. Since the sum net speed is exactly the same or higher depending on the cam chosen, the alternator and water pump see the exact same operating speed. If its an issue, there are overdrive pullies available for cars not increasding the idle speed. There is no lost cooling or charging since they spin at the same speed they did stock.

Not a single person with a corvette complains of heat or electrical issues because of this and they are used universally by all tuners. I'm just curious but do you actually know of a single person with a charging or cooling issue that has a corvette with an UD pulley? I know hundreds that say its a myth.

UD pulleys gain 8-10rwhp and has been proven. I did a thread in C5 tech about 5 years ago on this with dyno sheets. I know 2 people (4 if you count cam only guys with no UD pulley) that had a stock internals engine and no UD pulley with a chain break. I did the repairs/rebuild after the fact.

 

when i go CAM it will be the LGM g6x3 i believe. I Their kit comes with a double timing chain and i figured they have done enough of them to trim what ever needs to be to make it work right. I figured since it all has to come off anyway... why not have a UD pully thrown on at the same time. Might make up for the fact that im sticking with the 08 NPP instead of a more agressive catback.

 

There are many of those who install a UD without a cam swap. and therefore dont raise their idles.
in fact there was someone here who had that exact issue here a week or two ago with a dipping voltmeter.
The question I have for you is. What happens at 3000RPM(for example) while driving down the road making alot of HP on a 100 degree day. not at a raised idle to make up the 25% loss in flow. 3000RPM minus 25% flow of the stock pulley? Seems to me that car might run hotter or overheat more easily and quickly than one with the stock pulley.Maybe Im mistaken.

 

I was told that LGM's cam kit comes with a Katech C5r single roller timing chain. I'm not sure but maybe Anthony or Bobby can confirm this.

 

There is not a charging issue with my ASP underdrive. After alot of unknowns on the timing chain failures on highly modded cars, i have come to agree with spin that the likely cause is the whipping of the chain on manual trans cars and lots of road course guys banging down through the gears without revmatching, that is also very hard on a chain. If I were to buy an underdrive now there is no question that the ATI superdamper is the best out there.

 

While I've never seen or heard of anyone with an actual waterpump/cooling issues as a result of an underdrive pulley install, I have seen a few cars with the dipping voltmeter/dimming lights syndrome, especially at night with the headlights/AC/radio on.
Again these were 'stock cam' cars with stock/near stock idle speeds.





Those are generally regarded as being of a higher caliber/quality than the usual ASP/SLP versions but isn't the ATI only a 10% underdrive? Even though it might have superior balance and is very well made it also costs a lot more money and offers less power gains with that 10% versus the 25% reduction of the others.

 

I am running the IWIS c5r that I purchased from KATECH. $139.00. There
are low end IWIS chains out there for 49.00. The difference is not visible but the C5r chain comes prestreched & tested so I understand. Spin points out that most failures come from improper valve train installation.

 

then there sure is ALOT of improper valvetrain installation