Standard S trim and cog drive?

**Mike SVOR** · 08-25-2004, 11:24 AM

Hello,

I keep hearing from Vortech that I can't run a cog drive with a standard S trim because I have to "Upgrade" it.
I ask what is different between the S trim and Heavy Duty S trim and the guys say it's the bearing.
No Gear changes,
No Shaft changes,
Just a bearing.

Now my question is, If I pulley my setup to make the same 6 to 9 psi of boost that it has always made on the 8 rib setup, Why in the world would a cog system put Any more strain on the bearing than a HIGH Tension serpentine drive would at the same Boost Level???

Then I've heard that the serpentine drive allows for slippage. But I ask about the 10 rib setup and say, Isn't that supposed to stop all slippage?

I swear, it sounds like a total scam.

If there was danger of harsh acceleration and deceleration with a cog drive, wouldn't they upgrade the GEARS also?

I mean, a cog drive has WAY LESS tension on the bearing than a serpentine drive. I used to Crank my serpentine belt so tight so it wouldn't slip at 9 psi, it was crazy.

So I'm asking,
Who has a cog drive on a standard S trim that can give me any feedback on these statements?

Any input is appreciated!

Thanks,
Mike
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**frdfandc** · 08-25-2004, 12:04 PM

With the gear drive, there is NO belt slippage. With the standard 8 rib belt set up, the belt setup is more forgiving. When you are running stock components (stock block) there is a lot of additional strain on the crankshaft snout when using a cog drive compared to the 8 rib setup.

Personally I would call Vortech and ask them their opinion. I personally think that the cog setup is for race applications only.

**Mike SVOR** · 08-25-2004, 02:31 PM

Thanks for the reply.

I already know what vortech will say. They say, "You better send your brand new S trim back to us so we can give you a 500 dollar credit and charge you 2000 dollars to install a heavy duty bearing."

I just don't see the added force that a cog system puts onto a shaft.
If it was an initial "slap" of the gears going from decel to accel, then that would make a little sence. But a 10 rib setup will have just as much force going from decel to accel.

Has anyone ever changed bearings themself on an S trim?
There is probably a Super Heavy Duty bearing that can be bought from a bearing company that would work great.

I'll try a search, but if anyone knows if this has been attempted, hit me up with a link or something.

Thanks!!

edit: Oh, by the way, I have a 351 block with forged steel crank and good internals. I'm not worried about hurting this crank with a belt.
:D

**RSNovi** · 08-25-2004, 03:33 PM

If you are not worried about hurting the motor, why mess around with cogs on an S-trim. It sounds like you are not worried about the extra side load from running a very tight serpentine belt.

I switch between a Novi 2k and a S-trim both reaching 17 - 18 psi of boost using an 8 rib setup. The Renegade guys are running 30 psi of boost using an 8 rib belt. I just don't see the reason to run cogs on an S-trim.

If you are changing over for looks, then that is different.

Originally Posted by Mike SVOR

Thanks for the reply.

I already know what vortech will say. They say, "You better send your brand new S trim back to us so we can give you a 500 dollar credit and charge you 2000 dollars to install a heavy duty bearing."

I just don't see the added force that a cog system puts onto a shaft.
If it was an initial "slap" of the gears going from decel to accel, then that would make a little sence. But a 10 rib setup will have just as much force going from decel to accel.

Has anyone ever changed bearings themself on an S trim?
There is probably a Super Heavy Duty bearing that can be bought from a bearing company that would work great.

I'll try a search, but if anyone knows if this has been attempted, hit me up with a link or something.

Thanks!!

edit: Oh, by the way, I have a 351 block with forged steel crank and good internals. I'm not worried about hurting this crank with a belt.
:D

**Mike SVOR** · 08-25-2004, 03:47 PM

Originally Posted by RSNovi

If you are not worried about hurting the motor, why mess around with cogs on an S-trim. It sounds like you are not worried about the extra side load from running a very tight serpentine belt.

I don't know what you mean here.
I Hated the amount of belt tension I had to run on my 302 to overcome my 11 pound pulley slippage issues. I'm sure it wasn't good for the Blower bearings either.

Originally Posted by RSNovi

I switch between a Novi 2k and a S-trim both reaching 17 - 18 psi of boost using an 8 rib setup. The Renegade guys are running 30 psi of boost using an 8 rib belt. I just don't see the reason to run cogs on an S-trim.

The Novi uses a different drive ratio than the vortech S trim. They usually have better traction and less belt slippage. (from what I've heard)

Originally Posted by RSNovi

If you are changing over for looks, then that is different.

Although the 50 mm cog pulleys look killer, that is not my reasoning.
I want the same amount of boost every time.
I'm sick of looking at the boost gauge and watching it bounce up and down at only 10 and 11 psi.

That's why.

:)

**WOHORSY** · 08-25-2004, 07:57 PM

i had the same belt slipping issues on my standard 7 x 2.95 8 rib setup. i upgraded to a 8 x 3.15 8 rib renegade setup and the slipping is gone. no more belt dust on the inner hood. i stayed away from the cogs because this is still a street car, and cogs will put more strain on the bearings mainly because as airflow increases in the head unit it gets harder to spin the pulley, which in turn will tighten the drive side of the belt increasing the load on the bearings. the serpentine setup will "buffer" the belt tension, reducing the load on the bearings. if you run a cog setup there is no slipping on accel/deccel so increased strain is put on the bearings.

**Mike SVOR** · 08-25-2004, 08:15 PM

That's a good point.
But if I were to upgrade to the renegade 8.0 inch crank pulley, and use their largest blower pulley of 3.33, that would put me Way past the PSI I'd want to be.

How much boost was your 8.0 crank and 3.15 blower pulley setup making?

**WOHORSY** · 08-26-2004, 06:50 PM

8 x 3.15 @ 5600 rpm i see 15 psi. what pulley setup are you running ?

**Mike SVOR** · 08-26-2004, 09:47 PM

was running the standard 6.87 crank and a 3.33 blower seeing 7 to 9 psi. It would sometimes fluctuate between 8 and 9.

Then I changed blower pulleys to a 2.95 standard profile and the boost went up to a horribly erratic 8 to 11 psi.

The pulleys are aligned Perfectly. You can run a straight edge from my blower to my crank without any deviation.

I just want a solid 8 to 10 psi on my new 351.

I'm figuring cog.

**Racer LX** · 08-27-2004, 08:45 AM

Dude,

You sound pretty much set on running cogs, though as everyone has pointed out, running cogs on a non HD S-trim is a bad idea. I'll tell ya bro, once bearings fail in a blower, it will crash the impeller into the housing, putting metal into your engines oiling system. If you're lucky, all you'll do is kill the blower. If you're kinda unlucky, you'll kill the blower, and you'll wipe out the bearings in your engine. And if you're really unlucky, you'll suck a big enough piece of metal past the pick up screen, lock up your oil pump, and kill the whole engine along with the blower. Good Luck if you choose to do cogs. You might get away with it at the track for really short periods of time, but full time on the street, probably not. If you're just trying to keep a steady boost level, us an 8" crank pulley as folks have mentioned. Much much more grip. As RSNovi mentioned, Renegade guys use them way into the high 20 PSI range. They work. Use a 3.33" blower to keep the boost down.

Jim

**Mike SVOR** · 08-27-2004, 09:08 AM

I'd love to put the 8" crank pulley on. But the problem is, with an 8" crank and a 3.33 blower, that would put me at ~15 psi of boost and probably around 600+ hp. I'm trying to dial it down a little and keep the boost around 7 to 10 max.

Here's what's bugging me. I haven't heard of anyone blowing up their S trim from running a Cog system. Just a lot of "hear-say" (if you will) about what Vortech has told people.
I've called Vortech and asked them for dimensions of the Standard S trim bearing and the HD S trim bearing. All they could tell me was the HD bearing is "Wider". Now I ask,,, How is it possible to have a Wider Ball Bearing without going taller too?

If it's just a bearing issue, I'm sure I can replace all the bearings in the case myself. It doesn't look too hard.
http://jobyteknik.homeip.net/corvett...arger_rebuild/

I've had my A trim apart before also. Not that hard to replace bearings.

But the "failure" issue is still making me wonder.
Will it fail because of quick accel and decel?

oh yea, found this on Ebay.
Do you think I'll have to upgrade my alternator bearings and water pump bearings?
http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

lol, j/k :D

**WOHORSY** · 08-27-2004, 09:35 PM

it is very uncommon to run cogs on the boost levels that you are at. you can try a 7.5 inch crank pulley or a ultra grip head unit pulley to get to the boost level you want. you can run cogs if you want, but as mentioned above it is only a matter of time until the bearings fail. if the impeller contacts the scroll you will be SOL. you never mentioned your shift rpm but hypothetically, 6.87 x 2.95 @ 5500 rpm will give you about 44,200 V-1 head unit rpm. a 8 x 3.33 @ 5500 rpm will give you about 45,600 rpm. you can lower your shift rpm by about 150 rpms if you are worried about the 1400 rpm rise, but from my experience the difference will be insignificant. as for the bearing issue, under hard accel/deccel, as belt tension increases the head unit will "pull" closer to the crank. that is the main reason blower braces are used. if you can picture the blower trying to pull closer to the crank and a brace that is keeping it from doing so, the only thing left in the equation is a thin film of oil that keeps the bearing from welding itself together. i hope this helps, head units are still pricey.

**regattacoupe** · 08-28-2004, 07:17 AM

For the price you pay for a cog setup you can buy the SCH plate and tensioner setup.

**Mike SVOR** · 08-28-2004, 09:31 AM

If I choose to run the Renegade 8.0 crank and 3.33 blower, what should I do about the belt slippage on the blower?
There was always particles of belt all over my blower. Even running the 7 to 9 psi.

shift rpm was 6000 rpm