How tight should the vortech supercharger belt be.

dj65falcon

dj65falcon

Well-known member
Need help on how tight my vortech supercharger V-3 belt should be.. I have a manual tensioner. I check my crank pulley and the supercharger pulley. They are spot on. I put the belt on, an torque the tensioner to 85 ft lb. Went out for a test drive. When I hit second gear the belt flew off.. would like to know if I need to give it more torque. I heard someone said to torque it to 100 ft lb on the tensioner. I don't want to hurt the supercharger crank. Has anybody had this problem? Thanks for your guys help
 
I don't have any experience with a supercharger but remove and reinstall your tensioner bolt to lubricate the threads and bolt shoulder/washer. I assume it would be like tightening a timing belt: in about a foot of belt length you should be able to just twist the belt 90 degrees by hand.
 
... not clear on how the belt tensioner works on your setup and how 85-100 Foot Pounds is being measured, I'd like to know - pics may help'.

I had belt derail problems after switching to very small driven pulley (2.5") on a V2 SC / 250. The idler roller alignment was critical to keep belt on and at higher RPM's/boost, the Vortech was getting pulled in slightly on mounting plate by the increasing belt tension. Critical alignment of the Idler and an additional support from for Vortech mounting plate has kept it spinning' ... (steel rod - triangled' to V2's front from bellhouse )

have fun



250 Cubic Inch Displacement Straight Six with Vortech V2 Centrifugal Supercharger and Holley 2300 350 CFM 7448 2Bbl heavily modified for Blow-Through boost levels. Extensive Fuel supply, Ignition and Drivetrain mods to handle increased power under boost. Boost levels monitored at Supercharger, Carb and Intake Manifold, with real-time Air Fuel Ratio monitoring. Previous forced induction 250 attempts yielded piston ring lands blown off as boost neared 20 PSI. Currently limiting Boost to @ 6-10 PSI pending further engine mods.

Vortech V2 specs are @ 680 HP at 20PSI boost at 50,000RPM Impeller speed.
With serpentine 6.125” (5.0 SBF) Crank Pulley and 2.5” Supercharger pulley, the two pulley sizes and internal SC step-up gearing yields an IMPELLER rotation speed calculated at @ 22,000 RPM at cruise speed with engine RPM @ 2500RPM.
At typical 250 SIX upper shift point of @ 5,000 RPM the Supercharger impeller speed approaches 45,000 RPM !. Calculating to an Impeller speed @ 750 Revolutions per SECOND. ​
 
powerband said:
... not clear on how the belt tensioner works on your setup and how 85-100 Foot Pounds is being measured, I'd like to know - pics may help'.

I had belt derail problems after switching to very small driven pulley (2.5") on a V2 SC / 250. The idler roller alignment was critical to keep belt on and at higher RPM's/boost, the Vortech was getting pulled in slightly on mounting plate by the increasing belt tension. Critical alignment of the Idler and an additional support from for Vortech mounting plate has kept it spinning' ... (steel rod - triangled' to V2's front from bellhouse )

have fun



250 Cubic Inch Displacement Straight Six with Vortech V2 Centrifugal Supercharger and Holley 2300 350 CFM 7448 2Bbl heavily modified for Blow-Through boost levels. Extensive Fuel supply, Ignition and Drivetrain mods to handle increased power under boost. Boost levels monitored at Supercharger, Carb and Intake Manifold, with real-time Air Fuel Ratio monitoring. Previous forced induction 250 attempts yielded piston ring lands blown off as boost neared 20 PSI. Currently limiting Boost to @ 6-10 PSI pending further engine mods.

Vortech V2 specs are @ 680 HP at 20PSI boost at 50,000RPM Impeller speed.
With serpentine 6.125” (5.0 SBF) Crank Pulley and 2.5” Supercharger pulley, the two pulley sizes and internal SC step-up gearing yields an IMPELLER rotation speed calculated at @ 22,000 RPM at cruise speed with engine RPM @ 2500RPM.
At typical 250 SIX upper shift point of @ 5,000 RPM the Supercharger impeller speed approaches 45,000 RPM !. Calculating to an Impeller speed @ 750 Revolutions per SECOND. ​
Click to expand...
 
my tensioner is the same as on yours, on the same side.I have a 4.00 Pulley, and the tensioner is manual. It has a square plug on the tensioner so you put a half inch ratchet on.. when I get home I will send pics on here thanks for your response
 
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Is it possible that the supercharger alignment is not quit parallel to the crankshaft?
Is the supercharger pulley in line with the crankshaft pulley and the tensioner wheel?
 
pmuller9 said:
Is it possible that the supercharger alignment is not quit parallel to the crankshaft?
Is the supercharger pulley in line with the crankshaft pulley and the tensioner wheel?
Click to expand...
Yes. I use a pulley alignment tool. And it is aligin with the crank and pulley perfect.
 
pmuller9 said:
I don't remember.
Have you run this supercharger before without any belt problems?
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I ran it with the Paxton supercharger. It only gave me 4 lbs of boost. No issues. Now since I put the vortech on. Now it giving me 8lbs.. I blow the belt off when I hit second gear. Someone told me to make sure the belt is tight like a guitar string. But I got it were you can push down a little on the top. And on the bottom I can flip the belt have way over. He said that to loose. I torque the tensioner to 85 foot pounds. Now he said I should torque to 100lbs and it would be alright. . I am just worried about the supercharger shaft that it might get bent.
 
When you shift second gear the engine rpm drops suddenly, and the supercharger is now driving the belt and creating a lot of slack on the long side of the belt and it is coming off the crankshaft pulley.
All I can say is, try making it tighter and see if it cures the problem.
 
pmuller9 said:
When you shift second gear the engine rpm drops suddenly, and the supercharger is now driving the belt and creating a lot of slack on the long side of the belt and it is coming off the crankshaft pulley.
All I can say is, try making it tighter and see if it cures the problem.
Click to expand...
Ok, thanks for help. I will get a little more tighter and hopefully that will help
 
"... the engine rpm drops suddenly, and the supercharger is now driving the belt and creating a lot of slack on the long side of the belt and it is coming off the crankshaft pulley".

> good advice, when revving and snapping throttle closed the belt will look almost fluid as it moves over idler, driven and drive pulleys. When you observe belt (with care) and rev motor does belt move sideways on idler or climb segments?

Presume you are running a blow-thru system with typical Blow-Off valve on charge pipe?. What's your RPM's at shift points?.

(pics ? ! )

have fun
 
powerband said:
"... the engine rpm drops suddenly, and the supercharger is now driving the belt and creating a lot of slack on the long side of the belt and it is coming off the crankshaft pulley".

> good advice, when revving and snapping throttle closed the belt will look almost fluid as it moves over idler, driven and drive pulleys. When you observe belt (with care) and rev motor does belt move sideways on idler or climb segments?

Presume you are running a blow-thru system with typical Blow-Off valve on charge pipe?. What's your RPM's at shift points?.

(pics ? ! )

have fun
Click to expand...
Here is my set up. I shift it at 6200
 

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your setup is well presented, and appears a potent build.

any pics of pulley setup?. what did you use for 6 rib (?) Crank drive pulley? . The V3 is the self contained lube' version and somewhat simplifies SC build with no engine oil line/pressure feed and return needed.

have fun

.
 
powerband said:
your setup is well presented, and appears a potent build.

any pics of pulley setup?. what did you use for 6 rib (?) Crank drive pulley? . The V3 is the self contained lube' version and somewhat simplifies SC build with no engine oil line/pressure feed and return needed.

have fun

Click to expand...
 
Here are the pics. I might have found out what the problem is. I try torque the tensioner plate the 90 ft lb. When I did that, I watch my supercharger move just slightly forward. I think I need to secure the mounting plate for the superchargers and it doesn't move. I think this has my issue all along. If it just moves a little bit forward. I will assume that it would make my belt fly off at top end.
 

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So what I am going to do, is put a adjustable tensioning rod below the supercharger bracket to the frame rail. This should keep it from tweaking forward
 
dj65falcon said:
So what I am going to do, is put a adjustable tensioning rod below the supercharger bracket to the frame rail. This should keep it from tweaking forward
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That could be a problem because the motor mounts allow the engine to move away from the frame rails on the driver's side under torque
A tensioning rod needs to attach back to the engine block
 
My engine has solid motor mounts. That are attached to the frame rails. A friend of mine says I should get a brace that hooks to the front of the supercharger back to the shock Tower with a turnbuckle in the middle. So I'm looking at and trying to figure out what to come up with a good plan.
 
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