Setup of a VR4 conversion help/suggestions/experience

[Buck-Strickland]

I shimmed my SN2000 today in preparation of the VR4 impeller installation. I have a couple questions, or at least some confirmations.

I inspected all the internals balls measure 1.063+/- all with even wear, races where clean, output shaft smooth.

The internals of the SN2000 are different than SN89 I have.

The shim pack measured 0.022; I added shims to the pack which netted 0.043. This was way too much, after torquing the race retainer to 150”lbs (12.5’lbs) the rotational torque was 85”lbs. Stock with the 0.022 shim pack it was 27.5”lbs. Long story short, after four tear downs and tests, I ended up with 0.029 shim pack and 120”lbs (10’lbs) on the retainer bolts. This setup resulted in 55-57.7”lbs of rotational torque. (With all seals in place and balls lubed)

Is 55”lbs okay for a street/strip blower? I have a larger fluid cooler.

Does the shim pack size sound correct? I would have thought a lot more shim would be needed. I ask because the SN89 unit I was given had a 0.058 shim pack.

Is adjusting the torque of the race retainer bolts okay for adjusting the final rotational torque?

Any thoughts from the VR4 owners out there?

I took step-by-step pictures which I will post in a new thread once I sit down and edit it.

[pavement pounde]

It sounds good, remember by torqing the casebolts you also alter the rotational torque to turn the pulley.

[Buck-Strickland]

Thank you.

How do you check the clearance between the impeller and rear cover?

I set the impeller to base at 0.026", thats easy, but I don't know excatly where to measure the impeller to rear cover clearance from. At the blade tip? under the cover? Does somebody have a clear idea where to measure at? I know it does not hit the cover, but I don't want too much gap.

[suede57ford]

To check the impeller clearance to the scroll housing, just stack some impeller shims under the impeller until the impeller begins to touch the scroll cover then remove the amount of shims to give you the clearance you need. You will also need to to check the clearance between the diffusor plate as well.

I often spray the impeller and inside the housing with machinist spray marking dye so you can visibly see anywhere it is contacts while mocking it up.

You do not want any thing too close, as the VR4 impeller builds more heat and expands more than a SN would.

[Buck-Strickland]

Okay. Thank you. I did color the inside to check for clearance and had no contact. The closest point was the impeller fin near the inlet.

[Buck-Strickland]

Any suggestions for holding the impeller in place when torquing the retaining bolt? I could not hold it by hand and torque to 25ftlbs, so I just zapped in once with the impact gun with the air pressure turned down low. I'm not real excited about doing it that way. Any other ideas?

Thanks

[pavement pounde]

I used gloves and hold the impeller and used locktide on the bolt, onestley I just used a normal wrench and just tighten as hard as I can.
Never came loose on 4 different units.

[Buck-Strickland]

Ya, I used locktite too. I guess it's okay. I will keep an eye on it.

[speedytang]

Everything I have read you are right in the ball park. Never forget the locktite because it will come out if you do.

[Buck-Strickland]

Thanks Speedytang,

How much clearance should I have between the impeller and the rear cover? See attached photo(couple threads up); does that look okay?

I fired it up yesterday, seems to work fine, no odd noises. I will test it as soon as the weather is better and I finish the inlet modifications.

Also, I will put together some pictures as soon as I can sit down and review my notes.

[speedytang]

Since case tolerance changed during casting I always color and shim till I hit the housing then remove just enough shim to clear.