How tight should the MFI drive belt be?
 

I've started to re-install the engine tin and I replaced the MFI belt with a new OEM belt. Right now the pump is as far as possible away from the pulley on the left cam but the belt still has a fair amount of deflection. Before I tighten everything down, I thought I'd better know how tight the belt needs to be. Thanks!

you should be able to twist it 90°, midway between the pulleys, with minor effort, but not with no effort.

Thanks John! I guess my belt is too loose. It looks like I need to open up the slotted holes in the MFI pump base a little bit as I'm up against the stops already.

That doesn't sound right. Sure the belt you have is new, and the RIGHT belt??? Maybe you can compare it with others for proper length.

Bill, it's the same part #, looks the same, and fits no tighter than the old belt.

maybe the sprockets are worn out.

Hmmm. I don't think they're too worn; however. So I've got a dilemma...I was planning on putting the engine back in the car tomorrow AM. If I do, the new belt is as loose (or tight :) ) as the old one. If I run into problems down the road, is it reasonable to replace the sprockets (pulleys) and belt while the engine is in the car, or had I better play it more conservative and order new sprockets and delay putting back in the engine? Thanks for your advice!

they do seem to hang in there with a somewhat loose belt. you will at least be better off with the new one on there. it may be fine as is. hard to tell from here.

That sounds encouraging. Well, here's some pics that may or may not be helpful to evaluate what I'm talking about. Whatd'ya think?
MFI Pump Sprocket:
http://forums.pelicanparts.com/uploa...p sprocket.JPG
Cam Sprocket:
http://forums.pelicanparts.com/uploa...m sprocket.JPG
Professional hand model showing MFI belt deflection:
http://forums.pelicanparts.com/uploads/73E MFI belt.JPG