'69 911E MFI Belt Tension

[jtsilverfox]

Hi guys,
I’ve searched for an answer to this and found a lot of ‘sort-of’ answers, so let me illustrate with some pictures. Question: Does my MFI belt tension ('69 911E) look about right (I can twist the belt about 90° - about 135° max)

Measurement before deflecting:


Moderate squeezing together:


Moderate pull in one direction:


Moderate pressure in the other direction:
https://oi1101.photobucket.com/albums/g429/jwt69/Porsche%20rebuild/MFI_belt_moderate_push.jpg

Without removing the lines to the injectors, I’ve tried loosening the 4 12mm nuts holding the MFI pump and tried moving it, but it won’t budge. I’d of course prefer not messing with those lines if my belt tension is fine.
Any comments/thoughts would be appreciated…
Thanks, cheers, jt

[jtsilverfox]

Sorry about the missing last photo. Don't see why it didn't paste. The link works.
cheers,
jt

[manbridge 74]

Looks about right, though your sprockets look fairly worn. The final test will be when the engines running. Too loose and it looks floppy, too tight and the belt can start to walk off the pulley.

I like to confirm final pump timing with an adjustable advance timing light and mirror. Set light to strobe on FE mark and then see if pump gear mark is also lining up while engine is idling at operating temp.

[jtsilverfox]

Okay. Thanks Jeff. I'll ck the belt as you suggest. But, got a long way to go before I'll have her back in the car & running - car's been sitting for several years so still gotta do the fuel/tank/lines, brakes/lines/mbc/calipers, etc.
cheer, jt

[ed mayo]

My only test is that the belt should able to do a 90 degree twist. That's a little subjective I know, but point is that it isn't 'TOO' tight. You can move the pump without loosening lines, there is a Porsche tool for that is basically a foot at the end of a shaft that fits between the pump and the support plate so you can lever the pump in whichever direction you need. I also try to put a little 'angle' in the pump to ensure the belt doesn't try to 'walk off' the pump sprocket.

[jtsilverfox]

Thanks Ed. As for the twist, I can fairly easily get 90° - more if I apply more pressure. Hence my fear that it's maybe too loose, and hence the other pictures/measurements. I tried prying it to the right with a 2' pry bar (HF) but I couldn't see any good places to pry against & was afraid of breaking something. So I ended up marking the position of the pump's base with a dot of white nail polish and tapping it with a 3/8" extension & hammer. Never saw any movement, so it might be as far right as it can go already - or those lines may be holding it up. The last cpl of them were a bit of a ***** to position when I put them on and I was afraid of cross-threading. Hence my reluctance to take them back off - unless someone yells:"JHC! That belt's way too loose/tight!".
cheers, jt
BTW: Anyone interested - degree symbol is Alt+0176