Slant block to 904 bell-housing bolt specification

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ConfusedMuchOfTheTime

ConfusedMuchOfTheTime

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Hi everyone

I'll keep this short and sweet.

Is the bolt circled a (2" under head shaft length)
  • 7/16"-14 TPI UNC
  • 7/16"-14 TPI UNF
  • 3/8" -16 TPI UNC
  • 3/8" -16 TPI UNF
Asking because circled bolt I have (7/16"-14 TPI UNC) won't go into the bell-housing. Screwdriver pokes right into bell-housing (deeper than 2") so there's no blockage. There seems to be a smaller diameter shaft in the bell-housing than the block flange after running a screwdriver from the back of the shaft forward and I can't easily determine if the thread is UNC or UNF. Obviously I don't want to force a UNC thread if the bell-housing is UNF for this bolt. Will try flushing hole with WD40 as there maybe road crud down there but thought I'd ask this question first. Adjacent 7/16"-14 TPI UNC 2" bolt goes in just fine.

This is my reference Bolt Size and Tightening Information 170, 198 & 225 Slant Six Engine

Thank you
Chris

Starter with bolt.jpg


Starter without bolt.jpg
 
Have you tried a 3/8 bolt in that spot? They aren't all 7/16. Also, I would not use those bolts to bolt the engine and bellhousing together. They are grade five. Should be grade eight or even ten.

I'm blind. I looked again and those are grade eight. My bad. I should have had my glasses on.
 
RustyRatRod said:
Have you tried a 3/8 bolt in that spot? They aren't all 7/16. Also, I would not use those bolts to bolt the engine and bellhousing together. They are grade five. Should be grade eight or even ten.

I'm blind. I looked again and those are grade eight. My bad. I should have had my glasses on.
Click to expand...

I did slot a 3/8 UNC in there just to see and will try again with light tooling as only used my hand before. Def grade 8 7/16" x 14 TPI UNC Coarse Zinc Hex Bolts Part Thread High Tensile Grade 8 AS 2465. Looking around the web tells me the spec should be 7/16 but will fiddle around again.
 
ConfusedMuchOfTheTime said:
I did slot a 3/8 UNC in there just to see and will try again with light tooling as only used my hand before. Def grade 8 7/16" x 14 TPI UNC Coarse Zinc Hex Bolts Part Thread High Tensile Grade 8 AS 2465. Looking around the web tells me the spec should be 7/16 but will fiddle around again.
Click to expand...

So, the 3/8 UNC spec threads in nicely now with a bit more torque than my hand :) and some WD40. Weird though as all my research has come up with a 7/16 UNC for that hole and my 7/16 shank does not even bite the threads. Oh well, you live and learn.
 
3/8-16 and 7/16-14 arent both NC and NF thread, each one you list is NC ("National Coarse") NF is more threads than that per inch. 3/8 NF would be 3/8-24 and 7/16 NF would be 7/16-20.
 
Cool. Glad you got it sorted out. Probably just had some dirt or something in the threads.
 
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