454, 1987, lower oil dipstick Bolt

[Sgt Gus]

Bolt at the block is missing, and haven't figured out.
Google AI says 1/2" - 13, but no.
The power steering Bolt on front of water pump is that size.
Definitely seems 1/2", but finer thread.
Could be 1/2" - 14 npt, but that is pipe thread?
1/2" - 20? Seems to fine, but clearly I don't know.
Can't hurt to ask men. One damd Bolt.

 

[legopnuematic]

Got a photo?

I'm not a big block guy but a 1/2" bolt sounds rather large for a bolt on component. I'd suspect 3/8-16. Thats what (on small blocks at least) is used on the water pump/brackets.

 

[WFarm]

1/2-13 is coarse thread. 1/2-20 is fine thread.

 

[Ricko1966]

I imagine it's 5/16 18 which would be a 1/2 wrench size.

 

[Sgt Gus]

Ok, I agree with y'all. Thinking maybe I left in engine when I took to shop so I wouldn't loose it. That would be something stupid I would do.

 

[Sgt Gus]

Here are picks,
1st two shows open hole.
3rd shows me holding larger than 3/8 - 16 stud.
4th shows the 3/8" - 16 on left with larger stud I held in there on right.
5th show me starting the 1/2" - 13 in the hole. To coarse.
Last below, shows the lower portion of dipstick next to bolt which clearly won't fit.

 

[Sgt Gus]

Crazy, yes? Maybe there was a stud with smaller thread on top?

 

[Sgt Gus]

Well, I looked at my fabulous pics. Zoomed in...and PO didn't have a bolt there. Least I'm not stupid.
Guess I can put the RTV pooky on it and move on.
I'm thinking it might be some stud with reduced thread like the one in the pic but...bigger.

 

[legopnuematic]

Could it be metric? M14 or M12 both can be had in 1.5 pitches, which converts to 16.93tpi.

1/4npt is 18tpi, with a basic major diameter of .540.

1/2npt is a basic major of .840.

 

[Sgt Gus]

Could it be metric? M14 or M12 both can be had in 1.5 pitches, which converts to 16.93tpi.

1/4npt is 18tpi, with a basic major diameter of .540.

1/2npt is a basic major of .840.

You da math major, or been turning bolts for a long time.
Seems strange for it to be something different. Gut says it should be a stud.
I'll call engine builder to see if he has a source; otherwise, it will live without which it had been apparently.

 

[Sgt Gus]

I put a winky and smiley face. Where did go.
Don't want to come across as smart a$$.
Appreciate the input! @legopnuematic

 

[legopnuematic]

No math major here, just a machinist.

Do you have a set of pitch gauges (tap and die sets typically have a set of them) and a caliper?

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Even with just a caliper if you measure the minor diameter of the hole (or you could use known size pins or drill bit shanks like pins) that can provide a starting point to figure out the major diameter.

 

[legopnuematic]

Also, have you tried a 7/16-14 bolt?

 

[Sgt Gus]

No math major here, just a machinist.

Do you have a set of pitch gauges (tap and die sets typically have a set of them) and a caliper?

You must be registered for see images attach

Even with just a caliper if you measure the minor diameter of the hole (or you could use known size pins or drill bit shanks like pins) that can provide a starting point to figure out the major diameter.

Sweet, no sir. I do have a caliper. I could try next available bolt size. 1/2" - 20? Or the metrics you suggested. That 1/2" - 13 started but wrong thread, just finer. So, close.

 

[Sgt Gus]

Also, have you tried a 7/16-14 bolt?

See my post #6. I definitely think 1/2" size, probably stud, then reduces to something. Weird.