Set screw size for orifice in top of block BB.

Posted By: VernMotor

Set screw size for orifice in top of block BB. - 02/09/13 10:11 PM

It looks like a I need 9/32 set screw ? 9/32 is .2812 and hole is .270... what tap would I use ?

This is for the top of the block to cy heads oil feed for the rockers. I going to put a .080 hole in them. had .100 in the other motor and seems like a bit much.

Posted By: Stanton

Re: Set screw size for orifice in top of block BB. - 02/10/13 12:25 AM

seems to me that for a 9/32 set screw you'd want a 9/32 tap - with the pitch to correspond to the set screw as well i.e. 9/32 nc or 9/32 nf

FWIW the recommendation seems to be a .060 hole, although a 1/16 bit is more common and I didn't think .002 would make much difference

Posted By: VernMotor

Re: Set screw size for orifice in top of block BB. - 02/10/13 12:28 AM

So set screws are NF or NC and not NPT.. I was not sure.

Posted By: RoadRunnerJD

Re: Set screw size for orifice in top of block BB. - 02/10/13 01:12 AM

.080 won't be any problem but if you are trying to restrict the passages, .060 will be fine. That's what I have always run and no problem even with roller rockers.

Posted By: hustlin hoosier

Re: Set screw size for orifice in top of block BB. - 02/10/13 04:30 AM

9/32 is not a standard size you have something other than an sae thread it might be 1/16 pipe or metric .280 would be 7 mm. I have been atool & die maker for over 40 yrs and have never run across a 9/32 screw . If it were a "number screw" the formula to detemine a number screww size as follows 0 is.060 for every number you add .013 in such as a 10-32 , 0 is .060 , 10 times .013 is .130 add the 2 together is .190 that is the major dia of a 10-32 screw at 100% thread. But I think you really have a 1/16th pipe thread. The problem is I am not a plumber I am a toolmaker.

Posted By: Stanton

Re: Set screw size for orifice in top of block BB. - 02/10/13 05:29 AM

Well I don't know where that .270 hole came from ... I seem to recall those oil passages in my block were only around 1/8 and I used 1/4 set screws.

Posted By: MR_P_BODY

Re: Set screw size for orifice in top of block BB. - 02/10/13 06:22 AM

.242 is the drill size to tap for a 1/16 pipe plug
(or letter bit C)... .332 is the drill size for a 1/8
pipe plug(or letter Q).... both of taps have a 27
threads per inch(1/16 and 1/8).. if its threaded
now and you have a .270 it MIGHT be 1/16 NPT... that
would be like .014 per side but since pipe is a taper
it might be that much.... that could be what your
looking at
Jamie.... see if its a tapered hole

Posted By: dogdays

Re: Set screw size for orifice in top of block BB. - 02/10/13 06:31 AM

If it's a factory hole for fluid flow it's NPT.
If it's for holding things together it's UNC.

These are what I've observed.

R.

Posted By: MR_P_BODY

Re: Set screw size for orifice in top of block BB. - 02/10/13 06:51 AM

Quote:

If it's a factory hole for fluid flow it's NPT.
If it's for holding things together it's UNC.

These are what I've observed.

R.

I believe Jamie is trying to plug the oil supply hole
coming up out of the deck surface.... I did my SM
with a 1/16 NPT to close it off... I did the upper
side of the head under the rock base(I went to PR
oiling and the TD rocker base left a bit of the
hole open... on my W-5s) so that hole isnt tapped
for anything... its just a hole and I think its cast in
EDIT
Jamie... a .277 is the drill size for a 5/16 X 18
if you want the 50% thread factor(which can be used
in iron) .277 is a J bit.... normally I use a F bit
which is .244 but that is for 75% thread factor....
just giving you more to think about

Posted By: VernMotor

Re: Set screw size for orifice in top of block BB. - 02/10/13 04:00 PM

OK Thank you all. This is the info I was looking for. I try'ed to get the plugs/screws out of the old block to see what they are.. but could not. Did't try hard LOL. Been 3-4 years since I put them in and don't remember what I used. I will remeasure the hold again but I think Mr.P is right about using 5/16.. 9/32 confused me LOL.

Posted By: VernMotor

Re: Set screw size for orifice in top of block BB. - 02/10/13 04:40 PM

Ok so a 1/4 tap will fall in the hole. 5/16 NF will work good and a 5/16 NC would need to drill a hair !

Posted By: VernMotor

Re: Set screw size for orifice in top of block BB. - 02/10/13 08:01 PM

Went to the hardware store bought some set screws. they are so hard I can't drill them !! LOL have to find some cheap ones..

Posted By: Von

Re: Set screw size for orifice in top of block BB. - 02/10/13 08:31 PM

Quote:

Went to the hardware store bought some set screws. they are so hard I can't drill them !! LOL have to find some cheap ones..

Did the same thing last weekend. Bought 2 set screws, just as you did. Drilled through the first without any issue. 2nd one, no dice. They came from the same box at the hardware store. Went back and bought all they had. None of the rest were soft. Finally gave up and drilled through one of the hardened suckers. Took a hour and 3 bits, but finally got through.

Posted By: Cab_Burge

Re: Set screw size for orifice in top of block BB. - 02/11/13 07:44 AM

Quote:

Quote:

Went to the hardware store bought some set screws. they are so hard I can't drill them !! LOL have to find some cheap ones..

Did the same thing last weekend. Bought 2 set screws, just as you did. Drilled through the first without any issue. 2nd one, no dice. They came from the same box at the hardware store. Went back and bought all they had. None of the rest were soft. Finally gave up and drilled through one of the hardened suckers. Took a hour and 3 bits, but finally got through.

Two things, buy brass set screws to start with or deharden the steel ones by heating them up to cherry red(annealing them) and let them cool down to room temps. very slowly, or do you need to quench them in water to remove the temper or heat treating

Posted By: 1_WILD_RT

Re: Set screw size for orifice in top of block BB. - 02/11/13 08:25 AM

I've seen it suggested here in the past to put the restrictors in the oil passage in the heads rather than the block so if you decide to tune the oil supply to the heads it can be changed without pulling the heads...