Installing guages now..question about drilling and tapping

[HDerrick]

Gents



I am in the process of installing guages into my CTD. Boost, fuel pressure, and pyro. Problem I have at this moment is drilling the air intake manifold and exhaust manifold. Heres the delimina



Boost pressure install--drill with a 11/32 bit and tap with 1/8 npt tap



I have UNC and UNF tap set, but dont have the npt tap set and wonder if I used the 3/8 unc tap, would that be the same or close to the 1/8 npt tap?



Exhaust manifold--drill with 7/16 bit and tap with 1/4 npt tap



If I used 1/2 unc tap, would that be the same or close to the same as 1/4 npt tap?



Since I am not a math genius, I'd love to have someone point me out in the right direction. Thanks!!

 

[JARichard]

I would have to go to my office to get the right tap sizes. If you dont have them by tomorrow I will post them. Why drill the intake when a Boost Bolt is $8 or $9. If you buy gauges from Geno's it is FREE!!!

 

[Briman]

For the exhaust manifold go buy the proper taps or learn how to swear.



For the intake, put the project off until you order and receive a boost bolt and directions for it's use from Geno's.



If you do a search on the boost bolt you will find some recent posts that are informative and may sway your decision on taping the intake horn.

 

[HDerrick]

Which shows more accuracy? Boost bolt or drill and tapped? Guages and 3 pod pillar package that I ordered came with the drill and tap boost kit. Don't know if it makes much difference. I'll check the search and see it whats going on regarding boost bolt. Thanks

 

[grabinov]

The boost bolt takes intake air from the hole which the stock intake manifold bolt fills. The bolt is directly in the intake path, and, since the manifold is essentially evenly pressurized, the pressure should be the same whether you tap or use the boost bolt. The hol in the boost bolt is slightly smaller than the one in the tap fitting, which suggests that the gauge could react to changes a little more slowly with the boost bolt than with the tapped fitting, but the difference is probably so small as to be un-measurable - without using another gauge that is!



In terms of the manifold tap, I used the "plug the exhaust pipe, get your tools ready and tap the manifold (exhaust) with the engine running" method. It sounds hokey, but it worked beautifully for me 3,000 miles ago. I have never heard of anyone having a problem with this method if done carefully. Just wear eye protection and long sleeves - the hot shavings come right at ya!

 

[JHardwick]

Originally posted by HDerrick

Gents



I am in the process of installing guages into my CTD. Boost, fuel pressure, and pyro. Problem I have at this moment is drilling the air intake manifold and exhaust manifold. Heres the delimina



Boost pressure install--drill with a 11/32 bit and tap with 1/8 npt tap



I have UNC and UNF tap set, but dont have the npt tap set and wonder if I used the 3/8 unc tap, would that be the same or close to the 1/8 npt tap?



Exhaust manifold--drill with 7/16 bit and tap with 1/4 npt tap



If I used 1/2 unc tap, would that be the same or close to the same as 1/4 npt tap?



Since I am not a math genius, I'd love to have someone point me out in the right direction. Thanks!!

NOOOOOOO!!!!!!!



NPT taps are a tapered pipe thread, and have a different pitch to boot ... ... ... get the proper taps please!

 

[Fireman]

Second !

JHardwick is right ! Go out and buy NPT taps, it won't cost that much and will save you a lot of grief.



Fireman

 

[HDerrick]

Alright, thanks, I just needed to know what the tap differences were. I just hope my small hometown parts store has some npt taps in stock since I have the truck taken all apart in the interior and need it back together by tomorrow.



Thanks again for the tips up!

 

[nickleinonen]

home depot [and competing stores] should have 1/8npt and 1/4npt taps on the shelves...

 

[tpuig]

Get the boost bolt from Geno's. I ordered gauges and pod a while back but never got around to putting them in. Since then, Autometer has come out with a new gauge pod for the dash to fit the '03-04. I had intended on using the earlier version and modifying it.

Called Geno's to exchange the gauge pod, and she said since the boost bolt wasn't available when I purchased the gauges, they'd throw it in at no charge. What great customer service. Geno's rocks!

TP



Now if can only get around to installing the gauges...

 

[HDerrick]

I was able to get the NPT taps I needed this morning from the local parts store. I didn't order the guages and pods from geno's so I'll just make use of the boost kit I got when I ordered the stuff. Since no body could point out the accuracy between boost bolt and tapped boost screw, I see nothing wrong with going with the latter.



Thanks for all the tips, they were appreciated!

 

[Briman]

Originally posted by HDerrick

Which shows more accuracy? Boost bolt or drill and tapped?

The boost bolt is measuring pressure right inside the intake plenum next to the valves. As someone Else pointed out in another thread this is where it is most likely the lowest, but probably the figure that is most relative.