Eat Beef

Well, it seems I've encountered another problem. The manifold fittings that came with my boost guage are too large to fit into the intake manifold. What size fitting goes into the bolt hole on the manifold? I assume it's metric??? And where would I get the proper fitting?
Andy

StealthDiesel

Hi Andy, it sounds like you are using a boost bolt.

The boost bolt should 1/8 NPT fitting.
If your gauge doesn't have this, any shop that has a Weatherhead fitting cabinet will have it.

1/8 NPT with a compression fitting to match your plastic tubing.
Bring the boost bolt & a small piece of the plastic tubing with you to match up for size.
Be gentle with the boost bolt. It is not that strong at all.

Leave plenty of slack & extra length in the plastic tubing. It is easy to kink & break & it can break off right at the engine fitting due to vibration..


I skipped all that and just tapped the rear of the aluminum intake horn.

It comes off easily to drill and tap. The aluminum is very thin though so don't run the tap in very far. In my case it was 1/8 NPT.

...Joe

Eat Beef

Yes, boost bolt that came with guage package. I thought it should fit???

StealthDiesel

Sorry, I added more info to my original post.. I hope it helps.. Joe

Eat Beef

Thanks Joe. I think I have the 1/8 NPT but I can't get it to fit in the bolt hole on the manifold. Next ? What is a "weatherhead fitting cabinet"?
Andy

1-5-3-6-2-4

just a brand of fittings.

StealthDiesel

Sorry about that Andy. I hope I am following you correctly.

Weatherhead is a company that makes numerous brass fittings.
Most autoparts stores, Autovalue, Autosource, Napa etc, will have a cabinet labelled "Weatherhead" with a selection of brass fittings.

I suspect your boost bolt has a 1/8 NPT (National pipe thread) fitting hole in the head.
Your compression fitting that came with your gauge kit is likely 1/4 NPT.

As was mentioned, bring your boost bolt & a piece of the plastic tubing hose to a parts store to find a fitting that will work.
The fitting will be 1/8 NPT male on one end to fit the boost bolt & a compression fitting with a brass ferule (ring) to seal the plastic tubing.


Here are some links that may help. ... Joe

Boost bolt:

http://www.dieselmanor.com/dm_products/DM-BSTBLT.asp


Plastic tubing with 1/8NPT compression fittings:

http://www.dieselmanor.com/dm_products/DM-TK14.asp

Eat Beef

Thanks again for the responses. I was missing the boost bolt in my guage package. I have the fittings but no boost bolt.
Andy

Lil Dog

You could pull the aluminum intake horn off and punch it out to 1/8 NPT and make it aim in any direction you like!.. The bolt is handy but if you don't have one, you can make do..

Tate

Thats what I did on both my trucks. Quick and easy, and if that bolt is as fragile as Joe says, then less chances of having something break as well. Letter R drill bit (or 11/32 if you don't have letter bits) and a 1/8 NPT tap and you're good to go.

Eat Beef

Thanks you guys. I might try the horn drill and tap. How deep do you tap the hole?

Dr. Evil

Dont go past 3/4 of the tap Andy. If you do, your fitting will be loose.

If you can find out exactly what size of fitting you need Andy, I probably have it. Let me know.

Eat Beef

I've got the fittings. I just need the boost bolt that goes into the intake manifold. The boost bolt receives the 1/8 NPT fitting. Do you have a boost bolt or know where to get one?
Andy

Dr. Evil

sorry - I was misunderstanding - I thought you just needed a 1/8" NPT fitting.

pind

I built a boost bolt out of a grade 8 bolt of the appropriate size. gives you a 13mm hex head, to which I brazed a 1/8NPT female coupling. Then simply attached the boost line with the assorted pieces of junk from the slider trays in my side boxes.

Worked like a charm. Including drilling, brazing, and installing, I was 20 minutes into the whole project. I must be getting old. tooooooo slooooowwww.