Hi all, I've been chipping away at bits and pieces of my '26 T and I think next up is the carb. It's a Holley NH and while I do have the book, I've never done this before. Right now I have all of the stuff that's going to come off marinating in penetrating oil (most notably the throttle and choke are seized) but once I have it apart, then what? Should I be sand blasting and painting it? What kind of finish should the inside of the Venturi have? Any special precautions to keep in mind?
Any and all advice appreciated on this one.
If you want it rebuilt, contact Russ Potter. Carbking@soltec.net. 217-759-7592. It is among the best. He did a four ball carb for me. Got to meet him at Home Coming. He does great work.
I blast them before doing anything else. With Hugo's book you should be able to do it yourself.
If you don't drill out the passageways and clean them out, you're probably in for a big rebuild disappointment. I learned this the hard way with Holley NH's. I used to just soak them in cleaner and/or glass bead them, followed by blowing compressed air through every orifice I could find. Sometimes the carb worked properly afterwards, sometimes it didn't.
I finally re-did a troublesome NH that I had gone through years before, but hadn't drilled out the passageways. It always started REAL hard and didn't seem to develop the power that other NH's I owned did. 'Sorry, but the MTFCA carb book is rather vague, if not useless, in this area. I studied posted photos and recommendations on this website that showed the pathways of what needed to be drilled. The lowest passageway in this particular carb was almost completely clogged with crud, which I cleaned out with a drill bit and guitar string (per Stand Howe's advice). The other passageways weren't as bad, but they were at least partially clogged. After re-plugging the drilled-out openings, I couldn't believe the difference! The engine starts now almost instantly and has more power. Lesson learned.
Some may say not to bother drilling out these passageways, rather soak them in cleaner. I can only say that in at least two cases, this did no good for me. DRILLING and CLEANING were what turned those erstwhile balky NH's back "on".
Noted, she'll get a thorough cleaning. From the looks of things the carb was full of water for some time, the float chamber is horrifying but the surface shouldn't be critical so long as the needle seats and the float floats. I can see how the internal passages are almost certainly going to be plugged up. The venturi has a fair bit of spotty surface rust in it and I was thinking about maybe cutting small circles of Scotch Brite and putting them on the end of a long bolt to clean it up.
Do the throttle and choke plates come off easily on the NH? It looks like mine are held in by tabs that spring open on assembly. I'd like to get every last bit apart to thoroughly clean it if I can.
Throttle and choke plates: Depends on what you mean by easily. I find the tab type you describe a little tricky, but not impossible. The type held by a clip/staple are easier, and are the ones available new.
If this carb is for show, you'll want to replug the passages with brass rod as original. If not, I'd use Stan's trick of tapping the holes and plugging them with 8-32 set screws.
I like Rustoleum satin black for an exterior finish, but some prefer glossy. Nothing inside.
I went with Rustoleum gloss black because there's gloss on just about everything else. Looks like I'll be blasting and repainting the bowl again tomorrow, outside only this time.
I've also found that the float needle is stuck fast for now, fully open. I have it soaking in oil for the night to try and extract tomorrow, how would I best clean that up as well as the valve's seat? A bit of valve grinding compound perhaps, or is this a replacement item now?
Everything's a replacement item. I think every NH part except the body is available new. BUT for the float valve I would use only the original style, not one of the "upgrades".
This morning the float valve was wiggled out, looks like it was just gunk holding it in place and it should clean up fine. Later tonight I'll take a look at the float valve's seat and see what I can do to tidy it up. For a little bit of surface rust on small parts can I just throw them in a vinegar bath or something for an afternoon then thoroughly rinse?
You can test the air passages with carburetor cleaner spray to see if they are clear. The main jet and needle are typically worn out, I recommend replacing them with the excellent reproduction parts.
If the original needle and seat are good you can clean the needle up as seen here:
The method Royce shows for repairing the valve needle also applies to the spray needle.
Well, the valve needle seems to have cleaned up decently but I'll have to make a tool to get its seat out to see how that's weathered the years.
Thanks to everyone who has helped out so far, I'm sure I'll be calling on you again before this thing is done.
Being as I am truly lazy, I have wonder at the need to remove the float valve seat without testing it first. It could be just as easy to work on it in place in my experience
I'm all ears, Les. I've never done this before so parts of the process are being made up as I go.