The Cessna 120-140 Association Forum

Hi,
I just got my engine back from an overhaul shop. My mechanic noticed that the studs (part # 402711) that screw into the carb body are missing. These 4 studs allow the airbox to be secured to the carb. Evidently these studs are slightly oversized so they lock into the carb's threaded holes. This is a Marvel Shebler MA-3SPA carb that was overhauled by Marvel Shebler as part of the overhaul of the whole engine.

A couple of questions:

-Should my overhaul shop have provided the studs since I dropped the engine off with the studs installed in my old carb?

-If my overhaul shop doesn't want to cooperate, how do we know which size studs to order? They evidently come in standard and several sizes oversized. These studs are approx. $50ea. for a total of $200 for the 4 of them. I don't want to order studs and find out they are too loose in the carb holes and waste $200+ shipping/tax. Hoping I can get some guidance on how to know what size is right?
Josh

8413 wrote: ↑Fri Mar 13, 2026 8:32 am This is a Marvel Shebler MA-3SPA carb that was overhauled by Marvel Shebler ...

-Should my overhaul shop have provided the studs since I dropped the engine off with the studs installed in my old carb?

Short answer, yes.

Longer answer: Did they take them out before they sent the carb to Marvel? Unlikely, so Marvel is responsible, but, you are not Marvel's customer, so the shop should still handle it.

Oversize studs are for worn holes in the carb. You only need them if the standard size is too loose. Then it's selective fit.

Studs are standard MS parts. You shouldn't need to pay $50 each to get them from Marvel, if it comes to that (but it shouldn't).

Another short answer to add to what my fellow moderator John has already said -

Those studs are a TCM part, and not a Marvel Schebler part. You can locate them in the Continental Parts Manual for the C-85, C-90, and 0-200. Specifically they are TCM p/n 402711 which is a plain 1/4" x 7/8" long stud.

Now the bad part, those puppies sell for approximately $42 each from Aircraft Spruce. I think I would go back to the folks that overhauled the carburetor as John suggested, and require them to give you those studs back.

https://www.airpowerinc.com/402711

A little cheaper but doesn't solve the initial issue. 1/4x20 on one side and 1/4x28 on the other.

My rebuilt carb came back from D&G Supply with the studs still on them.

6597 wrote: ↑Fri Mar 13, 2026 7:31 pm https://www.airpowerinc.com/402711

Interesting dimensions!
3.85L x 4.6W x .85H inches

-Should my overhaul shop have provided the studs since I dropped the engine off with the studs installed in my old carb?
YES My thoughts are what ever you sent out should come back either new or your used in a bag? I'm exhausted of chasing things down.

If my overhaul shop doesn't want to cooperate...

Do you have reason this will be the case? Do you owe them any money, or have you paid them with a credit card?

Thanks for the helpful replies.

My overhaul shop went back and looked at pictures he took of my engine when I dropped it off and confirmed the studs were there. He did the right thing and overnighted the studs to me. This is the only thing about this overhaul that went quickly. It's been 2.5yrs since I found metal in the screen during an oil change. I'm a patient guy, but this process has stretched my patience to it's limits. My poor 140A has been sitting for far too long (in a hangar thankfully).

Now, I have a difference in opinion on these studs. The overhaul shop says they are not an interference fit in the carb body and that the retaining nut that holds the airbox on locks the stud in place when it's tightened. My mechanic says every plane he's ever worked on these studs are secure and not loose (or able to be unscrewed easily) in the carb body. He thinks they should be slightly oversized so that he would torque them into the carb body.
Josh

6643 wrote: ↑Sat Mar 14, 2026 7:22 am

If my overhaul shop doesn't want to cooperate...

Do you have reason this will be the case? Do you owe them any money, or have you paid them with a credit card?

No I don't owe him any money. The only thing I did wrong was to be too nice. I should have put more pressure on him to get my overhaul done sooner. It took 2yrs and 1 month from the time I dropped the engine off back in Dec of 23' to get it back on New Years Day 26'. I finally had to call and seriously question things with him when I heard of another person get their Lycoming back after only a few months. I was very close to demanding all my parts back and have someone else assemble it. And this shop has the best reputation for quality work in my region. I expected at least a year for the overhaul since we were coming out of Covid and the supply chain issues, but not 2yrs. His original time for the overhaul was quoted as approx. 7mo.
Josh

At this point, I had to just laugh and shake my head when my home airport notified me that they will be closing the runway for the summer due to repaving . Right about the time I'll be getting flying again. What's that saying?....good things come to those who wait. I sure hope so