Dipstick Tubes

[LTZ C20]

Let's see if you guys can make some sense of this. I'm getting rid of the chrome dipstick and shorter dipstick tube on my 350. I got a brand new dipstick from the chevy dealer, they couldn't get the tube, I searched O'Reilly's and the tubes they can get are either chrome or billet flexible so and so's. I went to the local pick and steal and got 2 tubes, one from a think was a 77 350 truck and the other a 75 or 76 350 truck.

So I cleaned them up, painted one of them, tried to put it in today and it don't fit! The old one, fits snug and small taps from a hammer seat it nicely, this NEW to me tube is loose, I can wiggle it and pull it out and push it back in no trouble.

I used a digital micrometer to measure the area that presses in the block, the old one measured .436 OD, the NEW one measured .430 OD. Why is there a .006 difference in tube diameter?? It should fit, I don't understand.

My truck is 73 c20, bored 350, block is originally fast burn crate engine, but I got it as just a block, unknown year.

[enaberif]

I've heard the holes for the dipstick tubes can become enlarged causing the dipstick tubes to not fit properly.

[Blazin]

If that was the case the old tube would be flopping around too.

[LTZ C20]

I'm note sure how easy it would be to enlarge a hole that's has 1/4 inch thick walls. My old tube is a stock tube that was cut down short for the shorter style chrome stick. If it was original length I wouldn't bother but it's not so that's why I got a new one. Same goes for the old stick, was worn down from years of use and no longer read properly. The chrome stick that was installed just had skewed measurements, I've figured out where proper level is but it's better to use the correct stick than decipher the one that reads wrong.

[Captkaos]

Fill it up with the proper amount of oil.  Pull the dipstick run a hacksaw across where it stops and call it good.  You can also do one quart less and mark the range.

[Dr_Snooz]

Fill it up with the proper amount of oil.  Pull the dipstick run a hacksaw across where it stops and call it good.  You can also do one quart less and mark the range.

Exactly what I did with my trans dipstick, except I cut it a little long and engraved the marks on it with an engraver.

[LTZ C20]

Thanks Capt but ide rather not, it's a brand new dipstick. Literally, brand new.

[fitz]

  Isn't the fast burn crate motor a 1 piece rear main seal block?
   Those blocks use a different dipstick & tube  then the older 2 piece rear main seal blocks.
  I have a few 1 piece 350 blocks in my fleet.  The dipstick tubes have a tab so the dipstick is bolted to the motor, not just  firmly tapped into place like the older 2 piece blocks.
  I bought a new dipstick and tube from GM about 1 year ago. If my memory is correct I paid over $100 for it.  I remember it wasn't cheap.
  I can grab a picture of this set up if you need it.
  I'm just throwing my hat in the ring on this one, I've never compared the diameter of the tubes but I don't think that they interchange.

[LTZ C20]

  Isn't the fast burn crate motor a 1 piece rear main seal block?
   Those blocks use a different dipstick & tube  then the older 2 piece rear main seal blocks.
  I have a few 1 piece 350 blocks in my fleet.  The dipstick tubes have a tab so the dipstick is bolted to the motor, not just  firmly tapped into place like the older 2 piece blocks.
  I bought a new dipstick and tube from GM about 1 year ago. If my memory is correct I paid over $100 for it.  I remember it wasn't cheap.
  I can grab a picture of this set up if you need it.
  I'm just throwing my hat in the ring on this one, I've never compared the diameter of the tubes but I don't think that they interchange.

Fitz,

I'm not sure on the 1 piece rear main, when I built the engine I used a 2 piece seal. That's what came with the block, along with all the bearings from the machine shop that did all the work to it. In my area they are a very reputable shop.

A picture would be great. That way I can see. I thought most would be the same up until the 90s but I guess I'm wrong.

The dipstick wasn't too terribly expensive,  don't remember how much it was exaclty, 20-30 bucks I think.

A picture and maybe a part number if you have one would be great so I can get the right tube, or at least just a tube with the right size insert area. I would hate to have to go and get another stick to go with a new tube just cuz I can't find a tube that will fit.

The old chrome tube that belonged to the chrome stick got damaged, so I cut my old stock stick down to match the length of the chrome one. Both the chrome one and the cut stock one fit fine, no problem.  So why another stock tube won't fit makes no sense to me.

Unless the old engine that the old tube came off of (my old motor, not original to truck) was from the same period as the fast burn block, which would explain the easy crossover. OR, when I painted this new tube I just got, I didn't paint the "press in" area, maybe I should have painted the whole tube and let the paint take up that extra .006 area of space.

[enaberif]

The part numbers for the tubes which I bought from Ebay are GM #3951600 which is the lower tube part and part GM #12337946 which is the upper part.

Putting the bottom piece in was a lot of fun and I had to use some ingenuity to get it started then used the upper tube to seat everything perfectly. Also put a bit of rtv on the top half to help any possible leaks.

I can't give measurements on the sizes but they are the two parts I required for my block which is a 1980 and older.

[LTZ C20]

Thanks enaberif, I will check those out tomorrow and see what I come up with.

[fitz]

I will grab pictures tonight after work.

[LTZ C20]

Sweet. Thanks.

[fitz]

  Working late tonight, I didn't make it home to take pictures of  the engines I have on stands.
  This one is of my work trucks 350 vortec motor.  See the bracket where the dipstick tube bolts to the block? I think all of the 1987-2000ish 350 blocks use this set up on the passenger side.
  I should have asked earlier if you dipstick was on the drivers or passengers side.

[LTZ C20]

Yea my mom's truck is the same setup. 97 chevy silverado with a 350. That don't work for me. My dipstick is on the drivers side.