Distributor won't seat all the way
 

I just got done doing a head gasket job and when I go to put the distributor in it slides in the gear and in place and when I turn the crankshaft it turns with no problems but it has about a quarter of an inch gap between the head and the distributor what do I do?

If it's a 3VZ-E you're exactly 180° off. The gear on the distributor shaft won't properly mesh with the gear on the camshaft, and you won't be able to push the distributor until it fully seats. I know you say it is in gear, but it isn't. Spin the crank one more time and try again.

If another engine, then disregard. I wouldn't know. I'd be guessing.

You are correct it is a 3VZE and I put it top dead center when I align the distributor and then when I got your reply just now I turn the crank shaft one more full revolution and still the same thing

When I install the distributor it has that gab like I said before about a quarter inch but I can still turn the crank shaft and The distributor will Turn like it is in gear and there's no resistance

Then your cam timing could be off. Speaking of which, BTW, why are you not telling me you're sure you're not 180° off, because you have all the timing marks lined up(camshafts, and crank)? Did you accidentally install the timing cover and water outlet first? And now you don't want to take it apart again?

If so...bad news. Your cam timing is probably off. So you'll need to back up a few steps and try again.

Just out of curiousity. Are you able to get the distributor fully seated by rotating it, or just the shaft, to the right or left a bit slightly first? That would eliminate the possibility that one or both of the gears is damaged. As well as verify the cam timing is off.

I might have the answer here for you!!
 

I hate to say it but i think you might have swapped the cylinder heads for one another i had the same problem and couldnt sit the distributor all the way only about a quarter inch off, but would still rotate. Enyways i ended taking the heads off and tried the right side cam on the head i had on the left side, what do you know it goes all the way down so there just probably put the wrong head on the distributor cam.

I think Yova just nailed if for you.

I can't remember what the years were that have it, but while looking for a used distributor I went in to Yota1 and they explained how some distributors have a slightly longer shaft that sits into a divot in the cylinder head. If you have a head without the divot and a distributor with the longer shaft, you'll have about a 1/4" gap from the shaft bottoming out

Well we're not likely to hear if this was the answer, OP hasn't used his account since this post

The bolt.
 

I just did a rebuild, when reattaching the timing chain cover i replaced all the bots.
I even used washers and locking washers, plus thread locker. The bolt that goes straight down from the head onto the timing cover (right under where the distributor gear goes) I put washer, lock washer, smaller washer. This created enough height to block the dist from going all the way in. As soon as I lowered that bolt, the distributor went right in. If that's the case, you will need to remove the timing cover.