ready for teardown, need specs

[68C15]

I have what I believe to be a 68 472 that I am getting ready to tear down & inspect. from that point i will then decide what mods to do & what parts need replacing. the problem is I have no source for stock specs (journal dimensions, clearances etc). any help?
this is going in a '67 stepside 2wd Chevy with 3.07 and the caddy TH400 with 31ish tires. I have been inspired by Cadiac & a guy from ohio named Longhornman

[~JM~]

MTS sells a Tech Guide.

[Clay]

68C15
Try this on for size.
Clay

[STDog]

A good idea would be to get a Cadillac shop manual. It'll cover the engine and trans (you do plan to use a BOP TH400 right?) and the carb.

If you'e staying stock, then 68, 69, or 70 manuals will work fine. There were some carb changes though, different jets and such. Also the '70 engines didn't have the A.I.R. system, or the exhaust manifold mounted valve. Both Items you probably plan to remove.

As far as replacing parts, they are 2 schools of thouight there. If the engine has been treated well, you can hone the cylinders and replace the rings/bearings, and valve springs. And probably be good to go. Probably polish the crank, and check the size. New gear in the oil pump. Get a valve job, and normal head cleanup.

The other method is replace the pistons, after boring the cylinders .020-0.30 over, replace most other parts (rods, push rods, big valves...), regrind the crank .010 under, etc. ...

I expect you could go the first route, and be fine. If the engine wasn't oil starved, everything should still be fine, just new bearings either standard or .001 under. The crank and block are really strong and tend tio not wear much.

[68C15]

as it turns out there is an evil twist (or lack thereof) to my plans. while trying to seperate the TH400 this morning I couldnt turn the flywheel to get at more that 1 converter bolt. also all the exhaust bolts on the pass head broke off. it sounds like this is gonna cost more than I planned. :cry:
I guess I better take the digi cam to work in the morning. hopefully the PB blaster does some good. I filled all the cylinders this afternoon. <fingers crossed>

[Terrible One]

Yeah, the manifold bolts always break off in the heads on these things.

[STDog]

as it turns out there is an evil twist (or lack thereof) to my plans. while trying to seperate the TH400 this morning I couldnt turn the flywheel to get at more that 1 converter bolt.
Hmmm. How long has this engine been sitting? Did it have a bad head gasket?
What you describe is either bearing problems, thus you may have a spun bearing:!:
Does it turn at all?
.. or rust in the cylinder, and thus probably need to bore the block and replace pistons.
You may get lucky, and be able to hone it out, but if it's locked it up, I doubt it.

Then again, I soaked the cylinder on a 425 overnight with oil and worked it past the rust slowly (to not break the rings) and it's been running for a few months. But this was a quick, get the car moving job, and the 472 is waiting for a rebuld (needs crank work, and money).

also all the exhaust bolts on the pass head broke off. it sounds like this is gonna cost more than I planned. :cry:

If the bolt can be reached, you can probably get them removed cheap/easily. Soak in penetrating oil for a few days first. Heat from a good torch will help too. If they are too short to reach, a shop can drill them out.

Note, I've drilled them out myself but, you need a good selection of drills (bits)so as to not damaget the threads. Then either a steady hand, of a way to position the head for a drill press. A good bottoming tap will be handt to ckean the threads up afterwards, but that should be done on all the holes anyway.

[68C15]

I looked in the cylinders this morning. :( :( :( full of rust. this thing sat in my garage for a year. before that is a mystery to me.
I did manage to seperate the trans. I left the converter intact 7 slid the tranny back, then used the torch ti heat the lugs & turned the bolts out with a wrench. still no crank rotation. judging by the amount of rust I can see I will have to go about .020 or .030 over. oh well
just how far can a guy safely go with these things? :twisted:

I did clean off the block & head to get some #s

block is 14686238
head is 1486250 (I think)
the head also has a large 106 cast into it
no pics yet as I am waiting for the full teardown.

[Nashalac]

At least .100 to .120 without any block fill.

[Terrible One]

Nash, what pistons are available at that bore though?

[Nashalac]

Custom Forged

[dave_brode]

68,

Think it'll clean up at +.060"? If so, that'll make for 484". KB has +.060" hypers that should give you about 10-1. Iirc, Al has a similar piston in a hypo.
Dave

[Terrible One]

Custom Forged

Thought so

[68C15]

Dave, from the looks of it it should clean up at .030 over. is there any advantage in going more than necessary? (other than bragging rights)
it took some major fanaggling & creativity to get it torn down without spinning the crank. I now have the pistons at the bottom with the crankshaft removed. I was thinking of using a bead style hone to take most of the rust awaybefore I pop the pistons out the top. I have heard horror stories where the blocks have cracked from forcing them past the rust.

BTW, Al, if you are following this what pistons would you suggest? daily driver 1/2 ton 2wd that thinks its a 1 ton at times. I also like to suprise "Honda Boy"

[fleetwood472]

Hey 68C15,

You should be ok popping the pistons out without cracking the block. Do you have any pictures of the bores? The same thing happened to me when I tore my 472 down. It sat for a while and the bores rusted. I sprayed them down a few times within an hour and then unbolted the rods and crank and tapped them out with a 2X4. It probably wasnt the best choice but it worked. Just tap firmly but not too hard and oil everything up real well before you tap them out. It worked for me and I had the block magnafluxed and everything was ok. That could be true though about the block cracking from that but there really is no other way to get them out is there? What sucked for me was that the block was already bored .030 over so I had to go to .060 for it to clean up and to find the .060 over low compression pistons fro my 76cc heads was a bitch. I'm not sure what your building high or low compression motor but they still do make the dish style silvolites in up to .060 over. Just some of the vendors arent able to get them since they are backordered. I did some searching on the internet and found a place in AZ that had the pistons. Good luck and keep us up to date on this. If I were you I would try .030 to clean them up but if they are really rusted go to .060 over. Good luck man - Justin

[dave_brode]

68C15,


"]Dave, from the looks of it it should clean up at .030 over. is there any advantage in going more than necessary? (other than bragging rights)

No, but realize that a .030" over bore allows just a .015" cut all around. Rust is often deeper than that. Your machine shop may be able to guess better is it'll clean up at .030".

Dave

[68C15]

well, I got the pistons out. I went at it with a flat screwdriver to scrape as much as possible. then used a radial flap wheel on my straight die grinder to get it down to bare metal. (this is some HARD metal). then they almost slid out on thier own after a good oiling.
I took a scotch brite brown pad and some PB Blaster to clean #1 (it was the worst). the pitting is about .012 deep. I will take it to the machine shop on Monday to see if .030 will do it. first I need to run it a few times through the cooker-blast cabinet at work. he likes it when I bring him clean & dry stuff.

I am somewhat concerned about the heads though. #3 exhaust pushrod was bent pretty bad. but I did not see any indication of damage to the piston. the machine shop gets the heads next week after i tear them down & clean them.

funny thing is I noticed all the rods were number stamped correctly for the respective hole. was this done at the factory or has it been gone through?

[STDog]

funny thing is I noticed all the rods were number stamped correctly for the respective hole. was this done at the factory or has it been gone through?

Factory. Every 425/472/500 I've been inside of had them marked. Notice too that the main caps are marked, not only numbered, but direction too. The dimples all go to the same side (I forget which side at the moment though:( )

A friend's 68, didn't have something marked, but I don't remember what it was now, either the rods, or mains, So they may have started marking in late '68 or '69. Sure makes rebuilds easier :wink: :D

[Nashalac]

The main caps go on so the bearing notches in the cap are on the same side as the block

[dave_brode]

68C15,

> the pitting is about .012 deep. I will take it to the machine shop on Monday to see if .030 will do it. first I need to run it a few times through the cooker-blast cabinet at work. he likes it when I bring him clean & dry stuff.

Fyi - The selection for +.040" rings is limited. If it will not clean up at .030", you might want to check ring choices for +.040" and +.060" before deciding.
Dave

[MilesO]

Al can get you pistons for whatever bore size you need.

I use this site for paper planning purposes; www.kb-silvolite.com

check out the tech section and hypereuctectic pistons diametrical listing for your bore size.

Al's tech guide and other informational material is a good source of quick Cad info and interchangeability.