Once again I've been sidetracked by another project. In the course of servicing our "new" motorhome I dropped the pan on the transmission to change the fluid and found chunks of the aluminum case floating around. Seems the intermediate clutch retaining ring tabs were breaking off and it was only a matter of time before they failed altogether. This is a not uncommon issue with the Turbo 400 but is usually only found in high rpm applications. So the decision was made to yank both engine and trans together out the front, a job that took a whole day due to the limited access and lack of reach of my engine hoist.
Although I have rebuilt Turbo 400's before and they are not difficult, I was able to buy a newly rebult one for $325, which is less than it would have cost me to find a new case, buy a rebuild kit to do it myself. Plus the guy who built it incorporated some enhancements to help it survive in the motorhome while towing a trailer.
Since the 454 was out I thought it would be a good idea to tear it down and see what condition it was in. First surprise was finding out it was already rebuilt once with 30 over pistons and a 10/10 crank. Second surprise was finding the left head was cracked, right between the two valves in #7. Last time I started it I noticed white smoke from the left bank which I now know was caused by coolant leaking into the cylinder. In an amazing coincidence a pair of heads with the same casting number popped up on Craigslist the same day and I drove to Indiana to pick them up for $80. Being small valve, small port heads they are not very popular and I was able to buy them cheap. One of them was missing a valve and had a broken valve guide but I only needed one anyway.
Reassembling the short block
The bores were in pretty good shape with minimal wear with the exception of #7 which was pitted a little from the coolant leak. Crank was also good except for some wear on the thrust journal where a small piece of bearing got wedged. As I'm doing this on the cheap (the motorhome will see less than 500 miles a year probably), I am just re-ringing and replacing bearings. I have what I call a "dingle berry" hone, otherwise know as a ball hone, to clean up the bores a little and put some cross hatching on the walls to help the new rings seal.
The cam bearings looked pretty bad so for $16 I bought new bearings and thought I'd install them myself, how hard could it be? And with the right tool, its a piece of cake. I bought a installer/remover from Ebay for $75 plus shipping. Take your time, be sure to line up the oil holes and its just a matter of a little hammer action. Torque down the main caps before installation. Freeze plugs also get replaced with brass ones, using some Napa gasket shellac to seal. Block has been degreased, pressure washed and painted black.
Install new crank bearings using a good assembly lube drop the crank in. I'm not going to mic or plastigauge the clearances as I'm replacing with the same 010/010 bearings. Oil pressure before tear down was acceptable so nothing should change. In a perfect world I'd have the crank turned and bore it to 040, but we're on a budget. Give the crank a firm tap on the snout to align the thrust bearing and torque main caps to 110 lb/ft using engine oil to lube the threads.
Check crankshaft endplay with a dial indicator on a magnetic stand. I have .008" play which is a little loose, it should be between 5 and 7 thou but there's nothing you can do about it except replace the crank so 8 thou it remains.
Install the new rings on the pistons following the instructions in the box. Oil the bores and the piston rings, lube the big end bearing with assembly lube, use a ring compressor to drive the piston home in the bore. Install the big end rod cap and torque to 50 lb/ft. And there you have it, the bottom end is together.
While you have the head off and apart, might as well lap the valves before reassembling them. A suction cup on a stick, some valve grinding compound, and liberal elbow grease does the job. There are bunches of youtube videos that show you how to do this. I used some Dyechem to stain the seats blue so you can see how good the valve is sealing.
Here is a before and after showing the nice clean circle the valve makes when it's contacting the entire seat. I got lucky and all seats are in good shape and should seal well. If you have nicks or high and low spots you will need to have a machine shop cut new seats and angles on the valves. I had this done to a previous set and with surface milling, was out the door for $240.
After lapping on the left, see the nice shiny ring around the seat? I had also bead blasted the heads, and the best way to clean up after blasting is to pressure wash or put the parts in the dishwasher! Just don't try baking your powdercoating in the kitchen oven, everything you cook will taste like paint.
