To my other GT6 Pages

October 19, 2020

Prepping the Block


The engine (minus head) has been sitting patiently in its stand in the garage for over a year.  With the weather getting colder now, it's time to start to move operations into my warm basement shop.  It's the ideal time and place to turn focus to the engine.




I stripped from the block everything that would unbolt or pry or press out.

The crank, rods, pistons, and cam removals were uneventful.  But some things didn't really want to come out very bad, like some of the plugs for the main oil gallery, or the front and rear plate dowel pins.  I had to weld something to some of them to encourage them.




Then there were the headless aluminum plugs that have to be drilled .




The core plugs put up a fight, but eventually came along peacefully.




The distributor bush, while not difficult to remove, is a little fragile and hard to replace, so it took some special care.  This is an impromptu puller that gently moves the bush without any pounding.




At this point, I had a bare 130-or-so pound chunk of greasy cast iron.  I took it to the DIY car wash and used some high pressure hot soapy water to clean it up some and make it more pleasant to handle.

One of the first things I had to determine was whether I'd need a re-bore.

I'll interject a little history of the car here.  I bought it in 1977 or so, and in 1981, I decided to "refresh" the engine.  It had a little under 50,000 miles on it at that point.  The shop I took the block and crank to told me that the bores and crank journals were all in spec, so at the time, I just installed new rings, had the crank journals polished, and installed new standard size bearings.  I also had the block "boiled".

Fast forward 39 years, but less than 10,000 miles, and I was looking at a block that had small but detectable ridges at the tops of the bores.

Measuring them, I found that most of the bores were actually still in spec, but close to the limit.  A couple of them were just outside the limit.




Based on this, I decided to have the block bored 0.020" oversize, so I ordered the pistons and rings.

In the mean time, I set about doing some more internal cleaning of the block.  I plugged up all of the core plug and other holes in the water jacket and filled it with a phosphoric acid solution.  This is a medium strong acid that is good against rust and scale.

 


Since the block had so few miles on it since it was last cleaned, the foaming, which indicates the acid is reacting with something, was not all that great.  On my TR6, which had more miles and had never been cleaned, the foaming was prodigious.  I left the solution in the block overnight.




A week or so later, the pistons came in.  I took the block and pistons to a machine shop for boring.  I asked the shop to bore to fit the pistons with about 0.0035" clearance, and to deck the block just enough to clean it up, but no more than 0.010".  He thanked me for bringing in a clean block.

Two weeks after that, I picked up the block.  It looked pretty good.




Masked it and painted it with engine primer and paint.




Installed new core plugs.  These theoretically are self-sealing, but I try to appease the sealing gods with a thin coat of Permatex 3D.




Here is where the first fly appeared in the ointment. 

I bought the core plugs as a kit from one of the major suppliers for these cars.  When I came to the small plug on the front of the engine, something was obviously wrong.  The recess for the plug is only about 0.200" deep, while the plug is over 0.250".  The plug can't be proud of the block surface or the front plate can't seat properly.

 

I considered just trimming the plug, but finally decided to just get a disc-type plug for that location.  The vendor should have known this.

While in a plug state of mind, the plugs along the main oil gallery were next up.  I first cleaned out the main bore with a solvent-soaked swab, then did the channels to the cam and crank journals with pipe cleaners, all blown out with compressed air afterward.




I chose to use some stainless allen type plugs that come with a sealant already applied.  I installed five of these 1/8" NPT plugs.  It looks like two more are needed, but one hole is where the oil pressure switch goes, and in the other, I'll install a takeoff for an oil pressure gauge.




Then there is a plug at each end of the main gallery.  The rear one is a standard 1/4" NPT plug, but the front one, where the factory had one of those aluminum plugs, is tapped 1/2-20, so it needs to be a set screw.




The last oil gallery hole to be plugged is the big one above the oil filter location.  It also has one of those mysterious aluminum plugs.  Though replacement aluminum plugs can be had, I don't see the point.  On the other hand, the hole can't be plugged with a pipe plug since the threads are 3/4-16.  A 3/4-16 bolt goes in there, but it just doesn't look right.




I chose to make an adapter to convert from the 3/4-16 to 1/8 NPT.




The adapter gets Loctited onto the hole, followed by the smaller pipe plug.




At this point, I took the block off the bench, and mounted it back in it's stand, where frequent rotation will come in handy.




This is the start of a longish road for the engine, but it's pleasant work.  Next up is the crank and pistons.

Comments to Ed at elhollin1@yahoo.com

To my other GT6 Pages