Monday, September 24, 2012

1971 Triumph GT6 Engine and Gearbox rebuild

Well, since we're doing that we might as well do this too....that's how it always starts...

Ok, after several requests I have made a blog to document the rebuild project for my '71 Triumph GT6 MkIII.   I acquired this car in mid March of this year.  Overall in pretty good shape however I have one very low cylinder (50lbs) and a pretty noisy gearbox in 1st, 2nd and 3rd gear, so decided to do the rebuild over the summer.   The car was partially restored after sitting for 11 years in a driveway in San Diego, abandoned.  Much work had been done to get it to this point.  No rust, no accident damage, traditional paint color for Triumph at the time (an acquired taste for some).

This is a straight 6, 2L engine, two Strombergs.  Pretty simple really, and very easy access under the hood.

The engine was pretty well restored already, kind of a shame to have to pull it out.

Started in early August, figured it would be done by the end of the month, or no later than 9/14 when my assistant, son Scott, went back to college.  How hard could it be?

Fortunately I have a flat parking pad in my side yard so started the project there.  Was able to rent an engine hoist, pulled out the engine and gearbox with out too much fanfare, made easier since removing the hood basically left it free and clear.

The gear box had to be unbolted from the inside so removed the seats and much of the carpets.   There was a transmission tunnel cover that was in very bad shape and not even bolted down, new one on the way.   The dash was dried and cracked so ordered a new one as well.  Seats covers were in pretty good shape however the foam was shot so having them rebuilt as well.  Somehow these projects all seem to escalate like this.
Out of the side yard and into the garage, fortunately had help from a mechanic friend Majid.   This thing is heavy, over 500 lbs I'd say, either cast iron or dark matter, not sure.

With the engine out there is not really that much left on the front end.   The bumpers were pitted and warn so off to have them re-chromed.

Manged to get the engine on the ground propped up by 4x4's.  This means the end of my parking spot for a few weeks.  At least that was the plan.  Note the red engine stand which unfortunately did not fit the narrow bolt pattern of the Triumph.  But we solved that problem later.

Rocker shaft and lifters came out easily, and looked in very good shape so wont have to replace them.  We were expecting damage to the valves #5 cyl which was low on compression but that was not the case.  Must be rings, yep...a broken ring on #5.   I should note that we are converting this to run unleaded so new hardened valves, seats and guides.  And while we're at it, new pistons as well.

Most everything on the engine came off pretty easy - except the head.  Lots of rust around the studs so took a lot of muscle and a "persuader" aka the large 1/2" breaker-bar wrench at the top of the photo.  Overall engine was in good shape for 40+ years and about 65k miles.

Had to improvise since we didn't have a working engine stand.  With the block on its side we were able to get the oil pan off.

More improvisation.  Used an old skateboard to transport the engine block.  Surprisingly it handled the weight.

The gear box is rather small but very heavy.  Looks like some damage to the gear surface from rust, probably from moisture in the case while it sat for over a decade.  Have to replace a few gears and maybe the lay shaft, lets hope that is all.   Scott demonstrates how the the gears shift for his grandfather, who was a mechanic in his younger days.  

Meanwhile back at the dash, lots of "filddly bits" as they say and a nest of wires and vent tubes behind the tight dash.  Took these pictures in hopes of making it easier to get it all back together.

After a few weeks we got the engine block back from the machine shop.  Looks great!  Water jackets were cleared out by soaking in rust dissolving solution.   Cylinders were in pretty good shape except for some minor scratches.  They are now .020 inches larger which is about 25cc increase in capacity (check Scott for the calculations).
 As I mentioned earlier, my garage became the shop, worked pretty well but will be glad to have my indoor spot back.
 Found an old engine stand on Craigs List for $20, just what we needed.  It was old and faded yellow so Scott cleaned it up and powder coated it to look like new.   Time to get busy reassembling the lower end.
 Main bearings are in, crankshaft next.
 Pistons went in without a hitch.
Freeze plugs in along with the crank, getting very heavy now, maybe too heavy for the engine stand, not the wood post holding up the end of the block.  
 Timing chain and front cover on now, getting very heavy, note the 4x4 holding it up now.
Front, real seals, thrust bearings, oil pan all on now.

Next step is to connect the transmission and put it back in the car, then put the head on along with the manifolds.

Stay tuned...