1974 TVR 2500M driver restoration

   Yeah, I think you're onto something there.  I can't tell which one is off, but they definitely aren't in proper alignment.  I suppose they both should be parallel to the inner mounts, or at least close. 

Definitely looks like a problem to me.  Your trapezoid is overly trapezoidal.

Keeping things going here, not as quickly as I'd like but it's warming up here so now there's more vehicles competing for attention. I had the control arm tabs realigned and they look much better now. Unfortunately there is still a severe misalignment where the upper control arm meets the frame. I'll have to get more methodical with figuring out what the issue is. In the meantime I wanted to get SOMETHING done, so I finished cleaning up the differential case so I can paint it and installed new seals. Being a TR6 diff I'm sure it's been covered numerous times in other forums and websites, but I'll add my own info here in case anyone is wondering what's in the TVR's, as the TR6's had a couple different versions.

The biggest variable has to do with the pinion nut and whether the preload is set using a fixed or collapsible spacer. Theoretically if you have a version with a fixed spacer you don't have to worry about setting preload, just torque values. According to the 'net fixed spacers were used up to diff casing CC61570, which I believe corresponds to 1972 from other research I did but I could be wrong there. This type of spacer should also correspond with a castellated pinion nut. After CC61570 they switched to a collapsible spacer with a nyloc nut. After I cleaned up the diff I could see a marking of CP18393. I also could see the nut was not castellated. So the method I would use to set preload is to count the number of turns the nut went through to come off the pinion threads. For anyone interested I came up with just over 10 turns.

There are a variety methods for keeping things from turning while you try to undo the pinion nut. Since I had the diff on a bench and was replacing the cover gasket I just put a big screwdriver in the ring gear carrier and spun it until the case kept it from turning. I was surprised at how little torque it took to loosen the pinion nut. Probably was a combination of using a breaker bar and rock hard 50-year-old nylon in the nut. Once the nut was free it was just a matter of unbolting the front mounting bracket, then sliding the pinion flange off, removing the old seal and tapping the new one in. Very easy. I also put in new axle stubs/seals/bearings as one unit from Rimmer Bros. Pretty nice looking pieces.

Will have to find a replacement for this nut given it's not really locking any more. Most websites are out of stock but I'm thinking my hardware store should carry one, even if I have to get a normal height version and have it turned down.

Nasty old seal:

Much better:

Teeth on the pinion, ring, and spider gears all looked happy so all i have left to do with this is the rear cover gasket, reinstall the front mount and drive flange, add fluid and do some paint. More to come when I figure out how to make the rear suspension go back together again.

And there was much rejoicing! Spent this evening trying every possible combination of parts, swapping between left rear and right rear.

Every combo where the lower control arm which I had repaired was on the right rear had the same misalignment at the top wishbone mounts. Every combo without swapping lower control arms worked on the left side.

Once I put the repaired control arm on the left rear it worked on both sides, as did every subsequent combination. So I'm not sure what the issue was as I can't see that things in the rear are handed. Maybe the toe adjuster has a slight combination of angles front/rear and left/right that makes it only possible to use on one side? Either way project seems back on track!

In reply to ViperT4 :

Sweet!  Nice work!

I'm still here! Was away for a somewhat extended family trip back home but happy with progress made over the weekend:

-Used the left over paint from the chassis to repaint the mended areas of the bent control arm as well as little knicks I'd put into various areas of the frame from installing different parts dozens of times. Should be ready to refit all of the rear suspension and braking components very shortly.

-Finished assembling and resealing the differential case and painted the front portion and the mounting bracket. Should be ready to fill with oil and get back into the chassis.

-Refinished the steering rack and installed into the chassis with new poly bushings

-Degreased  and refinished the transmission crossmember, it ready to reassembly with new rubber mounts and then go back in the car

-Refinished the parking brake assembly, ready for new hardware and installing into the chassis with cables that are on hand

-Refinished the sway bar. Will be able to put in the car shortly with new poly mounts. The end links are toast and currently trying to figure out what to do with that. Probably can have a fab shop modify another set with the eyelets in the TVR links and find a set of universal bushings to go at the end of the sway bar.

-Started degreasing and generally cleaning up the transmission. About halfway into that. Brake clean and a wire wheel on an air grinder are making pretty quick work of it but ran out of brake clean yesterday... Also replaced the real oil seal and the paper gasket between the main box and the tail housing or "rear extension" as the Triumph manual calls it. I have the top member gaskets and the front oil seal to do plus finishing cleaning up the case. Anything else to service while I'm in there? I saw some TR6 forums mentioning dodgy clutch pivot rods/fork or their attendant hardware? The pin was already safety wired so maybe someone has already seen to it?

I took plenty of pictures in progress but I'll post them later once I have the payoff to go with them.

ViperT4 said:Anything else to service while I'm in there? I saw some TR6 forums mentioning dodgy clutch pivot rods/fork or their attendant hardware? The pin was already safety wired so maybe someone has already seen to it?

That taper pin is notorious for shearing and causing lots of trouble.  When it breaks, it usually leaves some amount in the joint preventing the release fork from being removed, but not enough to release the clutch.  A hardened taper pin is available, but it can also shear.  I've seen people cut the cross-shaft to get that thing out.  I've also seen the release fork welded to the shaft, which is great if you never need to replace anything.  One better fix is to drill a hole through the side of the fork and shaft and run a bolt through both to help support the taper pin.  What I do is replace the taper pin with a grade 8 bolt that threads directly into the shaft through the same hole.  This requires the tapered hole be drilled out and threaded to accept the bolt, which off the top of my head is 3/8"x24.  It's the largest bolt that will fit into the clutch fork hole without enlarging it.  Torque that bolt to 35 lb/ft and you are good.  Add some blue loctite or safety wire for extra certainty.  I've never seen this modification fail, but YMMV.

Also, check the condition of the release fork.  If the nubs that push on the bearing carrier are worn, replace it.  I've spun those 180 degrees to move the worn side around when the part wasn't available, but if that loose they could rotate back.  It's also not a bad idea to replace the bushings in the gearbox case that the cross-shaft rotates on if there's any play in the shaft.  Basically you want to maximize the throw of the clutch fork by removing all wear in the system.

Thanks for the details!

In reply to ViperT4 :

New to the group here and loving all the great content , currently working on my 77 2500M that I picked up at the of 2020 and you can see it sitting next to my 74 survivor.  Currently the 77 has a 3.8 in it but getting ready to replace with a 302 & T5 combination.  Luckily the 77 came with a salisbury differential so good there. Only thing done so far is replace front and back glass and strip interior.  

Very cool to have ying and yang versions! Also looking at the first picture I didn't realize they changed the taillight arrangements on later cars.

Viper, on your clutch question, I detail the most common (and bulletproof) way to deal with the fork pin on the clutch cross shaft. Near the bottom of this post.

http://coventrysfinest.blogspot.com/2017/07/resolving-leaks-in-tr6-od-transmission.html

I made some good progress over a couple weekends so I'll post some updates. I postponed further transmission/clutch work in favor of tying up a lot of loose ends on other areas of the car. A lot of this stuff was ready but waiting on me to figure out what hardware I needed to put things back together. In no particular order:

Steering rack installed with new bushings

Sway bar end links... Mine were knackered, as they say, and TVR specific replacements are not available to my knowledge. Luckily they're simple, and TR6 end links are similar enough. TVR on top, TR6 on bottom:

So a day with a local fabricator and $100 later I have new end links:

Installed with repurposed hardware from the TR6 endlink kit:

Assembled and reinstalled the transmission mount. Mine was just disgusting. Covered in old MTF and dirt, and the bushings were shot. The load on these bushings is not completely vertical; there is an element of side loading to them as you can see in the finished picture, so I'm not surprised they looked the way the did. The new ones are from Moss. I hope they hold up for a while but they are just stock replacements.

Nothing special, just rebuilt drum brakes. I had the pleasure of doing this twice as I installed the differential and the inner axles halves after this and didn't have enough space to fit the axles without pulling the hubs out again... Oh well, not the end of the world.

Onto the diff. After cleaning up the case I had painted the front half black and buffed out the rear cover so the appearance is similar to factor. I had already resealed it so it was just a matter of installing the drive flange and painting. I did get a new nylock nut like I talked about previously. The only issue I ran into with the diff was that when I removed the old nut I counted a hair over 10 turns to get the nut off. When I installed the new one I could only get it to 9 full turns before I was putting an uncomfortable amount of force on it. I stopped at 75 ft-lbs of torque on the nut. With a beam style torque wrench I am at 9 in-lbs of torque to spin the diff so I think I'm in the right ball-park at least.

Nothing sexy about this filling method but it works for me. MT-90 seems to be what was recommended most on the TR6 forums.

And diff's in the car! I hoped to drop the mounting bracket and pumpkin in all at once but that was a no go. I separated the two and had to go through all manner of stupid Mickey Mouse antics to align the mounting bracket with the chassis pick-ups. There was just too little leeway in any of the mounting points. The strategy which result in success was a combination of using [multiple] ratchet straps as come-alongs, hammering, and cursing. In the end the bracket went home and attaching the diff to the bracket was inconsequential.

Also ran the new parking brake cables and installed the inner axle shafts with new boots as I mentioned.

As she sits now:

It's been a while since I could say that and mean it literally. It hasn't had wheels on it and been capable of holding itself up for some time so I feel pretty satisfied with the progress. Gotta keep pushing it along though. With all this finally off my plate I'll move on to finishing the transmission reconditioning. I've decided to drill & tap the cross shaft and clutch fork base to add strength there as recommended.  From there it's on to engine cleaning and deciding how far I want to go in the search for more power, doing the new wiring harness, and bending brake and fuel lines.

More reasonably good progress the past couple weeks. Finished sealing up the front covers on the transmission and turned my attention to the clutch fork and pivot shaft in light of the advice provided here and more reading online. The shaft and fork were both worn so new parts were ordered along with new bushes.

Ugly wear on the pivot shaft.

New wider bushes should play much nicer with the pivot shaft.

Second hole drilled and tapped in the fork and shaft and Installed.

Turning then to the engine, I started on cleaning the grime off before disassembly and inspection.

Absolutely covered in old oil and dirt.

It was really interesting to me that the timing marks were hand scribed onto the front engine plate and cam sprocket.

One of the first things I went after was checking crankshaft end float and then measuring then seeing what thickness the current thrust washers were so I could get new ones ordered. Measurement came out right at .010", which if it was just a check in a together and running car I don't think would be enough to make me replace them. But since we're rebuilding new ones will go in. One of the thrust washers measured just a bit of wear and one was actually slightly thicker than the stock .0921". Math tells me one stock thickness thrust washer and one .005" oversize will bring my end float to just under .050" which I think will be a good place to start, since spec is .060"-.080".

Checking the appearance of the crankshaft and bearings itself all seems ok if just with normal wear. New bearings will be going in and I'll get the machine shop's opinion if the crank needs any polishing but at first blush it seems like that won't be necessary.

Main journals 1-2-3-4. #1 showed the most amount of discoloration, not sure what to take from that.

The camshaft was also generally in good shape but had some interesting markings. There's a dark triangle mark on the same spot on either side of each lobe. I can't tell if the polished metal has worn through or if it's just discoloration.

Tappet surfaces all looked very nice except for two which had some slight pitting.

So next steps for the engine;

-I didn't snap pictures but the cylinders show some spotting which looks like pitting, though they are still smooth in those spots. I plan to run a ball hone through them and if that doesn't clean them to my satisfaction will have the machine shop evaluate.

-Will likely have the block zero decked as the initial step in increasing compression to take advantage of the benefits the smaller squish area yields.

-Cylinder heads will receive the most attention, getting milled to bring compression to 9.5:1, as well as hardened valve seats and new valve stem seals installed. Probably do a 3-angle valve job as well. Nothing out of the ordinary here  really, just using what's already known about these heads for a modest bump in performance.

The biggest decision in front of me is whether to keep the cam (if it's serviceable) or go with street cam. I've come this far so I'm leaning towards can but haven't committed yet. Deciding between the BPNW 270 cam and Goodparts GP2. I'll be keeping carburetion the same with just reconditioning the Strombergs and having the distributor recurved to match the rest of the build.

Viper, your engine looks in better shape than the one I just built. 

For your thrust washers, look up Scott Helms on the goojle and have him make you some of his custom washers. Much longer lasting and not expensive.

^^ good resource. Nice to know someone is making some better thrust washers. 

For the cam, I'd go with the GP2 cam for a street build.  Replace the tappets as these are a real weak spot in these engines.  You'll also need to run an oil with zinc because of the flat tappet design such as Valvoline VR or Brad Penn.

I'd also consider cleaning up the intake and exhaust ports.  You can't do very much, but the flow can be improved.  Take a look at Kas Kastner's book on improving these engines.

In reply to oppositelocksmith :

Thanks for the tip. I did check out the website. I didn't get as far as asking for a quote but I assumed it couldn't be less than the $50 Rich Good charges per individual HD thrust washer. At $5 a pair for factory style ones from Moss I decided to order a pair of standard spec washers and +.005" from Moss and use one from each. Even if they only last 10k miles I'll be good for a the better part of a decade and can evaluate as time goes on.

In reply to JoeTR6 :

Thanks Joe, totally in sync here. The GP2 cam was actually the one I was heavily leanings towards. This morning I committed an placed a large order with Rich Good for basically everything I need to have the heads rebuilt plus the cam, tappets, and valve springs. I have been considering having the machine shop port match the head while they have it, have to see how much they'll charge for that effort. Looking forward to all the shiny new parts!

Well, I took my haul of engine parts to the machine shop Monday. They'll be hot tanking the block and head and then examining the bores. They will let me know if I need oversize pistons or stock replacements. They'll also let me know if I need standard or undersized main and rod bearings. Once those questions are settled and I have the new parts in hand they can determine how much of the block surface needs to be removed to be even with the pistons and once that's figured out we can do the head. I'll be tending to other things in the garage while the engine's away. Time to get serious about bending the brake lines and assembling my wiring harness...

Sounds good.  Nice progress.

What are you doing for a wiring harness?  Did you buy a stock one somewhere or are you making your own?  That'll be on my to-do list eventually.

I have a box full of many, many different colors of wire plus a few fuse panels, connectors and loom etc. waiting for me in the garage. I used a TVR diagram I found online and essentially mapped out where each wire should start and end mostly as an exercise to know what I was dealing with. I'll use that and go one by one cutting to length. I don't intend it to be a 100% faithful recreation but it will be fairly close and I will make improvements as necessary or where convenient. 

And so on down for about 86 lines.. It's just an Excel file I'm going to use as a checklist. I can share with you if it would be helpful.

Keepitcleanwiring has some appealing options. You'd lose some originality with the lack of the fuse blocks and different connectors but such an easy solution. Wiring had me so stressed out until I just resolved to scrap all the original wiring and spring for one of those.