U20 Broken Timing Chain - What to Expect

[WHFred]

Hi;

I have what seems like a great opportunity to buy a 69 Roadster 2000 with very straight body which had all rust cut out and new metal put in, functional but worn interior, and rebuilt 5 speed. I think the 69 2000 is such a sexy car and I do love projects. Call it a midlife crisis, I guess.

According to the seller the engine is now bored 35 over and was upgraded to make 150hp at the crank, although I didn't quite catch what he did (or maybe prev owner) to make this claim. What did catch my attention was his statement of "it needs a timing chain". Yeah, no interference motor just needs a timing chain after one snaps while racing someone on the street, as he described.

Still, even with this possibly catastrophic event and the prospect of needing a new engine, there is a price where it still makes this car extremely desirable. From what I can research, this car with a reliable engine should be over $22K, maybe closer to $26K.

I'll just assume right away that the valves are toast and head needs to be redone. Possibly the rods and pistons are also toast, and worst case could be that the cylinders are damaged. With the cylinders already bored at 35 over, how much more could they be bored out or could they possibly be sleeved? Is that a thing for U20s? If I needed to replace the motor with a long block U20 what do those cost? FYI, this car is in the Los Angeles area.

Thank you in advance for your advice, with a little luck I'll be able to attend a future 311s event in style!

[Alvin]

You could take the seller's word regarding timing chain needing to be replaced, or simply inspect it yourself. Maybe it just needs a new tensioner?

What induction does it have, SU or Solex? Got any photos to share?

The U20 head and complete timing setup is several thousand $, but easily sourced from vendors. Lots of options for pistons as well. It's really hard to diagnose remotely. If you can pull the cam over a the minimum, savvy U20 folks here can give you pretty good idea of what you are dealing with.

[theunz]

It’s not uncommon to only need to replace the bent valves, and not all will be bent. Of course you will need a new chain and gears. Datsunparts.com and Datsun Restoration products LLC in the vendor section (link under vendor list at top of page) for parts and pricing. Both are excellent parts sources. If he has upgraded to 150 hp specs the car will have side draft Solex’s (look like Webbers) and a different cam. There should not be a vacuum advance hose coming off the distributor but some still leave it. The complete Solex setup is bringing 4 or 5 thousand these days. Then again there’s always the chance for catastrophic damage

[WHFred]

Hi, TheUnZ;

That sounds encouraging that it's common to just need new valves. From what I hear, breaking a timing chain on the U20 is pretty uncommon but having one slip is more common. I think I saw some suggestions on hacks to increase tension, especially before the oil pressure comes up at start up.

Do you run your 2000 with completely stock timing setup, or upgraded to make it more reliable?

[SLOroadster]

Breaking the timing chain was common when people drove these a ton 40 years ago. Now its a little less common since not many people use them as a daily driver.

Yes there will be bent valves, it is an interference engine. There will likely be damage to the pistons as well. Hard to know what you will need until you get it pulled and opened up. I would plan on a full rebuild, complete head rebuild, likely new pistons, crank, rods, should be fine. Timing components may or may not need to be replaced. Again, you won't know until you pull the engine and open everything up.

No, the engine rebuild won't be cheap, however it should be a one time deal.

Will

[Solex68]

I agree with Will. I would expect valve and piston damage to some extent.

[fj20spl311]

You might need a timing cover and valve cover if its the top chain that broke.
I would expect about 2K in parts and machine work on the low end.

[theunz]

I broke two timing chains (don’t ask) on my U20 years ago with nothing but a slight ding on the pistons. I then put tens of thousands miles on the engine with no issues. However my advice when buying an unknown is to expect the worst and pay accordingly.

[drieseck]

WHFred,
First, congratulations, yes, you bought a sexy, vintage car and have begun a fantastic experience. Merry Christmas. Likely you know it was very rare in 69' to have 150hp, so strap in for some fun. Don't worry about what-it's-worth, you'll never sell it.

Those with more wisdom (like the guys above) may respond, but, in brief:
1. yes, you there is still room to bore-some-more (if currently 35 over), and the pistons will be available (-----very likely not necessary),
2. yes, mostly stock timing is standard, but the vendor's mentioned have gears that are now adjustable (not OEM) and electronic ignition is common,
3. yes, long blocks are around-----but rare, likely you'll more easily find a "parts car" with a U20. (as not-actually-said, you'll likely not need a block, they are almost indestructible.)

But, first------as described above, all these experts need to see what you have before lending diagnosis. Take a few pic's, take the valve cover off and these guys will walk through a proper build-or-repair path --------before you spend a dime.

Welcome to the family.

[WHFred]

Thank you to all who have responded. I’ve been a part of this community for just one week and feel like I have a world of support. That is so awesome!

This will be a fun family journey. I’ll be submitting pics and questions.


Happy Holidays!

[TriniGriffin]

Welcome WHFred to the addiction! As commented by drieseck above, ' you'll never sell it'.
That said, this community of SPL/SRL owners/custodians is an invaluable source of knowledge and valuable advise re: Roadsters.

Your description indicates that you/and SRL are in the Los Angeles area, I'm in San Pedro, where might you be within the LA vicinity?

Dave

[JT68]

Datsun Restoration products LLC in the vendor section (link under vendor list at top of page) for parts and pricing. ...excellent parts source.

Thank you for the mention Mike! Yes, we have EVERYTHING needed to save it:

https://www.datsunrestorationproducts.com/

Major parts like blocks/heads/cams too! NOS, Repro, Reman/Rebuilt, used Nearly everything

[jamesw]

My timing chain jumped a gear once (had a big backfire w/ a loose chain - it sucked) on a previous car (don't own it anymore) and I ended up bending valves. It wasn't that big a deal to pull the head and replace the valves. The pistons were in pretty good shape but did have some new eyebrows Car ran fine for many miles after.

If you're just not sure then buy or borrow a boroscope and stick it into the spark plug holes. The top of the cylinders should tell you what you need to know to buy or pass on the car.

HTH
James

[jrusso07]

I'm just curious...did the seller say the chain broke or that it just needs to be replaced? There are two chains on the U20. Upper and Lower. Have not ever heard of lower chain failure but I assume it can happen. Either one breaking would be bad. The upper chains do stretch, and the tensioner may not be able to take up the slack without shimming it. Then the chain hits the "evil L" bracket and makes a really disturbing rattle/grinding, mostly upon start up. People call this the "death rattle" as now the chain is hitting metal.

Pull the cam cover and have a look if you haven't already. It's two nuts and the gasket is a rubber seal that is re-sealable (not a cork or composite gasket)

[WHFred]

Thank you all for your help. *Finally* heading over to do my inspection. I'll post pics!

It would be a really pleasant surprise if both chains are intact and it's just death rattle.