Five & Dime (my 30 year project)

[Fostin510]

All my posts can be moved here, please.

Tonight's big question is this; With all the smog nonsense removed from my L20b, I still need to let the block breathe. What's the best way to deal with the breather hole in the block? 

 

Thanks

[ggzilla]

The best way is to put positive ventilation in there, Keeps the piston rings from leaking excessively

 

* Clean-air breather on the cam cover. Either to an open-air filter or to the air cleaner housing

* positive breather hose in the block, to the positive crankcase valve on the intake manifold

 

Alternatively you can use an oil catch can, but if you do be prepared to change the oil more frequently and don't let the engine idle too much. Race cars use these catch cans, not to make more power, but because they are required by track rules, to prevent excessive blowby from oiling the track. Which is not a problem with a street engine unless its the rings are really worn out. Another reason people use catch cans for street is with racing manifolds that don't have a breather port, but it's easy enough to add one and smells better than an open road breather too

[datzenmike]

Definitely get the block vent connected to the PCV valve on the intake. The PCV valve is totally benign in function but at least doubles you oil change interval and engine life. Basically for free. The PCV draws crankcase fumes (gas, water and combustion vapors) out of the engine preventing them from condensing over night and contaminating the oil. The air drawn out is replaced by filtered fresh air from the air filter. Ingenious idea!

 

 

[Fostin510]

Yes, I thought about running a hose from the block to the PCV. Noticed they are different sizes, also what would be the correct type of hose to use?

[ggzilla]

1. On my Datsun the hose to the valve used a rubber insert to go from large hose to smaller valve. At the other end, the block breather tube was larger than the hose, but it stretched onto it. This was the factory setup. So I'd say ... use "whatever works"

 

2.

On the air cleaner hose, it is a special hose with a flame arrestor in it. Kind of a fine-mesh pipe cleaner. People with old cars use whatever ... but a factory hose is best to prevent the small chance of flame from backfires. Use any factory hose for either the engine or the car. The 510 hose is fine even if the engine is newer. It was around 1971 when they added flame arrestors

 

While I was waiting for a new hose, I jury-rigged a replacement with a 1/2" copper pipe elbow (for Datsun 1200). The original 1972 hose is the braided one. The new one I bought from Nissan in 2006, and it is still available from Amayama

 

That solved that. The jury-rig worked fine, but the new hose looked better

 

My other Datsun had had twin carbs with no positive ventilation with an open-air filter on the rocker cover. Even though the engine didn't smoke I would come home smelling like oil vapor after a long drive

[datzenmike]

One of my engines d piece of garden hose clamped into the larger one out of the block vent and into the PCV valve. As long as sealed it's not under any pressure and will work. The PCV valve will close itself if there is a backfire in the intake to prevent a flame going back into the block. I assumed the flame arrester was in the top of the L series valve cover where it's baffled to catch any oil droplets.

[Fostin510]

How about the "Ported Vacuum Switch". Important it keep?

[ggzilla]

In California, it used to be important to keep, you couldn't get your car registered if any of that stuff was missing. Have they changed the rules? Last time I did an emissions test in CA was 2012

[ggzilla]

The ported vacuum switch speeds up the engine if it gets too hot. So it is a helpful part for performance. On the other hand, if the part is broken and not working you can reroute the distributor hose and keep going. Just leave it on the engine. It won't hurt anything

 

 

Unless it is a TVS vacuum switch. That reduces performance during low speed driving to reduce emissions. On earlier engines they had an electric wire on the switch. Keep it if it's working. 1969 510s didn't have this (?). Since the wire doesn't connect to your car, the switch won't do anything

 

What year is your L20B and what did it come out of

[Fostin510]

I think the engine is out of a 74 or 76 620. I bought it years ago. I dismantled the car and have totes of parts. Not sure if I have one on hand. Will I need one if I install a weber carb? BTW, I talked to the DMV and the car doesn't need a smog test since it's a 69, even though I'm dropping a newer engine in it. I bought the car back in the mid 90's and the original L16 had been replaced with an L18, but it was toast because it blew a head gasket and the prior owner parked it...with water in the block and head. Didn't drain it, not pretty. 

I did get the L20b running for a few minutes the other day. Did a compression test. Only one cylinder came back above 140, so off to the machine shop in the near future.

[datzenmike]

Though after all these years the '74 620 would have come with an L18. '75-'77 L20Bs were the same other than emission differences. Thesecan be identified by having the intake bolted to the top of the exhaust manifolds and having the U67 head.

 

140 is ok if all are within 10% of the highest reading and it's not blowing blue out the back. If the highest is 150 then the lowest should be no less than 135. Less difference is better.

[Fostin510]

it's got a w53 head and let's just say the lowest cylinder came back at 30, so I think I have a bit of work to do. This goes back to a question I asked earlier about the performance difference between a w58 and a 219 head? Since it looks like I'm looking at a rebuild, is this the time to swap out the w58 for the 219 and turn up the performance a bit?

[datzenmike]

Make sure the valve lash is set. An over tight valve won't close and seal properly and leak compression. 

 

Put a couple of tablespoon fulls of engine oil in the plug hole and repeat the test. If no change then the valves are suspect. If big change the rings are worn out and the oil sealed them temporarily. I'm saying the head may be the cause not the engine... maybe...

 

 

The W53 is a closed chamber head so not as much advantage going to the 219 so not worth it unless the W53 needs to be rebuilt.

[Stoffregen Motorsports]

2 hours ago, Fostin510 said:

it's got a w53 head and let's just say the lowest cylinder came back at 30, so I think I have a bit of work to do. This goes back to a question I asked earlier about the performance difference between a w58 and a 219 head? Since it looks like I'm looking at a rebuild, is this the time to swap out the w58 for the 219 and turn up the performance a bit?

Do you actually have a 219 head?

[Fostin510]

I do...

[Stoffregen Motorsports]

Nice. I'd go out of my way to use it. Unless of course, the CR is too high. 10:1 for street use is fine. Anything higher than that and you'll need a bigger cam to use up all that cylinder pressure.

[fiveoneO]

How long has your L20 been sitting? Maybe the rings are just stuck? Run the engine for a bit to get some heat into it, maybe the rings will unstick. Did you do a leak down test?

[Stoffregen Motorsports]

Good point. They can get gummy from sitting. ATF in the oil helps free up sticky rings.

[Fostin510]

So, long ago I bought some parts from some one and he gave me the 219 head. At the time I had no idea what I had. It is missing the cam, the sprocket and the fuel pump cam. Thought it would be kinda cool to install it for no other reason that's it's pretty rare. The engine has been sitting for 15 plus years. I did get it running for about a minute the other day, though I think I installed the oil pump drive spindle without figuring out where #1 TDC was. The vac advance bumps into the water inlet pipe. I'm going to look into that. Anyway I let it sit for a while and did a compression test and it was bad, 125, 105, 115, and 30. So today I did a cold valve adjustment then another comp test and saw pretty big improvement other than #4, it came back at 40. Most all the rockers had no gap at all. I was a bit surprised to see the numbers that low, the compression test was done when I originally bought it and all came back above 140. I'll give ATF a try. (so would this be, pour a bit of ATF into each plug hole and crank it over multiple times or does it need to actually fire up for a bit?) This is uncharted territory for me. I don't know what I don't know, so I'll let you know. 

I have been considering hooking up a cooling system, so I can run it longer. It will be a bit before I can report my results, in the middle of a honey-do project, but I will check back in for more words of wisdom from the group.

Thanks Guys.

[Fostin510]

BTW, I have not done a leak down test, but great idea. I will and let you know.

[datzenmike]

The valve seats might be corroded/rusty and this would also leak compression but 30 is really bad. Possibly a burnt exhaust valve? Possibly a broken piston. I little engine oil or ATF should separate if it's the rings or valves.

 

Any L20B cam/sprocket/eccentric will do on the 219 head.

 

A leak down test will locate the leak by the sound of air escaping out the exhaust pipe or the carburetor. It also gives a relative sign of overall wear in each cylinder. 

[fiveoneO]

I just pour a little ATF into the spark plug hole and let it sit. Occasionally turn the engine over by hand. You're just trying to get the ATF to soak into the piston ring lands and hopefully break the rings free.

[Stoffregen Motorsports]

Add a quart of ATF to the engine oil and run it for 500 miles or so. If the rings are stuck, it will smoke like a chimney for a while, but as the rings loosen up, you'll see the smoke go away.

[Fostin510]

ok, I'll do the leak down test. I will also try the ATF and report back.

Just for the sake of argument, if I do have a bad valve. Is it wise to just rebuild the head? Also what a head rebuild run these days?

[ggzilla]

Leak down test is warranted when compression is really low, like 30psi in one cylinder. If it's more like100psi in all cylinders, the leak test won't pinpoint anything (it almost for sure worn rings)

 

The 30 psi is probably a leaking valve. Although I guess a stuck ring might cause it?

 

2 hours ago, Fostin510 said:

if I do have a bad valve. Is it wise to just rebuild the head?

 

I wouldn't. Just inspect it first. I've fixed several engines by either lapping the valve. or replacing one valve and hand-lapping it in. Those engines ran for years thereafter. I had a valve grinding machine, but used it more to rebuild american engines. With Datsun's hardened valve seats, they rarely go bad even when one a valve is burnt. Now of course everyone uses hardened seats, but Datsun started using them in the 1960s! Also one reason why Datsun engine last forever on unleaded fuel