Another L20 question

Engine, Transmission and related drivetrain.
Button
Posts: 122
Joined: 25 Jun 2014 14:13
Location: Thousand Oaks, CA..

Another L20 question

Postby Button » 16 Dec 2016 00:10

I will start this by saying the only car I have ever driven with an L series was a 510 that had a Robello built 2.3 liters. It was a lot of fun, but I am assuming it was not indicative of the typical experience you get with an old stock L20.

I am looking to put a stock L20 in my project 510 for now and I was able to go today and look at an L20 with a W58 head that a guy is selling out of his daily driven old Datsun truck (620 I believe) because he is swapping in a Nap Z with a 5 speed. The engine looks clean, relatively speaking, and didn't seem to be leaking any fluids. The truck fires right up, idles nicely, doesn't smoke, and doesn't seem to make any unusual noises. So far everything seems good. It's also worth noting that he has a Weber carb (I'm assuming a 32/36 by the looks of it), a header, and the engine is mated to a 4 speed. He is selling it without the intake and header which is fine since I have a header and an intake with a Weber 32/36.

So when I got there today he hands me the keys and let's me go drive it around. When I start driving the engine immediately feels choked as if there is some type of limiter on it, so much so that I stopped and had to check that I wasn't taking off from third gear. After driving it for a bit it seems that there is a major lug especially in first and second that seemed to have absolutely no power up to about 3000 rpm and then would kinda of wake up but it wasn't smooth, it was either off or on. In third and fourth it would more or less get up to speed to go with the flow of traffic but to say the least the driving experience was underwhelming. When I got back he said "I'm sure you noticed the hesitation, it's the carb that needs to be tuned."

So after that long winded lead up my questions to you guys are:

1) Are stock L20s generally underwhelming?
2) Does this sound like a just a carb issue?
3) Does any of this sound like symptoms of a potentially larger mechanical issue or just that it needs a good tune up?

I'm not sure if it's a somewhat tired L20 with a mechanically sound top and lower end or if it's something I should walk away from.

Any feedback would be appreciated.

Chris

User avatar
Byron510
Moderator
Posts: 11476
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

Re: Another L20 question

Postby Byron510 » 16 Dec 2016 00:22

If it idles fine and ran fine otherwise, I would rule out ignition for the most part and also rule out some crazy lumpy cam that might generate this (been there, done that on an L motor) - I'd and say the carb was never jetted correctly with this minimal information...
The power band should be smooth, from 1500 on up, with it getting a bit better above 4500 until the carb runs out of air somewhere around 6800-7200 RPM is all things are in good shape.
I have only ever run an L series in any of the some 20 plus 510's I've owned and driven. Have driven VG, SR, L6 and rotary 510's, but only owned L series (insert comment here Jeff :-) ).

Byron
Love people and use things,
because the opposite never works.

User avatar
okayfine
Supporter
Posts: 14098
Joined: 12 Nov 2007 23:02
Location: Newbury Park, CA

Re: Another L20 question

Postby okayfine » 16 Dec 2016 06:05

Definitely sounds like a carb issue, but I'd run a quick compression check just for giggles. I have a gauge you can borrow if you don't have one handy. I'd also pull the dipstick and check on the condition of the oil, and/or pull the valve cover and have a look inside.

Stock L20s would be a noticeable step up from a stock L16, but a stock L20 would be underwhelming even by mid-'80s standards (for the same engine size).
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

Button
Posts: 122
Joined: 25 Jun 2014 14:13
Location: Thousand Oaks, CA..

Re: Another L20 question

Postby Button » 17 Dec 2016 14:38

Thank you for the input guys and I really appreciate the offer on the compression gauge Julian but I recently purchased one. I want to run an L series so I will do the things you suggested and if that looks good I will go for it. The guy pulled the motor today so I will go pick it up in the next few days. I will give an update when I find out more.

datzenmike
Supporter
Posts: 5168
Joined: 24 May 2006 12:40
Location: Van. Isle.

Re: Another L20 question

Postby datzenmike » 18 Dec 2016 16:00

I've had several L20Bs (the L20 is a six cylinder) with good torque from 1,800 to over 4K. This is with stock carb and cam. While it will easily hit 6K, by 5K that push back in the seat is long gone and you would have been farther ahead to have up shifted. I imagine the L16 torque range is much higher though less. From 2-4K it's a rush though. It's smooth powerful low speed torque makes it ideal for daily driving between the lights.

The L20B is about 20 pounds heavier for about 20 more hp over the L16.

Take for a romp again but as this is a progressive carb stay below half throttle so you are always in the primary. Drive out somewhere in the open for ten minutes and ASAP safely pull over and pull the plugs and 'read' them. Likely very light or even white porcelain would indicate the primary is lean. Normal would be light brown or tan color. Bright white porcelain is extremely lean. Ah I see the engine is pulled....

Well before you install quickly check that all rockers have enough clearance to wiggle slightly when not on the cam lobe. If you find any tight ones set properly when the engine is warm.

If no strange noises and no blue cloud following it's just an adjustment.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

Chickenman
Posts: 445
Joined: 06 Sep 2010 15:10
Location: Coquitlam

Re: Another L20 question

Postby Chickenman » 20 Dec 2016 18:31

One item that is often missed is that the mechanical and vacuum advance mechanisms in the Dizzy are often seized. That makes a huge difference to performance and should be checked.

Button
Posts: 122
Joined: 25 Jun 2014 14:13
Location: Thousand Oaks, CA..

Re: Another L20 question

Postby Button » 26 Dec 2016 09:30

Thank you for the input Mike and Chickenman. I will check out the stuff you mentioned.

So I got the engine and have pulled the head and oil pan off, and I am about to pull the timing cover off and so far everything looks pretty good.

My next question is about cleaning the block deck off before putting a new head gasket on. Everything I read says to stuff rags in the cylinders to catch debris which makes sense, and in the Keeping Your Datsun Alive book it says to put a pipe cleaner in the one oil hole. So my question is is it ok if all the debris falls down into the other holes, such as the water passage holes in the block? Is it only the oil and cylinders I need to worry about?

Thank you.

datzenmike
Supporter
Posts: 5168
Joined: 24 May 2006 12:40
Location: Van. Isle.

Re: Another L20 question

Postby datzenmike » 26 Dec 2016 11:12

Why take it apart if running so well? If it ain't broken why fix it?

Well, if you timed it to TDC only two cylinders need rags. But I never worried about the water jacket holes or the oil jet hole. Have a care on the soft aluminum head it will gouge if you work on it hard enough.

If the oil pan is off maybe check the bearing clearances with PlastiGauge. New bearings will only improve the clearances.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

Button
Posts: 122
Joined: 25 Jun 2014 14:13
Location: Thousand Oaks, CA..

Re: Another L20 question

Postby Button » 26 Dec 2016 21:44

Thanks for the response Mike. I pulled it apart because it turns out it was leaking. There was a ton of oil between the head and the timing cover that appeared to be a leaking head gasket, and also because I can be anal retentive and have a hard time putting dirty car parts back in. what bearings are you referring to check? The crank? I'm new to messing with the internals of motors so I wasn't sure.

In other news while I was cleaning the top of the block tonight I realized that it appears that the block is cracked on either side of the middle head bolt hole on the driver side. I can't tell if its just at the surface or it goes down far. Is this block done, or could I run it and pray for the best?
Attachments
Cracked_02.JPG
Cracked_02.JPG (93.31 KiB) Viewed 315 times
Cracked_01.JPG
Cracked_01.JPG (111.62 KiB) Viewed 315 times

Chickenman
Posts: 445
Joined: 06 Sep 2010 15:10
Location: Coquitlam

Re: Another L20 question

Postby Chickenman » 28 Dec 2016 14:48

Personally, I would toss the block. Those cracks are directly to the water jacket, will expand and contract as the engine heats and cools.Will only get worse with time. As well it goes to the thread portion of a head bolt. You will get water leaks there and eventual failure of threads due to the spreading of cracks.

I don't think that can be repaired at a reasonable cost or with reasonable expectation of a long term fix. ..... :-(

Other members may have some ideas, but to me it just wouldn't be worth the hassle and worry.

Three B's Racing
Supporter
Posts: 950
Joined: 03 Mar 2009 11:58
Location: New Hampshire

Re: Another L20 question

Postby Three B's Racing » 29 Dec 2016 06:28

Chickenman wrote:Personally, I would toss the block. Those cracks are directly to the water jacket, will expand and contract as the engine heats and cools.Will only get worse with time. As well it goes to the thread portion of a head bolt. You will get water leaks there and eventual failure of threads due to the spreading of cracks.

I don't think that can be repaired at a reasonable cost or with reasonable expectation of a long term fix. ..... :-(

Other members may have some ideas, but to me it just wouldn't be worth the hassle and worry.


A friend of mine had those same cracks on an LZ2.2 block. He used head studs and I believe threaded inserts. This was in I believe 2005 but anyway he ran that until he sold his 510 to Fisch on Ratsun and he's been driving it issue free since about 2011. Another friend has an L20 with 5 of those cracks using typical head bolts with no leaks some 10 years now but he did park it reading it for a KA24DE carbed project. Riskey as you say? yes it can be.
"Lastnight the wife said oh boy when your dead you can't take nothing with you but your soul oh "Think"
- John Lennon

User avatar
Byron510
Moderator
Posts: 11476
Joined: 01 Jul 2003 23:06
Location: Maple Ridge, BC

Re: Another L20 question

Postby Byron510 » 29 Dec 2016 08:02

Button wrote:
In other news while I was cleaning the top of the block tonight I realized that it appears that the block is cracked on either side of the middle head bolt hole on the driver side. I can't tell if its just at the surface or it goes down far. Is this block done, or could I run it and pray for the best?


The ARP head stud kit is readily available for these engines at a very reasonable cost, and due to the fact that it doesn't exert the twisting force when torquing down, it helps put less stress on the block while achieving the correct torque. I, like Lou, have seen a block with a crack like this see many more years of service without issue in my own vehicles.

Personally, I'd run it if it's a stock or mildly tuned motor with the ARP stud kit.

Byron
Love people and use things,
because the opposite never works.

Chickenman
Posts: 445
Joined: 06 Sep 2010 15:10
Location: Coquitlam

Re: Another L20 question

Postby Chickenman » 29 Dec 2016 10:18

I guess I'm being overly cautious...

User avatar
funwithmonkeys
Supporter
Posts: 710
Joined: 05 Sep 2013 09:34
Location: Vancouver, BC

Re: Another L20 question

Postby funwithmonkeys » 29 Dec 2016 10:37

Chickenman wrote:I guess I'm being overly cautious...

I've heard that happens as you get more mature/older. :P
If no one from the future comes back to stop you from doing it then how bad of a decision can it really be?

datzenmike
Supporter
Posts: 5168
Joined: 24 May 2006 12:40
Location: Van. Isle.

Re: Another L20 question

Postby datzenmike » 30 Dec 2016 09:47

This engine was in a running vehicle I believe? I bet there are lots of blocks out there with small cracks in them if you look really hard. A crack is a sign of stress relief and not an indication that it will get worse. This crack might be over 30 years old. Have to ask where is the coolant going to 'leak' ? Can't go up the bolt. If I was building a 'race' engine I might give it some thought but for a stock DD?

Weld and have it 'decked'?

Image
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs


Return to “Powertrain”



Who is online

Users browsing this forum: No registered users and 2 guests