mhub91 Posted November 19, 2014 Report Share Posted November 19, 2014 I'm about to begin rebuilding an L20 for my 620. It's a later smog model L20 and I plan on putting my peanut head on it with a weber. I've rebuilt Toyota engines before, but are the L20s like the Toyota engines in terms of finding what bearing size to use? For example.... A Toyota engine will have a string of numbers on the crank shaft counter weight like this " 4 3 4 4" for a 4cylinder. These correspond with what the journals were machined to. Now, individual rod caps with have numbers on them as well, example "3 4 4 3". You would then take those two numbers and determine what bearing you would need, in stock form of course. Are the Datsun engines like this as well? If not, how would I determine which bearings to use? Of course I can go to the machine shop but it's always nice to save a buck or $100. Thanks. Quote Link to comment
datzenmike Posted November 19, 2014 Report Share Posted November 19, 2014 You should be able to buy replacement rod and main bearings in standard sizes and they will fit. Naturally check clearances with plastigauge. If you have a damaged journal it can be machined to an undersize bearing that you can order separately. I've never heard of an L or Z series built by the factory with an odd size bearing in it. Quote Link to comment
mhub91 Posted November 19, 2014 Author Report Share Posted November 19, 2014 Hey, thanks Mike. Always quick with help. Quote Link to comment
banzai510(hainz) Posted November 19, 2014 Report Share Posted November 19, 2014 If bearing journals look good just buy STD size Quote Link to comment
67_1600 Posted November 19, 2014 Report Share Posted November 19, 2014 If bearing journals look good just buy STD size That's assuming it's a virgin crank that hasn't been ground already... I'd measure the rod and main journals to see what you have before buying any bearings. 1 Quote Link to comment
banzai510(hainz) Posted November 19, 2014 Report Share Posted November 19, 2014 true but I had 2 lower ends done and the machinst said they were OK just polish. Another L20 just as good. If bearing had been redone of coarse they are already marked with a size in MM or SAE But really how many people rebuilt Datsuns back in the day. They just put them in the back yard till Ratsun guys come along. unless bearing spun or total lack of oil Quote Link to comment
banzai510(hainz) Posted November 19, 2014 Report Share Posted November 19, 2014 I gave Ted a Clean L20 crank last year I think he might still have it Tdaaj. He lives down south Quote Link to comment
bananahamuck Posted November 19, 2014 Report Share Posted November 19, 2014 For example.... A Toyota engine will have a string of numbers on the crank shaft counter weight like this " 4 3 4 4" for a 4cylinder. These correspond with what the journals were machined to. Now, individual rod caps with have numbers on them as well, example "3 4 4 3". You would then take those two numbers and determine what bearing you would need, in stock form of course. Thanks. My wife being a hardcore Toyota person since she was 16 ,, pretty much made me one too,, and I have never in my life ever heard of this ,,, ever. The bearing size on a Toyota is marked on the bearing just like every crank bearing in any engine built after about 1960 . I have never taken any Toylet motor apart newer than 95 but i can't imagine the industry would change such a standard procedure. Quote Link to comment
Rocket Dog Posted November 19, 2014 Report Share Posted November 19, 2014 My wife being a hardcore Toyota person since she was 16 ,, pretty much made me one too,, and I have never in my life ever heard of this ,,, ever. The bearing size on a Toyota is marked on the bearing just like every crank bearing in any engine built after about 1960 . I have never taken any Toylet motor apart newer than 95 but i can't imagine the industry would change such a standard procedure. You sir, are a bird. You have no thumbs. I seriously you doubt your ability to repair automotive engines. 3 Quote Link to comment
mhub91 Posted November 19, 2014 Author Report Share Posted November 19, 2014 Only toyota engines i've done are late model, surprising. theres actually a string if numbers on the rear counter weight, the rear driver side of block, and on rods denoting what theyve been machined too. i can positively confirm this on toyota's 5.7L found in tundras. Quote Link to comment
datzenmike Posted November 19, 2014 Report Share Posted November 19, 2014 KA engines have numbers all over the crank throws. It allows you to build sloppy engines cheaper and make up for it by using the correct bearing to correct for the mistakes. The L and Z series were make better than that. Quote Link to comment
mhub91 Posted November 19, 2014 Author Report Share Posted November 19, 2014 I'd agree. To me, personally, I feel like Nissan went down hill real fast here in North America right around mid to late 90s. After the Altima / Maxima / 240SX / D21 / Z32 is when things got real shitty, in my opinion. If I remember correctly, that time was hard for Nissan financially and they also hired a new President. (iirc.....) Quote Link to comment
Stoffregen Motorsports Posted November 19, 2014 Report Share Posted November 19, 2014 Even L series bearing were available in different thicknessessss. I don't mean .010,.020, .030, I mean tenths of a thousandth. The KA bearings are color coded for the hig, medium and low thickness. Quote Link to comment
banzai510(hainz) Posted November 19, 2014 Report Share Posted November 19, 2014 Napa in Kent /Renton had the OSK(japan) L20 timming sets if needed also(or if still sold) Quote Link to comment
mhub91 Posted November 20, 2014 Author Report Share Posted November 20, 2014 Cool, thanks! Quote Link to comment
flatcat19 Posted November 20, 2014 Report Share Posted November 20, 2014 Off-topic. You're rebuilding Tundra motors? 2AZs and any FXE, sure. I haven't seen anything really NEED a re-ring. The only real thing I have seen on the Tundras is the cam carrier housings leaking oil. Quote Link to comment
mhub91 Posted November 20, 2014 Author Report Share Posted November 20, 2014 Off-topic. You're rebuilding Tundra motors? 2AZs and any FXE, sure. I haven't seen anything really NEED a re-ring. The only real thing I have seen on the Tundras is the cam carrier housings leaking oil. No, not rebuilding them. Just took the Engine Repair 151(?) course with T-Ten a while back and remember that. My only true repairs with an engine working with Toyota are the 2AZ-FE, of course. They days of rebuilding components in the dealership land are dead. Quote Link to comment
Z-train Posted November 20, 2014 Report Share Posted November 20, 2014 PLASTIGAUGE? Quote Link to comment
mhub91 Posted November 20, 2014 Author Report Share Posted November 20, 2014 Lol, what's wrong with plastigauge? It's a practice that's been used for .... well, forever. Quote Link to comment
datzenmike Posted November 21, 2014 Report Share Posted November 21, 2014 Depend on how crazy the build is. For most of the time the engine ran fine on worn bearings. New ones should bring it back close to stock clearances but not likely tighter. The proper micrometers are not always available to the back yard mechanic but Plastigage is. Quote Link to comment
mhub91 Posted November 21, 2014 Author Report Share Posted November 21, 2014 Using an oil pump from a KA24E would help fill those clearances too. If I remember correctly, someone stated their L20 was bumped up to 29 psi at idle by using the KA24E oil pump. Quote Link to comment
datzenmike Posted November 21, 2014 Report Share Posted November 21, 2014 But that is only at idle. Once revved up the pressure release valve is set at about the same 50-60 PSI. You could shim the relief spring to raise the oil pressure, usually 10 PSI for every one thousand RPMs you expect to run is normal. It's not the oil pressure that cushions the bearings. It's the oil film trapped tightly between the properly clearanced bearing that carries the load. If there is too much clearance, the oil is simply squeezed out and the metal parts just hammer together. Quote Link to comment
mhub91 Posted November 21, 2014 Author Report Share Posted November 21, 2014 But that is only at idle. Once revved up the pressure release valve is set at about the same 50-60 PSI. You could shim the relief spring to raise the oil pressure, usually 10 PSI for every one thousand RPMs you expect to run is normal. It's not the oil pressure that cushions the bearings. It's the oil film trapped tightly between the properly clearanced bearing that carries the load. If there is too much clearance, the oil is simply squeezed out and the metal parts just hammer together. Exactly. The technical term for the oil slick that the journals float on is called a "hydraulic wedge". ...That'd be bad news if the bearings were to float on the oil, haha! Quote Link to comment
banzai510(hainz) Posted November 21, 2014 Report Share Posted November 21, 2014 the KA pumps more volume. the bearings like I said earlier if look fine(crank/rods) then just get STD size bearings. No need to over engineer it. 1 Quote Link to comment
mhub91 Posted November 21, 2014 Author Report Share Posted November 21, 2014 Thanks Banzai. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.