datzenmike Posted September 30, 2017 Report Share Posted September 30, 2017 So on an average day with a stock 620 with l20b how far can someone push the rpms regularly? The red line is at 4k on my rpm gauge, i replaced gasket, and put arp head studs in. I bought the studs because they were tested for way higher psi. Can a safely rev higher than 4k on a stock l20b? Gauge is wrong. Factory tach '76 L20B... That's the correct mileage. Mileage not Km, this is a US car. No... that's the brake light. Floor it and when power drops off north of 4,800 shift. 2 Quote Link to comment
8m0untainman8 Posted September 30, 2017 Report Share Posted September 30, 2017 The dash in my truck has the egr light and seatbelt light on top of the center of the dash, my speedometer goes to 100, and the rpm gauge is not the original so i suppose it could be wrong. Lol 1 Quote Link to comment
datzenmike Posted September 30, 2017 Report Share Posted September 30, 2017 4K redline probably for a diesel. 1 Quote Link to comment
wayno Posted September 30, 2017 Report Share Posted September 30, 2017 4K redline probably for a diesel. Yes 4000rpms is redline for the SD22/25 Nissan diesel engines. They sound over revved in all gears except 5th above 3000rpms, I have never taken mine above 3300rmps until I put the turbocharger on it, I did run it up to 3500rpms once going thru the gears fast showing off to a buddy that don't have a turbocharger, when his dad asked him about the drive, all he said was it was fast. I did take the Datsun 720 dually up to 3200rpms in 5th gear, it has 3.3 gears in the rear, it has P195/75R14 tires on it with good tread, I don't know how fast that was but it looked really fast to me and I have been going 140mph twice in my life, so I know what fast is for a stock car, fact is the Chrysler New Yorker Brougham didn't actually look like it was going that fast but the speedo went to 160mph and I was going in a straight line. 1 Quote Link to comment
datzenmike Posted September 30, 2017 Report Share Posted September 30, 2017 195/75R14s are 25.5" diameter. Diesel 5th gear is 0.813 X 3200 = 2642 driveshaft rpm with 3.364 differential that's 88.7 MPH !!! 1 Quote Link to comment
wayno Posted October 1, 2017 Report Share Posted October 1, 2017 Seemed faster than that, but I don't normally drive that fast anymore, the freeway was straight and clear of vehicles so I gave it the pedal to see what it would do, I had a little pedal left but 3200rpms is about where I draw the line on these diesel engines. This particular diesel has the torque to turn 3.0 gears if there were such gears for the H190, and it would not surprise me if it could 2.73 gears, but I would have to use another axle, I don't think it would have the torque to get started towing another vehicle with 2.73 gears in certain situations, it tows great right now the way it is, and I don't need to be going a 100mph anyway. This thread is about top speeds of stock engines so I suppose I should quit yacking away about my modified diesel engines. :lol: 1 Quote Link to comment
Charlie69 Posted October 1, 2017 Report Share Posted October 1, 2017 Top speed for any engine depends on how big the drivers balls are. Enough said! 3 Quote Link to comment
G-Duax Posted October 1, 2017 Report Share Posted October 1, 2017 I've only had my Cressida to 150-ish at the Texas Mile, but my son has out run a modified Yamaha R1 sport bike on top end with it. (175-ish) I told him to remember that if any thing goes wrong at that speed, he wasn't going to walk away. Didn't seem to phase him... My 4-spd 521 w/ Weber, L16 & 235x75-15 would barely do 70 indicated, until I retarded the cam for better top end, then it would do 100. No idea how fast it actually was going. Current 5-speed 620 with 4.3 rear gears & 225x60 15 tires, when it had an L18, Weber, header, 2.5" exhaust, and a 264 cam would put the needle strait down on the speedo, but the trans was out of an early '80s Z-car, so the speedo was way off. Had the white speedo gear (19t), needed a 22, so probably around 105 mph. Now that the thing has 4.6 gears, I will probably never have a speedo that reads correctly. :( Quote Link to comment
datzenmike Posted October 1, 2017 Report Share Posted October 1, 2017 I'm also looking for a 22 tooth Orange speedo pinion. The JDM Cedrics had them. Quote Link to comment
8m0untainman8 Posted October 1, 2017 Report Share Posted October 1, 2017 Pushed to about 4500rpms before shifting, instead of average shift in the 3500 range, was going a lot faster upon shift, picked up quite a bit of speed in the last 1k rpms, stock l20b in a 76 620 4spd. 0-60mph is a lot faster like this, motor sounds really nice past 4k, i thought the engine sounded topped out at 3200,didn't realize it would sound so willing and able past 3k. Still not going to push too hard too often, but it was fun lol. Quote Link to comment
datzenmike Posted October 1, 2017 Report Share Posted October 1, 2017 I've hit 5k before on a stock L20B....but it's making noise only, not pulling. It's pulls much harder in the next gear rather than going above 4K. Quote Link to comment
8m0untainman8 Posted October 1, 2017 Report Share Posted October 1, 2017 Definitely, i shifted when i felt the speed pick up stopping. Quote Link to comment
wayno Posted October 1, 2017 Report Share Posted October 1, 2017 I hit 4500rpms all the time in the work truck with the bed loaded(LZ23), and I have seen over 5000rpms in 5th gear on level ground on the hiway(bed empty), but normally I shift just above 4000rpms, after 4500rpms it starts falling on its face except in 5th gear. That is a strange phenomenon to me, it even happens on my diesel engines, in every gear except 5th the engine sound over revved after a certain RPM, on my diesel engines it anything over 2600rpms, but in 5th 3000rpms sounds alright, anything over 4300rpms on the LZ23 sounds over revved, but I revved it over 5000rpms in 5th and it didn't sound that bad. 1 Quote Link to comment
G-Duax Posted October 1, 2017 Report Share Posted October 1, 2017 Mike, the orange 22t gears are still available in Japan, it just costs more to get them over here than what they cost... I think I need the 23t green gear. Can't find that little devil for any price. Closest thing I've found is the 23t from a Mazda. Correct pitch, but different shaft diameter. Looking at pressing it off the shaft, and making it fit the Datsun shaft. If I succeed, I'll sell you my newly installed orange one (for a outrages price :) ). Quote Link to comment
datzenmike Posted October 1, 2017 Report Share Posted October 1, 2017 The plastic gears are formed around a knurled rod. I wish they would press off without disintegrating. Maybe heat them in an oven to make them plastic? I made a 22 out of two red gear pieces of 11 teeth with JB weld. It lasted about two turns and flew apart. My theory on how they work.... The diameter of the gears are the same yet they have different numbers of teeth. The tooth depth changes. Like coarse and fine threads that are the same diameter. The worm gear on the mainshaft has no problem engaging them this way without crushing. Quote Link to comment
G-Duax Posted October 1, 2017 Report Share Posted October 1, 2017 Well, they have different holders for different tooth count ranges. The holder for the 19t gear is different than for the 22t I have now. I am going to bore the shaft out from the center of the gear, then machine a bushing to fit the Datsun shaft (from a spare 19t), after I machine it's gear off. That's the plan...... May just end up the same as yours did. Still don't have any idea if I'll need to jack with it, as I haven't got out on a highway to check the speedo against a stop watch. Quote Link to comment
datzenmike Posted October 1, 2017 Report Share Posted October 1, 2017 Yes, I think so too. The sleeves have different offset for the pinions. 15-18t 19-22t? Pre '80s sleeves can be used in later transmissions buy cutting a new key 180o around. Quote Link to comment
G-Duax Posted October 1, 2017 Report Share Posted October 1, 2017 Have that info somewhere....... But pretty sure the 19t belongs with the smaller gears, and the 20-23 use the different holder. Quote Link to comment
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