Crashtd420 Posted May 24, 2021 Report Share Posted May 24, 2021 24 minutes ago, d.p said: Yeah I agree but still no answer to my question, everyone wants to talk some nonsense about cam timing, a z24 block, what I set my redline to, etc...someone just tell me at what RPM I should stop rev'ing to on a bored and cam'd l20B? Its not nonsense, your setup will determine your redline.... Safe is probably 6000/6500 Anything beyond that is a guess.... I have heard you can rev these to 8000 if you want..... But you better have the right components to do that, like upgraded valve springs, etc... Now is your head even capable of breathing at 8000 rpm, how about 7000.... These are all unknown variables.... If I remember right my L16 started to level out on power about 6500 rpm so for me there is no reason to go any higher..... I wont make any more power without modifications.... 2 Quote Link to comment
d.p Posted May 24, 2021 Report Share Posted May 24, 2021 Oh and I have no idea if my valve springs are upgraded but I do know whatever the caps are called that hold them down are. 1 Quote Link to comment
datzenmike Posted May 24, 2021 Report Share Posted May 24, 2021 58 minutes ago, Crashtd420 said: If I remember right my L16 started to level out on power about 6500 rpm so for me there is no reason to go any higher..... I wont make any more power without modifications.... L16 red line is 8,250 but the 210 head isn't really capable of delivering enough air at that high a rev. A 219 SSS head probably would but not with a downdraft carburetor. I noticed it was a long wait to get near 6k with my stock 2bbl. With R-1 carbs that changed to 'you'd better pay attention". 1 Quote Link to comment
Crashtd420 Posted May 24, 2021 Report Share Posted May 24, 2021 21 minutes ago, datzenmike said: L16 red line is 8,250 but the 210 head isn't really capable of delivering enough air at that high a rev. That was more my point, just because the math says you can run that high of an rpm doesnt mean your setup can.... 1 Quote Link to comment
d.p Posted May 24, 2021 Report Share Posted May 24, 2021 Yeah well I was getting at what number can I safely REV it to? But I guess without knowing all the details I won't ever get a specific RPM answer. 1 Quote Link to comment
Crashtd420 Posted May 24, 2021 Report Share Posted May 24, 2021 Just now, d.p said: Yeah well I was getting at what number can I safely REV it to? But I guess without knowing all the details I won't ever get a specific RPM answer. One thing I know is my cam specs say 1850 - 6000 rpm range .... I think yours is slightly bigger, my guess is rpm range is 2500 - 6500 ... So you could probably hit 7k without an issue before it starts leveling out the power.... 6500 your definately safe.... 2 Quote Link to comment
banzai510(hainz) Posted May 24, 2021 Report Share Posted May 24, 2021 maybe 7k in 1st gear after that only lower. your dist spidel will be wiggling to much and dist backs off anyways that why they went to crank fire for more relaiable accurate spark 2 Quote Link to comment
mainer311 Posted May 24, 2021 Author Report Share Posted May 24, 2021 (edited) I started machining my downpipe flange today. I forgot how much it sucks to machine 304SS. Twin 1.75” pipes will feed 2” 304 all the way back. Not sure where I’ll dump it yet. Edited May 24, 2021 by mainer311 3 Quote Link to comment
Crashtd420 Posted May 24, 2021 Report Share Posted May 24, 2021 10 minutes ago, mainer311 said: I started machining my downpipe flange today. I forgot how much it sucks to machine 304SS. Twin 1.75” pipes will feed 2” 304 all the way back. Not sure where I’ll dump it yet. Just realized this is your thread not Dp's.... gotta love how that happens... And ya stainless can suck, i was playing with some inconel the other day and I have been dealing with nitroloid( not sure if spelled right) for the last 2 weeks.... not fun either.... 1 Quote Link to comment
mainer311 Posted May 24, 2021 Author Report Share Posted May 24, 2021 Just now, Crashtd420 said: Just realized this is your thread not Dp's.... gotta love how that happens... And ya stainless can suck, i was playing with some inconel the other day and I have been dealing with nitroloid( not sure if spelled right) for the last 2 weeks.... not fun either.... Haha. I don't really care about the banter. Figured I might learn something. Yeah, I bought the "easily machinable" version of 304 from McMaster. It has some weird brand name. Cutting with solid carbide on our DPM2 and taking it slooowwww. Like 5 IPM. 1 Quote Link to comment
datzenmike Posted May 24, 2021 Report Share Posted May 24, 2021 1 hour ago, Crashtd420 said: That was more my point, just because the math says you can run that high of an rpm doesnt mean your setup can.... It can rev that high but likely already past peak hp and on the decline so no advantage. 1 hour ago, d.p said: Yeah well I was getting at what number can I safely REV it to? But I guess without knowing all the details I won't ever get a specific RPM answer. 7k is 7k whether in neutral or under load, 2bbl Hitachi or side drafts, big or little cam. 1 hour ago, Crashtd420 said: One thing I know is my cam specs say 1850 - 6000 rpm range .... I think yours is slightly bigger, my guess is rpm range is 2500 - 6500 ... So you could probably hit 7k without an issue before it starts leveling out the power.... 6500 your definately safe.... Definitely safe. Is there an app for acceleration in a lap top? Is there a way to accelerate and data log engine RPMs at same time? Maybe a dynomometer? If so log all 4 gears. If the next highest gear is starting to make more torque than the gear you are in then that is your up-shift point. 47 minutes ago, banzai510(hainz) said: maybe 7k in 1st gear after that only lower. your dist spidel will be wiggling to much and dist backs off anyways that why they went to crank fire for more relaiable accurate spark This! Maybe even 2nd gear also. A quick buzz to red line won't hurt anything. This. A quick buzz to 7k in first, maybe second won't hurt anything. 1 Quote Link to comment
Crashtd420 Posted May 24, 2021 Report Share Posted May 24, 2021 1 hour ago, datzenmike said: It can rev that high but likely already past peak hp and on the decline so no advantage. You always explain it just one step better..... 1 Quote Link to comment
Charlie69 Posted May 25, 2021 Report Share Posted May 25, 2021 d.p drive your truck and watch your tac when you feel that your revs are not producing any more power that is the RPM limit of your motor. Set your redline 500 rpms less than where your power drops off or levels out to be on the safe side. On race engines we would run the rpms up until we would float the valves and then redline the engine 300 rpms under the rpms of where the valves would float. 1 Quote Link to comment
Stoffregen Motorsports Posted May 25, 2021 Report Share Posted May 25, 2021 Yes, revving an engine past the point at which the power starts to drop off is pointless. A built L20B/Z20 can rev to 8500, and make good power there, but that's not what you have. I would assume since you have custom retainers, you probably have stiff valve springs, but who knows for sure? Unless you spend the money and time to tune it on a dyno, you need to be able to feel the power through the seat of your pants. That will tell you what RPM you can go to. Sometimes a short shift will be faster than wringing the life out of it. 1 Quote Link to comment
d.p Posted May 25, 2021 Report Share Posted May 25, 2021 I have the money and the time, whether I have the desire remains to be seen. I can get it dyno tuned by a somewhat local shop https://datsunspirit.com/ but will cost me north of $1k. He said he could tune it minus the dyno for a couple hundred but when I was going to do it my jets were loose and the truck drove like shit so I had no interest in even attempting to make the drive over there (80 miles one way). Hell I was even contemplating getting AAA to just have it towed there because I had no confidence it would make it there and back. But since I solved the loose jet issue the truck has been driving great and I am sure there is more in it but whether its worth it to me I have yet to decide. 1 Quote Link to comment
Stoffregen Motorsports Posted May 25, 2021 Report Share Posted May 25, 2021 If the shop is a Datsun specialist, I would do it. They should know all the tricks to get what you have dialed in. I'd spend the money and have it done. They might find a problem, which can cost you plenty if you ignore it. They could also find you a bunch of HP by making a few tweaks and adjustments. There are so many things that the average home shop guy doesn't know that specialists can spot right away. 2 Quote Link to comment
d.p Posted May 25, 2021 Report Share Posted May 25, 2021 2 hours ago, Stoffregen Motorsports said: If the shop is a Datsun specialist, I would do it. They should know all the tricks to get what you have dialed in. I'd spend the money and have it done. They might find a problem, which can cost you plenty if you ignore it. They could also find you a bunch of HP by making a few tweaks and adjustments. There are so many things that the average home shop guy doesn't know that specialists can spot right away. You saying have it dyno tuned for $1k or just tuned for a couple hundred bucks? 1 Quote Link to comment
banzai510(hainz) Posted May 25, 2021 Report Share Posted May 25, 2021 (edited) I say drive it and who cares. You might get 5 extra hp at 1000$ at 7k rpm = 200$ per HP you might have 100-105hp at the ground just be happy you dont have the L16 in ther anymore Edited May 25, 2021 by banzai510(hainz) 1 Quote Link to comment
d.p Posted May 25, 2021 Report Share Posted May 25, 2021 Just now, banzai510(hainz) said: I say drive it and who cares. You might get 5 extra hp at 1000$ at 7k rpm = 200$ per HP you might have 100-105hp at the ground haha the voice of reason!! And at that cost to benefit I would pass hard on it but I really have no idea how much HP I have to gain by doing it. 2 Quote Link to comment
Crashtd420 Posted May 25, 2021 Report Share Posted May 25, 2021 3 minutes ago, d.p said: You saying have it dyno tuned for $1k or just tuned for a couple hundred bucks? A dyno run is the only way you'll know the true redline .... Do you really need to spend 1000 to be told.... are you even going to run the truck to that rpm ? 1 Quote Link to comment
Crashtd420 Posted May 25, 2021 Report Share Posted May 25, 2021 Just now, d.p said: haha the voice of reason!! And at that cost to benefit I would pass hard on it but I really have no idea how much HP I have to gain by doing it. I dont think you'll gain to much if its setup good right now.... If it ran like shit there would definitely be gains to be made. 1 Quote Link to comment
d.p Posted May 25, 2021 Report Share Posted May 25, 2021 2 minutes ago, Crashtd420 said: A dyno run is the only way you'll know the true redline .... Do you really need to spend 1000 to be told.... are you even going to run the truck to that rpm ? Haha know it wouldn't be a $1000 to find out what my redline is, it would be a $1000 to have a baseline HP/TQ on a dyno (all of this on a dyno) , tuned and jetted if need be, after HP/TQ so I know how many ponies I am making and finally what my rev limit should be. I think. 2 Quote Link to comment
Crashtd420 Posted May 25, 2021 Report Share Posted May 25, 2021 11 minutes ago, d.p said: Haha know it wouldn't be a $1000 to find out what my redline is, it would be a $1000 to have a baseline HP/TQ on a dyno (all of this on a dyno) , tuned and jetted if need be, after HP/TQ so I know how many ponies I am making and finally what my rev limit should be. I think. Well true they would probably let you take a few pulls on the dyno for $100 - $200.... Dyno is the best way to get it done right..... The guy up by me just charged me a couple hundred, I was there for probably and hour or 2... he would do stuff inbetween dyno pulls while I was doing the rejetting, since know one up here deals with Datsuns or weber's.... Unless your having issue or you think it should be giving you more I'd say just run it to 6500 and have fun... then keep bumping the rev limit up by 100 till you find where it's no longer happy.... Dont over think it.... 1 Quote Link to comment
banzai510(hainz) Posted May 25, 2021 Report Share Posted May 25, 2021 (edited) pay for my flight over and I will drive it and tell you your REDLINE. and you can still buy me lunch with the money left over. PS I dont have Tachs in my Datsuns!!!! Never needed them I would wait for a Dyno day that is cheaper so you can have the readout. Who ever had that motor before spend the money to get it right as I remeber the plugs looking pretty dam good. Edited May 25, 2021 by banzai510(hainz) 1 Quote Link to comment
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