scooter Posted January 8, 2015 Report Share Posted January 8, 2015 hey guys, im just trolling for some ideas you may have come up with to make things a little more comfortable and functional for todays world. my ratsun is a 1972 620 that is pretty much stock other than dropping in an L20b. the to do list so far is: disc brakes on the front weber 32/36 5 speed take a leaf or two out of the back so its not so spine busting. do you guys have suggestions to get the interior noise down? dynamat? insulation? are new body mount rubbers available? cheers guys. 1 Quote Link to comment
qwik510 Posted January 8, 2015 Report Share Posted January 8, 2015 The 5 speed and the disc brakes will help a lot. I have had good success with Dynamat Extreme. It is expensive but works well to keep the cabin cooler and quieter. I would add some sort of insulation over the Dynamat and then full carpet. Also, replacing worn out door seals and changing out the window Bailey channel (felt) will help with noise too. 2 Quote Link to comment
datzenmike Posted January 8, 2015 Report Share Posted January 8, 2015 A five speed is more useful if there is highway driving during your commute. Otherwise it doesn't get much use. The best thing about disc brakes are not having to adjust the drums regularly and they are easier to change. Now that improves your driving quality. Not good to remove any leaf springs. The differential is positioned latterly by the combined strength of the leaf pack. The 620 is not known for a harsh ride but they did come with nylon 6 ply sidewall tires which resist flex. Look into some 'softer' radial tires for it. You can't mix nylon and radial tires and best not to mix different brands. Keep them all the same if possible. The 32/36 will add a small performance boost but not as drivable as the original Hitachi. Mounts are fine but sound deadener is good and some carpet. Sound deadener up under the dash as far as you can and the back and sides of the cab as well as inside the doors. 2 Quote Link to comment
abbylind Posted January 8, 2015 Report Share Posted January 8, 2015 Remember the rubber hoses, gaskets etc are over 40 years old (if they haven't been replaced)...as you can afford it start replacing them. I had a small leak in my brake hose due to age...replace them! 2 Quote Link to comment
Charlie69 Posted January 9, 2015 Report Share Posted January 9, 2015 I have been running Webers on Datsuns since the 1970s and have daily driven my trucks and cars many many miles withe the Weber. I had a 1970 521 that i put a Z20 5 speed in. and when I out a used Weber on it it came lo life. I drove over 300,000 miles with that setup and did not have one problem running the Weber. Mike would you please explain your statement "32/36 will add a small performance boost but not as drivable as the original Hitachi." What makes the Weber less drivable? 1 Quote Link to comment
datzenmike Posted January 9, 2015 Report Share Posted January 9, 2015 It's slightly too big for one. Better for performance but harder on mileage. This doesn't mean it won't work or is no good just that you can stand on it too soon and it will bog slightly. Part of this is the progressive secondary with the second barrel opening on demand at about 3/4 throttle. The Hitachi runs only on a smaller primary no matter how floored it is. The secondary is vacuum operated and only comes in when needed. Much smoother and saves gas. The weber is far less complicated and simply dumps fuel and air together. It's generically designed for larger 4 cylinder displacements other than Datsuns and so really should be tuned for your application. A weber needs slightly more work to be driven in order to drive seamlessly in stop and go. Once rolling and reving up it has the advantage. The Hitachi is very complicated but also tailored for the L series engine's needs of mileage, emissions, drive ability, performance under all driving and weather conditions. The Hitachi is well matched to the engine it is on. I know weber owners will disagree on the driving traits but if you compare them to a non worn out Hitachi you'll have to agree it runs smoother. (not faster) A smaller carb is always smoother to drive. If your Hitachi is worn out, plugged up, problematic (as it is a very complicated carb and more to go wrong with) a weber is a great improvement. If you have a good running Hitachi the difference is... less. 2 Quote Link to comment
Charlie69 Posted January 9, 2015 Report Share Posted January 9, 2015 Mike you are correct on the bogging. I have re jetted mine for a L20B in a 521, re jetted Z20 in a 521, re jetted my Z24 in my 720 and I have no bog. I am and have with all 3 setups gotten 28 miles to a gallon in town and 30 miles per gallon on the freeway. It does take some time and understanding of the Weber to get it to perform and run smoothly but it is completely doable. There are several parts that can be changed out to properly tune a DGEV Weber. Jets emulsion tubes and air venturies. Main problem I have seen is to much fuel pressure. The Holley Carbs we ran 70s and 80s had the same problems out of the box as the Webers do. They have to be tuned to the engine. Mike where are you going to find a non wore out Hitachi? The Hitachi carb was designed for each application from the factory. There are literally hundreds (probably more than that I really do not know total number) of different configurations of the Hitachi Carbs. They were not and are not 1 carb fits all applications. This being said neither is a Weber or a Holley or an Edelbrock, they all have to be setup and tuned to each application. Mike your theory of being to big is correct. How do you explain factory dual SU's? In theory those are to big for the engines they came on! It is the setup and the tuning that makes them work. Quote Link to comment
datzenmike Posted January 9, 2015 Report Share Posted January 9, 2015 The SUs are a 'constant velocity' type and the carb adjusts it's size (internally) to suit the engine. Not a very good explanation but... close. An L20B at 6K needs just over 200 CFM of air. The 32/36 (I have heard) is about 270 CFM. A larger carb requires less work to suck air through it so there is a slight performance gain here, but, there also has to be sufficient volume of air flow in order to generate a vacuum signal at the venturi to draw in fuel. If larger and larger carbs made more and more power, we would all be running 1180 Hollys. Generally factory carbs are a compromise and good mileage and driveability are very important so smaller is better. From a strictly performance perspective all engines will run better with a slightly larger carb but now the compromise is usually mileage, easy all weather starting, idling and around town stop and go. 1 Quote Link to comment
]2eDeYe Posted January 9, 2015 Report Share Posted January 9, 2015 hey guys, im just trolling for some ideas you may have come up with to make things a little more comfortable and functional for todays world. my ratsun is a 1972 620 that is pretty much stock other than dropping in an L20b. the to do list so far is: disc brakes on the front weber 32/36 5 speed take a leaf or two out of the back so its not so spine busting. do you guys have suggestions to get the interior noise down? dynamat? insulation? are new body mount rubbers available? cheers guys. 5-speeds are nice, but not necessary, The L20B revs to 7000 rpm quite well, but without a tach 5000 rpm can sound like too much. Do you plan to lower it or anything of that nature? If not, I would suggest new shocks and suspension bushings throughout. Then decide if you want to remove springs, or better yet get some later model springs with a less progressive rate or 720 4x4 springs to lower it. People tend to assume more leaves = stiffer ride when in reality more springs = a more progressive spring rate. If you are going to dynamat don't forget to do the roof, it is the largest panel in the interior and is the biggest culprit in the tin can sound effect IMHO. You should be able to use 720 body mounts and they are still available, rubber is better than poly as it transfers less vibration to the cab. The two best mods I have done to make my 620's more comfortable is nice seats and a nice stereo. I think if the interior is nice, it's always a much better driving experience. :) 3 Quote Link to comment
scooter Posted January 9, 2015 Author Report Share Posted January 9, 2015 that's a good idea using 720 springs. in not looking for moar low, just looking for a bit of a smoother ride. I do need to do all the front end bushings and replace a bunch of shit. if I can get new 720 cab mount bushings ill do that. 5000rpm on the highway? try 5800 ;) hahahaha... when I get a moment i'm going to try and find the lowest ratio 5 speed I can. ive taken this thing on some long trips (Kelowna to Calgary) and it does wear ya down. carb swap is because my hitatchi is a piece of shit and its going to meet death by sledgehammer once the weber goes on. basically girls don't like riding in it because theyre boobs are allways going all over the place, even though its entertaining. 1 Quote Link to comment
Z-train Posted January 9, 2015 Report Share Posted January 9, 2015 Not good to remove any leaf springs. The differential is positioned latterly by the combined strength of the leaf pack. The 620 is not known for a harsh ride but they did come with nylon 6 ply sidewall tires which resist flex. Look into some 'softer' radial tires for it. You can't mix nylon and radial tires and best not to mix different brands. Keep them all the same if possible.This.Not to mention removing leafs will screw with the brake system. 1 Quote Link to comment
Charlie69 Posted January 9, 2015 Report Share Posted January 9, 2015 The SUs are a 'constant velocity' type and the carb adjusts it's size (internally) to suit the engine. Not a very good explanation but... close. An L20B at 6K needs just over 200 CFM of air. The 32/36 (I have heard) is about 270 CFM. A larger carb requires less work to suck air through it so there is a slight performance gain here, but, there also has to be sufficient volume of air flow in order to generate a vacuum signal at the venturi to draw in fuel. If larger and larger carbs made more and more power, we would all be running 1180 Hollys. Generally factory carbs are a compromise and good mileage and driveability are very important so smaller is better. From a strictly performance perspective all engines will run better with a slightly larger carb but now the compromise is usually mileage, easy all weather starting, idling and around town stop and go. Good answer Mike you sir have a great knowledge of Datsuns and cars in general. Quote Link to comment
]2eDeYe Posted January 9, 2015 Report Share Posted January 9, 2015 basically girls don't like riding in it because theyre boobs are allways going all over the place, even though its entertaining. This is the exact reason for my two best mods, well that and my comfort level :lol: 1 Quote Link to comment
77Adam77 Posted January 28, 2015 Report Share Posted January 28, 2015 I have a question to add then. I would LOVE to keep my hitachi but how and where can one get a real rebuild kit for these? And I hear everyone always saying they rebuild them and they still run rich? Is this mainly due to desmog? Or just irreparable aging factor? Tryin to put all my smog stuff back together to get my truck running like factory floor but don't want to bother if any and all hitachis just can't cut it after a period. I do lots of stop go driving as well as highway and love how perfectly gradual it steps in. Plus moving to Cali or somewhere I gotta get it running for the inspections every once in while... 2 Quote Link to comment
ericsb210 Posted January 28, 2015 Report Share Posted January 28, 2015 If one is to rebuild a carb, the most important factor is the throttle. If it isn't tight, it must be repaired (sleeved). I also like to use o-rings. You can not get any carb to run properly if it is getting more air than it was designed to have. I am not sure when this part of carb rebuilding was forgotten. I believe it is the single most reason for the hatred of carbs. 1 Quote Link to comment
Javin Posted January 29, 2015 Report Share Posted January 29, 2015 My only suggestion is cup holders. 4 Quote Link to comment
orangie Posted January 29, 2015 Report Share Posted January 29, 2015 I think if I was to do it all over again. I would have just got a 720 chassis and dropped the body on it. Not sure if the hardbody frame are the same dimensions. 1 Quote Link to comment
MantisX620 Posted January 29, 2015 Report Share Posted January 29, 2015 A radio that accepts an aux cable and some good front speakers. BMW ellipsoids and properly pointed HIDs make driving at night a joy. Sound deadening! A new set of wiper blades. A bitchin set of carbs and exhaust to sing you the song of your people. These are the things so far that make my 620 a cool daily so far. Cup holders are coming up! 3 Quote Link to comment
]2eDeYe Posted January 29, 2015 Report Share Posted January 29, 2015 My only suggestion is cup holders. 3 Quote Link to comment
Madd Engineering Posted February 3, 2015 Report Share Posted February 3, 2015 ball joints and disc brackes in the frontnew rubber everything bushings hoses etc. massively helps ride and reliabilitysteering ball joints 720 4x4 springsthere is nothing wrong with carbs but ka24de and 5 speed make life better and parts are cheap and plentifuljust my 2cents Quote Link to comment
rharm78 Posted February 3, 2015 Report Share Posted February 3, 2015 I drive a 78 620 to school everyday in so cal with no ac. Even though its hotter than hell in the summer its just a blast to drive. I actually find my truck more comfortable than my parents late model cars. I believe the main reason for that is because its so much easier to see out of the truck and even though its a long bed its easier to park. My truck came with ac (not working) and automatic trans. the automatic is great around town but on the freeway 65-70 is pushing it even though ive had it up to 80. The only modifications ive done to the truck is that we removed the ac box that was under the dash until I have the money to get the ac system going because it was just taking up space. Also I found a period cassette player and hooked that up under the dash, and installed a speaker on the drivers side kick panel so that way it was stereo because my truck originally had 1 speaker. The final modification was that the music wire under the seat had been trashed so my father re did all of the metal strings and then used foam from an old couch so the seat is really comfortable because well, its like sitting on a couch. under the hood everything is original down to the hitachi carb with all of the vacuum lines(it passed smog with flying colors) , and shes a great daily driver 1 Quote Link to comment
5t341tH Posted October 22, 2015 Report Share Posted October 22, 2015 Can you guys with a 5spd help me out? I daily my truck a lot on the freeway and I have the 3spd auto right now. At 70mph indicated (only 65 in reality), I am turning at 4200rpm. I'd like to lower it to around 2500-3000 rpm so its not so damn loud. What do you guys with the 5spd get on the freeway? I am running 205/55/16 tires with stock rear end if that matters. I want to know if the 5 speed swap would be beneficial for me. Thanks in advance Quote Link to comment
Outta_OC Posted October 22, 2015 Report Share Posted October 22, 2015 Didn't read all the posts, but I have manual air shocks in the rear, and I really like the adjustability of them. That's my $.02 Quote Link to comment
Outta_OC Posted October 22, 2015 Report Share Posted October 22, 2015 Also, I have 2x5.5 speakers and a Sony mx2020 stero powered amplifier that hooks through a headphone jack to my phone for tunes. My truck never had a radio, so this little amp fits under mybdash and doesn't have an exposed head unit some tweeker might want to steal Quote Link to comment
Z-train Posted October 22, 2015 Report Share Posted October 22, 2015 Can you guys with a 5spd help me out? I daily my truck a lot on the freeway and I have the 3spd auto right now. At 70mph indicated (only 65 in reality), I am turning at 4200rpm. I'd like to lower it to around 2500-3000 rpm so its not so damn loud. What do you guys with the 5spd get on the freeway? I am running 205/55/16 tires with stock rear end if that matters. I want to know if the 5 speed swap would be beneficial for me. Thanks in advance2500 isn't gonna happen without a gear change. Quote Link to comment
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