ggzilla Posted October 28, 2012 Report Share Posted October 28, 2012 Turbos are for hauling. What do you think the big-rigs use? as it is I can barely hit 60 Well just fix it -- dont' try to do a custom turbo swap if you can't even get your 720 stock engine to do 80 mph. Quote Link to comment
Zlich Posted October 28, 2012 Author Report Share Posted October 28, 2012 Its cause I have oversized tires and its got low gearing. Quote Link to comment
ggzilla Posted October 29, 2012 Report Share Posted October 29, 2012 low gearing (4.625) balances out oversize tires. So you should still get close to stock performance. Are you putting your foot down and letting it rev up to 4500 RPM? That's what Z24 engine wants. It will go faster in 4th than in 5th. Now if you have oversize tire and high gearing (3.89 gears) then you'd need more power. Quote Link to comment
Zlich Posted October 29, 2012 Author Report Share Posted October 29, 2012 Yeah my Rpms go up anywhere to 4500 to 6k sometimes. I'm normally going 5th gear 5k or so and just barely hitting 60. Quote Link to comment
Zlich Posted October 29, 2012 Author Report Share Posted October 29, 2012 It might also have something to do with my whole carb having problems to. I'm rebuilding it here soon to get by till I can get the cash for a weber. But as far as I know it's a completely stock z24 only had 8 hours put on it when it was dropped into my truck. The only thing iv done is straight piped it to a 2" to 6" custom muffler and I have all the back pressure I need. Quote Link to comment
ggzilla Posted October 29, 2012 Report Share Posted October 29, 2012 With that overall gearing (5000 RPM at 60mph) -- it sounds like you need a taller gear ratio. Instead of 4.625 drop it to 4.11 and it would do over 70mph at 5000 RPM. Quote Link to comment
sinner720st Posted October 30, 2012 Report Share Posted October 30, 2012 HORY SHET... 5k at 60? :blink: ... my 720 had 4.625 (pathfinder rear) and small tires at 70mph it was humming along at 3k rpm... so you with 33" tires and 5k at sixty sounds like 9.29 gears... and that stock carb is so much very holding your truck back... i bought the 32/36 new... and totally wished i had got the 38... you should get the 38. you have a nice header, and plenty of exhaust... the next step is a carb, then maybe an "RV" cam (they do great for wheeling) schneider or web cams has great selection, i think comp cams makes on for your truck... as for the carb, they go new for 3 hundo. you should be able to find one used for half that (count on a rebuild kit, and rejetting it) also check out the "weber carburetors hp book" and the "turbochargers hp book" amazon sells used books like that for about ten bucks a pop... Quote Link to comment
JoeCool Posted October 30, 2012 Report Share Posted October 30, 2012 So what is the difference between a Weber 32/36 and 38. All I know is I have only seen kits to do a 32/36 on 720. Quote Link to comment
izzo Posted October 30, 2012 Report Share Posted October 30, 2012 32/36... smaller carb, and only one barrel is open first half of throttle, secondary opens up when you get past about half way down on the pedal. 38, larger carb, more air, more gas. I can't recall but its either both barrels open or one large one?? Someone else can chime in on that. I've never owned a 38 Keep in mind, thats a Naps motor (nissan anti polution). They have poor air flow, and were never intended for high rpms or performance. Emissions based head... You get most of your performance low and mid RPMS, not a lot left at the top. So the 38 might be almost pointless. Quote Link to comment
Lugnutz Posted October 30, 2012 Report Share Posted October 30, 2012 A Weber might be the right choice. Then again, I chose to rebuild. Here's my DIY post for the carb rebuild. You definately have a Hitachi carb and the rebuild kit is pretty cheap. http://community.rat...vy/#entry515654 Here is my guide to where all the vacuum lines go. The post used my 1986 720 with a Z24. Yours might have minor differnces. You can tell from all the vacuum line pics that it is a real mess, so go slow when examining the vacuum lines and make sure you put them back the way they came off. Good luck! http://www.nicoclub....pair-guide.html Quote Link to comment
danrgmc Posted October 31, 2012 Report Share Posted October 31, 2012 What did you think of the 38 on your z24? Im trying to figure out what weber carb I should get for my truck and cant decide if I should get a 32/36 or the 38. I put a 32/36 on my '86 720 and it's been running great for about 3 years. Lots of power for 207000+ miles on Z24. I didn't do anything special with emissions rat nest either; just plugged everything up with only carb-dist vacuum advance left hooked up. Here in Tucson, I get about 20 mpg in town and 28-30 on hwy. I just bought an '85 720 so am selling the '86 in a few days. (I didn't want to go through fixing up for emissions.) The '85 has 'ST' on the rear of the bed, I can't seem to find any info about different versions of this truck. I've seen references to 'Deluxe', 'Sport', or 'base', any idea what this means? Quote Link to comment
FiveSeventyZee Posted October 31, 2012 Report Share Posted October 31, 2012 st is sport truck. it was the 2wd short wheelbase model Im pretty sure and to the OP...when your truck doesnt run right due to carb issues probably isnt the best time to fuck around in the engine bay modding shit. I've found that the most reliable car is one left stock. weber would be a good place to start, you say you can't afford a $300 carburetor but youre asking about turbo setups? don't buy a turbo yet, save your money and buy that weber, used to have a weber on my dime and I kept it when I sold the old engine because they are awesome and if I ever have anything L powered again I want to have that option still open. but the point is, fix the carb issues first, then see if you can't go more than 60 Quote Link to comment
Z-train Posted October 31, 2012 Report Share Posted October 31, 2012 ST was an option on all models. Quote Link to comment
Sealik Posted October 31, 2012 Report Share Posted October 31, 2012 ST came in 85...to 86. Options included....PW,PL,sunroof, ST decal package, ST steering wheel, tack, clock, brushed aluminum 'facade' on dash, console with oil and volt gauges, molded armrests and upgraded interior door panels Some STs came fully loaded......some not Both of my 85 STs, 2 and 4WD KCs came with all the above options Quote Link to comment
Zlich Posted November 4, 2012 Author Report Share Posted November 4, 2012 HORY SHET... 5k at 60? :blink: ... my 720 had 4.625 (pathfinder rear) and small tires at 70mph it was humming along at 3k rpm... so you with 33" tires and 5k at sixty sounds like 9.29 gears... and that stock carb is so much very holding your truck back... i bought the 32/36 new... and totally wished i had got the 38... you should get the 38. you have a nice header, and plenty of exhaust... the next step is a carb, then maybe an "RV" cam (they do great for wheeling) schneider or web cams has great selection, i think comp cams makes on for your truck... as for the carb, they go new for 3 hundo. you should be able to find one used for half that (count on a rebuild kit, and rejetting it) also check out the "weber carburetors hp book" and the "turbochargers hp book" amazon sells used books like that for about ten bucks a pop... Right now it has 29in tires on it. I want to throw a set of 31's under it. Iv also heard that getting a 38 makes the motor stall or something like that when you stomp the pedal down? I cant remember exactly at the moment. Quote Link to comment
Zlich Posted November 4, 2012 Author Report Share Posted November 4, 2012 st is sport truck. it was the 2wd short wheelbase model Im pretty sure and to the OP...when your truck doesnt run right due to carb issues probably isnt the best time to fuck around in the engine bay modding shit. I've found that the most reliable car is one left stock. weber would be a good place to start, you say you can't afford a $300 carburetor but youre asking about turbo setups? don't buy a turbo yet, save your money and buy that weber, used to have a weber on my dime and I kept it when I sold the old engine because they are awesome and if I ever have anything L powered again I want to have that option still open. but the point is, fix the carb issues first, then see if you can't go more than 60 the Whole turbo thing Is just an idea at the moment Im trying to figure out what all Ill need to do it first. I am focusing on the carb the most right now and this whole post started before my carb took a dump on me. Im about to rebuild the old carb and if that doesnt work im gunna save up for a weber. dont know what size yet ether a 32/36 or a 38 for sure. Quote Link to comment
Zlich Posted November 4, 2012 Author Report Share Posted November 4, 2012 Now if you have oversize tire and high gearing (3.89 gears) then you'd need more power. so I just found out by looking at the stamp on the fender my gears are 3.89. but I only have 29' tires on it at the moment. Quote Link to comment
Sealik Posted November 4, 2012 Report Share Posted November 4, 2012 3.89???? 81 4x4 should be a 4.38?.........HF43 83+......4.11 Quote Link to comment
Sealik Posted November 4, 2012 Report Share Posted November 4, 2012 HE38 You sure that plate hasn't been swapped from a 2WD? (from 1981 factory service manual) rwd manual trans: 3.889 rwd auto trans: 4.111 4wd both + rwd one ton: 4.375 All my early 4x4 720s are HF43. The way you are revving at 60 MPH...you have at least 438s in the 'rear' Quote Link to comment
Zlich Posted November 5, 2012 Author Report Share Posted November 5, 2012 .The way you are revving at 60 MPH...you have at least 438s in the 'rear' your whole post kinda lost me. but yeah Im pretty sure its a stock 4x4 I can always run the vin# to find out for sure. and are 438s good or bad? Iv never really had to deal with gearing before and dont quite understand it. a quick rundown if you could give it on the basics would be great. this is my first truck and its gunna be around for awhile. Quote Link to comment
Zlich Posted November 5, 2012 Author Report Share Posted November 5, 2012 Are there any other ways to find out what gears I have without opening up the rear differential? Quote Link to comment
Sealik Posted November 5, 2012 Report Share Posted November 5, 2012 your whole post kinda lost me. but yeah Im pretty sure its a stock 4x4 I can always run the vin# to find out for sure. and are 438s good or bad? Iv never really had to deal with gearing before and dont quite understand it. a quick rundown if you could give it on the basics would be great. this is my first truck and its gunna be around for awhile. The heavier 4x4 needed a lower gear ratio to get it moving...(numerically higher....ie 4.38s/4.11s) Your truck came stock with 4.38s, thus the higher RPM at 60MPH......the lighter 2WD didn't need those gears, thus the 3.89s and or My guess that ID plate has been replaced.......it should match the one on the dash, door well and frame Lower gears (4.38s/4.11s)....good for bottom end.....'around town'...out of the hole. Higher gears (3.89s > etc)...better for cruising/top end...but less torque. Not conducive for the 4x4 Quote Link to comment
Zlich Posted November 5, 2012 Author Report Share Posted November 5, 2012 well I ran the vin and its a stock 4x4. but i wouldnt know if it was changed out my dad (who had the truck before me) bought it from a junkyard with a hole in the stock motor. He didnt even know about this badge untill i told him about it. so enless the guy before him that had it switched it I would belive its the stock badge. Quote Link to comment
Sealik Posted November 5, 2012 Report Share Posted November 5, 2012 Are there any other ways to find out what gears I have without opening up the rear differential? Yes... https://www.google.c...iw=1166&bih=653 10 to 1 it doesn't match that ID plate.......possibly.....maybe. Quote Link to comment
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