Newkid Posted February 22, 2012 Report Share Posted February 22, 2012 well since ive got it the gas mileage has been in the toilet, when i first got the 620 i did: spark plugs spark plug wires cap and rotor air filter fuel filter oil change made sure all the tires are properly inflated( might have to check again to make sure they are still at correct psi) idk what it could be idk the rpms im running on the freeway since i dont have a rpm gauge in there yet, i intend to get one soon, but it seems like im at the gas station a lil too often.. i know there are other things i can check to see what else can cause bad gas mileage but i dont have a clue, im still learning about CARB vehicles, i was so used to EFI cars so what do u guys think it could possibly be?? Quote Link to comment
Z-train Posted February 22, 2012 Report Share Posted February 22, 2012 Define"crap milage". Quote Link to comment
Newkid Posted February 22, 2012 Author Report Share Posted February 22, 2012 Less than 20 mpg I was expecting to get at least 30 mpg or so Quote Link to comment
Laecaon Posted February 22, 2012 Report Share Posted February 22, 2012 My friend gets 15mpg in his 521, L16, weber 32/36, 3.889 rear end. I get close to 30 in my goon with the exact same gearing, L18 and same carb/jets, but I do have shorter tires. Quote Link to comment
datzenmike Posted February 22, 2012 Report Share Posted February 22, 2012 If this is around town, short trips to work and home, to the store and back with the motor cold with the choke on much of the time.... I can see that. Check that your choke shuts off in about 7 minutes or so. By off I mean completely open. Quote Link to comment
ggzilla Posted February 22, 2012 Report Share Posted February 22, 2012 Sounds about right. Too much Choke would definitely hurt mileage. But consider it's a truck with low gearing, a relatively large engine, and higher therefore less aerodyamic. It's not going to get what a 510 gets even with the same engine. My EFI minitruck Mazda gets 16 in town and 24 on the highway. Quote Link to comment
datzenmike Posted February 22, 2012 Report Share Posted February 22, 2012 Weight is a big factor as well. Every pound takes gas energy to accelerate up to speed. Driving habits are another. Some people are on the gas off the gas on the gas off the gas... this is how they drive. Others don't anticipate stops and speed along only to hit the brakes at the last possible moment. Every time you use or have to use your brakes you are throwing away the gas you just used to get the vehicle up to speed... thrown away. See the light changing way up ahead?? Well slowly begin letting off on the gas and begin slowing down. It might be even possible to get there after it's turned green so you've saved some momentum. What the fuck is your hurry????? I go a few over the posted limit and if some asshole behind me is in a hurry he can fuck himself. I'm in no hurry and I'm going faster than the limit so rub salt. Have to get to work? Who would speed to go to work??? Leave 5 min sooner and take your time, enjoy the ride/music/scenery and stop filling up as often. Speed? In town you drive at 30 MPH. On the highway you drive 60 MPH. Did you think you only need twice as much power to go twice as fast? Think again... it takes at least 4 times as much. Going the speed limit saves big time out on the highway. Quote Link to comment
Laecaon Posted February 22, 2012 Report Share Posted February 22, 2012 I still dont think 15 mpg is reasonable. Unless the L16 is simply under powered. I have seen many reports of people in trucks getting high 20's, skib reported just shy of 30 in the 620 with SU's. Quote Link to comment
Newkid Posted February 22, 2012 Author Report Share Posted February 22, 2012 Ill have to check the choke to see if its the choke is turning all the way off tomorrow but when I usually start the truck I just lightly step on the gas to warm it up till it can idle under its own power, if I don't do this it will just die, I don't think the idle will turn on when I start the truck.. is there a manual choke cable in the cab somewhere I'm over looking Quote Link to comment
ggzilla Posted February 22, 2012 Report Share Posted February 22, 2012 Weber carb is almost guaranteed to get worse mileage. However if your stock carburetor is not adjusted correctly, the weber might do better. Quote Link to comment
Str8_69 Posted February 22, 2012 Report Share Posted February 22, 2012 Maybe throw a timing light on it too... see where it's at? Quote Link to comment
datsunaholic Posted February 22, 2012 Report Share Posted February 22, 2012 Normal mileage for a 620 with 4.38 gears and a 4-speed is around 23-27 mixed. You can GET 30, but you have to work at it. Sub 20 means something's wrong or your driving habits don't equate to good mileage. Quote Link to comment
ggzilla Posted February 22, 2012 Report Share Posted February 22, 2012 Isn't sub-20 normal for around town driving? Quote Link to comment
chester Posted February 22, 2012 Report Share Posted February 22, 2012 With my kc620, when I had L16 with u67 head, weber, 5spd and decent cam, with 4.37s I pretty much always got 17. When I went to 4.11 and peanut head it went up a little, about to 19. When I finally put the L20 in with the decent cam, weber, 5spd, 4.11 and peanut head I started getting 23-25. I had a stock carb on for a bit and was getting 28. This is with both city and highway driving. So I agree with checking the timing and the carb Quote Link to comment
Icehouse Posted February 22, 2012 Report Share Posted February 22, 2012 my KA truck always got high 20's. L20 only lasted a month so I can't remember what it got. Sounds like carb problems to me! Quote Link to comment
Newkid Posted February 22, 2012 Author Report Share Posted February 22, 2012 I believe its carb problems cuz yesterday it drove fine to work and this morning it was really sluggish and it felt like I had to push it harder just to get it up to speed...my morning commute to work every morning is about 20-25 miles on the freeway, so about a 45-50 mile round trip. So going with a lower gear and puttin this five speed I have in should really drop down the rpms and help with gas mileage..right?? Quote Link to comment
DanielC Posted February 22, 2012 Report Share Posted February 22, 2012 Have you checked the ignition timing yet? What was it? Quote Link to comment
Newkid Posted February 22, 2012 Author Report Share Posted February 22, 2012 havent checked have to buy a timing gun first Quote Link to comment
1lo620 Posted February 23, 2012 Report Share Posted February 23, 2012 I run an L18 with a 32/36, nothing fancy and I get around 25 plus on freeway, and just a bit less around town....but I also have a 5spd, not sure how much difference that makes... Quote Link to comment
Newkid Posted February 23, 2012 Author Report Share Posted February 23, 2012 a you running stock gears in the rear with your five speed? Quote Link to comment
Radiant-Designer Posted February 23, 2012 Report Share Posted February 23, 2012 Just remember if you put a 5 speed in you have to drive for years to recoup the cost of the swap with any savings in gas mileage.... but I agree and i am doing a 5-speed swap too ;) I just found an 83 280ZX thats being parted out, just have to drive an hour to take the trans out. Its funny i just looked at my carb yesterday, tightened up the nuts holding it on (they WILL vibrate loose if you dont use locktite) and adjusted the ide mix a little and it seems to have done better on the drive back home and to work this am. Quote Link to comment
Newkid Posted February 23, 2012 Author Report Share Posted February 23, 2012 well when i bought the truck, he had a 5 speed he planned to put into it, now its just sittin in my garage, needs to be cleaned up a lil so i can go ahead and swap it in Quote Link to comment
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