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73-87 Chevy _ GMC Trucks => Performance => Topic started by: 75chevyred on October 26, 2007, 08:44:33 pm
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OK , im the new guy here. I got two trucks. One 75 1 ton dually, with a 350 in it, the other is a 85 GMC was a 6.2 diesel , now has a 350 in it also..
Here my problem. I need to tow 10,000 pounds of rock in a dump trailer. Currently the dually is struggling at 48 MPH. It had a 454 originally. th400 ( big one)
The 85 GMC can be reinstalled with a 6.2, i have 2 of those bad boys. It has a 400 tranny, short shaft. problem is im not a diesel man.
Any suggestion would be helpful? I dont have a lot of money to spend on these trucks right now
thanks HJ
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A 350 can handle it. I'd look more at the whole package here. What's the final drive gear ratio? What happened to the 454? What trans do you have in there? IF you're carting around 10k lb of rock I don't think speed is your concern as you'd probably want to keep it low. I hope you've beefed up your suspension too for this pay load
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OK, the truck is stockl 1 ton dually, strong springs under the truck. It hold the 2000 pound trailer well. Pulling the 2000 pounds you cant tell its back there.
The transmission is stock 400 like the bmw type 3 speed, not the short tailed type. Drive shaft bolts to the tranny, i think its about a 4 incher?
The 350 has headers and a 4 barrel Elderblock intake and carb, still has stock radiator and cooling system seems ok.
I just when throught the brake system, they hold good , Im going to have to put a trailer brake control in the dually to help stop the rig when loaded. Trailer has electric brakes
Ive only pulled the trailer about 35 miles so far , Just brougth it home and parked it so far. The Dually seems to be the truck it with? However, it did backfire about 5 times coming home under the load
OH, it does NOT have a good breather system on the 350. Im going today and look at a preformance air intake
thank HJ
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I had to read your post a few times but don't get what you are saying especially here?
The Dually seems to be the truck it with?
thank HJ
What is your rear end gear ratio? If the engine is stock You might consider a better cam and ignition system too.
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Basically i'm saying the truck will pull the 10k but just lacks the power to maintain 60 mph
I have another truck but don't think it would pull 10K
thanks for you help, i'm working on this problem
HJ
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A 350 shouldn't have an issue maintaining 60 mph with a 10k load if its appropriately geared and running properly...
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OK, I agree, its a 350 with headers, M40 - Turbo Hydra-matic Transmission, Im quessing its a 4:10 rear end according to the 73 - 80 GM Chart
what do you think?
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That should pull it without issues with that setup, but you said it backfired when pulling it home? When is the last time it had a tune up, wires, plugs, etc...
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actually ive never tuned it, Just adjusted the valves and set the timing to 8 degrees. I did clean the plugs , oldtimers method of sand blasting plugs.. the igintion is Malloy , wires 8.8 MM, there nothing out of the ordinally, in that area.. I think the values are to loose now. My neighbor mechanic, suggested the valve adjustment..
Heres a thought, before i bought the truck, it set up a lot and I beleive it got a little water in the top side of the engine due to a hood leakage. I change the oil after running it about 30 minutes.. the oil was a little cloudy. I havent looking in the lower side of the engine, but the motor runs to darn good to be hurt ( I think)
HJ
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Don't just clean the plugs, replace em. They're cheap. I pay <$10 for 8 champion or AC delco plugs, depending on which is on sale at the moment. As for the moisture issue, change the oil and filter and do NOT use any kind of additive, and run it out on the highway for a little bit, long enough to get good and HOT, full operating temp, then cruise it at a steady 10-20 mph with minimal stops for about 20 minutes to keep it good and hot. That should dry the entire engine out thoroughly, if the oil is still milky white, you've got more serious problems (ie, leaking head gasket, cracked head, etc.).
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You shouldn't ever have to re-adjust the valves on a hydraulic lifter. What procedure did you use to adjust them? Having them too tight will cause a loss of power.
I agree on the plugs and oil, buy new plugs and check the gap, and drain the oil and change the filter.
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And get a new neighbor! lol
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heres a question, what kinda MPG will a 1/2 ton (GMC) 6.2 diesel with a th400 3 speed automatic and 311 rear end ,a set of 31x10 15's GET?
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thanks for all the help on my Dually, Ill get it fixed or sell it later...
Also I picked up a frame and guts of a 86 surburban 4x4 today, 6.2, tranny is ok the truck came with 273 ratio rear and front ends,,
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A friend of mine has an '82 1/2t 4wd with 4.11 gears, 6.2 diesel and sm465 and gets about 22 mpg in town, and about 26 on the hwy at 50 mph, but with those gears its screaming at 60 and sucks some fuel.
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A 5.7L 350 V8 will have more power than a 6.2L diesel.
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A 6.2 has potential to be significantly cheaper to drive (especially on biodiesel) and still have some power available for pulling, thats its only real advantage..I'd still say go with a 350 instead, unless you're really into diesels.
I'd like to build a good diesel in one of these trucks (maybe a 4x4 crew, or a 3/4t 4x4 burb) and run it on biodiesel, but it wouldn't be a serious towing rig...
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I 100% agree with that, but if you plan to pull 10,000lbs all the time I would skip the diesel. If you were into them it would be a different story.
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guess what, I just found out that the TH 400 tranny on the 75 chevy dually, didnt have the electrical hook up to the carb. any help here? can i buy a kickdown kit?
HJ
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There is supposed a switch on the gas pedal bracket, this is where the hookup goes.
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yep these trucks had the switch on them on the pedal not the carb.
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yep i just found it, it on the gas petal, and runs to the back of the tranny, hot wire comes off the inside panel fuse box , goes to switch, then through firewall to tranny. maybe it will do better now, ?
going to change the filter and tranny fluid today
Also i found out that the tranny that came out of the subruban frame I just bought, was a thm400 with electric kickdown, that means she's a 3 speed right?
thanks HJ
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All Th400's are 3 speed.
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How is a 350 better for pulling than a Diesel? If I was going to be towing anything heavy at all I would much rather build a Diesel to pull it than a gas engine, the torque will be way way way more on the diesel than the gas engine. But that's just me, but for what your trying to do a gas 350 sould do the job fine.
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How is a 350 better for pulling than a Diesel?
The factory 6.2 diesel was a dog from the factory. It had 240ft/lbs of torque. The 350 had 295ft/lbs. It was a light duty setup originally.
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Exactly. The 6.2 was a vast improvement over the olds 350 diesel used up to '81, but without dropping dough for a twin turbo kit and all that fun stuff, a 350 gas engine will make more HP AND torque with comparable cash spent on engine mods when compared to a 6.2.
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Okay, I see. That makes sense then.
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OK , I did some work on the ole truck this week end and it has more power now. However lifters on # 4 is clicking after several adjustments. I got it down to a minor click,, I put a peice of PVC pipe about 5 foot long to each header and listen to the sound, and #4 has this clickity klicity sound . It sounds like it's on the exhaust valve !What would be the best thing to do to? New lifters? partial lifters? any suggestions?
Amazing all the other sound like a sewing machine at about 250 rpms :)
also i set the timeing at about 12% @ 1000 rpm's seems to have more power now. I beganing to believe that the rearend and the 350 just dont go together... still at 50 mph the engine starts to work hard to gain more speed.. would burn a lot of gas if i pushed it pasted 50..
HJ
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...its a carbed 350 without an overdrive, its gonna burn a lot of fuel going over 50 mph anyway.. At 85 mph, in a 2wd truck with 2.73 gears, mine gets ~6 mpg.