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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: deluxe77 on June 08, 2009, 03:40:47 pm
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I have some technical problems i need help with. Im not a mechanic but am generally mechanically inclined. I am trying to revive my '77 custom Deluxe. It has a Stock 350 with a holley 600 carb. Factory Transmission and Transfer case. All original is my understanding. Tranny has been rebuilt once. My problem is the truck has been sitting in a field for about three or four years. It does start and run. I replaced the carb, changed spark plugs and wires, and adjusted the timing. The motor seems to run fine when idling but when driving down the road had no power what so ever. Its almost like when you shift out of first it falls on its face... I think i topped out at maybe 45 mph. It backfires through the carb when warming up and when you press the gas pedal to first start out. Any ideas on what could be the problem would be greatly appreciated and checked on... This is a new problem for me... Right now i am down to my motorcycle being my primary vehicle and need the 77 up and running.
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Change the cap and rotor too. Set the timing. Drain the gas and put fresh gas in it. Change the fuel filter
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Ok ill get the cap and rotor... but the gas has been changed due to it running out of gas while setting the timing and i replaced the fuel filter at the same time as the carb. Thanks for the sugestion will let you know if that solves it.
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Ok ill get the cap and rotor... but the gas has been changed due to it running out of gas while setting the timing and i replaced the fuel filter at the same time as the carb. Thanks for the sugestion will let you know if that solves it.
I talked to Adam the other day and he had said something about you having issues. I also said something about the gas....but didn't know you had changed it out! Do you still have a header leak or broken header bolts? I think Adam was saying something of that nature but I could be wrong. I'll try to remember to talk it over with my buddy in the morning and see if he's got any idea's to add to the mix. Oh, is this carb your running the one you had issues with awhile back or is this the other one you got??
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Not to speak for Eric but this is yet another carb, this one was from a Co-workers Bronco. This isnt the original one to him, or the other one I asked you about LOL...
I think this is #6 :D
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This is a different carb. And Adam is Correct it is the 6th carb i tried. It is the only complete carb that i received all others had serious issues with them. As for the Header leak. I have one bolt that i believe is stripped out. I can't get a bolt to thread into the hole. But this has never been an issue before I have had header bolts back out and fall out many times before. All this does is make me have to change header gaskets alot more often than usually necessary. The bolt in question that is missing is on the passenger side 2nd one back from the front of the motor.
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when a vehicle sits for years, usually the fuel pump goes. It'll push some gas up to the carb (letting it idle) but when put under a load, it may not be enough gas gettin to it due to a rotted diaphram.
Just an idea.
If not that, then perhaps on the carb, you have a sticking float/seat needle (unless it is doing the same thing on all the carbs you tried.
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Backfiring through the carb sounds like a valve or lifter sticking. Pour half a quart of atf in with the oil to free it up. Just a thought.
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Well i put the new cap and rotor on. It alleviated the backfiring problem but it still has no power through the range of gears. I guess i am going to break down and save to buy a brand new carb instead of using hand me downs... :P
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By chance, when you changed the cap and rotor, did you check to make sure the advance weights in the distributor weren't hung up?
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Unless he messed with it after I left, I dont think the distributor ever actually came out. He set the timing on it, I believe 2 degrees advanced and it idles good....but he's not kidding when he says there's no power. It kinda gets up to "speed" and you can MASH the gas and NOTHING happens.
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Everything inside the distributor or under the rotor is should say, that was supposed to move moved freely. I heard again that it might be the fuel pump so i am going to replace the fuel pump before the carb. Thanks again to everyone for all the help!!!!
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Well I replaced the fuel pump and its still doing the same thing. All i can think of now is that the carb i put on it needs rebuilt. So i think i will save money and just go ahead and buy a new carb for it. eventually i will go through the carb i have and learn to rebuild it myself just for a spare.
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D'oh, I was hoping the fuel pump would do it!
At least it wasnt hot out when you did the install. :o
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Just an update for you fellas....
Borrowed a carb from a friend of mine last weekend that he KNOWS is good (Was from his running Cobra Mustang) and put it on Erics truck, and it had the same symptoms....so back to the drawing board on that.
Eric picked up a compression tester this week, we did that this morning and found less than desireable results....7 of the cylinders are between 145-155....but that "other" one is only at 35, sooooooo we have a dead cylinder. I think he's going to put some oil in the cylinder and test it again and see what happens, then take the valve cover off to try to determine if its a sticky valve, or bad rings or maybe something else...one step at a time.
On the positive side, he scored a basically complete 350 today for free...needs to be cleaned up but he's talking about throwing that on an engine stand and maybe punching it out a bit...could be fun :)
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Just some reading for Eric...
http://www.chevymania.com/tech/383.htm
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To add to what adam already said. I retested the bad cylinder with adding a little oil like i was told to try. The compression pressure didn't change at all. I'm still going to pull the valve cover to make sure the valves are moving.. After that i will pull the head and replace the valves if needed. Im thinking about taking the head to a shop and having it looked at? Any recommendations at this point would be helpful as im not familiar with what to look for in the internal of the motor.
I am also unsure if this will solve my lack of power issues. I have seen cars that still operated fine with one cylinder down, granted they didn't run great but were still able to make some kind of power. The friend that let me use his carb to test the truck also suggested that maybe the timing chain jumped a tooth. Does anyone have a take on that.
And as Adam also posted i acquired another motor to do as i want to with. I am looking for suggestions on what i should build with it. It is a 350 block that has been bored .030... Everything is there with the motor except the intake.... I can start a new post if needed but would like some ideas on what to do with it.
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'Nother update.....
Pulled the head off today, cylinder walls showed no scoring so thats good, but on one of the cylinders that built compression, the rocker arm stud had pulled out some and the pushrod was all kinds of loose. Noticed that pretty quick, so thats another issue to work out. I took the head home with me, talked to my uncle and he suggested a water test to see if the combustion chambers hold water, and low and behold the one that doesnt build compression leaked right out, so I think we probably found two of our culprits.
He suggested a local shop, so I think Eric is going to look around this week and see what he can find out, and maybe drop the head off next weekend to get it checked out.
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Ok another update just incase someone is interested in what is wrong with the motor and could cause my problem. I took the heads to the machine shop to have them tested and worked on. It seems from what the guy told me "all the valves have basically been sucked up into the heads, More than likely cause by an intake leak and or a bad carb" So he is replacing all the Valves and Reseating the one stud that backed out. I should have the heads back by Friday. So Ill post the outcome of the install and see if it solves all my lack of power issues Just incase anyone is still reading this thread.
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What year are the heads? Do they have hardened seats? A cylinder leakage test would have revealed where your loss of compression was.
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I dont know what year the heads were manufactured i can tell you the year they were purchased. I bought them from a shop back in '98. the only number i remember from talking to the guy is 883 ??? and when we did the compression test only one cylinder showed a loss of compression. and it was the number 4 cylinder. But visually inspecting the heads you could tell something was wrong with the valves. I had a second set of heads with me and the smaller of the two valves (I dont know which are the intake and which are the exhaust valves) were not the same as the ones on the other set of heads. and this was the case with all 8 cylinders. So they are doing a complete valve job on both heads... side note the other set of heads i was given had a crack in the number 1 cylinder :(
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correction might possibly have been 882 heads
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Can you not physically look at them and give us the casting number?
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I could have if they weren't at the machine shop. But they are 882 heads for a small block 350. Which i also found out that one of the heads off of the truck was bad as well. I have a good working set now and will be installing them shortly.
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Ok heres the latest.. Got the heads back and installed them. Took it for a test drive and it is gaining speed in 3 and 4th (it is a 4 speed tranny). but not a drastic gain. Still seems to be a loss of power from what i remember the truck having before. Im out of ideas of what could be wrong.
list of new parts...
Heads reworked. New distributor cap and rotor. New wires and plugs. Different Carb. new fuel pump and fuel filter.
Any other ideas??????
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Oh yeah i forgot to mention. On the test drive i spun the U-joint and dropped the drive shaft :-[
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Any reason that your exhaust might be severely plugged? Is your throttle cable working correctly? Any reason that the fuel line might be pinched somewhere?
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i guess there could be a possibilty something got up in the exhaust while it was parked.... fuel lines are ok i replaced the rubber hoses and all metal lines are fine. And the throttle cable has no kinks or hangups. Goes through full motion when floored...