350 crate engine was great but now stalling

[LordDevlin]

So I got the plates on my truck finally last week and it has been driving pretty well... until this evening.

All of a sudden it seemed like it wasn't quite taking the gas right... other times i would give it gas but nothing would happen except its like I could hear the gas being fed in, like liquid from a tap.

then the truck just stalled altogether, did this a few times but would start up again and drive for a bit until it would stall again. Then it would start but not keep running, and would run rough for a few seconds and then stall again. Then finally I got it to stay running to drive it home.

Since I've had it (Feb 16), it has only been filled with 87 gas for running it in the garage, and for the past 5 days actually on the road. Earlier today i put in 91 and filled it. I drove it most of the day though around town before this happened (20 miles perhaps). Could it be the higher octane gas?

its a 350 crate engine with a cam, with a 4 barrel edelbrock carb. LIke i said, just got this truck. My father and i are used to 235's and most recently a 283 and 336, but never anything along the lines of this "performance" setup. Not too familiar with this newer stuff.

Any help or suggestions would be appreciated.

Thanks.

[mr48chev]

Stock tank? Make sure that the gas cap is a vented cap. Next time it stalls slowly open the cap and see if a woosh of air goes into the tank.

Also old tanks on trucks that haven't been driven for a while are famous for dirt and crud breaking loose and clogging the carb up. I always put an inline filter between the gas tank and the fuel pump. Sometimes I end up replacing that filter several times before the tank cleans out or I end up pulling the tank and cleaning it out.

[joedoh]

a lot of time when there is crud in the tank, suction pulls it into the fuel filter and eventually it is enough to restrict flow and stall the truck, then the crud falls down by gravity and it opens the filter enough to let it start again. then the suction blocks the flow again. and so on.

also, a lot more people buy 87 than 91 so when you suddenly have problems after a tank of higher grade gas, it may have water in it from sitting around unmixed! if your filter is ok get a bottle or three of HEET or some kind of fuel dryer with alcohol and see if that is the problem.

[LordDevlin]

Thanks for the advice guys. I will look into the filter condition after work. If its good, I will get some of this HEET stuff.


The tank is a new one moved to under the bed. It is vented but not from the cap.

[Divine 59]

If you have water in the gas I would choose sea-foam to take care of it. The cost will be about the same as 3 bottles of HEET.
Most boat owners use sea-foam to kill water in the gas tank.


Was the crate engine from GM?
possible another item to consider is vapor lock?

[solidaxel]

Is there anyway you can check the fuel pressure after the fuel pump and before the carb?
Are you using a Pertronic Distributor?

[LordDevlin]

The truck is pretty new to me, so I will have to try to figure out the answers to the questions as they relate to the engine and its components.

I appreciate all the help so far. Thank you.

[Jemezcrusher]

Is it intermittent, or all the time. Heat soak could be a problem if only when hot. Do you have a spacer between the manifold and carb?

Also, water removers (heat, Seafoam) clean everything else in the system too, which can end up in your filter, and carb

[mr48chev]

I don't think it is a fuel problem as far as the quality of the fuel unless you went to a real old station with real old tanks that may have water in them or crud in them. As a rule I never buy gas in any rig in those cute old gas stations with just a couple of pumps out front. Locally most of my rigs won't run right on ARco gas.

I'd still say dirt in the tank if it's an old original tank or the tank isn't vented right and air isn't getting in to take the place of the gas you are pulling out when running creating a vacuum in the tank. Contrary to some folks belief gas/fuel tanks have to vent both ways. One way to relieve a bit of pressure if the rig is sitting in the hot sun and the gas expands but more so so it lets air into the top of the tank to fill the area where the gas used to be. No air in, vacuum created and the engine stalls until the vacuum is relieved and the pump will pull fuel again.

[dsraven]

it sounds like a venting issue or junk in the fuel plugging a filter.
venting: when you were just running a bit of fuel in the tank, for testing etc, there was more volume air in the tank that is compressable or vacuumable. so the fuel pump would be able to draw from it longer even though it is running a bit of vacuum overall. plus it didn't run as long at a time so it could slowly vent some air back in when shut off to make up for the fuel taken away while running. now, with a full tank, there is less available volume of air above the fuel to draw a vacuum from, plus you are driving it longer than you would have before it was "on the road", so the pump is not able to draw enough fuel against that vacuum in the tank. ensure you have a vented cap that is working and also do the cap removal test, as mentioned above when your engine is having issues, to see if your tank is drawing a vacuum. what are you running for a fuel pump, mechanical bolted to engine? electric mounted on frame? electric in tank? can you "t" in for a pressure volume test, cold for a baseline, and then hot with engine issues? with fuel cap off as well.

OR, there is just some junk in the tank that is restricting flow. check the fuel line all the way from the front to the tank to ensure it is in good shape and not running too close to a heat source that may be causing the fuel to heat up and vapor lock. check all the rubber hoses to make sure they are good and no possibility of a flap inside a line that can cause a restriction. also, are the lines all the same size or is there a necked down or crimped/squashed section? is there an inline filter you can check? would you be able to swap it out for a clear filter so you can see at a glance if there is fuel flowing through the filter? can you remove the old filter and drain it into a clean container so you can see if anything drains out along with the fuel. then cut the filter apart to see what it contains for debris, if anything? I like to drain the filter into a clean white plastic container from yogurt or something, that way I see dirt right away, or water "bubbles" in the bottom of the container etc. you could also slip the top off the carb to see if there is junk in the float bowl that may have made it past the filter. if you have a flexible fuel line, like neoprene fuel hose, from the frame to the engine say, you could pinch the fuel line off at that location, after shutting off the engine during a "trouble time". then check what you have for fuel in the carb. if it is low then you know you have a supply problem or a fuel inlet valve problem. you could also do a volume flow test at these times when the engine is having issues, to see what you actually have for flow per minute. if you install a "t" with a shut off in the fuel line after the fuel pump and attach a fuel line to the "T" and run that line to a container, you can leave the valve shut off until you have issues, then do a flow test by turning the valve on and see what you get for flow into a container. just remember to play safe and possibly not inside for this test. it would also help to have an assistant for this test. a fuel pressure gage could be installed in that line as well, so you know what you are dealing with for pressure.

remember,keep a fire extinguisher handy any time you play with hot engines and raw fuel.

[LordDevlin]

Spoke with the previous owner. Apparently his mechanic checked the truck all over and one things he noticed is that the carb had some crap in it and told the po that he should consider changing the braided fuel line. It has braided line all the way from the under the tank bed, to the fuel pump, then again to the carb. There is also and enclosed filter in the line just below the back of the cab.

Not long after the tranny crapped out on him and then he decided to sell, and never changed the line. Now I have it and hopefully this is the cause of my problem.

Going to look into installing a hard line from the tank to at least the fuel pump, if not past the pump to the carb as well. I was also told that if not hard line, I should use newer Teflon lines.

Does anyone have any recommendations? should it all be hard line? Or is it fine to have a Teflon flexible line from the pump to the carb? What size hard line should I be using?

Thanks for all the help.

[Jemezcrusher]

I use 3/8" hard line from the tank to the pump for sure, you can buy a single roll of it and have one piece but need to flare both ends yourself.

Hard lines will dissipate the most heat

[OrrieG]

I used 3/8" hard line too from NAPA with sections that come with fittings. You can run the full frame length with only coupling flare. I ran from the tank to a frame mounted cartridge filter before the fuel pump. I ran fuel rated hose from filter to fuel pump to allow for engine (350 sbc) and frame movement. I ran hard line from fuel pump to carb.

[mr48chev]

I've always hardlined the with sections from the parts house but recently bought a 25 ft roll of 3/8 steel line off Amazon that came with a bag of fittings. The jury is still out on how straight I'll get that line when I go to install it though.

You need a piece of flexible line from the end of the steel line to the on engine fuel pump but other than that can run the whole line in steel. If and when you bend the tube make sure you don't flatten or kink it.

[dsraven]

steel line is the way to go but be aware that not all coupling unions are the same. some have a restrictive bore in the centre so check before you buy. flexible line over that length can suffer from friction loss, more so than steel line. you could always go with a size up of steel line if you are afraid of the necked down coupling unions then bush it down for the final sizing at each end.

[mr48chev]

Originally Posted by dsraven

be aware that not all coupling unions are the same. some have a restrictive bore in the centre so check before you buy.

In the mid 70's I bought a 57 Chevy panel truck with a built 327 that had and Engle solid lifter cam, Jahn's 12.5 pistons, 2/02 heads, and a 2x4 early Corvette intake. The thing ran like Jack the Bear but when we first got it going it would go like gang busters for about 30 feet and die and then pick up and pull like crazy again until it stalled out. After fighting it for a week or two I took the fittings and lined going to the carbs apart and the fitting that connected the line from the pump to the carbs had a hole that was probably 3/32 of an inch in diameter and was probably intended for a natural gas line on a heater in the house. after changing the fitting the truck pulled like crazy through all three gears. The truck was fun but got around 4 mpg most of the time.

[LordDevlin]

so if I go ahead and change the whole line out... I guess I need to drain the under the bed tank?

[Highsider]

Originally Posted by mr48chev

In the mid 70's I bought a 57 Chevy panel truck with a built 327 that had and Engle solid lifter cam, Jahn's 12.5 pistons, 2/02 heads, and a 2x4 early Corvette intake. The thing ran like Jack the Bear but when we first got it going it would go like gang busters for about 30 feet and die and then pick up and pull like crazy again until it stalled out. After fighting it for a week or two I took the fittings and lined going to the carbs apart and the fitting that connected the line from the pump to the carbs had a hole that was probably 3/32 of an inch in diameter and was probably intended for a natural gas line on a heater in the house. after changing the fitting the truck pulled like crazy through all three gears. The truck was fun but got around 4 mpg most of the time.

I have a thing for TF panels, especially '57s...Imagine that.

[dsraven]

just as a rule of thumb, if the line size is doubled the flow capacity is quadrupled.
yes, dump the tank, remove the sender and check the sock filter on the end for integrity 9if equipped) then you also have a chance to see inside the tank and check for debris etc. put that all together after ensuring the size of tubing on the fuel line adapter is large enough. then run a piece of flex hose of correct diameter over to a quality high flow fuel filter on the frame, secured with a quality clamp system. then steel line from there forward to the point where it will bend over to match up to the fuel pump. use flex line again to connect the dots here. then more steel line up to the pressure regulator (if equipped) and finally into the carb. use a tubing bender if possible, for the steel line bends. less chance of over-bending plus the system looks way more professional. if using rubber style hose try to get the stuff intended for fuel injection. it is tougher (more fibers embedded in the reinforcing) plus they make nicer clamps to fit the diameter of the hose. better than a gear clamp. also, there is a tool sold that makes a nice bump in the end of a steel line just for rubber hose style connections. that way the hose won't blow off the steel line unexpectedly.
take your time, the system usually looks and works better if you are not in a rush.

[mr48chev]

Originally Posted by LordDevlin

so if I go ahead and change the whole line out... I guess I need to drain the under the bed tank?

I would just to make sure the inside of the tank was clean and to check the pickup sock that DSRaven mentioned if there is one on the pickup tube. Drain or siphon the gas off into a clean gas can. You can then look at it to see if it is clean or dirty and use it back in the rig or in something else.

Over the past 40 years or so I've probably fought dirt in gas tanks more than any other problem on my own rigs. That comes from using used gas tanks on my rigs that were sitting for some time before I used them and from driving my 51 Merc after it sat out behind the corral here on the place I now live in for 11 years while I was gone in the service and living in Texas before moving back here. I killed the fuel pump on the 48 in the early 80's on a road trip to Texas and Back when we drove through Yellowstone on the way back and I forgot the gas cap on top of the pump at the gas station at Grand Teton park HQ early in the morning and then drove about 50 miles over fresh gravel seal coat that afternoon on 90 going into Montana. The sand that was kicked up off the gravel got sucked right into the capless gas filler on the 48.

[LordDevlin]

Thanks for all the help and advice.

After some investigating and talking to some old local car guys, one being an old gm mechanic, we figured out our problem. Luckily this happened before we got into changing the fuel lines from front to back.

Turns out the distributer coil was shot. Changed it out and its running great.

[solidaxel]

Was your first coil new or a used one!

[LordDevlin]

Originally Posted by solidaxel

Was your first coil new or a used one!

The one that was failing was in the truck when I got it. It ran great for a few weeks then had problems when things got hot.

Put in a used one that we borrowed off a friend and it worked. Have since replaced it with a new coil and still running well.