Fuel spark delivery question

[Robert8096]

I have a 69 truck with a 283 and have a nagging problem where the truck runs fine up till about 50 mph. After that it will start bucking and acts like it is not getting spark or too much or not enough fuel. I can back off and it will continue for a few min and then go back to running normal. Did a compression check and all are 150 to 153 PSI. Vacuum gauge reads a steady 19hg and responds correctly when working the throttle. It was an original point type ignition and I have changed it to HEI, replaced the wires and plugs. I replaced the 4 barrel carb with a known good one and my problem still exists.

Things that have got me saying WTF:

I looked for a fuel filter between the fuel pump and tank and there does not seem to be one. Is this the norm for the old girl? I have one between the pump and carb and I am seeing a little bit of rust in that one but nothing major. Is there a sock on the end of the pickup tube in the tank? I ask this because LMC shows no sock but CPA shows a sock on their sending unit. I also see that there is a difference between the 6 and 8 pickup units for the tank. Is this because of fuel line size and if so will that make a difference in running a stock 283 in a truck that was an originally a six?


When I changed the plugs I came across what is in the pictures below and see no reason for it. There was nothing wrong with the threads of the plug hole as I replaced the plug and had no issues. The extra piece looks to be a compression tester attachment. Any ideas on this PO install?

Thanks
Robert

[68gmsee]

I think the pics show an anti fouling adapter used when the rings or the valve guides are shot. I've tried them and they work like crap! Get rid of them.

RE: fuel delivery. Things I would check .

I would check the fuel pump for proper delivery. Disconnect from carb and place in a plastic container. Have someone crank the engine and check to see how the pump works. Should be a strong stream of gas as the engine turns.

Check filter inside the carb. Maybe remove the top and clean inside.

Check and/or replace the sock in the tank -it should have one unless it was removed like I did. I installed a filter before the fuel pump instead.

[cdowns]

yes by all means get rid of those antifoulers//then i'd check the timing starting at physically setting the number one cylinder at TDC by using a piston stop to get TDCexact and check that the marks on the balancer match the pointer

[Robert8096]

Plug looked fine and a compression check of that cylinder was 150 PSI. Have not done a leakdown test but I am going to do one.

No filter in the carb it's an Elderbrock 650 version and the Holley carb that was on there to begin with did not have one. Two different carbs same symptoms.

Going to drop by the autoparts store on the way home today and pick up a fuel pump (35.00) and rig some kind of filter before the pump since I don't see one between the tank and pump. Then this weekend I am going to pull the tank and check it out and if it has rust issues. I am going to try to find a decent tank for a decent price, if I don't then I am going to contact Fuelcell Guy and get him to build me a tank for the bed.

Timing checks out, I installed a HEI unit, new plugs and wires last weekend and set the timing. I had the same symptoms with the old points unit.

Thanks for the info.

[68gmsee]

Since the compression is good and the plugs look fine, a leakdown test is good, however, it may not show wear on the valve guides. Sometimes a good indicator is smoke when you first start it after it sits for a while.

[cdowns]

filter b4 the pump not good idea

[Robert8096]

I have not noticed any smoke on startup and it does not use any oil, but it could be valve guides because I don't think the heads have been re-done to use our crappy unleaded gas. I miss those days of high octane leaded gas.

Originally Posted by cdowns

filter b4 the pump not good idea

Please elaborate.

[mr48chev]

Originally Posted by cdowns

filter b4 the pump not good idea

Why would you think that or make such a suggestion?

I've run a filter before the pump on every vehicle I've put together for the past 30 years. It has saved countless fuel pumps.

When I do that I still run the filter at the carb also.

I'm very particular where I buy my gas and the local stations I buy from are fairly new. But sometimes when I am on a road trip I may not have a choice in gas stations and that is usually when I have had problems. Or the lost or left off for some reason or gas cap that seems to be a great attractor for dirt

.