Needed: Advice from a Slant 6 Master!

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CommieHook

CommieHook

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Hot Springs, AR
Okay guys, I really need some help here. I have owned my '65 Valiant with the 170 /6 for about a year and a half. It ran fine when I bought it but I went ahead and put a new kit in the Carter BBS. Smooth running little car. Then about a month ago, it started stumbling, and it only got worse. There doesn't seem to be any rhyme or reason to when it does it. I had an old Holley 1920 that I put a kit in and then tried it. It was terrible. Couldn't tune it right, just awful. So I put the Carter back on. I have replaced the dist cap and rotor, plug wires, spark plugs, fuel filter, fuel pump, and air filter. Also adjusted the valves. One thing that makes it so frustrating is this: On a trip to pick my kids up from school, a 40 minute drive total, the first part of the trip the car might do okay, only stumbling 2 or 3 times..... then it might smooth out and be perfect....then it might stumble and backfire and just about be undriveable for a good 10 minutes, then semi-straighten up again. It doesn't seem to matter if it is under a load like pulling a hill or not. High RPMs and/or low RPMs. I just don't know what to try now.
I would love to swap another good working carb on there just to see if it is that. I have even looked at buying one on this forum. But finding a good rod-actuated Carter BBS is pretty tough...
Any ideas?
Thanks for reading.
CommieHook
 
i wonder if the float is on the verge of being to high of fuel pressure is surging
 
I would put a lead on the coil + and run it into the passenger compartment and attach a voltmeter and monitor that to see if the coil + varies when this happens. This will be a check on the ignition switch, the firewall connection, the ballast and the interconnecting wiring.

I woudl also go under the tank and check the rubber line out of the tank; some small cracks in this could allow air to get into the fuel line form time to time; it will be really erratic. Eventually it might pay to clean the tank.

Have you checked all the vacuum lines for cracks?
 
Has the tank been removed and cleaned? Sounds to me like you have a recurring problem of trash getting into the fuel system. This is one of the first things I do to an older car. Without fixing the problem at the source, you are bound to keep having similar problems.
 
You mentioned all the tune up parts but the points. Did you replace and/or clean and adjust them?

Also when is the lat time you checked the valve lash?
 
You need to verify if it's fuel or ignition related, or even a mechanical problem. You can't just assume carburetor problems from the seat of the pants driving. Your gonna have to have some tests done.
Some suggestions might be; Is it points or electronic ignition? Worn points will cause backfiring & hesitation/ stumble. Check the gap & dwell of the points. Make sure they aren't burnt & the rub block isn't worn too much. You also need to verify good electrical connections throughout the ignition system. What did the old plugs look like when you took them out?
Fuel pressure & volume must be consistant. Fuel pressure gauge needed along with a container to check volume. Is the choke operating correctly? Fully opened when warm?
If ignition & fuel check out, then you have to start checking mechanical condition. Compression test, cylinder leak-down test(preferred), valve timing, vacuum leaks etc. Intake manifold bolts tight? Carb getting too hot -vapor lock?
What did you adjust the valve lash to?
Without seeing the car 1st hand, I'd probably start by checking the point/ ignition 1st, then go fuel then mechanical.
It may seem like more work initially, but you'll save a lot of time & certainly money in the end.
 
Get an in-line spark tester and install it on a spark wire next time it happens. Even easier, use a clamp-on timing light on each plug wire and verify each flashes. Get a dwell meter. Can't adjust points well without one. All are cheap - Harbor Freight & garage sales.
 
Expanding on RRR's point, older fuel hose can develop "flaps" inside due to this stuff that they now sell as "fuel" being pretty aggressive towards older type of fuel hose rubber. Sometimes the flaps obstruct flow and sometimes they don't. And sometimes they don't until they do, other times they do until they don't. It's enough to make you crazy!
Strongly suggest replacing ALL of the fuel hose on the car. Use the more expensive "barrier" hose with either the spring-wire type of clamp or the EFI type of clamp. Don't use the typical worm-drive hose clamp with the perforated band as those will slowly eat into the hose and cause problems. Even if this doesn't solve the current problem doing this will head off a future problem.

A real radiator shop can boil out the fuel tank, and some can line it so that rust doesn't continue to be a problem. If they don't, once clean you can line it using either "Kreem" or POR-15's "U.S. Standard" fuel tank liner. If it's really bad I bought a replacement fuel tank for my '65 Valiant from Rock Auto.
 
How pissed would you be to find out it was just the condenser?

They can and do fail intermittently.
 
Hey guys, I've been out of pocket and unable to reply. Thank you for all of your suggestions. I'm so freakin' happy to have it fixed that the good feelings are out-weighing my feelings of stupidity.
I had to put a new tank in it right after i bought it (It was running on a boat tank in the trunk!) and when I did that I installed all new gas line, so I knew it wasn't anything like that.
I had installed a new condenser, just forgot to mention that.
I bought a new/reman Carter BBS carb. It idled smoother, started easier, stopped leaking gas, and even had a little more power! But it still stumbled, just as it did on the original carb. Ugh.
I replaced the coil, and that made it run worse. Would even idle worth a darn.
I had already replaced the condenser, and I was told that the points looked fine. But I couldn't think of anything else to replace, so I swapped them out.
Tada! The old points looked terrible terrible terrible. Installed the new set, the car started right up, idles like a dream, and drives great, like new again even!
It was kind of strange that it ran so much worse after I replaced the coil, before the new points were installed. Anyone know why that might have been?
Thanks again guys!
CommieHook
 
I could make some semi-educated guess', but I think that I'll save myself that embarrassment.

It does sound like it's time to start acquiring the bits to convert to electronic ignition. There's lots of ways to go on that. I tend to favor something OE rather than aftermarket.
 
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