Slant Six 225 (1975) Post Valve Lash

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theFightingFew

Always Learning/1975 Valiant Custom/1974 Valiant
Joined
Apr 9, 2020
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Location
Philadelphia, PA
Quick video of my 1975 Plymouth Valiant running post valve lash. I picked the car up with 36k original miles and have close to 66k now. It never really sounded/felt exactly "right" to me but I won't get in to the whys of that. I don't know why it took me so long to get in to it... guess I was nervous about screwing it up - but today was the day. Big improvement for sure. Thanks FABO for the wealth of information I dug through over and over again to help me do it. Let me know what ya think.



Intake set to .010 exhaust set to .020. I don't know if the valves have ever been lashed previously. The exhaust was super tight and the intake was super loose, almost as if they were set backwards at one time. In any case, I drove the car around town for 15 minutes to make sure it was good and warm, popped the hood and brought the idle speed way down and lashed the valves hot. I did them and did them again and will check them in a week or so.

I do have a tick I can only hear through the exhaust that is frustrating me. I thought that it may have been my mechanical fuel pump going bad as I had developed low fuel pressure and would end up stalling when stopped at idle especially after coming off of higher speed. I had read that the pump arm mechanism going bad could create a "hard to find" tick that would go through the whole engine. Pump was replaced but I still hear it... maybe it's "normal" but hopefully someone could chime in. Thanks.
 
Looks and sounds like it's running really well! I'm not hearing any valve tick.

Stall at idle after coming off a higher speed is not caused by insufficient fuel pressure. Low fuel pressure causes the engine to stumble and sag under high-demand conditions (heavy load, high RPM) when it's gulping the fuel outta the carburetor faster than the fuel pump can refill it.
 
Looks and sounds like it's running really well! I'm not hearing any valve tick.
Thank you for the feedback Dan. It's really helpful.

As for the fuel pressure issue, thanks for the info. It first happened coming off the highway @65mph up the exit ramp to a red light car started to "sputter" a bit then stalled out. Took a minute to fire back up drove for a bit and got to the next light and the same thing happened... ended up making it home... stalling as I was turning into the driveway and decided to check it out the next day.

Fuel bowl was almost dry and float was super low (it's a holley 2 barrel with the "sight window") which was strange because I spent the weekend before tweaking the carb which involved adjusting the float etc and it was great. Cranked it over a few times which got the gas up in there but the fuel pressure gauge I threw on the line was at like 2 where before it was reading around 4-5 (which still seemed a bit on the low side to me)...

So, I was thinking that something inside the pump was shot, that when the engine was running at a decent clip it was managing to force enough fuel up the line to fill the bowl but at idle it wasn't refilling fast enough and it would clear the bowl out and stall.

That's what I put together in my brain anyway... don't know if it mechanically/technically makes sense. In any case I replaced the fuel pump (did the lash) and I'm get'n at 6+ on the gauge and everything is run'n smooth...
 
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