454 valve lash

[Blk n Blu]

I was having an issue with back firing through the exhaust. I tracked it down to the #1 cylinder, pulled the valve cover and checked the lash on the exhaust valve. It seemed to be just a little tight at .004 cold. Intake was .0025 cold. Same settings for the rest of the train. Normal settings are .024/.028 for intake/exhaust without cam. I don't have cam specs for the build, I found a number on the chevelle forum for camed 454s at .016/.018. Any thoughts or input out there from anyone?

[Vet65te]

I'm guessing your solid lifter cam is a LS6 454 from the .024/.028 lash settings?  Is this Bigblock a new installation meaning the .004 lash you found on the #1 exhaust valve was the way it was when you got the engine?  Sounds like that valve is hanging open a bit.  Since you have no info to go on, it's a flip of the coin as to what the right lash settings might be and too much of a royal pain to pull the cam to see the stamped markings identifying it so...maybe just try opening that one exhaust valve out to .024 and see if that helps.

Good luck,

Mike T - Prescott AZ

[Blk n Blu]

Mike thanks for your input, I pulled the other side and it was closer to the .024. Redid all to  .016/.018 and still having issues and is running hot. I will reset back to the factory .024/.028 tomorrow and see how that runs. Will pull the #1 plug also and see if there might be a problem there also.

[Vet65te]

Good luck and keep us posted.  Any history on this Bigblock you're working on?  I know you said you don't have cam specs, but any info on other stuff like compression, types of heads, etc?  

I've been working on the Maroon 65 NOM 396 Roadster I picked up last November and cam issues were at the top of the list but the problems I encountered were the opposite of yours.  Valve lash was way large and the sellers mechanic first thought someone had backed off the valve adjustment since it sat for 10 years or so but that wasn't the case.  I adjusted them cold, still running like crap.  Got it running, adjusted the valves again and still...running like crap.  In my case, the .060 over 454, which only had 100 miles or less in the last 10 years, had a flat cam.  Pulling it out of a midyear is not fun since they kept that damned steel-rod X-brace welded to the core support opening and the outgoing cam ran right into it, making it necessary to start disconnecting things and hoisting the engine a few inches so it would clear.  The old cam was a hydraulic with 228/238 duration but I've replaced it with a slightly milder 218/228 Edelbrock Performer cam with the same .500 lift.  Got the engine buttoned back up but have now started ripping into the rear suspension and found one trailing arm axle that's loose to the tune of .014 so...it's time to pull and fix.  

 

Mike T - Prescott AZ