When I start my FE 390 first thing, the cam has a nice lopey {cackle} sound, sounds really good, but once the engine has reach operating temp{180+} the lopey sounds goes away. Sounds like a stock 390!! So the question is, can the oil psi cause the lifters to be weak enough to change the duration and lift at idle? Cam is Comp 280H, 230 @050 duration, lift .530. oil psi cold at idle 75psi, oil psi when at temp 20psi. Any insight in this would be greatly appericated.
Are you running an automatic choke? Is it working and adjusted properly? Is the choke pull-off working and adjusted properly? Are you using cast exhaust manifolds with a working heat riser on one side? Is the exhaust cross-over passage in the intake manifold blocked off or plugged up?
I’ve not run that large of a cam, but I’ve never heard of lifters doing as described. One thing that does stick out is the 75 psi cold v 20 psi warmed up. What’s the history on the engine?
*None of that stuff...no choke, headers, *I wasn't sure that if the lower oil psi was pumping the lifters up to full capicity, but then it doesn't rattle or anything, *The oil psi is by way of a Melling HV-HP pump and a somewhat loose bottom end. I have never had an engine sound good while cold then sound like a stocker when at temp.. I'll keep looking or swap out to a different cam..
This is a very common phenomenon with almost any engine. Every car I've owned with a bigger camshaft sounded more lopey, or radical when started up cold than it did after warming up well. The only thing you could do to sound similar is lower the idle after it's warmed up, or put a manual choke on it and choke the carb a little when it's warm to get the same sound. Back in the 60's I knew guys who would have a manual choke and when they pulled into a cruise area, or hamburger stand, they'd pull their manual choke to make their engine idle rough. I thought it was hilarious!
I based my response on yours and “swap to a different cam”. I don’t believe a different cam is a solution
This is a very common phenomenon with almost any engine. Every car I've owned with a bigger camshaft sounded more lopey, or radical when started up cold than it did after warming up well. Thank you, that is what I needed to hear,
Rhoads lifters will do that, they bleed off more oil when the oil is hot. If its quiet when idling, then you have stock lifters, if they clatter, then you could have Rhoads.
Spot on reply here. Don't worry about it! If you want a radical idle when warmed up , just build a more radical engine
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