Thread: 454 Backfires - Problem Identified

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Sune - Thanks for sharing your experience. It helps to rethink this a little more (seeing the big picture). I took the car for a nice long ride yesterday, getting on it a little bit here and there. It seems to be running good, but I notice at the top of the RPM range (about 4 grand), it starts a little hesitation until I shift into the. It almost feels like a misfire or cutting out. I did replace the plugs when I repaired the valve keepers, and gapped them at 45 like the guy at the autoparts place recommended. Maybe I need to revisit this?

I have been very frustrated with this 454, as it was sold to me as "just freshened up" with less than a 1000 miles on it. What I am seeing now is that it is possibly an old tired motor, and needs a rebuild. Reason I say that is the oil pressure is fairly low, compression is not as tight as to be expected, and it has far too many leaks to have everything "freshed up". The plan is to try and make it through summer (I think I just cursed myself), but I want to have a ride to go to meets and an occasional skip work and play day..hehe.

As far as the pushing down of the rockers to identify the problem, it was not very hard. It is more of a gentle place the palm of your hand on the rocker, and if it pushes back against your hand (due to spring tention, etc), then its fine. In my case, when we lightly pushed on the intake of cylinder 1, it almost killed the motor immediately. The idle dove quickly. I see your point about pushing it down a valve onto a cylinder head, but we didnt push that hard. The rods and springs keep it pretty much intact, unless of course you have a broken spring or keeper.

Originally posted by Tabers71
but I notice at the top of the RPM range (about 4 grand), it starts a little hesitation until I shift into the. It almost feels like a misfire or cutting out. I did replace the plugs when I repaired the valve keepers, and gapped them at 45 like the guy at the autoparts place recommended. Maybe I need to revisit this?

I don't know what that might be??? About the gap... I can't really remember, but it is either 30 or 45 or both depending or what type of heads... anybody??

I'm looking forward to hear what you find out hesitation..


Sune Larsen