HELP! Please :confused:

AZChevelle · Nov 6, 2003

I have a '70 Malibu that I rebuilt the 350 motor on after the crank broke in two. My problem is a knocking that is very slight when idling , but hell when in gear. I thought I had fixed this when I changed out the 58cc heads for some hi-po 327's that are 67cc, yet it remains. Valves are adjusted as per Haynes except I stuck with a 1/2 turn after play is eliminated. What could this be? Any ideas? Need more info? Please respond. Thanks in advance,
Brian

67malibuEFI · Nov 7, 2003

Did you re-use the harmonic damper and flex plate/flywheel?

AZChevelle · Nov 7, 2003

The dampner is new. the old one was small, like 6 1/2" diameter. the new one is 8 1/2". The torque converter is new. The toothed starting wheel is new. The cam is a Comp Cams, Jegs #12-242-2. Used new lifters but old push rods and rocker arms.

Schurkey · Nov 7, 2003

Any chance that big damper is intended for a 400, and is externally balanced?

Proper clearance for exhaust, and for trans cooler tubes? No parts rattling against the frame when the enging shakes harder when put in gear?

AZChevelle · Nov 8, 2003

Pretty sure the dampner is what should be on the motor, but I could be wrong. The guy that had this car before me built the motor out of parts in his uncle's wrecking yard. I think the small one was the wrong one. This is what I got from checker when I asked under the cars' make and model for a 350cid. I will look, how can I tell if it is supposed to be for a 400, and how would this cause the problem I am having? thanks, Brian

SS70SS · Nov 8, 2003

A 350 dampener is round, a 400 has a scallop cut
out of it.
If you need a pic of both let me know and I will
post them.

BillK · Nov 8, 2003

Brian,
You are saying that you have a "knocking" ??? Are you talking about a mechanical noise, or detonation like from lousy fuel ? It sounds like you are talking about detonation since you tried reducing the compression ratio to help it.
I think the first thing you need to do is to get someone familiar with engines to listen to the noise. They can get you in the vicinity and then you can narrow down the problem. There are a bunch of things that can cause noises in an engine, any one that builds them for a living should be able to give you some idea as to what it is by listening to it. The rest of us are all guessing because we cannot hear the noise.
Hope this helps,

AZChevelle · Nov 8, 2003

The noise was described to me by a friend as a "floating valve" or detonation noise. Is it possible that I am not getting enough fuel to the cylinders? The plugs were a light brown color when I changed the heads. Currently I have an rebuilt Holley 600 single pump with whatever jets it came with stock.

HELP! Please :confused:

AZChevelle

67malibuEFI

AZChevelle

Schurkey

AZChevelle

SS70SS

BillK

AZChevelle

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