I have an HT with a Chev 327 & Powerglide. When I cruise at 60mph it has a rattle from the engine bay, but I don't exactly know what is causing this. If I slightly tweak the accelerator, & before there's any noticeable change in road speed, it can be reduced or eliminated. It doesn't happen at any other time, load, acceleration or speed.
The rattle is like pinging in it's frequency and volume.

Possibilities I have considered & tried to eliminate are pinging, speedo cable vibrating against firewall plus various other cable rattles. I've started using 98 fuel and the timing is set at 3 degrees BTDC (engine is from 1965 Impala so has 10.5 compression ratio). Everything seems fine under the dissy cap & I have swapped dissy weight springs from another Delco but nothing changed. Also has a new vac advance can. I also checked #1 TDC against the timing mark which is correct.

Have recently adjusted all valves for clearance & I'm pretty sure it has hydraulic lifters.

Ive had the engine for about 18 months, never taken the heads off, just replaced welch plugs.
Compression wise #1 is 180 & others are 200 to 220.

Haven't checked engine mounts & attachments. I would welcome any thoughts or suggestions.
(This is a repost of an earlier one. Thanks to Premier350 for his thoughts at the time.)

Edited by user Thursday, 28 July 2016 7:01:09 PM(UTC)  | Reason: Not specified

Sounds like a cracked piston skirt to me. Heard this one a few times before.

Dr Terry

I got hold of the harmonic balancer and gave it a pull & push and heard a knocking noise as I did this. Assuming this to be end float, I did a measurement with verniers (don't have a dial indicator) and found about 15 thou. I understand the max should be 6 thou.
So presumably the thrust bearing is worn, but it could also be the crankshaft. According to the specs for the engine it has a small journal, forged crankshaft but this would need to be verified.
So I guess my next job is to remove the engine from the car and dismantle the bottom end to see what's worn & needs replacing.
I still have the 307 engine which came with the car originally which has bore wear of 36 thou and also several spare large journal cranks to suit.
I'd appreciate any thoughts on whether the rattling noise when cruising could be caused by the crank end float as well as options for overhauling either of these engines on a moderate budget.