Technical 350 chev clatter

Giday fellas I have a SBC in a HQ Holden and it seems to have a bit of clatter or chatter at very light loads at 60mph, I've googled a bit and nobody seems to have the same symptoms.
I runs great and has good oil pressure and no other issues except for the chatter at light load.
It's 40thou over with some 4 into 1 headers, junky old 882 heads, RTR msd ignition, edelbrock victor ram and 450 holleys.

Cheers

 

If your sure it's not inside the motor and if you are running an automatic behind it check out the Flex plate. I have seen some flex plates crack right around the Crank shaft flange and that makes a very strange sound and difficult to pin point. Then one day out of nowhere it stops going forward and suddenly it's real obvious. It's most often a very jagged fracture and hangs together for a long time before total failure.

 

Not 100% sure where it's coming from sounds like it's up front somewhere.
I have had a flecplate crack right around the bolts on a old 4.1 inline six ford and It was knocking like a run bearing.
No noises at idle or accel or decel only seems to be around what I'm guessing is 2800 rpm area with very light throttle.
I will check the flex plate though

 

Try dropping the timing back a bit..

 

Could be a bad fuel pump. I just about had a grabber after I first fired up a new crate engine with a used fuel pump. Sounded just like a light rod knock, but still just enough to REALLY PISS YOU OFF!

 

Yes, back the timing up a bit or bump the octane up. Lippy

 

pulley's some time crack

 

A bad or loose Fuel pump arm can be heard with a motor stethoscope.

 

Losing a Valve Guide will make that noise also , not consistent , i chase that noise for a few weeks , will cause valve to have to center its self on valve seat when closing. , not all the time , deferent rpms speeds load Sometimes idling..

If you think fuel issues Run shiny plugs ( for reading heat rang ) and buy a good wideband O2 gauge for tuning carbs from idle , cruise , wide open. tuning more then just Jet change

 

It was pinging and I took some timing out which took care of that.
If it was too advanced it would do make the noise under load wouldn't it?
It's a new fuel pump aswell motors quiet as at idle nothing obvious, any one had issues with noisy dizzy?

 

Vacuum advance will sometimes cause pinging under high vacuum conditions, such as light load. A couple degrees of extra initial timing can be enough to bring it out under high vacuum.

 

A quick way to test would be to disconnect and plug the hose at the vacuum advance canister.

 

Yes , on Noise.

Tuning yr motor
total avance in the distributor
Most chevy Even stocker like about 15 degs pluse @ idle 35- 42 total , its something to play with @ total
For pinging / Detonation. (Modifications to inside of dizzy to control how much advancement)

 

Valve lifters worn? Had a sbc that would run quiet until it got to highway speeds and the oil got warmed up and then the lifters would make a slight clatter.

 

Part throttle pinging in a '66 Ford I had was due to no EGR and a later distributor. An early distributor solved it.

 

I cant remember off the top of my head but I think it runs 16 initial and a blue bush which is 21 so looking at 37-38 total.
I'll pull back advance and check it.
And as for worn valve stems it is quite possible I will be getting some alloy heads when the funds allow and a new cam and lifters at the same time, the bottom end only has 2000ish miles on it.

 

Yep,
These would be the first things I looked at.
Sure sounds like the issue

It's much like ,,, if the cure works you have the disease

 

I just read through this whole thing again and, was just wondering, if maybe, perhaps, you might have a cracked blade on that damned flex fan causing the noise? Just something to consider before you dive in too deep.

 

I'm not sure what your clatter is, but I would get rid of that Fram filter.

 

Will it make the noise in neutral or does it have to be moving down the road. I was going to suggest running it with the belts off to eliminate anything up front that's belt driven.

Do you have aftermarket rocker arms? Maybe look for any fresh witness marks on the inside of the valve covers.

 

Flex fan is gone. Keep hearing bad stories about them not to mention how bloody sharp they are when working on engine. Fram filter is gone now and can sort of hear it in neutral at certain rpm. Definatly not pinging and yeah I suspect it must be rocker/lifter related as the heads and rockers were not touched.
I'm looking at getting a summit k00172 cam same as crane 274/h06 cam and lifters to eliminate that, will look at getting some e-street 64cc heads aswell hopefully that wont raise compression too much.

 

Just changed a mech fuel pump that was making similar sounds like the rockers are loose.just a thought

 

Hopefully not fuel pump as it only has a few thousand miles at max.
Anyone hazard to guess what kind of cc these pistons would be? I know I should of checked before I assembled engine but now I'm looking at new heads and not sure if I should go 70cc or 64cc.
Cheers

 

I've had 2 new out of the box pumps make the noise

 

Wow, you got way ahead of where I would be. Wish I could have come to your place and lent a hand. I doubt that motor would be on the floor.

 

Lol dont panic motors still in car that picture is from before it went in

 

That makes me feel better. Be sure to pin point the issue before tear down if that's even necessary.

 

If you're going to stick with the tunnel ram, I would go with 64cc heads. That should give you a solid 10:1 compression ratio with the steel shim gaskets.
On another note, in the picture, it looks like #4 piston is slightly twisted counter clockwise a few degrees compared to the others. Hopefully it's just an optical illusion. But if it is, it could possibly be the problem.

 

^^^^
That piston sure does look twisted

 

I'd look into that piston and rod, just out of a sense of caution.