Weird noise
 

Just finished the new engine for the '64. No it didn't need it, but I like building engines and wanted one just for this altitude (5000') and with more torque and compression just for up here.

Specs:
Dart SHP block, 4.155" bore, 3.75" stroke.
Callies crank and rods.
Mahle pistons, 11.6 to1 with 64cc chambers AFR 195cc heads.
Howard hydraulic roller cam with 272/278 duration, .530" lift.
Comp 1.5 roller rockers.

Compression checks 195 to 200 in all cylinders. Oil pressure 50+ psi and steady.

The engine is running on a test stand and the noise is loudest from the bellhousing area(flywheel installed, but no clutch). Laying the stethescope on the base of the distributor produces the loudest noise, and follows the rpm as it comes up. It sounds just like a loose rocker, but it is not.

I've talked to techs from both Dart and Howards and both thought oil pump and or distributor were the source of the noise, so I pulled it apart and replaced both parts with new pieces. No change. While the pan was off I pulled all the main and rods caps and everything looks dandy.

I'm about out of ideas at this point never having had an engine do this before, so I'm looking for thoughts, positive, negative or otherwise.

Any help appreciated.

Dave

Can you pin down the frequency? Crank speed, cam speed or erratic?

Tom

Cam speed. It follows the throttle exactly and sounds like a loose rocker. If I stick the steth probe on the distributor it sounds like a nasty knocking noise.

Gotta take the dog to obedience class now, back in a couple hours.

Are you using the mechanical fuel pump? They have been known to "Tick" like a rocker.

Are you using a cam button or retainer plate? Retro roller cam/lifters or stock GM style?

be sure the dist. is not bottoming out on the pump shaft....pull the dist and set it back in without the round gasket, it should fit snugly atop the intake manifold....any gap is bad news, maybe need two gaskets or a nylon shim??......just thought i would take a shot...good luck....:rock:

Same issue did it as a new 350 and right off the bat when I stroked it.


Thought maybe the endplay was loose or a lifter touching another lobe.
Cant pinpoint it everything checks out just running it anyway.
Done/checked everything else known to man lol.

Yes, but it's quiet at the front and all around the pump.

There's a thrust plate behind the cam gear and a roller button against the timing cover. All Cloyes parts and set up with their recommended .003" to .005" end play.

It's almost like there is something out of line in the distributor shaft/pump drive shaft/pump. I'm using a ARP drive shaft which is constant OD and I've noticed that some shafts have a reduced diameter through the mid part. I saw no evidence that the shaft was hammering inside the clearance hole, but I may swap shafts since I'm probably tearing it apart again anyway. There's no big rush to get it in the car since I wasn't going to put it in until next Spring anyway, but I have to find out what's doing it. Not being correct just drives me nuts.

Yes, checked that during assembly and the distributor easily goes in all the way to the bottom of the collar without a gasket. If it comes down to experimenting I can make an adjustable collar and turn the shaft to accept it. Pretty easy actually but I hope I don't have to. I actually loosened the clamp slowly while it was running and as I suspected it started to lift the distributor with no change in the knocking noise. I let it come up about .060" or so before I pushed it back down. Just an experiment.

Thanks for the comments. I'll keep digging.

I'm building an engine now and also using a roller cam, although it is from Comp Cams. They require a composite distributor gear for use with the retrofit roller cams. A quick look shows that Howard offers one as well. Perhaps the same exact part. Did they mention if one is needed for their cam?

Sounds like a challenge to find. A distributor noise should sound off at 1/2 engine speed . The cam rotates at half crankshaft speed.

I have seen a odd noise like this cause by Flywheel mounting bolts, one was just long enough to hit on the back of the block on each rotation. Made one heck of a noise and was hard to determine.
A cracked flex plate can make this noise also but I think I read you have a flywheel on this engine.
How much piston to cyl head clearance do you have? Any chance you have one tapping on the cyl head? Sounds like a minor rod knock when you have this issue.
I may be off base but trying to kick out a couple new possibilities.

This engine is stroked, any chance the Connecting rods are tapping the block or a piston skirt. This was an issue when 383's GM engines were first being created. ARP offers Rod Bolts that offer more clearance and many have had to grind on blocks for clearance.

Is the flywheel cover installed?

You are likely using a solid roller, correct? For hydraulic roller cams it's not required, but as easy as it is to try one, I'm tempted. What could it hurt? Whole bunch easier than tearing down the engine again.:willy:

Thought about the flywheel but I checked the bolt clearance so that's out. Checked for being loose too but no go.

Piston to head is .043", and I put the scope probe on the heads at each cylinder. All quiet. Also tried pulling one plug wire at a time, no change.

Thanks for the thoughts.:thumbs:

Checked during assembly. This block can go to a 4" stroke without interference. The only clearance issue could have been rod to cam, but I don't have near enough cam to make that happen.

Nope. And the flywheel isn't hitting the bellhousing either.

FWIW, my 3.85" stroke 427 SB needed a special cam with a smaller base circle AND cam clearanced rods and rod bolts so the cam and rods would not touch each other.

You have only .050" less radial distance than my crank, my cam has a .050" smaller base circle. And it isn't a radical cam

This was on a std deck height Dart Little M

Doug