Knock upon starting, new engine

[mtnmankev]

Chev 350 86 vintage one piece rear main seal block.
After running the fresh engine off and on for about 20 to 30 minutes at 1500 to 2000 rpm to break in the cam and lifters, the engine started a new issue.
After it sits a while and we restart it, there is a knock that sounds just like a worn out rod from an engine with a million miles on it.
The sound goes away in about a second as the oil pressure builds.
The original crank was out of round on one throw, so the machine shop ordered one in.
It came with correct bearings, and plastigage is showing .001 to .0015 clearance on the first two throws, will check the other two after I eat some food so I don't collapse working in the heat.
I see some microscopic "scratches" on the bearings, but no deep grooves or scores.
Everything in the engine had liberal amounts of assembly lube so nothing was run dry.
I am not sure if mains can cause that noise if they have too much clearance, but I will check them also.
If the rods were not reconditioned properly at the shop, could that cause them to make the knock and not show up on the bearings as wear?
I am at my wit's end, and out of ideas what to look for now.

 

[Vbb199]

Not by chance a top end noise and its the lifter ticking is it?

 

[legopnuematic]

Sounds like it is top end to me as well, hydraulic lifters can be hit or miss in today's market, even from reputable manufacturers I've heard stories of them either being made of inferior materials or having issues with collapsing and on holding oil. Or it could be an oil gallery has dirt in it and may be causing a restriction somewhere, but once there's enough pressure it can push past it.

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[mtnmankev]

NOPE, nice try though ....
The rockers were ticking a small tad due to needing final adjustment, but this was a solid KNOCK, KNOCK, KNOCK coming from deep in the block and it went away as soon as oil pressure built.
The valves kept ticking a tiny amount, but when I heard the deep knock sound for the third time upon startup, it was time to yank the engine out and disassemble it to find the cause.

 

[mtnmankev]

Here's a pic of rod caps for #5 and 6.
I did plastigage and it was .002 for #5 and #6 was WIDE and off the scale for .001 to .003
Going to pull the last 2 rod caps off now and check them.

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[mtnmankev]

The bearings for #'s 7 and 8 show a little bit of scoring marks, and the plastigage showed .0015 to less than .001.
The plastigage did not flatten out evenly, it was wide at the edges and narrow in the the center.
And this was also the case in many other rod bearings.
I am now suspecting a defective crank, it may not have been machined properly.

 

[mtnmankev]

Since I have to go in to the big city tomorrow to pick up some chainsaw parts i ordered, I am going to drop off the block with the crank and pistons still in it to the machine shop, and hopefully they can figure out what went wrong on their end before I took delivery of the machined components and did the assembly.
I'm hoping it will all be under warranty and no money out of my pocket.

 

[DoubleDingo]

I sure hope it's warranteed. Frustrating to install a fresh build only to have that happen in short order. Good call on pulling it back out.

 

[mtnmankev]

Just got home from the big city, the machine shop looked over the block and determined the cam and lifters are wiped bad, due to soft steel.
Here's a pic of the worst lifter.
Makes me skittish of getting a replacement cam from Summit.
Rumor has it there are only two or three places that produce camshaft cores now, and it's almost impossible to get a guaranteed good cam.
I need a cam as close as possible to the Summit 1102 specs if anybody has a suggestion who to call.
Thanks !!!!

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[Bextreme04]

Delta Camshaft in Tacoma, Washington did a full regrind of my stock hydraulic roller Gen VI BBC cam. The work looks great and they have been around with great reviews for a long time. They can custom grind whatever you want, they do all their work in house. I would suggest calling them and see what they can do for you.

Also, what did they say about the odd plasi-gage reading on the rod bearings?

 

[mtnmankev]

They hadn't removed the crank when I was there today, but they plan to take it apart and double check EVERYTHING for dimensional specs, etc and will call me.
He actually understood when I said the plastigage looked like a paramecium when I did the test.

 

[Ricko1966]

Delta Camshaft in Tacoma, Washington did a full regrind of my stock hydraulic roller Gen VI BBC cam. The work looks great and they have been around with great reviews for a long time. They can custom grind whatever you want, they do all their work in house. I would suggest calling them and see what they can do for you.

Also, what did they say about the odd plasi-gage reading on the rod bearings?

Roller is a whole different animal.Flat tappet is rubbing metal to metal lifter,on camshaft lobe.Thats why the big deal about proper break in.ZDDP, making sure lifters travel smooth and can rotate in their bores, running as little spring pressure as you can with your cam etc.etc. I use rotella T4 in anything flat tappet, it still has old school formulation with ZDDP. I like the specs on the summit 1102 but I think I'd be hunting for a new old stock 929 chevrolet cam or a new old stock aftermarket equivalent,and don't run cheap lifters.

 

[nabeshin]

Just asking, but did you have the zinc break-in oil for the flat tappet lifters?

edit: Ricko beat me to it, on the oil type.

 

[mtnmankev]

I used generous amounts of moly assembly lube, castrol GTX 10w30 oil with some ZDDP added too, so the engine had plenty of lubrication.

 

[Ricko1966]

Did you make sure all the lifters moved freely in their bores with no tight spots?What are you running for valve springs?