Catastrophe, there's a knocking noise once the engine warms up. It's there at idle and speeds up as the rpms are increased. I don't have a stethoscope so haven't been able to isolate it yet, but it probably means the engine is coming back out.

 

Seems like new timing gear sets do this on occasion...and have to be changed out.

 

Ugh, I'm sorry to hear that. That's never what anyone wants to hear.
I do hope it's something simple, or at least relatively simple, like the timing gears.
Keep us posted.

 

Dude, I'm so sorry to hear that. I wouldn't wish that on anyone. I have been there. I had a new engine that ran the break in, and 30-40 miles fine. When I started it up the next morning my heart sank b/c of the sound. Mine turned out to be the t. gears, new. I changed it--which is no small job, but easier than an engine change--and have been driving it since.

I hope yours is a minor problem. I would ck the t.converter bolts/flywheel bolts . Those, if loose or missing, can make for nasty knocking. Good luck.

 

Earlier you pointed out that the pistons were fairly far below deck. This is because the cast replacement pistons are "de-stroked" in overbore sizes. The old catalogs stated this near the front of the catalog. Typically a 0.030" oversize piston had the compression height reduced that amount, ostensibly to retain the stock compression ratio. Unfortunately this is counterproductive so far as anti-knock behaviour is concerned since the increased squish area is more prone to knock.
I have seen this de-stroking policy defended more recently by saying it's to counteract expected decking of the block.

I would bet that the piston makers still do it because they don't want to have to change the molds.

 

Alrighty then, bringing this one back from the grave.

The engine is still knocking - around the cam area near cylinder 5 I determined - so it's coming out.

Just for fun I cracked open the engine that came out of the Bronco and it was super clean. The head/valvetrain had zero sludge, looks like it has less than 1,000 miles. One bent pushrod, which explains the ticking noise it had. The bores appear to be in good shape too. Cleaned the carbon from the top of #1 and couldn't feel any ridge at all. Cleaned the top of a piston enough to see it's .040" over which isn't what I wanted to see but oh well.

I took it to a different machine shop around the corner with a very good reputation to have them check the cylinder bores. If they're okay with just a hone then I'm going to have it freshened up to replace the one knocking now. Five of the six balancing pads on the rods have been ground so I think it's been balanced already. He's going to measure the deck height too in case I want to get new pistons and/or have the block machined to put the pistons at zero deck.

The threads in the crank on the engine in the Bronco now were messed up. After I pressed on the balancer it took a three foot cheater to get the bolt snugged up to the balancer. I told the shop to fix it and that's one more reason I'm using a different shop. So starting with a different crank is a plus for me. I'd also be swapping the mid-sump block that's in it now for the correct rear sump block/pan that came out. I can't imagine the oil pan mounted dipstick boss won't start leaking eventually.

Shop estimated two to three weeks for a short block but he said he should have it broken down, cleaned, and measured this week, so we'll see. I'm gonna speak to Comp about a custom cam just for fun in the mean time.

 

From several posts back:

Baron, if it wouldn't be so personally embarrassing to ME, I'd start a thread with the subject, "I Am Such a Moron!!!" I have more than one story, alas . . .

from Harte3, again last September, (QUOTE) "Seems like new timing gear sets do this on occasion...and have to be changed out." (end QUOTE).

Harte3, are you telling us that new timing gears can start doing this some while AFTER the initial start-ups and run-in of a new engine?? If so, that ain't good news. A guy can check the lash of the gears while building an engine, rotating the crank two turns to see if the lash is the same all around, but if that checks out I have assumed that that part of the build is good-to-go . . . ???

 

Stopped by the shop to ask about custom pushrods (he doesn't and said to call Smith Brothers in Oregon) which is a drag because I was hoping to just hand him the measuring pushrods and be done with it.

The old Bronco engine is stripped down and the block on the hone to be honed tomorrow. He felt a slight ridge but said it may hone out. We shall see. It already had hyper pistons (H519P to be exact). The crank looks good too and will hopefully just need to be polished.

 

Try Trend. They sell them in ,050 increments.

 

Got the engine out of the Bronco and took it apart. To recap, I neglected to scrape the gasket face of the intake manifold around #1 & 2 specifically and had a huge vacuum leak on a newly rebuilt engine. Once corrected the engine ran okay but there was a knock after it warmed up that increased with engine speed.

Cylinders 4,5,6 had some funky build-up on the pistons. Almost like the goop you see in an old engine accumulated on top of #4 piston. The rod bearing on #4 is worn down to copper all around. I assume that was the source of the knock. When I pulled the spark plugs the one in #4 looked almost new, like it hadn't been firing. The rods have been balanced and have ARP bolts so I'm going to use them in the new engine.

The block honed out at .040" over but he said pressing the rods out of the old pistons would probably wreck them so I've got a new set of H674P pistons on the way. Same compression height as the old pistons so there's a little room to square the block at zero deck.

The cam and lifters looked okay but I'll have the shop inspect the cam and see whether he agrees. If so I'll reuse it and the timing set.

Gonna have him check the head too while it's off and at least resurface. The engine ran super hot when I did the cam break-in so hopefully there's no damage.

 

Who is putting the engine together after machining, you or the shop?

If you, mike everything, double-check. Shops do goof sometimes. Especially mike the crank, the bearing thickness (done most easily with a bearing mike but you can figure out how to do it with a regular mike). Sometimes new parts are not right. Plastigage the assembly. Etc. Etc.

 

I had the shop assemble the short block. I didn't use them again because they either didn't listen or forgot to do work I asked them to do. The threads in the crank snout were boogered up and I told him to fix it, use a different size balancer bolt if you have to. He didn't. Told them to take it to zero deck and they didn't. I took it back to have the block milled down and short block reassembled plus reminded him about the crank and he still didn't fix it.

I'm having a different shop build the new short block. I've used him before, he's a little pricey compared to the other shops but has a good reputation with the local racing set.

 

Wow, yeah, I don't think I'd ever grace their shop with my presence again. The damage you described to the block sounded a bit much for it simply overheating. I wonder if their hands all over it had anything to do with that, too.

 

I'm perfectly willing to own up to the mistakes I made with the engine. I was reasonably sure it was a cam problem brought on by the vacuum leak and all the starter cranking to get and keep it running. A bottom end problem though? Maybe. Or maybe sloppy work when it was assembled the second time. Water under the bridge now. I know I won't make the same mistake again so there should be no worries.

 

Number four rod journal:



Number 4 rod bearing:



That's after maybe one hour running time.