I'm in the planning stage for a basic rebuild on the '93 300 I have and have a question. How much can be milled off the head and block before you need different rods? The engine appears to be in great shape.so I don't expect to have much done to it.
Thanks. john

 

Personally, I wouldn't even think about the rods until you're all done, since no matter how much (or how little) you take off, you might still need new ones.
Many things in a rebuild can affect the push rod length. Grinding the valves for new seats, or even a different thickness head gasket all factor into push rod length.

After I rebuilt my engine, I got a push rod length checker, and I went through each valve one at a time and checked for proper length. I ended up needing 3 different lengths of push rods to get it all lined up right, but it made it run super smooth.

Cover the valve stem top with dry erase marker, and then put the rod and rocker in place. Turn it over a few times and take the rocker off.
If the wear mark on the valve stem tip is centered, you're good.
If it's to the side further away from the push rod, you need a shorter one.
If it's to the side closer to the push rod, you need a longer one.
Once you find a length that's centered, write it down for that valve. Continue with all 12.
This process also works better if you get a solid lifter for the test. That way you don't have to accommodate for lifter bleed down. You only need 1 since you can move it through the 12 valves as you go.


That said, obviously, the less amount of material you take off, the higher your chances of using the original push rods. So, after you do all your measurements, IF you can get away with the stock rods, then so be it. But it will probably not be the case.

If you look online, you'll see that most places carry stock length rods, and rods that are slightly shorter. Such as 0.060" undersized. These are for rebuilds where material will be taken off the head and block. So, it's very common to end up needing shorter ones.
Then, there are places that will just sell you whatever precise length you want (which is what I did)

So, don't plan your build, or limit yourself, so that you can get away with using your current push rods. Measuring push rods is one of the last steps, not the first.
Also, taking some material off of the head and block can be beneficial, since it'll raise your compression and help with quench.

 

AbandonedBronco
Don't forget that the '93 300 engine has pedestal mount rockers and the rocker to valve stem geometry is set unless a person uses shims under the pedestals.

 

I forgot about the pedestals. But still, from my experience with pedestals (one of my 300 heads had them), all they do is limit adjustment. You still need to check pushrod length and geometry. Sometimes you need to add shims to get it right, but pushrod length can still change based on what's done to the head/block.

 

Thanks for the info. I already need one push rod as I found one was bent when I removed the head. So measuring and ordering what's needed sounds like a good plan. How much of a ridge do people find at the top of their cylinders when they open things up? This motor has no ridge. The tops are measuring 3.996 ish (cheap digitol caliper), but the bearings are all showing copper. I would have expected more wear in the cylinders given the bearing wear.
Thanks again for your help.
John.

 

Its uncommon for bores to be less than 4.000". To measure accurately and to measure the amount of ridge and wear beneath the rings you need a dial bore gage and a micrometer. I would expect to see a ridge if the bearings are worn out.
Don't re-ring if there is a ridge without removing it. It may break the new rings.

 

I once re ringed a 292 Y block and had to buy a ridge reamer to remove the ridge first. All I had to do on the 300 was scrape the carbon buildup off of the top of the cylinders and then push the pistons out. I figure the under 4.00 measurement was due to using the cheap digital micrometer.

 

Just ran across this thread. Saw you were a moderator so i figured I'd ask you. I do have my own thread started though about this. No responses yet. I have my push rods ready to go in but noticed there are no copper ends on either end. I have all my pics on my thread. If you wouldnt mind, can you check out my thread and let me know what you think please? Thank you in advance. -Dustin

 

Hey Dustin,
I've never heard of copper ends on pushrods. It's not something I've seen or read about when I was doing my engine build.
However, I'm seeing that you're working on a diesel. I'm pretty unfamiliar when it comes to diesels, but I do know they're their own animal. Maybe they have some sort of requirement for copper ends due to the oils used? I'm not sure.

Do you have any diesel shops in your area that you could call and ask? Honestly, you could probably call one Anywhere, USA and they'd be able to give you some insight.

Otherwise, the pushrods you are running look just fine. I don't see scoring or damage on the ends, so it doesn't look like anything negative is going on.
But being a diesel, I'd at least call a shop and ask. Good luck!

FWIW, here's a link to your thread:

https://www.ford-trucks.com/forums/1...-rod-ends.html