Replacing bent pushrods in a 390

[HighwayThunder]

Replacing bent pushrods in a 390

The procedure for measuring clearance and installing new pushrods in a 390 requires having on hand pushrods that are of nominal length, +0.060” length, and -0.060” length.

This may seem like a rhetorical question (to which the answer is obvious) but, not knowing in advance how many of each will be needed, do I really have to buy 3 complete sets of pushrods (48 pushrods)?


Is it possible to purchase a nominal set, test for fit, record the results, and then purchase individual replacements?


Cheers,

[HighwayThunder]

Pre-Load

FYI...from http://www.fordracingparts.com/downl...terPreLoad.pdf

"Lifter pre-load by definition is the distance the plunger, inside the tappet, is depressed from the fully extended position. This movement takes place inside the tappet itself. Both hydraulic flat and hydraulic roller tappets contain components that meter and retain a small reservoir of oil. This pre-load correctly positions the plunger into the working range of the tappet body. Total plunger travel is approximately .140". For hydraulic valve train systems, the lifter pre-load can be adjusted by using a threaded adjuster and locking device, by shimming the rocker arm pedestal and by push rod length."

[simplyconnected]

No! I totally disagree with your finding. Lifters in all Ford Y-Block engines are totally solid, with NO plunger. Our pushrods are solid as well. I suggest you consult a real cam company like COMP CAMS.
"Setting Hydraulic Lifter Pre-load (Non-Adjustable Valve Train)

COMP Cams® recommends using an adjustable pushrod to check the pre-load. Typically, only one cylinder needs to be checked in this process. After applying lube, install the adjustable pushrods and assemble the valve train. Using the same procedure mentioned earlier, adjust the intake and exhaust valves to zero lash by changing the length of the adjustable pushrod for precise fitment. Order a pushrod that is .020"-.070" longer than the pushrod length at zero lash to ensure the proper pre-load." <---Notice these numbers are well within the number I gave you (.040").

In my last post I described such a pushrod. It's not a set but ONE pushrod, commonly sold by most speed shops.

To be honest, I use .020" preload as my target and .040" as my absolute limit. Yes, it's that important. Here is fair warning; preload is not .120". If you believe this number your pushrods will bend or your valves may hit your pistons.

After careful measurement, I ordered a set of 16 pushrods from a company here in Detroit for under $100. Sometimes you can get lucky and find the length you need is already available at places like summitracing.com or jegs.com. Because my cam is a roller, that little wheel at the bottom of the hydraulic lifter made my pushrods ~1/2" shorter.

In my last post I went through a lot of info and asked questions. Please answer them. I'm trying to get you back on the right track. - Dave

[HighwayThunder]

More answers

Dave,

The unanswered questions were those of which I was uncertain. Responses follow.

• The machine shop re-bored the cylinders in my block to .030” over using a Sunnen CV-616 Cylinder King. The cylinders are a constant diameter from top to bottom.
• The block deck was not shaved. During the upcoming rebuild, I’ll shim the rocker stands to compensate for the unused oil baffle plate. Then I’ll measure for each rod using an adjustable rod measurement tool, record the results for each valve, and order new pushrods to match. Thank you for the heads-up regarding the correct lifter pre-load.
• The hypereutectic pistons and moly rings were specified for a .030” overbore application. The machine shop inspected the pistons prior to assembly to verify fit. I have not measured piston-to-wall clearance (being satisfied that it is correct).
• Owing to inexperience, I didn’t know to crosshatch the cylinder walls (or why) before inserting the pistons. This will be corrected.
• I did not measure/adjust the moly ring gaps, trusting that the manufacturer sized them to tolerance. I will be pulling the engine soon, so there will be an opportunity to crosshatch the cylinders and measure/adjust the ring gaps.

I hope that covers all the questions and will do my best to answer any further.

I’ve learned a lot from these exchanges. Thank you.

Cheers,

[Yadkin]

Doesn't the machine shop do the cross hatch for you? Have a conversation with your engine builder.

[simplyconnected]

Something is missing between the machine shop and the owner. Steve is right, I have never heard of an engine machine shop that let the block go without proper honing. "Proper" is the operative. They usually under-bore, then 'finish hone', then 'brush' the cylinders to match the pistons. Also, I've never seen newly bored cylinders that are shiny-smooth. Cast iron requires honing after boring so how did they get so smooth?

Honing is done at 45-degrees both ways and it leaves deep grooves. This is important. It's all important. They measure the pistons and brush the tops off the cylinder walls to meet each piston size.

Ring gaps come two ways, 'File-to-Fit' or 'Pre-Gapped'. Isn't that wonderful? The problem is, you have not compensated for the type of alloy you are using. Find out what brand of pistons you are using.

Hypereutectic Alloy pistons are great. I use them, all the auto manufacturers use them and they are much better than your original pistons. Hypereutectic alloy also transfers MUCH less heat, so they run hot. You need to consult your piston manufacturer regarding the correct gap for your bore and rings. There is a big difference between piston alloys. If a ring sees too much heat, it expands, the gap closes and if you get lucky the ring breaks because it has nowhere to go. Otherwise it scuffs the cylinder walls. You need adequate gap; too much is always better than not enough.

How do you measure? Pull the rings off the piston, then put each ring in the bore it will live in (one by one) using the piston to shove it down at least two inches. The bare piston will make sure the ring is square and the end gap will be exposed for measurement with a feeler gauge. File or lightly touch a grinding wheel to the end gap until it is correct. Keep the top and second rings in order and pay attention to which way faces up.

Blocks are normally decked before they leave the machine shop, just to make sure they are square and not warped. A normal block needs very little shaved off, sometimes just enough to remove coolant pitting. I am bothered by the fact that one bank's pushrods bent but the other bank didn't. Right or wrong, both banks should be identical. - Dave

[HighwayThunder]

Valve varnish

Here's a pic that conveys what old bad gas can do to your valves. This valve is for the #2 intake port. Once the springs are compressed and removed the valve should just slide out. This one had to be tapped free with a rubber hammer. The gummy residue on the stem caused the valve to be stuck.

This valve's pushrod is one of those that bent.

Cheers,

[HighwayThunder]

Hydraulic roller lifters and cam conversion

I'm planning to covert to a roller camshaft and hydraulic roller lifters. Summit has COMP Cams Xtreme Energy Retrofit Cam and Lifter Kit (CCA-CL33-432-9) that has the cam and lifters. My engine is a '66 Ford 390-FE with Edelbrock Performer RPM Heads. I plan to re-use the stock rocker arm assembly.

What size Pushrod Length Checker tool should I get to measure for the pushrods?

Cheers,

[simplyconnected]

Did you roll this valve to check for straightness?
I'm looking at the carbon witness mark where it seals to the mating valve seat. It appears to be low on one side and high on the other.

I have also seen valves much dirtier than this from the days when gasoline contained lead. Sometimes a bad running engine only needed a high speed run on the expressway for an hour or two so the valves would clean themselves.

The procedure for determining pushrod length was already given in Post #18. Whether you use a roller or flat, hydraulic or solid, the setup is the same. You must measure your 'stack'. Everyone will have a different height depending on the head gasket and splash pan (used or not). - Dave

[HighwayThunder]

Cylinder crosshatch

Something is missing between the machine shop and the owner. Steve is right, I have never heard of an engine machine shop that let the block go without proper honing. "Proper" is the operative. They usually under-bore, then 'finish hone', then 'brush' the cylinders to match the pistons. Also, I've never seen newly bored cylinders that are shiny-smooth. Cast iron requires honing after boring so how did they get so smooth?

- Dave

I got in touch with the machine shop. They did hone the cylinders. The cylinders looked smooth because the photo I posted didn't have sufficient resolution for the crosshatch to be visible. Upon closer inspection the crosshatch is visible.

Cheers,

[HighwayThunder]

I ordered an adjustable pushrod. I was expecting it to be marked with a graduated measurement scale, but it's not.

My digital caliper is only 6". Do I need to get a bigger caliper, or is there another method for determining pushrod length?

Do you have any tips on how to take accurate measurements?

[simplyconnected]

Set the adjustable pushrod to the correct length.
Unscrew the rocker shaft and gently lift the pushrod out.
Take the pushrod to a local machine shop and ask them to measure it.
Order 16 of them.

When a machine shop decks a block, it is sitting on the main journals so all cylinders are the same exact height and it is square with relationship to the crankshaft.

You have CNC-machined aluminum Edelbrock heads, so they are geometrically correct. When a rebuild is machined correctly, all cylinders are the exact same size and length. Measuring ONE pushrod should be the same length for ALL pushrods. If there is a slight variation, after all, these are hydraulic lifters that do compensate for one or two thousandths here or there. Just make sure your pre-load is correct and you'll be good.

Those of us with solid lifters (like all Y-Blocks) MUST have individual means of adjustment. Sometimes the rocker arm has a jack screw and sometimes adjustment is done on the pushrod. Either way, when you add up the 'stack' of tolerances, none of the valve trains are exactly equal after running for some time. Oiling and other factors play a huge role in how metal wears or how metal parts wear-in to mate with each other.

Valve seats wear just from running unleaded fuel. When that happens, the preload becomes deeper because the spring pulls the valve stem up higher. Cam, lifter and pushrod wear does the opposite, relaxing the rocker arm which makes preload more shallow.

You can see that preload becomes more important later than sooner. What happened to your initial preload? You said your new build ran well at first, then it started bending pushrods. Your preload had to be WAY down there on the lifters. So much so that they bottomed out then kept going.

I know you said, 'bad gas'. Each valve is in a bronze (oilite) guide with two hundred pounds pulling up from the spring. I have seen engines go through a whole tank full of bad gas without damaging valves. If this were my engine, I would pull each valve and spin them to make sure none are bent.

Before you start the engine, check your piston-to-valve clearance. Think about this... even if a valve sticks part way down, the rocker arm relaxes on the pushrod. Then the piston pushes the valve up. The problem with that is, pistons are at an angle from the valve. They touch on one edge of the tulip and the guide is not straight up. So, valves tend to bend and guides tend to chip off inside the runner.

Carefully inspect the tops of your pistons for collision witness marks. It will explain your bent pushrods. - Dave

[HighwayThunder]

A bit of good news

I finally got around to pulling the engine to install the new roller cam/lifters and to fix the oil leak at the back of the engine.

The good news is that the leak is not from the rear crank seal. The leak is from two of the oil passage plugs -- the crankshaft will not have to be removed.

[Yadkin]

I ordered an adjustable pushrod. I was expecting it to be marked with a graduated measurement scale, but it's not.

My digital caliper is only 6". Do I need to get a bigger caliper, or is there another method for determining pushrod length?

Do you have any tips on how to take accurate measurements?

As Dave said, or I just measured several with a good tape measurer, ordered all the same length, and have adjustable rocker arms to fine tune.