Clearancing push rod holes

I need to clearance the push rod holes on my Eddy heads and have to buy a bit for my hand grinder to do so. Would like to know what type of bit works best. Should I get a single cut cylinder bit or a double cut or perhaps something else?

A double cut is easier to control and takes smaller bites. I usually recommend either turning down the air pressure or better yet getting a router control at Harbor Freight for you electric grinder. Keep your burr clean buy dipping it in transmission fluid or wd40. Lots of ways to go about it but that will get you started. If you need burrs quickly Summit sells them.

Buy the burr for cutting aluminum, not steel
Candle wax works well on the burrs cutting aluminum to keep them clean, manually spin the burr in the wax before starting and again regularly enough to keep them clean

This cutting fluid has always worked well for me:
http://www.tapmagic.com/

This is the best advice !! Aluminum cutters are much coarser so they don't clog as easily.

I have used the cutters that all those chinese tools vendors sell at the swap meets with no problems.

You'll also need cutters with a long stem to reach where you need to cut so get ones with 6" stems.

also, bar soap works for a lube. best stuff, [in my opinion, your mileage may vary] is machinist's wax. works super on aluminum using course cutters at a somewhat slow speed.
most guys crank the speed to max, but slow and steady does the best job.
make sure to use eye and face protection ! if not, "You'll take yer eye out, kid !" [to paraphrase a popular movie saying. ]

Did you think about opening the oil drain holes?I used a 1/4 double cut bit 4" long on both

Another piece of VERY good advice !! Whenever I do ANY grinding with burrs I always wear long sleeves and welding gloves with the sleeves tucked in. Those little pieces of metal are sharp as hell and fly everywhere. Welding gloves are thick enough the shards won't penetrate.

Remember that (although it's frequently the easiest way) a larger round hole does not track the actual path of the pushrod tube as it cycles.
The relief hole's actual shape has a length (on the crank axis) of the tube OD + safety margin, but the cross (left-right) axis is 2 holes this size joined by a relief that allows the full in-out swing of the rocker arm (not an ellipse, the sides are parallel). This will depend in part on your rocker ratio - high ratio rockers are commonly made by shortening the tappet (short) lever, which increases the sweep of the adjuster. If you're copying a known-to-be-safe similar engine, beware of cam & rocker differences.

Well said.I have center located push rods in the roller lifter 1.5 rockers.I opened the oil drain holes to help from the head gasket and after market block covering a lot of the holes open area but I think it would help in any case.

Someone needs to invent rat tail file pushrods. Put'm in, crank it, clean the oil filter, and go cat go lol.

That WOULD work! Terry Manton told me years ago I only need 10 thou of clearance as the flexing could use the help!

Been away on vacation so I haven't worked on clearancing the pushrod holes yet but I plan on picking up a bit this week. I will get a bit for aluminum but have one more question. Should I get a 1/2" diameter bit (the size of the pushrod hole), insert it in the hole and just work it upward till I have the needed clearance (basically ovaling the hole vertically) or would it be better to do the same but use a smaller diameter bit like 3/8" (the diameter of my pushrods) and just notch the hole at the top where the pushrod is making contact? I hope my question makes sense.

How good are your grinding skills? Stick with the smaller bit, if there's any doubt. Or, depending upon how much material needs to be removed, use cartridge rolls to slow down the process enough to avoid removing too much too fast.

You can’t be size on size with a burr bit. The bit always needs to be smaller than the radius, or you will get impossible to control chatter.

Terry Manton told me that 10 thou is all that's needed at it's closest point.It will act as a guide

What rockers are you using? I found that when I went to Harland Sharps for Edelbrock Heads on my Stealths, the material removal needed to clearance the pushrods was dramatically reduced. Fixed the scrub pattern too.

Depending on how much you are removing, a larger drill bit in the drill press gets the job done quickly.
Done that on small blocks a few times.

Comp Pro Magnums.

I've learnt over the years to use tootsie rolls to do this.. on my B1 I
could use the mill and a end mill but I had a lot to take out.. seldom
do I ever use a alum cutter in a air grinder.. its to easy for it to wobble
around the hole and it takes too much material off to quickly(I would
rather use a steel cutting bit which is much easier to control

I tried to tell him that in my post but others insisted on telling him to buy the single cut aluminum burrs. After a grinder wings out of control and you bend the burr it teaches you the right way. Slow and easy and it ends up looking like a professional did the job instead of a HACK. LOL

On my latest refresh I believe I could use a set. Lol Over the years a burr on the block that should have been removed did a little polishing on my pushrod. Can’t feel it just shiny.

I agree 100% with ya

don't forget to use a grease of your choice when using burrs. it will prevent them from clogging up.
tootsie rolls come in lots of grits, so start out with a rather course grit, then finish with 80 or 100. even finer if you are after a polished appearance.
if starting as a nu-be, grab a chunk of scrap material to practice on, so you learn the nuances of your grinder, and the way a burr or tootsie roll cuts.
use the shortest cutter you need to get the results you are after. this will prevent the dreaded bent cutter and out of control grinder.
however, 6" long cutters are made for a reason. slow and steady beats 100k RPM and hackin' away every time.

O.K., so I should get a double cut steel bit rather than an aluminum bit.



If the hole is 1/2" diameter, what would you suggest for the diameter of the bit, 1/4", 3/8"? This is my first (and probably last) time doing this so please excuse my lack of knowledge on the subject.

The steel burrs will clog up and chatter a lot sooner than the courser aluminum burrs will
I have both and as well as some very small diamond coated burrs for a much smaller hand held adjustable speed grinder like jewelers use, they all have their uses but I try not to use the wrong one on any job
You learn by doing
Once you get the burr to start chattering in a small enclose space you may have the grinder vibrate out of your hand or break the shaft of the burr, NOT GOOD

you may have the grinder vibrate out of your hand or break the shaft of the burr

And skip over to carve its name on something expensive... like a valve seat.

My last comment / suggestion, which I'm sure overlaps w/ others' feedback above:
1. Use some type of speed controller if the grinder is limited to ON/OFF; you can even use a cheap light rheostat from Home Despot or what someone else mentioned from Harbor Fright. Regardless, you have to be able to slow the grinder speed to have some level of control
2. Use 3/8" OD sanding rolls to limit the amount of material being removed; get 60 or 80 grit, not the finer grits which tend to be more for surface finishing
3. Mark off where you think you need to remove material
4. Wear safety mask & goggles
5. Take your time -->

Sorry, but I have a few more questions. I just want to be sure I do this right. So I can use sanding rolls (like those that came with my Dremel) rather than a metal bit or in conjunction with a metal bit? Either way I'll have to try and get a long stem metal bit and/or a long stem bit for sanding rolls as mine are all short stem. I was going to use a Mikita rotary hand grinder I borrowed from a friend but it is single speed and it does seem pretty powerful so I will have to pick up a speed controller as well. Could a Dremel be used to do this or is it not powerful enough for this kind of job?

Not sure where you live but if you live close to Freeport, Pa. 16229 bring them over. I have everything here to fix you right up

I don't know that a Dremel is going to be the best tool for the job. The cutters are very small diameter and the sanding roll setup a Dremel uses will wear out far too quickly. The Makita with an inexpensive speed controller would allow for using "Tootsie rolls" on a shaft that will both last longer and enable you to reach farther into the pushrod tunnels to do the work.

I clearanced my stealths for 1.6’s last year. I don’t think a small tool like dremel will be what you want. A bigger tool not only will have the power you need, but I think it will be easier to hold steady and be consistent with. I used an electric die-grinder with a variable speed controller, both from harbor freight. They worked great. I also bought a burr kit from from Harbor freight, decided on a shape that gave me what I wanted and used WD40 as a cutting oil. It went much faster than I anticipated.

Now the part that may make some gasp, As I assume this is not recommended: I did all the cutting with the heads on the block, in the car. Call me lazy; call me cheap, but I just really didn’t want to pull my heads for a second year in a row. I knew I was taking a big chance, but once I had the valley blocked off with tape, paper, and rags, I was convinced I could keep debris out of the engine. Once I had the grinding done, I blew the heads as clean as possible with air before exposing the valley. then used atf to rinse and clean them real good when done. I then put assembly lube on the cam just to be sure upon startup, and did a series of oil changes until I was convinced it was clean.

My project turned out great, and a substantial performance gain was realized.

I wasn't planning on using a Dremel. I am going to use a Mikita electric die grinder as I mentioned previously and I picked up a speed controller to use with it. I was just askng if the sanding rolls that came with my Dremel were the type of tool that was being referred to in a prior post. I would just get better ones for use with the die grinder. I am going to do this with the heads on the motor as well covering up everything as you did. I have found long stem burrs for purchase but I haven't seen any long stem sanding roll bits anywhere. Anyone know where I can find one of those (if there is such a thing)?

That should FINE.

That's how I do it...it stabilizes the push rod by reducing deflection.

I would give serious consideration to pulling off the heads to do this work, rather than risking any of the grinding debris finding its way into the engine.

Forty years ago I did a head swap on my '69 Super Bee one afternoon in the parking lot of the apartments where I lived. You'll be halfway there getting it to the point where you would be ready to grind, and the cleanup effort will be more straightforward.