Help?slotting sbc heads for pushrod clearance

[chimp koose]

Ok, today I milled the intake surface of my heads to correct for the deck surface milling I did before. Then I started to lengthen the pushrod slots in the head as I am using a .525 lift cam and there is sometimes a problem with pushrods binding in the slot at this much lift.Question, which side of the slot do I lengthen? I did the rocker stud side but I dont remember if that is the side that needs it. It will be a while before the heads are assembled and I can check for myself.Does anyone remember which side needs the extra clearance?

[Crosley.In.AZ]

generally you can open the push rod  holes up.  then use push rod guides under the rocker arm studs  with that lift of cam

[chimp koose]

Crosley, thanks ,but which side needs more room ,the rocker side or the lifter valley side . I have run .575 lift without guide plates before when using the slotted pushrod holes with no problem. The slots just clear the sides of the pushrods without the need for hardened pushrods . I am going to pin the rocker studs instead of machining for screw in studs and guide plates.

[wayne petty]

as i recall.. its the inside of the slots..

closest to the rocker arm stud that needs to be opened up just slightly...

i take it that you are going to do this on a vertical mill.. so you can keep the width correct and totally straight..

or you could use a round file...  of the proper size...  it won't take much removal to clear the push rods...

i also worry about the push rods bending with that much lift.. but thats just me...


(when going to a 1:6 rocker arm.. the push rod is closer to the fulcrum ball....)

while thinking about SBC valve train... when i worked in a machine shop..

we had a hydraulic stud puller that looked a LOT like this...

http://www.harborfreight.com/hydraulic-punch-driver-kit-96718.html

with a spacer to raise the power cylinder away from the head.(to clear the stud next to it) . and a  TEE handled insert to thread onto the studs to yank them out with ease..

i just thought i would mention it as pulling studs from these have sometimes been a problem ...

[Crosley.In.AZ]

Wow... pin the press in studs. I have not done that in 20+ yrs.

[chimp koose]

Wayne ,I machined up a drill guide that fits into the slot and has a 5/16 hole right where I need it. I turned a drill bit into a 'end mill' of sorts and when I feed slowly it cuts where I need it. There is a tool just like it for the job, I just copied it from what I remember. I am lengthening the slots 1/8" as there is no room to go further and this is probably more than I will need .If I use a file to lengthen the slots I run the risk of widening the slot to the point that it may not guide the pushrod properly.I am running over 300# open pressure at the valve and that is when the studs start removing themselves so I will just pin them. Crosley ,I have not pinned studs in about as long but I think it should be ok. This is a pump gas, hydraulic cam deal, not over 6500rpm, likely 6000ish . .040 over 350,flat tops,10.5:1,2.02/1.6 swirl polished undercut stem stainless,throat85% of valve ,bowl work,port match to 1205 gasket, chambers relieved& polished ,ported vic jr. ,254deg @.050 .525 lift 110LSA advanced 4deg .Eagle crank(remember , I dropped engine ,broke crank and instantly joined team smart!). This is the motor for my Anglia.I am using up my sbc parts inventory ,not a perfect combo, but it is using up what I have .I have owned these heads since '85 and would see better performance with aftermarket aluminums but,I do all my own machine work, so the cost is minimal. I started building it 2 yrs ago and then got sidetracked.Trans is done,PG (need a 3500 converter yet ), diff is done, 9" 4.11 /31 spline strange axles. Suspension was finished years ago,so I am eager to get the engine done and get the car running. 11 year build so far,off and on, other priorities. The Fun Run will be in Saskatoon this year,and I would like to have it running before then(AUG.)