push rod clearance Q

[YeLLowBoaT]

I have been looking at the 1.65(1.5stock)roller rockers; however, I have been told by some "experts" that I may or may not have push rod clearance issuse if I go with the 1.65s. Is there anyway of telling if I will have a clearance issuse other then throwing the heads back on and installing them? Not that it would be a big deal to have the heads clearanced, I would just rather know b4 hand so that I don;t have to make another trip to the machine shop.

[SmokinLowriderSS]

I can't see any way of finding out problems of rod-length in your valvetrain or rocker/spring bind without bolting it together and testing very carefully. Good luck. Maybe someone here has some experience with those rockers.

[YeLLowBoaT]

From what I have been told: the rods may rub on the head. Stock length rods are fine, atleast to the "experts" I have talked with. I just don;t want to make a $350 or more mistake.

[steelcomp]

I can't see the length being your problem, although I'd check that, as well.
When you start playing hi-perf games like changing rocker ratios, especially on some engine combos, you can learn to do things like this yourself. It's very easy, adn you do it with a die grinder and a long shank carbide burr.
I'll try and walk you through it. You'll have to bolt the heads on, and i'd recommend you assemble them with mock up valve springs. (very light weight so you can turn the cam by hand)
If your short block is already assembled, it's going to take you forever because you'll have to assemble everything, look down the pushrod where it passes through the head, mark the area that it's hitting, and then remove the pushrod, grind a little, then put the pushrod back in, rotate the cam through the cycle of that lifter and pushrod. If it's still hitting, do it again, taking little amounts off at a time untill you have about .020-.030 clearance. On a bare block, you can do all this on the block with just the cam installed, but on an assembled short block, you're going to have to pull the head every time, and grind somewhere away from the motor. I've only done this on aluminum blocks and heads, but it's the same. The only difference is that I could color the pushrod with a marker, and it would show on the head where it was rubbing. On cast iron it's going to be a little more difficult seeing where the push rod is hitting. You can do the same thing by putting marker on the push rod, and seeing where it is rubbed off, and know the spot in on the head is adjascent to the rub mark on the P/R. You just go down the line, doing each push rod in order. Some will need it, some wont. You're not removing nough material to worry about water or breaking into an intake port. Just take your time, and you'll get it done.
Now the machine shop may know exactly how much to take off of and where, and they'll probably stick the heads in a mill and just do it that way. If not, they're going to have to do the same thing you are. Bolt the heads on a block, and check each one. Frankly, I'd rather do it myself. :D
Hope this helps.

[BUSBY]

Well ... that sums it up ... a little long ... but correct ... good job Scott!
Brian

[Moneypitt]

I seem to recall the 421 engine family as 1) having 1.6:1 rockers, stock. And 2) The rockers have an actual torque, bottomed out. I also recall a situation where the retainers hit the guides when using a mild lift performance cam.. That engine family also changed dimensions and components in the early 60s, so beware that "one size does not fit all"........Pontiac did some wierd stuff back then...................MP
PS: upon further review I now recall they are 1.5:1 stock. The hot tip back a few years was to use the 1.7:1 BBC rockers on the exhaust valves to wake them up.........

[steelcomp]

Well ... that sums it up ... a little long ... but correct ... good job Scott!
Brian
Yeah, my editor was out yesterday. Thanks Buz. :wink: