So I have a 327 with 882 heads. I go some pro topline heads that I feel will give me a little bit of boost in the HP range. I have done head gaskets before so I have the general idea mechanically, but what I done is how to pick parts. I need gaskets, pushrods and rocker arms. How do I go about choosing them. I just want something basic. I started to read a thread but then they were talking about gasket matching, squish and other things to squeeze every bit of power out. I don't want to get that involved at this time.. so basically can I just but a head gasket changing kit from my local machine shop? And also what bare minimum work to them should I have machine shop do? And as mentioned before how do I choose rocker arms and pushrods?

 

1st machine shop doesnt need to do anything
2nd you can pick what ever rockers tickle your fancy.
3rd yes you can run a stock head gasket if you dont want to mess with the quench. Unless you are running a huge cam and have a super tight PTV clearances a stock gasket should be fine.
4th you need a pushrod length checker to get the rocker in the correct position.

 

the missing piece of information is whther the heads are brand spanking new or used.

If used, then i'd be taking them to a machine shop for inspection before I would even consider installing them

 

They are slightly used. They are the pro topline srt series. So if anybody has run them have you had any issues with valves or springs?

 

So to check pushrods do the heads have to be installed on block? And as far as rockerarms, how to I begin to go about choosing them. I see different types and sizes.

 

Let see if this helps.....

To do this right you need to know a good bit of information. Its never an easy task to just do a head swap, as lots of things need checked.

First, I have few questions... what is done to the 327? Is it a factory motor still or rebuild? Has the block been resurfaced/decked? If so, what is the new deck height or how far below top deck does the pistons sit in the block at top dead center?

SBC start at a 9.025" deck height. Most rotating assemblies are designed for 9.000" so most factory shortblocks have pistons sitting below deck about 0.020-0.025" or so. When you deck the block, its common to take the deck down to 9.000" This ensures a FLAT surface for best sealing with heads and also gives you ability to get the proper piston to head deck clearance...commonly refered to quench height.

Most motors seem to like the .038-.045" area of clearance...this is about the size of most head gaskets you see. 0.040-0.041" are most commonly used head gaskets.

Now if your pistons sit below deck 0.025", then to get a 0.040" piston to deck distance, you need a 0.015" gasket. Not many are made that thin, and these are common as steel shims. Factory iron head motors I believe had steel shim gaskets about that thin. Problem is a thin gasket like that is harder to seal up. they require a perfectly smooth flat surface and most factory finish deck surfaces are not that smooth, especially after years of use. Things move around and become unflat.

Few companies will custom make gaskets of any thickness but some other good gaskets exist in the 0.028 range that could work. This gives a bit higher quench height in the 0.050's but thats ok for a milder street performance build. Once you get up over 0.060" things start to become more detonation prone on hotter performance builds, but there are alot of factors that could change that from head design, spark plug location/type/heat range, fuel type, etc.

Once you got the gasket size figured out, you can put the heads on the motor in a mock up phase, and measure for proper pushrods. You need to have the heads on the motor to do this right. Need a lifter, preferably a solid lifter to measure length, or use light weight checking springs installed on the head so the hyd lifters wont collapse. Or use an old hyd lifter and fill the internals up with washers/nuts or whatever to make it not collapse under spring pressure. Dont have to have the headgasket in place, but remember the thickness gets added to the measured pushrod length when you go to order rods.

Basically have to install the rockers and pushrod measuring tool and mark the valvestem with magic marker. Install the rocker, rotate the motor over til the valve opens and closes completely. Take rocker off and inspect the mark the tip leaves on the valve stem. It will rub the marker off and leave a travel pattern. You want the thinnest pattern which may or may not end up centered over the valvestem. As long as its within the middle 1/3 of the stem and thin, thats the length pushrod to use.
Pushrods are commonly 5/16" but can be 3/8" Larger is stronger/stiffer and more stable at high rpm and required for high valve spring pressures. You likely will not need 3/8" so use the standard/smaller style. Need HARDENED pushrods for use with guideplates. 0.080" wall is nice for stability.

Rocker arms, you just pick whatever you want to run. Old sbc, you need a non-self aligning rocker arm, basically what MOST rocker arms are. Heads should have guideplates installed under the rocker studs for the pushrods. Rocker arms can be full roller type or roller tip only or factory style. Its up to you and your budget what you want. Full roller has less friction and generally give most hp (differences wont be much tho) but they are much more pricey.

1.5 or 1.6 ratio is common. Factory is 1.5. 1.6 just gives more lift at the valve. Comes in handy if you need the lift. Need to know if your valvesprings in the heads can handle the lift with 1.6 ratio with the cam you run.

Rocker studs are either 3/8 or 7/16. Bigger is stronger and more stable for high rpm useage. So get rockers to fit whatever the heads use.


Regarding the heads, being used, I'd check the head deck surface for smoothness and flatness before putting them on the engine. It be best to have a machine shop do a slight mill/surface refinish to ensure they are flat for best sealing. Then swap valve springs for fresh units to match your cam. Valvesprings wear out so new is necessary unless the stuff has very low mileage and used on a cam that does not beat up valvetrains that hard. Thats hard to know so replacing the springs is always good insurance. Then inspect the valvestem seals and replace if they look worn

Thats the basics I can think of right now. 882 heads SUCK so these toplines should improve power as long as they are not too big for the motor. You didnt give any details so hard to say what will happen.