While I have the motor down and building the lower end is there anything I should do to the Edelbrock Performer RPM heads for gain? any additional port or polish work that's worth the effort or are they best left alone?
You might be able to mill them to lose a couple CCs of combustion chamber volume. Aren't those 60cc chambers? I'd rather run a 56 or 58cc on a 302.
60 They are 60 cc, here is a thought that is bouncing around in my head, how can I increase compression, I know milling a few cc's will give it some but what about dome pistons, I have searched for some and I can't see anyway for a dome to work, the 60 cc chamber is not real big and I just can't see a dome fitting in there at all or am I missing something on how that all works?
Are you going over the river and through the woods with this entirely new roller block now? New pistons, rings, etc? You can get far more then a "few cc's" by 0 decking the block and milling those heads .040 thou(and FYI.. not that I'm suggesting it be done in this case.. but they'll take far bigger nips than that too). That should get you up around 10:1 SCR. That'll make for a fatter power curve everywhere without requiring a very conservative tune for increased margin for error. Even if you do find some smaller dome setups(nicely featured/lighter pieces will cost bigger bucks).. I'd suggest staying away from domed pistons on the street. Was what we budget builders had to do with the older bigger cc iron heads but not worth the trouble with better AL heads these days. Also consider that they'll pooch the flame fronts efficiency in the process of bumping CR with all sorts of walls and pockets. Basic porting will wake those little heads up considerably. An 82* throat cut combined with pocket porting/blending and valve guide profiling will net you 90% of most all gains to be had for this combo and also improve efficiency as well. But again.. how much is too much for a teenager considering that the new engine will already be up on power by about 40-50 horse over the prior combo anyways. Also keep in mind that roller cams also fatten up the entire curve too. And if you're power mad and want this thing to stay feeling fresh over time.. gapless rings are easily worth the extra $100 bucks over regular moly's. Plus the oil stays cleaner and they add another 5-10 horse out of the deal. Bonus. PS.. don't go overboard with cam selection. Bigger is not usually better unless you have really steep gears and manual trans(or fairly high stall) with BIG tires to even make use of it. Higher "average power" is what you'll want for the street and I'd stay under 230*. Around 222-228* or somewhere there abouts will easily pull to 6,500+ in these little motors. All of the above = around 400 horsepower.
When I bought my RPM heads I asked their tech dept. about milling and was told 1cc per every .010 cut off the heads and .065 is the maximum to cut.
Well maybe Yes I was thinking of new pistons, etc. however if the stock bottom end will make that power/compression just from milling and the port/polish work then I may just stay with a stock lower, also say the heads are good for 80 h.p. as sold, how many more h.p. do you estimate they will gain from said work?
The castings are plenty thick and the deciding factor is ultimately going to be what amount puts you into the intake valve seat. 1.90 valves are obviously more forgiving than 2.02's will be. Compression is good up to the point that you start sinking valves and destroying the short sides chamber entry which can lose flow. And IIRC.. and based on the chamber design.. I'd guess they're comparable to others and closer to .7 cc per .010 for flat mills.
The pistons will hold up with the proper tune but I wouldn't plan on those old rings holding up for very long. You could always lightly re-hone the bore and re-ring those pistons with total seal rings too. Depending on cam choice(the higher you spin it.. the more you gain).. expect around 20-30 horse increase and better average torque with the basic porting mentioned above. Might not be worth the $400-500 spent with this type of budget build-up though. The other alternative would be to just have them lay the bottom cut out via hand blending and take the extra 10 horsepower(plus slightly better average torque output) you'll get and be happy with less cash spent.
One thing to remember. Is how they test these heads to get that 80hp over stock. Its generally not on a stock engine. So, 80hp bolt on would be at the absolute best case scenario with everything perfect on the setup. My suggestion is unless you have a professional that knows port work. Leave it alone and bolt them on. I would however take .030-.040 off each head to bump the compression and unshroud the valves.
