Looking for opinions on this. I am looking at the ones with 1.90" valves for 289/302. I know the AFRs have 58cc chambers and the Es have 60cc. Can the Es be milled down to 58cc?
Most aluminum heads will easily allow upwards of 70-80 thou of milling. You can go even higher at upwards of 120 thou with angle mills. The AFR's are far superior to the Eddy's if you're looking to keep going with heavier mod's to move beyond their out or box potential. Otherwise.. they'll both make similar power on milder builds. Personally.. I'd spend the extra few bucks on the AFR's. Plus.. I'd still mill them to get to about 52-54 cc's(20-25 thou should about do it).. and enjoy the extra snap that compression jump brings with it.
No way it will cause issue with mild flat milling. Only when you get to around .050 thou and above.. or angle mill.. does it become a concern. But even then.. usually you can get away with just milling the block mating surfaces of the manifold since they can get pretty tight. Personally, I just use a body file with really coarse sandpaper to work the end rails down a bit and try to shoot for about .030-.050 gap for minimal amounts of silicone. But it takes far more than .020 mill to have to even worry about it. The slight gain you get from moving the intakes port upwards on the head is just a bonus. Of course.. port matching them up with the intake being about .010-.020 thou smaller than the head is best though.
I don't get your reasoning here. Milling lowers the port in relation to the block deck, thus lowering the "line of sight" into the cylinder, which in theory looses power. Still all in all, the amount's being discussed here don't amount to a "hill of beans" in regard to power gains. He also needs to understand that excessive milling also requires enlarging the intake bolt holes as well, actually this is more important than the intake milling is. The bolt holes are moved closer to the block's centerline after milling, thus the need to compensate via the bolt holes to get the intake on afterwards. I milled my Canfields .060, and on the first block they went onto, I had to mill and enlarge the intake holes (Vic Jr) on the second build they went on, nothing other than enlarging the bolt holes was necessary to get the intake in place and lined up (repop 3x2)
In theory yes.. but in reality there are small gains can be had on flow benches mainly because the line of sight of the intake as it transitions into the head is even more important because most entry level heads port floors(and even the pro's) have reduced airflow compared to the roofs. This is usually done purposely to maintain higher air speeds and therefore keep fuel in suspension a bit better. Unfortunately.. when you start cam'ing and increasing upper rpm airflow requirements.. the air moves too quickly at the lower portion of the floor and actually sheers past the short side and smashes into the far side of the valve bowl and causes turbulance. Which reduces flow and causes even more lopsidedness of the flow curtian coming around the valve. So, the higher the intake is mounted.. you can increase flow up top of the heads port as well as allow for an easier transition around the short side corner as the meat of the air column now rides higher in the port. This easily overshadows the lowering or "squashing" of the head to the cylinder since you can still improve the short side flow. Of course.. it's far better to keep the port tall off the cylinder and do the necessary short turn work while simultaniously reducing floor air speed to allow a better short turn flow number to gain a more uniform flow curtain around the valve head.. but that's far from necessary at this build level. But yeah, no doubt.. at that amount of mill.. hardly worth worrying about the need to enlarge holes or gaining 1-2 cfm of airflow. It was purely a mention of another bonus to milling the heads. And FWIW.. I never enlarge the entire hole on an intake. I just slot them like you would the pushrod guide holes on a cylinder head when running high lift cams. But.. some people just drill those out too since it's often quicker and often self aligns the bit. I just learned to use die grinders far more than drills when building motors. But hey.. drills work great for wet sanding and polishing valves. Flow bench's probably won't see the gains since shape is far more important than finish.. but they sure do stay nice and clean. PS. and why you gotta pick my posts apart? I didn't even say anything when you posted about higher ratio rockers increasing seat to seat duration. LOL I just tease a lot.. so no disrespect intended.
I'm not picking your thread apart here, only questioning the reasoning behind your implication that milling the heads, raises the port roof(that still doesn't make sense to me) and increases the airflow. But All in all, the gains you implied are probly no greater than the supposed duration gained from higher ratio rockers. That's a minor benefit of using the higher ratio rockers, there's far more gained in the reduction of friction via the roller trunion and the increased lift at the valve. So we're even there. As for the bolt holes in the intake, I'm with you there on enlarging the holes via grinding vs simply drilling the holes bigger.
I think what groberts was saying is that when you mill the heads it lowers the ports closer to the deck so that the intake actually mounts higher on the head/intake ports. And I may really regret commenting on this part but higher ratio rockers don't change duration. They change how quickly the valve open and close and the amount they open so in a sense the valves are open higher for longer but no longer seat to seat.
exactly the point. and that is absolutely correct in regards to the valve timing changes from higher ratios. You get more "area under the curve".. as the accelleration is increased to and from the seat.. but final seat to seat timing/duration spec is unchanged. It gets trickier the higher the rocker ratios go thopugh.. as the springs seat/open pressure have to be increased a notable amount to keep things under control if the motor gets spun hard. I have 1.8 intakes and 1.7 exhausts on my 385 Chevy and it's all my Manley Nexteks 165 lb seat pressure can do to keep up with my comp cams extreme energy street/strip profile(which is already an agressive lobe on/off the seat with stock ratio rockers). 8mm valves and Ti retainers help.. but you actually can have too much of a good thing and I may drop back to 1.7/1.6 since the gear swap a few weeks back has my rpm range broadened more than I would like. The extra low end grunt sure is nice to play with on street tires though. Now it feels like it has 600hp instead of its current 500. lol
For anybody who is following this, higher ratio rockers have the effect of making the cam more aggressive by opening the valves quicker which is a good thing for power. Different ratio rockers can actually be used as a tuning tool. They won't change the cams duration or overlap though so it shouldn't effect vacuum or cylinder pressure. Actually it may effect cylinder pressure a bit because the cylinders may fill better. But it "shouldn't" effect idle or low rpm much. Am I close groberts?
no.. I knew that and only teased about it. I usually say.. pick away.. since that's how we all learn something new everyday. Proper logic is hard to find these days.. and even harder to understand at times. And I'm such a cynical pessimist at times.. that I can't even see the obvious as I pick it all apart. lol and yeah.. that's about the size of it. A little here.. and a little there can all add up to measurable gains in the end. As I mentioned above.. all you're really doing is moving the intake port up on the heads mating surface and aiming the smaller intake ports air column a tiny bit higher in relation to the short side radius. Once you port match the manifold to the heads.. the effect of moving the air column up is lessoned since you're allowing the air column to drop towards the floor as you remove material to get the ports matched up. Another benefit of when the manifold sits a bit higher on the head.. is that manifold designs that have sharper turns off the floor can remove extra material off the bottom of the port to get things all matched up and that's usually a good thing since you can end up with a nicer/longer radii. As I'm sure you well know by now.. it's usually always better to raise the intakes roof.. than lower the floor and needlessly increase the CSA at the heads entry point just for the sake of matching things up. But.. when the radii at the bottom of the intake ports floor(as it turns down to the head port is improved.. quite dramatically with some sharply transitioned port designs).. the head can pull and scavenge more freely from the intake as a result. Especially at high rpm's.
Idle will be unnaffected and it won't affect static compression.. but dynamic compression can and often does increase as the cylinder can more effectively draw air at every intake valve event. When you get too crazy with the ratios in comparison to the lobe design of the cam(aggressive ratio + aggressive lobe).. it is possible to over scavenge the exhaust and lose some.. or all.. of the gains found on the intake side, though. Can be pretty tough on valve seats too. That's why many with decent exhaust ports and split pattern cams will only increase ratio on the intake side. To do it right and make the most power for a given cam/engine design.. it's usually best to have the cam ground for the rocker ratio intended to be used with it. But if the cam is less than ideal.. and most off the shelfs will be less than.. there is usually some aditional power to be had with higher ratio intakes.
Per Edelbrock, milling the Performer and RPM heads, each .010" gains one cc and you can mill a maximum .065". I have the 60259 RPMs and used to have AFR 185s. The Edelbrocks are ok for a budget head and well built with helicoiled bolt holes, but the AFRs are a way better design with a better valve components and make more power.
This is what he left out of the explanation. You get an A+:Handshake Both in effort and keeping it short and to the point.
lol.. didn't think I needed to point out the obvious geometry involved there. and that's where all the hubub came from about the manifold flowing more air towards the roof. Hence.. lower heads with higher manifold still equals positive airflow gain in most cases.
