THE most effective area you can massage right now would be to use your stone/carbide to blend where the bottom angle of the valve job meets the port's throat, as if you were hand grinding the throat cut of a multi-angle valve job. This area usually shows a solid 10-15 cfm gain on the flow bench...20-30 hp potential (if the air is needed). That type of improvement shows up throughout the lift range and rpm band.
Sorry to distract from the original intent of your thread, but did want to post some numbers to think about. The first two sets of numbers are from the Burek article. The last column is from the Greg Gessler ported heads I purchased here on this board. There was a comment after the exhaust numbers of w/o header flow tube. Since these results were done on two different airflow testers, the results will vary. That's why below the raw numbers you'll see the ratio of the exhaust to intake at that level of lift. The Gessler heads did use 1.92 intake and 1.55 diameter exhaust valves. My take away is that a cam with much lift over .500 doesn't get me much and the exhaust flow is restricted which would suggest higher exhaust duration than intake duration. Anything else I should takeaway from these numbers? How much would the header flow tube help the numbers on the exhaust side? [TABLE="class: grid, width: 448"] <colgroup><col span="7"></colgroup><tbody>[TR] [TD][/TD] [TD="colspan: 2, align: center"]Stock[/TD] [TD="colspan: 2, align: center"]Burek PAE ported[/TD] [TD="colspan: 2, align: center"]Gessler Ported [/TD] [/TR] [TR] [TD="align: center"][/TD] [TD="align: center"]Intake[/TD] [TD="align: center"]Exhaust [/TD] [TD="align: center"]Intake[/TD] [TD="align: center"]Exhaust [/TD] [TD="align: center"]Intake[/TD] [TD="align: center"]Exhaust[/TD] [/TR] [TR] [TD="align: right"]0.100[/TD] [TD="align: right"]66[/TD] [TD="align: right"]44[/TD] [TD="align: right"]74[/TD] [TD="align: right"]55 [/TD] [TD="align: right"]62[/TD] [TD="align: right"]59[/TD] [/TR] [TR] [TD="align: right"]0.200[/TD] [TD="align: right"]119[/TD] [TD="align: right"]93[/TD] [TD="align: right"]135[/TD] [TD="align: right"]110[/TD] [TD="align: right"]122 [/TD] [TD="align: right"]106[/TD] [/TR] [TR] [TD="align: right"]0.300[/TD] [TD="align: right"]169[/TD] [TD="align: right"]124[/TD] [TD="align: right"]187[/TD] [TD="align: right"]145[/TD] [TD="align: right"]183[/TD] [TD="align: right"]132[/TD] [/TR] [TR] [TD="align: right"]0.400[/TD] [TD="align: right"]198[/TD] [TD="align: right"]128 [/TD] [TD="align: right"]241[/TD] [TD="align: right"]167[/TD] [TD="align: right"]226[/TD] [TD="align: right"]146[/TD] [/TR] [TR] [TD="align: right"]0.500[/TD] [TD="align: right"]198[/TD] [TD="align: right"]130[/TD] [TD="align: right"]243[/TD] [TD="align: right"]176[/TD] [TD="align: right"]248[/TD] [TD="align: right"]154[/TD] [/TR] [TR] [TD="align: right"]0.550[/TD] [TD][/TD] [TD][/TD] [TD="align: right"]251[/TD] [TD="align: right"]178[/TD] [TD="align: right"]250[/TD] [TD="align: right"]157[/TD] [/TR] [TR] [TD="align: right"]0.600[/TD] [TD][/TD] [TD][/TD] [TD="align: right"]254[/TD] [TD="align: right"]181[/TD] [TD="align: right"]250[/TD] [TD="align: right"]161 [/TD] [/TR] [TR] [TD="align: right"]0.100[/TD] [TD="align: right"]66.7%[/TD] [TD][/TD] [TD="align: right"]74.3%[/TD] [TD][/TD] [TD="align: right"]95.2%[/TD] [TD][/TD] [/TR] [TR] [TD="align: right"]0.200[/TD] [TD="align: right"]78.2%[/TD] [TD][/TD] [TD="align: right"]81.5%[/TD] [TD][/TD] [TD="align: right"]86.9%[/TD] [TD][/TD] [/TR] [TR] [TD="align: right"]0.300[/TD] [TD="align: right"]73.4%[/TD] [TD][/TD] [TD="align: right"]77.5%[/TD] [TD][/TD] [TD="align: right"]72.1%[/TD] [TD][/TD] [/TR] [TR] [TD="align: right"]0.400[/TD] [TD="align: right"]64.6%[/TD] [TD][/TD] [TD="align: right"]69.3%[/TD] [TD][/TD] [TD="align: right"]64.6%[/TD] [TD][/TD] [/TR] [TR] [TD="align: right"]0.500[/TD] [TD="align: right"]65.7%[/TD] [TD][/TD] [TD="align: right"]72.4%[/TD] [TD][/TD] [TD="align: right"]62.1%[/TD] [TD][/TD] [/TR] [TR] [TD="align: right"]0.550[/TD] [TD][/TD] [TD][/TD] [TD="align: right"]70.9%[/TD] [TD][/TD] [TD="align: right"]62.8%[/TD] [TD][/TD] [/TR] [TR] [TD="align: right"]0.600[/TD] [TD][/TD] [TD][/TD] [TD="align: right"]71.3%[/TD] [TD][/TD] [TD="align: right"]64.4%[/TD] [TD][/TD] [/TR] </tbody>[/TABLE]
I would say this would entirely depend on what your goals were. If let's say, 500-520 hp were the goal based on seeing 250 cfm @28", then a 2" valve (with an assumed throat size) would have these characteristics; Induction allows peak torque of 5200+ (420 FPS), and the port would begin to choke out at 6500 rpm (mach .50) and at 7200 rpm (mach .55) would seriously limit continued power increase. (I'm ignoring the rest of the port and induction system for the simplification of this post) As you can see, a pretty big cam would be used here... well over .500" lift. I'll stay away from accusations and # differences, mainly because there can be huge discrepancies in flow benches and the fact that the correction factor can change the longer you run the bench in the room. Strategies such as the difference in swirl rpm can show 2 porter's heads being different.
Mart's picture # 2 shows an excellent example of what it should look like just prior to the valve seat.
Heads do look good Marty, Mine were done 20 years ago, your exhaust looks better than mine they must not have worked on them much. TA had someone do mine I sent to them for porting. Supposed to be 235-176.
Thanks Guy, You know who's look good without the endless hours of grinding/polishing are Steve's (Underdog). Saw them up close at his house and he only paid attention to areas necessary. It's a fine art porting heads:TU: Keep in mind my heads were done when I ran the Lunati 67003 Voodoo cam. They have some carbon buildup now, but like I told a head porter I know, "it's SMOOTH carbon":laugh::laugh:
Gary, not trying to start a fight here...The profiles allowed by a roller cam and their continual proof of performance disproves the concept of lift being wasted beyond the port's max cfm lift point. Another example would be when those heads were on a short block that was much bigger, such as Derek's stroker suggestions. A port limited peak torque would now be 4550 rpm or so (420 fps example) with 5700 rpm @ mach .50 and 6200 @ mach .54. This example would also be considered a long ways away from max effort. Peak hp rpm from 5500-6200, depending on how far you stretched the cam's events, would be quite streetable and a wonderfully responsive engine. As far as 'wasted' lift and wear, a different spring rate could be used. Thus, scaling things smaller for the stock short block would reign torque and throttle response supreme. If a smaller port and valve were used yet, the lift beyond peak flow would still not be wasted. The engine would have port limited power peaks at even lower rpms (more suited to stockish cam profiles) and rely less on swirl rpm to maintain combustion characteristics...part of what makes a Buick a Buick. The benefit to porting for mild combos has less to do with raw cfm increase and more to do with evening out the port's velocity profile (stability) and the increase in induction velocity. A perfectly sculpted port that is proportionately smaller works much better than a roughly cast one that's slightly bigger because of it's flow inefficiencies. Any time the engine is cammed in such a way that the power peaks are much lower than the induction system's capability, the engine is being starved, leaving a ton of room for improvement. Using lift beyond flow increase is one of the many ways a responsive combo is maintained, due to the physical limitations of cam profiles and the ability to meet cylinder demand. The major conflict in theory here is the prospect of the airflow-cylinder demand/valve opening curves crossing somewhere and losing depression differential (Delta P)... 'over camming'. You'll over feed the engine at the start point of the induction cycle and stop the flow long before you can do so at peak piston demand (70-75*ATDC) and continued until the valve closes. There is very little (reasonable) chance of lift being wasted beyond the head's peak flow, but there is the opportunity to begin the lift cycle too early.
I had hoped for that flavor of response. Really, the idea was to add from a perspective of having used a flow bench as one of the many tools needed to build exactly what these questions are asking, regardless of the brand. This stuff is nothing new. I'm offering that it's more than a few ponies when planned out that way. It could be 75hp+ that's designed right into the initial build. Getting longevity or streetability from things is also simple planning, albeit unfamiliar to what the general consumer is used to seeing. The Buick starts off as such a fantastic building platform, and although there is nothing wrong with stock... the final product could be outstanding, without necessarily throwing cubic dollars at trendy and new things like modern fuel and computer controls. There's no reason why the Buick shouldn't be executed as well as any other popular platform. Most of these builds are pieced together a little bit at a time and the best time to think about the most important things is when it's apart. It's rare these days to see an owner willing to start porting their own heads, just as it's rare to see any pro willing to put the time required to make it a worthwhile endeavor. This is a perfect opportunity to overcome that obstacle of $$ and the reason why some of these platforms get overlooked.
Also, speaking of higher lifts may become the norm here in the sbb section depending on what the flow characteristics of the new sbb 350 heads end up being. Just a small side track, I have another sbc build, but kind of a cool one, its a sbc 307 .060" with a sbc 400 crank that had its mains ground down, 4.0L jeep pistons on sbc 400 rods capped off with a set of 305 Vortec heads actuated by a Comp XFI hyd. roller cam with .550" in. and .546" ex. lift with 1.6:1 rockers and 202* in. and 212* ex. duration @.050" with 113 LS with air and fuel being fed by an FITech on top of an Edelbrock RPM Air Gap. http://www.crankshaftcoalition.com/wiki/Chevy_305_engine Scroll down after clicking on the above link for a flow chart of the 305 Vortec heads. The above's relevance is that the 305 Vortec's intake port is supposed to be done by .500" lift, we're going to see how that .050" overlift will help out without adding the higher durations of cams with similar lifts. :Brow: What do you think Tony? Derek
My last response you highlighted was entered before I read your post, fyi. Looks like a fantastic build! It will have very Buick like characteristics, if that could be said about it. Long stroke, high swirl port... I haven't done the 305 version of those yet but am looking forward to it sometime. There's a reason the swirl vane is there and that AFR among other more serious castings use it. Widmer caused a huge s***storm in Nascar with this strategy. Unheard of BSFC's at that time. I think a 1.940 or 2.00 valve would be better suited unless you are willing to take the entire bowl out that far proportionately...or the seats are really worn. The bigger valves shroud flow on the chamber side, even with the vortec's scooped-like chamber shape. To exceed the commonly seen flow #'s of pocket-ported vortecs require aggressive chamber and common wall mods, if you are using that large of a valve. 88-89% throat diameter works well. Don't be afraid to cut into the head bolt boss between the intake ports, volcano the VG's while you're there with large radius carbides. Leave the sealing angle maybe .005-.010" shy of the valve OD with just an edge break for a top cut (38-40* preferred). The throat and bowl need to be as large as practical. Working from the seat back up the port, you pretty much can't hog it too much to hurt anything with that much stroke and piston speed. The key to this one breathing so well and being streetable is the .300-.400" flow #'s. Whether there's better flow at that valve opening with respect to crankshaft degrees and piston position or by using a more aggressive cam profile makes no difference to the engine, other than to support Gary's viewpoint on unnecessary stress on the valvetrain. If you are looking for good pics for..."influence"...Larry Meaux bowtie and/or vortec would be the thing to search. There's lots to learn from there. The #'s I pm'd you about are achievable. Good fast flow and long stroke cures all evils with a build like that. I would normally apologize for the apparent tangent except I feel Derek's build is very relevant to the thread. It crosses brand boundaries with similar characteristics.
Sorry Tony, this is a "budget" build. Got a steal of a deal for the crank from eBay(less than the cost to have a 400 crank re-ground, let alone have the mains turned down from 2.650" to 2.450"), I have a few sets of 400 rods laying around to donate so the cost of bolts and the recon charge and wristpin bore opened up .004", and actually 2 sets of these pistons; https://www.summitracing.com/parts/uem-3238hc-060/overview/ Heads are slightly used that have already been pocket ported, factory stock size valves and will get screw in studs and will get the recommended Comp cams beehive springs for the cam.(springs bought slightly used from eBay for cheap, still like new) And the typical Vortec guide boss reduction of coarse. All cast internals, so the RPM will be limited to be under 6,500 PRM anyway so no reason to get carried away with bigger valves and a bunch of porting because the stock 221 CFM of flow @ .500" is enough to easily make around 400 HP(the quick rule of thumb, 2 times the max CFM is around the HP potential plus or minus depending on the cam) with 365 cid, even with that wimpy cam. :eek2: Haven't had the port work flowed but it is safe to say that it is probably at least 10 CFM more than the listed numbers so say around 230 to 240 range perhaps a bit over .500" lift? Its going into a truck anyway so its all about the torque with this one. I have the same cam in my '65 Impala with a 383 sbc and it works pretty good to move all that weight. In a lighter car that 307/365 with more porting and bigger valves and a better crank and bigger cam to spin it to 7,000 would be a fun driver!! I like the red headed step child the sbc 307 is, surprised the boost crowd isn't hip to this block, it has to be one of the thickest probably the thickest cylinders of all the production sbc blocks ever made! Most of them can be bored .125" over to a 4.00" bore no problem. Leaving the material in the block would make for some thick cylinders to hold in some pressure. A set of splayed caps installed and filled to the bottom of the freeze plugs and I bet that factory block would handle a butt load of boost to make 1,000 + HP no problem. And no one likes these engines because of its 3.875 bore. o No: Sorry for the side track. ou: Derek
No need to apologize for the budget build, it's a well thought out deal! My comments to budgets and pieced together combos are more to address that people have a hard time justifying spending time/money on 'old obsolete' castings like factory heads and...terrible 307 blocks (!). The ideology comes from marketing propaganda. It's funny how that architecture reigns supreme with other platforms, isn't it? The time to invest into the heads is right now. If your budget were huge, I would not do this any different. If anything, I would do more to the heads and go a smidge more aggressive with the cam. Your build has the potential to exceed the norms. You almost can't over port that one. The higher piston speeds will demand more from the cylinder throughout the induction cycle. It'll see higher VE's without such a radical cam profile. The relationship of the MCSA to the cylinder size and intended power band are why this one will surprise you. It works better here to have the MCSA at the throat (Smaller valve). There's a local using that cam with the 3.480" crank with much higher cfm heads (280) and there's no loss of bottom end. Rather than viewing the cfm as a potential torque loser, consider that when it's surprisingly higher [the engine's] than normal output is studied, you would find that the bsfc and VE curves will exceed the typical. There's a reason why the basic cfm x 2 (or so) hp suggestion carries a wide disparity... The engine's metric curves follow the velocities and relationships of proportions. You are basically building a very efficient breather! THE same thing would happen using more stroke and a really well ported top end on the SBB. Strong response and an atypical power curve. Those internals will handle 7000+ for longer than you think. The (lack of) main caps and short fill are the long term weak links. All the 400 rods I have are thicker in the beam and have the same weight as the 5.7 x's, disproving the myth that they are all thin and weak. The shorter rod will help the better induction stay responsive. VE via piston speed and a better flowing top end beats the traditional combo of a restricted top end and longer rod (needing the longer rod to help it hang on past peak hp). If you haven't used a piston like that before, you might want to use the ring gap formula for a more extreme application. Esp. when short filled, you might run into problems with ring butting prior to full warmup and temp. equillibrium. As far as your heads...if you can get away with bumping the 45* angle out a bit and re-cut the 60* and blend (or cut) to 75*, you'll be better off in every way. If I can give an example of not capitalizing on a well fit puzzle... I just did some 250+- cfm heads matched to a really big cam. The owner put a 200 cfm intake and smallish carb on because a dyno estimator program suggested ok results. (medium performance intake, no actual data) The actual dyno run showed it pulling 1.3" vacuum at peak torque! ou: It still hovers the 400 hp mark, but..... It would have done well with a much smaller cam. Or better intake and carb. Or stroker crank. You get the idea. Even that is misleading as a better intake would have showed more vacuum at the plenum. The heads however, are not going to contribute to any laziness. Good thing I didn't supply any flow sheet or suggest any power curve. As far as the OP's sbb build, the more you do to the heads the better off you will be.
Not really viewing the cfm as a torque killer, would love to stuff in 2.00" and 1.60" valves in the heads and go for max cfm, but rather I view the cost of the valves and the extra port work as a $$budget killer. The budget for the heads is the cost of the heads, the valve springs, the work to install the screw in studs, the screw in studs, machining the valve seal bosses down for more valve lift clearance and re-assembling the heads, that's it. If they want more done to the heads later then we'll re-visit that later. They claim that the max valve size is 1.94" on the intake for these but I think that is when bolting them to a 305 engine with its very small 3.736' bore size, with the 307 3.875" bore size and with this block that is .060" over making it a 3.935" bore, 2.00" intake valves shouldn't be a problem, just a bit of pre-unshrouding before machining. This would be a winter project if more power is wanted/needed, which I do believe will work out just fine the way its planned out now. Instead of all the extra work the $$ would probably be spent in a set of aluminum heads if an upgrade needs to be done anyway. The 305 Vortecs are a cheap short cut to the power range we're seeking. Speaking of unshrouding, using these heads on a larger bore should yield a bit more flow due to them being unshrouded with the bigger bore so a few more free cfm there. :Brow: Not trying to build a max effort, just a nice driver. Derek
Oh, I thought that might be misconstrued... I was intending that the casual reader might assume that CFM could be a torque killer. My bad that the context shifts from the general reader to Derek and back a few times. I am not assuming to know where people are at with their craft, just offering my perspective. I was suggesting that using the smaller valves will make your goals and budget so much easier. Verified by flowbench prior to the builds many times...the 1.940's work better until you do major work to the entire port and scoop out as much of the chamber as you can before going past the bore or having to offset dowel the heads. Think of where an LS locates it's intake valve and the shape of the chamber... The better breathing of the LS and many other heads is not just due to the valve size, the rest of the port and chamber have more to do with that. The 1.940 placed into a moderately worked port (complete with typical shop's seat work) shows better #'s due to the throat % being larger, the valve itself being less in the way, and the chamber out of the way. Even the larger, tall port alum's show the 2.020's better than 2.080's until you put serious effort into what's already mentioned. You would be trading off curtain area with a more efficient port by going with bigger valves. I see better results from trying to keep the bowl and port proportionately larger. The bore itself isn't an issue yet. It is a limiter when you max out everything else, which won't be happening here. I would keep the exh. valves small, too. Put the valve cost difference in your pocket and give them the port work instead, you'll be a hero. These current heads are capable of anything any aftermarket head is to this combination, and could easily supply a 575hp build. Maybe offer up 1/2 the difference in the cost of new heads and put it into your pocket for labor in porting. The beauty of this build is that you are making it more Buick like.
Marty, can you tell me which grinding and polishing bits you used? Where did you purchase them from, etc. Thanks in advance.
