Then if that's the case,id be inclined to go with 2.00"-1.50 valve combo Coefficient of discharge on limited port app is a good thing On this app id be thinking everything on the inlet side needs to grow sorta speak !
Since I used the heads on another project I am going to use a set that needs exhaust seats added to repair them. I don't like doing this but I've been assured by many that will not be an issue. I need to use the 72 heads with 72 over the exhaust port. The conical or beehive springs are out due to the oddball Buick 11 degree retainers and locks. Since I have the TA valves I'll use them for this upgrade. Next heads will use 11/32 valves from brand "X" that use more popular style retainer and 7 degree locks.
In process of installing the new heads and level 4 cam. New heads ended up with 53 cc chambers so my compression should go up a little to make up for the larger cam as Gary recommended. My old level 3 cam was installed 6 degrees retarded trying to get more top end but I don't think it helped. It was a torque monster. I set the level 4 at 2 degrees retarded.
Hmm. I didn't realize you had the cam installed at such a retard. While this would have raised your powerband some, my calculations were based on installing the cam(s) as they come, at 0* since there is 4* advance built into them. Ultimately this resulted in your timing being 2* retard, setting it 6* further up than 66* IVC, putting it at 72*, about where a stock cam would be. This means your 9.6:1 static compression results in a much lower DCR than 7.5:1...that alone is perhaps the reason why it didn't seem to help when you retarded it. The level 4 is also 4* advance built in, if I recall correctly, meaning you'll be sitting at 2* advance total by retarding it 2*. Are the combustion chambers polished? There are two level 4 cams listed: the Ultra Performance Compu-pro, and the Hi-draulic Hauler. Which one do you have? The former will have 70* IVC and the latter 72*. Retarding the cam 2* will put each cam at 72* and 74* respectively. You will need 10.3:1 or 10.5:1 static compression to have ~7.75:1 dynamic for each cam, respectively (if you retard it 2*). Gary
No polished chambers. Compu pro. I had retarded the level 3 hoping to gain top end power, and while it would rev to 5700 power dropped off after 5200. I blame the stock intakes long runners. I can't believe it made so much torque while being retarded. I never tried it straight up or advanced. It was hard enough to get it to hook up with treaded tires. Anymore torque would make it even tougher. That's why I tried a manifold with the divider cut out thinking the gain in top end would offset the loss of torque. However there was no gain, only loss of low end. Recalculated the original compression ratio and it was 9.79. With the new heads smaller chambers it is now 10.12
With 10.12:1 and 72* IVC, you sit on 7.61:1 DCR, so you're in good shape. Let me know what that level 3 cam looks like when you take it out, and tell me how many miles are on it. I wish I was wrong about those cams not lasting so long, because the way you describe the torque output of the level 3 makes me want to use one myself, despite the decrease in cam life. It would be very tempting! I probably won't though, but still would be tempting. I don't have a classic numbers matching car though, so leaving things factory isn't as crucial to its value. Thanks, Gary
So got the heads on today and checked the piston to valve clearance and have well over .200" on both. Pushrod length OK but would like them to be a little shorter. Pre-oiled and look OK. Go to fit the intake and guess what? Does not fit. Even with no gasket I can barely get the bolts thru the holes. I have no idea how much was removed from these heads in the past. I had .020" cut from the head deck and just to be safe had .020" cut from the intake face. They are at 53cc. Off to the machine shop tomorrow to have .025" cut from the intake.
Well, got it together and installed today. Still have the topside wiring , hoses, and accessory drive to finish. Hope to fire it up tomorrow. Was considering the head/cam swap with the block in he car. Glad I pulled it, the LH motor mount was completely ripped. Did have an issue with the RH exhaust manifold. Due to resurfacing the manifold and head face a couple times the manifold was hitting the rear locating lump on the upper block about the starter. Had to trim it down so the manifold would seal. LH was fine. Looks innocent enough.
I see your using the stock intake. Interesting . my thought is would the level 3 gain anything with the sp3 intake. Since my heads have a medium port. More so a stronger mid range(3000 and up) not to necessarily to move rpm range up as to make more power in the most useable range.
I took .025" off each side of the intake manifold and it fits. Actually the bolts were still tight but once torqued they were about centered in the holes. That manifold has had a total of .055" off each side now. Also the heads I just put on have had .020" off the intake face. That's what it took to make up for the .060" of the block and I had .020" off the heads. I don't know how much they were cut in previous rebuilds. At 53cc now they had to have been cut some. All this really makes me wonder how the original engine was designed. The spec compression ratio was not met as built. If you zero deck the block you will get the comp ratio as designed. If you cut the block that much then the intake as built does not fit. It's as if someone screwed up with the piston compression height or rod length if the deck height is at design spec. OR every part was made on the conservative side of the spec. Any other theories?
You would need to measure the compression distance of a oem piston and don't forget to factor in the .020" shim head gaskets the General used. You have to remember also that the replacement pistons are destroked with typically an extra .020" in the hole so weight and compression stays the same with the cast replacement over size pistons for balancing reasons. The "Power Forged" L2343F series of pistons were closer to the factory original compression distance of 1.852". If we look at the 340P with its 1.835" and add .020" to that you get 1.855" + 6.385"(rod length)+ 1.925"(half the stroke)= 10.165" which puts the piston .023" in the hole and stack a steal shim head gasket on that and you have .043" quench distance. Also consider that the sbb 350 rods are listed as 6.387" from some sources so if that is the case a blue printed engine would have a .040" quench if that is the correct measurement. The H644P hypereutectic sbb 350 pistons are listed as 1.800" so if you used these then it is no wonder you needed to have .060" + removed off of the deck to bring the pistons up to zero. A 1972 block if that is what you used for your build should be only up to .030" taller than the 10.188" spec. And that's my theory. Derek
You don't have to zero the deck to get the designed compression ratio, as the pistons (the true factory ones, not aftermarket "OEM" pistons), had higher compression height. Also, the figures for calculating compression and clearances all around the engine were based on prototypes of production engines, which ended up being different. The "on paper" specs and even the power ratings were way off from what the actual engines ended up being, which is why blueprinting (or as close to) the engine will net such huge gains, even stock. The head design was also not intended to flow like a chevy head, and is most efficient between .300 and .400 lifts, though heavy porting can increase this up to and slightly beyond .500. This is where a lot of confusion and disbelief comes in as to how and why camshafts work, and why everyone rags the stock cam when in actuality it is ideally engineered to suit the head flow, even with moderate port work (as long as there is no excessive material removed, which changes the engineering intent and design). Hog the heads out and you kill the low-mid range velocity, so you have to rev it up to get more airflow and get the velocity back up, but then the heads won't flow the same way they did compared to the original engineering intent. It will become a different engine altogether, and if nothing is done to the rest of it, who knows how the engine will end up behaving (or lasting). People do this with good results though, but only if you put a camshaft in to match the head flow design. You can't guess at it if you want your engine to perform optimally. Porting heads to flow beyond .500 lift (which you have to do to get big flow numbers), and then using a small(ish) cam is a mismatch and won't perform optimally. All this becomes moot if the heads are ported improperly (and they are not chevy heads, so different techniques are needed), which results in the heads becoming boat anchors. Build the engine like a chevy, and you'll end up with sub-par chevy results. Better off building a chevy. These engines were made on the conservative side to say the least. Engineered to last a long time and even survive several rebuilds, excessive material was added to decks and heads to accommodate future machining. Ever read the official Buick 430 engineering release notes for the engine when it was first designed? The specs were all over the place. No one cylinder was even close to having the same air flow or compression, and the engine's power rating was less than what was 'on paper' or advertised. Probably as a marketing ploy, or a 'guestimation' as to what the engine would actually do if put at those specs. But they weren't as powerful from the factory as the 'on paper' rating suggested. Rated at '10.25:1' compression, the engine actually had an average cylinder compression of 9.4:1, with some as low as 9.25 and others as high as 9.75...and still managed to produce about 340ish of the claimed 360 factory horsepower. I suspect this is the same for other mass produced factory engines as well, including the Buick 350. They come from the factory with less than the advertised power (and compression), but if blueprinted, will have well over what the 'on paper' ratings suggest. I guarantee you if you were to dyno 100 different engines that came off the assembly line, you'd have 100 different power ratings. Some would blow up at 6000 RPM while others will hold together at 6500. There's always going to be defects and some that venture outside of the spectrum of 'normal', on both ends (low and high). Nothing is so static and carved in stone (or iron, in this case), so to speak. Things are a lot more dynamic in the real world. For real world street use, very little beyond original factory engineering is needed (working WITH the engineering instead of against it), keeping the head flow characteristics similar to factory with slightly better flow and improved velocity while removing airflow turbulence. But doing this still doesn't change much the .400 lift limitation of the heads. Sure they'll flow past .400, but not much. Only a few CFM are gained from .400 to .500, and from .400 to .450 maybe one or two CFM are gained. The ONLY reason to bump cam lift beyond .400 is so the lobe stays in the 'sweet spot' zone of .300-.400 for longer periods of time. Making the lobe open faster and close slower also allows it to do this, only with less lift, making it easier on the entire valvetrain. (Increasing flow numbers up to and beyond .500 lift changes the engineering intent and creates a different engine) This will increase power beyond the factory results without decreasing drivability and will help the engine last longer than a few oil changes. It's not complicated. Keep lifts within a reasonable area for longevity and keep unnecessary overlift to a minimum, while putting the durations and lobe centers where you want. Less spring pressures will be necessary to keep it all stable and you'll have a cam that lasts much longer than your typical symmetric performance camshaft. This is especially true for flat tappet designs, but even holds true for roller cams. Break on through to the other side. The old camshaft paradigm is defunct. Embrace the new paradigm. Gary
The object of the game is to cram as much air/fuel into as much displacement as possible, when all that is desired is performance. When other things are desired, such as drivability, longevity, and fuel economy, other factors must be considered and weighed into the equation. The end result? The Buick 350's original engineering intent. The Buick 350 is king of the mid range powerband, with strong low and upper-mid RPM accents to compliment the broad RPM spectrum, from around 1500-5000 RPM, with its strongsuit concentrated between 2000-4500 RPM. The Federal Mogul CS647 camshaft is engineered to satisfy the engine's ideal powerband intention. To improve power within this RPM band, blueprinting techniques are required, which include head flow/velocity improvements, increased compression and compression ideally matched to the camshaft's IVC point, and improved air/fuel and exhaust movement/evacuation, the details for which have been explained elsewhere on this forum by yours truly and others. Suitable rear end gear ratios would range from 3.73 to 2.73 (ideal ratios would be 3.42, 3.23, or 3.08), with a 2000 RPM, high torque multiplication stall converter. Gary
Yes, I have it from the horse's mouth that they intentionally left plenty of room for error in production engines. You see this everywhere. From pistons .050 in the hole, to ridiculous .380 lift camshafts. Eliminating this "fat" and tightening up the engines specs and optimizing parts is what hot rodding is all about. They did test production engines for rated output, and those were the published specs. These were not "blueprinted" engines. For SAE power tests, they were allowed to block the heat riser in the intake, and correct everything back to 60* dry air. JW
Ironically, pistons sitting below deck and stock camshafts are not the problem... At least not for the small chambered, low lift flowing head Buick 350. The only real problem is the specs being all over the place, as is with other production engines and can be easily remedied with proper engine building techniques, dependent on engine application and desired outcome. Gary
