Well I didn't mention anything about a stock engine, but now that you do mention it...there was a racer here who tested the SP3 on his stock engine and said he slowed down. He was using the Qjet he pulled off his stock dual plane intake. I suggested to him to use a smaller square bore carb, and never heard anything back. I would be curious at those results to see how it compared to the Qjet, and would be applicable to this thread. Was the SP3 one of those three intakes tested? I don't believe it was. Apples and oranges comparison. There is already plenty of material online showing airflow dynamics using graphs... Understand that a narrower tube can move the same air that a large one can, but at a faster speed and greater pressure, up to a point. The more air flowing through the smaller tube, the greater the resistance to more air trying to be forced through, so on a naturally aspirated engine, particularly at higher elevations, this will be a limiting factor as to how much can reasonably be expected to flow through any port size. Matching the RPM band for any combination to the flow will determine the port size needed. There is also plenty of information already out there on the internet regarding this. The Buick 350 uses a tall, narrow runner which acts like '2 runners in 1'. Here's how: the narrow aspect acts like the small tube described above, with faster air speed (velocity), and the height of it permits it to flow greater volume of air than it would if it were round or even on all sides. So you get volume of flow along with velocity. If you open the runners up (even a little), you change how the runners behave. The more drastic the change, the more drastic the behavior. HOW you open them up is also a determining factor. The direction of airflow, how many curves/angles/turns it has to make, and whether or not the angle of said curves/angles/turns has been increased or decreased, all play an important role in how it will flow. Velocity will lessen while airflow volume will increase. This is ideal for higher RPM usage, since higher RPMs flow more air, and will bring the velocity back up. Larger CFM carbs can be used with these combinations because more airflow demands greater carb size. Johnny says a 650 CFM carb is about the best one for the Buick 350, even with his custom intake. This tells me that the heads of the Buick 350 are the limitation, since the intake can flow more air than this (as it does with other makes of engines). Remember that the Buick 350 iron heads won't flow much past .400 lift, even with moderate port work. You have to really hog them out to get flow up to .500 or .550 lifts, and this is pretty much the head's limit (as always, there will always be exceptions to any rule). Those aluminum heads will change things drastically, and will be a better match for this SP3 intake, particularly when the runners are ported. For now, the best bet anyone can hope for is to use a Holley DP 650 with an untouched SP3. This is my prognosis anyway. Take it for what you will. I'm in a bit of a hurry now that I've spent time here and having somewhere else to be, so I must cut it short. If I missed anything, or am incorrect/made a typo/used improper semantics, please will anyone feel free to correct it or add to it. Don't for one second think that I believe I know it all, because I'm far from it. I'm learning here too. We all are, I'd like to think. Let's put aside our petty differences and work together on this for the benefit of the community and the Buick 350! :TU: Gary
I find it interesting that so far the ONLY test of the SP3 to show a positive gain happened to be on a car running a Qjet carb That must be one magical QJET OR maybe the carb style isn't the issue after all???
Maximum lift aside, a well ported set of sbb 350 factory heads will flow close to the same air as a well ported set of BBB 455 heads, right around 280 CFM. What will be revealed with an SP3 is the CID is the limiting factor as to what CFM carb a sbb 350 or even a 355 CID engine will want without a HUGE duration cam with the SP3. And even then the engine will want to make max power at higher RPMs than 6,000. That's my prediction. Derek
You know what's crazy about this q-jet ordeal, your car ran 13.65 with this same carb the way it was. You'd think it would be good for more than one mid 13's track trip with any iron, stage 1, or SP3 without doing hardly any mods. They are too fussy of a carb for me. :grin: Wonder if you would run the same times with the stage 1 back on? Was running pretty good then everything went down the crapper.....
Im going to pull my cover this winter and replace mine, I NEVER gave it a second thought, or the wear pad not being there on aftermarket pumps anymore.
Im consistently inconsistent I know what yah mean tho, my 13.65 run was at BPG, when I did that I was "WOW where the heck did that come from?"
Just look thru the pump mount hole. Turn crank with socket, You should be able to see everything you need to see. Use a mirror if need to.
Think I mentioned to you about the Airtex pumps. I had one one my car for about 15 minutes about 29 years ago..:laugh::laugh: NOS A/C Delco's have done a decent job so far. I keep a couple spares on the shelf.:TU:
That would be an ideal setup with 8 total smaller bore barrels, delivering excellent fuel/air mixture to all cylinders. Lots of flow along with good velocity for superb fuel atomization. Damn near like fuel injection, and according to the pic, is a nice straight shot down to the heads with long runners. Gary
A lot of the problem I see here is there's a lot of conjecture (from myself too) based on memory and some information is conflicting. Could be that each combination is so unique in its fuel demand that there is no one correct generic answer. All in all though, I believe it's good to toss around ideas and try to figure things out, but again (as was said originally by Johnny I believe) more track testing is needed. So I guess that's that then. Shame all this started at the beginning of autumn and now winter weather will be around the corner with track testing needing to be put on hold. Maybe we can get some dyno runs using different setups for basis of comparison? There are some engines in the making as I type this, so with new finished 350's will come new information. Very exciting times for the Buick 350! Gary
I concour Gary! Everything from too much carb, not enough carb, more fuel, less fuel, more convertor, more gear, more engine LOL TONS to think about and very valid points and ideas, I REALLY appreciate everyones input and offers to borrow carbs:TU: Yep tis' the season for storage But it will give me time to check and critique things, maybe a lobe or two are going flat, maybe my heads are pooched, ignition wire giving up, who knowsuzzled: Im going to systematically go thru everything I can think of, CHECK CHECK CHECK, I have a lot of down time nowp
want to add one more little issue. what happens when you switch to port injection. the bosses are there for it.............
I know it's a 455, but I do like the quick and easy to change EFI tunability, plus the dozen or so other features that come with it. Going since 2009
Did a Compression test, cold engine, I know your suppose to do it on a warm/hot engine, but its raining and didn't feel like driving the GS till it got warm/hot. I just wanted to see consistent numbers. 170 psi on #s 1, 3, 5. #7 was 180 psi 170 psi on #s 2, 4, 6, #8 was 180 psi So I believe I still have an engine, and cam health is good. Had battery charger hooked up during test, and FINALLY used my 325.00 Snap On compression tester.
