Derek I certainly have done my share of ball honing, plasti-gauging and putting all the stock stuff back in without major machine work and ran them hard without any problems. There was a time where good junkyard engines were a dime a dozen so who wanted to put a bunch of money in a street engine anyway. I have also had cases where an engine was lost because the factory rod bolt broke. Buick blocks are no longer being given away for free and if Gary is looking at investing in a cam and head work it doesn't make sense to risk it over a set of rod bolts. So either leave the stock bottom end alone or once you go into the bottom, do at least the things needed to lower the risk of failure. For any engine, not changing out the original factory rod bolts once you have removed the rods is not good advice. I'm talking about the original bolts that were installed at the factory that have been through thousands of heat cycles and many miles. Paul
I hear you Paul,thats why I wrote that if it is done this way,"to be close to a stock configuration creation",that way the engine has a chance to live. If higher RPM and HP is the goal,to go the rebuild route.
Thanks Derek Its been fun sharing with you and the others on this thread and many of the others threads. Gary, I still think you are having way too much fun. You just need to find a 350. Paul
Sorry broze, I was elsewhere. Planned on coming back here to check on things The old days are getting further and further behind us, and we're turning into old men, and when that middle life crisis thing hits (which I think mine is), the old desires of youth and fast cars comes drifting back into the mind. I'm not as wild and foolish as I once was, but just to be on the safe side, I'd probably get into too much trouble again with a nice 455, and I liked the 350's too, so 350 it is. Not to mention practicality plays a big role: cheaper, better mileage, easier to find, etc. I realize that if I don't find a running engine, I'll be machining things and getting that 9 sprocket gear. Things are still up in the air, and my mind flits from one thing to the other so much who knows, I may hop it up a bit if I'm going to go through all the trouble anyway. I was checking out those 200-4r trannys (Raptor, I think the name was) and they look pretty nice. Choice of stahl from 1800-2800 and if the price isn't much different, that 2800 sure is tempting... But then comes the hotter cam, tighter springs, etc etc etc. Ah well.
Here are some high velocity 350 heads. http://www.gesslerheadporting.com/g...ebd9bf8032792df785256dec0059ab55!OpenDocument
Yes, I think those were the heads that went on the wild stroker engine. Wish I bought all this when I had the chance a few years back. Trying to remember the name of this fellow.... Drawing a blank right now.
Yes, it is very good. I think the usual progression was that when we were young and the SBBs (and similar engines) were new we had no money to put into them and no experience and we built our engines within our limits at the time. For most of us that meant if there were no signs of heat in the bearings they just got new shells. If the bores had only a few thousandths of taper they got a flex hone and new rings. If the valves weren't burned and weren't too wobbly they got lapped and re-used. And yes, far too many of us put in new cams and reused the old lifters, and even often got away with it. As we aged we learned and accumulated a few assets and gradually started paying more attention to the finer details and this allowed us to build more powerful and durable engines, until here we are 50 years after the debut of the SBB, doing some rather incredible things with it. I don't think that invalidates our early efforts, although it does give some perspective. Mainly that your expectations should be in line with your abilities. If all you can afford or accomplish is the cheapest possible rebuild there is still value in doing just that. Otoh, there is much to be gained by a study of the last 50 years of development, often at no cost but study. The oiling mods are a good example of that. Jim
Well, I posted this in another forum, but it's about as dead in there as all can be, so I figured I might put it in here in hopes of maybe getting some answers from all you gurus who probably visit this forum more than elsewhere. It's a question about the primaries vs the secondaries on the quadrajet. Here's the link to the forum: http://www.v8buick.com/showthread.php?263886-CFM-difference-between-primaries-and-secondaries Thanks! G
Gary, I know inquiring minds want to know:grin:, but I really don't think anyone has bothered to flow Q-jets that way. I think you would be better off simply PM'ing Cliff Ruggles, and then posting his response on the 2 threads, or ask him to post it. If anyone would know, it would be Cliff I think. What do you think?
Gary According to this article the primary flow rating of a 750 QuadraJet is 227 CFM @ 3.0" Hg I would get a second source as Larry suggested. http://www.rasoenterprises.com/index.php/technology/45-carburetion/18-carburetion Paul
Interesting article there, Paul. It appears there is no 'static' answer to my question then, as CFM is a dynamic dependent on a myriad of factors. It would appear though that the answer is actually twofold: 227 CFM @3.0" Hg, and 161 CFM @1.5" Hg for the primaries on a '750' CFM Quadrajet, with the '800' presumably 50 CFM more for each, since the venturi size change is the only real difference between the two. So from what I can gather, it's 227 CFM while the secondaries are locked into place, and once they open, it then becomes 161 CFM. I would think then that you would measure the total CFM of the secondaries by simply subtracting the 161 from the theoretical maximum of 750, to get 589 CFM for the secondaries, which is closer to a 4:1 ratio compared to the primaries. The butterfly rods for the secondaries were available in 60*, 70*, 75*, and 80* open positions, resulting in varying maximum CFM, since the rods would bottom out at those particular angles, restricting maximum air flow to better suit the demand of the engine it was used on. Buick 350's used the 70* and the big blocks used the 80* rods. The others were used for makes of engines other than Buicks. It is said that the full 90* open position is the place where maximum CFM is measured, but the fuel/air charge is better mixed at positions less than 90*. So with this in mind, the Rochester Quadrajet never really was a true 750 or 800 CFM. Using the aforementioned measurement of 589 CFM maximum for the secondaries, we can then calculate the realistic CFM @* of butterfly positions: (assuming of course that all this is correct, which it probably ISN'T, knowing my luck...but still gives a general idea) Humans love psychologically satisfying numbers. Nice round numbers. It's a comfortable anchor in our minds to reference something, such as 'that engine has 400 ft. lbs. of torque,' when in actuality it's only 399.xx @x,xxx RPM peak. Or 'that's a 750 CFM carburetor' when it's really only 728.xx max., with a variable of 689-714 CFM under most normal operating conditions for a particular combination, etc. etc. etc. (I just pulled those numbers out of my ass to use as examples, btw) So anyway, prattle aside, here's the figures @* of opening: For: 45* being closed, or 0 CFM, and 90* being wide open, or 589 CFM. There's 45* from closed to wide open, so I'll break it down into 5* increments, of which there are 9. Take 589/9=65 (rounded down for simplicity) so 65 CFM per unit of 5* open. The 60* butterfly rod gives 15* past 45*, or 3 units open: 65x3=195 CFM + 161-227 CFM for primaries = 356-422 CFM. The 70* butterfly rod gives 25* past 45*, or 5 units open: 65x5=325 CFM + 161-227 CFM for primaries = 486-552 CFM. The 75* butterfly rod gives 30* past 45*, or 6 units open: 65x6=390 CFM + 161-227 CFM for primaries = 551-617 CFM. The 80* butterfly rod gives 35* past 45*, or 7 units open: 65x7=455 CFM + 161-227 CFM for primaries = 616-682 CFM. I have read that modifications can be made to extend the 80* to 85*. These numbers aren't accurate, but give a general idea, since the number of CFM used for the secondaries was 589/161 ratio, and would realistically range from 523/227, but I'm not sure just exactly where inbetween it would be. We can also figure that the CFM will probably vary on the primaries AND secondaries simultaneously, based on the throttle position and the suddenness of the pressure drop when opening the secondaries and the butterflies begin to open based on RPM and engine demand, ranging from the 3.0" Hg - 1.5" Hg. The figures given above would be nominal, as the actual usable CFM would probably be greater, based on flow for primaries decreasing as the secondaries opening up. This is what makes the Rochester Quadrajet the ultimate carburetor, with its versatility so broad it can be used on 225 CID slant 6 mopar engines all the way up to a Buick 455 stage 1. Properly set up, it could flow as much as 800+ CFM and as little as 356 CFM with the 60* rod. Thanks for reading.
Without getting too involved with the physics here is the bottom line in regards to the Q jet 750 vs 800 CFM: - The Primary bores are larger on the 800 - The full throttle performance is aboutt he same between the carbs - The later 350 carbs are 800 and have the APT for adjusting the part throttle idle mixture - The 800 has better power on the street when just in the primaries - The secondaries are not required as often when street driving with the 800
It's not really a comparison between the 750 and 800, but the primary and secondary barrels on either. I guess it doesn't really matter, I was just curious. I would think the 750 would be better for the 350 unless you're just balls-out radical that can put that extra CFM to use. For one, you'll get better mileage with the 750, which is kind of the idea behind the spread bore carburetor. Buick engineers (according to what I read) limited the 350 to 70* max open butterflies anyway, so if you opened it up past that, there's plenty more CFM available for tuning the 750 to your needs. But from what I've read from other sources, 600 CFM is barely sufficient to feed a stock 350, so I dunno. At 70* on a 750, you'd have less than that, around 583 or thereabouts, and they came from the factory that way. A choked down 800 on a 350 would be nothing more than a glorified 2 barrel carb with a little extra at full throttle (as a stocker). The idea here was to find out what the Quadrajets were actually producing, because it's not the advertised CFM. I discovered that they have so many variables depending on application, you just really don't know exactly how much CFM they're producing because they self adjust so well to whatever engine they're on. That's just the coolest thing ever.
I was checking out carb spacers and came across this interesting design, and was wondering what you guys thought. It's basically a 4 hole quadrajet 1" spacer that has 'corkscrew' design engraved into the sides of the holes, and the manufacturer claims improved low-mid range power and better gas mileage. Anyone heard of this before? http://performancetruckproducts.com...spacer-holley-spread-bore-edelbrock-quadrajet It kind of makes sense, that it would swirl the fuel charge into the plenum. They claim to have dyno results with different models on newer vehicles using fuel injection, of power improvements of 10-20+ hp and tq. The downside is that it costs 115 bucks! G
