Do yourself a favor and get one of these for that carb; http://www.ebay.com/itm/Quick-Fuel-...ash=item2c966e6dad:g:8zsAAOSwo6lWKomK&vxp=mtr No more messing with springs and diaframs that rip every other time it is taken apart and put together! I swapped to one of those and NEVER looked back for my vacuum secondary Holley 750 because it works so good, and I paid $40 for mine! GL Derek
Mark, Never seen anything good with that K/N filter top.. the best you can hope for there is no difference.. Seen it screw up several carbs on the dyno, I was as surprised as anyone, as it looks like a great idea. My suggestion is to run no air cleaner at all. If you must, then run your stock one, with a 14" top from one of those cheapo chrome air cleaners. That will support 600 HP. JW
Jim, you have to remember I have an L88 Corvette drop base cleaner. (Sits very low, chokes it off), The chrome lid is very close to carb top, so maybe I'm thinking the filter top opens up some breathing....
No worries, Mark. It wasn't aimed at you, I was just speaking in general for anyone to whom it may apply. I wish you could get the Qjet to work too! I love those carbs! I just see this as a potential/probable issue with this particular engine/CID/bore-stroke ratio/intake runner design and this type of intake design, knowing what I do about airflow dynamics. A lot goes on inside an engine that we do not see, and we only get our information from our 5 senses. It'll get sorted out in time. Meanwhile, keep up the good work, and thank you for all you're doing for the community! :TU: Remember too this is somewhat unexplored territory, with some who have been here before, but with different single plane designs. You say the runners were ported. The way this intake works out of the box with smaller runners is those runners help keep velocity up and provide a harder draw on the plenum under 'normal' circumstances. You open the runners up, and you lessen the draw on the plenum, unless you raise the RPMs to compensate. You changed the way the intake works, so now have to change the way the fuel is delivered. Even with normal runner size, the plenum will be the 'weak link' in terms of velocity when used with milder/moderate combinations. Carb placement and throttle blade sizes, along with venturi sizes all matter in how the fuel/air is delivered. I discussed this to a small extent in another thread here not too long ago with carb placement. Anyway, we're all behind you on this, so you're in good hands. We're all building an information databank for the Buick 350 (or at least adding to it) with every new thing we discover and record. Imagine what the future generations will see when reading back through all this stuff (wherever they happen to read it from). Gary
Jim, I had this pointed out to me by Eric on 350 Buick Performance group, I never gave it a second thought. In the TA catalog, they show an SP intake machined for a Dominator carb, similar machining for a Q-Jet, and recommend hand finishing the roof entry to the runners for #5 and 7. The SP3 has the same issue with #5 and 7 after machining for the Q-Jet. I checked plugs 1 3 5 7 Saturday when I got home (70 mile ride) 1 and 3 were darker tan, 5 and 7 were waaay lighter tan, Im no plug reader, but there was a difference! Im wondering if 5 7 6 8 are good and 1 3 2 4 are fat or the rear is lean and the fronts are good? Would this hand finishing of the rear runners make THAT big of a difference?
Hey Gary, Take a look at my reply to Jim along with the pics of my intake runners give me your opinion on it. Thanks for the encouragement:TU: Im determined to make this SP3 RUN!!!
Steve, you're right! But I don't think K&N filter tops were even around back then. The turtle hump sounds like a great idea.
You aren't going to get even coloring on plugs driving around town simply because yoyr only using the front two barrels. And even during wot testing you sometimes have to stagger jet the carb provided its a 4150 style. I would lay port roof around a little to take the sharp edge off. Don't over think stuff too much all that math, equation , and principle stuff is fine and dandy but by no means is it law every engine is different I don't care what anyone says that's why in the world of circle track where the engines are sealed and all the same and the cars weigh the same but yet some cars just run more mph on the straight or pull harder out of the turn. There isn't a faulty intake here its just not on top of what it was designed for, put this intake on a 11.1 250 600lift bottom end and watch it pick up 50hp over the D/P
Anyone else notice the sharp edges left at the transition into the top of the runners left by the machining process for the spread bore carb That's something that will need addressed over the winter for sure. Good luck Ps. I have a very nice 4 corner idle 750 dp built by Chuck Nyetten you can borrow Send me ship info and I will send it to you. I will send gaskets to reseal it , and it should only need jetted. Just please send it back!!!!!lol Nick E.
The sharp edges on the bottom of where it was machined need to be rounded/smoothed to encourage fuel charge to follow through down into runners. The sharp edge creates a sudden turn, which can cause fuel to drop out of charge. Remember the straighter the better in terms of fuel charge direction from source (carb) to destination (valves). If you can contour the bottoms to eliminate any interruptions in air/fuel flow, this would be best. Anyone ever see those intakes that have the carbs sitting at an angle to encourage even distance runners? I forget what those were called. But there's a reason for the engineering behind it. Gary
Hey Gary, Im going to take the intake off and smooth and contour the roof of the runners to #5 #7 #6 and #8 I can reason why I didn't lose much low end torque, the air/fuel mix can make the turn, but higher rpm #s 5 6 7 8 are probably starved for fuel as it cant make the turn as easily at higher rpm as it does down low, at least that's my thinking. Foxes Den pointed out I only picked up 9 mph between the 1.8 mile and the end of the 1/4 SP3: Best 1/8 mph 79.38 Best 1/4 mph 88.90 Stage 1: Best 1/8 mph 80.51 Best 1/4 mph 98.84 Im assuming I didn't lose much low end, its the top end that isn't there. Everybody here has contributed VALUABLE info, I really appreciate it:TU:
Best way is using a bit for aluminum in a die grinder. It only needs to be done (I think) if the carb mounting pad was machined for a Q-Jet carb. Wish I could explain more, but I haven't taken my intake off yet.
Although I agree that that sharp edge should be rounded off I would not pull the intake just for that reason... Wait till the alum heads come out and do it then.
I think we are just beginning to figure this thing out. I think now Do Not cut out for the Q-Jet and maybe have it flowed then start to port it out for the intake to the head. Can that be done?
