I FINALLY GOT THE CAR ON THE ROAD IT IS A 302 INTERNALS UNKNOWN MY QUESTION IS THE CARB SEAMS TO BE TO BIG I THINK .......ITS A HOLLEY 750 WITH VACUM SECONDARY`S SOMEONE REMOVED ALL OF THE MECHANICAL CHOKE SET UP,THE MOTOR RUNS STRONG I HAVE TWEEKED IT AS FAR AS I CAN GO WITH OUT GOING INTO IT AND I STILL THINK ITS TOO BIG THE MOTOR DOES HAVE A LARGE CAM IN IT I CAN TELL THAT MUCH,WELL PUT IT THIS WAY I HAD A 588 LIFT CAM IN MY 355 CHEVY 68 CAMARO AND THIS SOUNDS BETTER.. IT JUST FEELS LIKE IT HESITATES WHEN U STAND ON IT. CAN I JUST JET THE CARBY DOWN OR WILL I JUST BE WASTING TIME, SHOULD I GO TO A 650 DUBBLE PUMPER. I DONT KNOW HOW TO WORK OUT THE STALL SPEED ON THE CONVERTER,AND THERE ARE 355 GEARS IN THE 9" REAR,ILL BE GOING TO 411 GEARS OVER THE WINTER AND PROBABLY A 3000 STALL UNLESS SOMEONE RECOMENDS SOMETING ELSE .HOW DO U WORK OUT HOW MUCH CFM THE MOTOR NEEDS..THANKS BARRY
Turn your CAPS lock off! There was a good article in last months issue of Popular Hot Rodding. The part about boosters is online. Good reading http://popularhotrodding.com/tech/0511phr_carb/
650 DUBBLE PUMPER sounds better but what rms are you turning ??i would say 6k under rpm a 600 dbl pump should do real nice
750 vac is about right, either that or 650 to 750 DP. If the vac carb hesitates on top, then you might have the wrong spring in the secondarys. If they open too soon, you will get a hole in the top end. If they don't open at all, then the engine just runs out of breath quickly, but no hole. You get the same hole if someone put a screw or something in the secondary linkage to make them mechanical. Without the second pump (double pumper), a mechanical secondary just causes a huge hole in the running until the secondary metering system can kick in. Don't mess with jets unless you KNOW that is where the problem is. You could also have issues with the squirter. Good luck Dave
I have to disagree. I have seen a 289 with a single plane, lumpy cam, and 3000 stall pick up ET and MPH by going from a 750 DP to 850 DP. 2 of my 302s also ran their best with a 750 DP and very mild single plane intake. Changes to many different carb and intake sizes/brands were all inferior. Both engines were very different combos as well. The formulas that you see for carb sizing are minimum cfm needed and they don't take into account many variables. On top of that, the sizing chart was concieved 4 decades ago and street car tech now was exotic race tech back then. Also, when you consider the 750 vac, the front 2 mechanical barrels are the same cfm as a stock 2v carb. Then the rear 2 are only called upon at the engine's descrestion when the carb is adjusted properly. Really it's a case of can't over-carb. Dave
glad it works for you dont see how you can adjust it right ..you must have the mix screws all the way in but like you said many variables...i know on my 393w 11.25-1 comp i have a 825cfm and need to jet down a size ..would not know that if i had dumps on the mufflers ..would not get the black crap on the rear of my car
Personally I think people fall into that bigger is better attitude with carbs and cam. If you are going with a Holley you can get by with 750 or 780 I ran a 780 on mine to see how it would do. It did ok. However my 625 Demon had better throttle response. I played with both and have the experience, know how to read plugs and race to prove the improvements. Demons are wet flowed Holleys are not. A 575 speed Demon is good for a mild street strip set up or a 625 Road Demon. For racing a 650 mighty demon works awesome. In Daves Case(maverick Grabber) he needs to Jet down, more than likely he would have gotten by with a 750 mighty Demon. What I like about the Demons is they are very specific in their useage. They list suggested Cam Specs and Comp ratios. WHen I up grade my cam this year I will be steeping up to a mighty Demon as the Road Demon will not be enough for the big Cam.Down Side to Demons, before running it buy a Barry Grant rebuild kit. They tend to come with machining residue inside. They know it's a problem I have talked to their Tech Guys many times. Good Luck Have fun
i have a holley 750hp on my 308. use 73 and 79 jets. only adjusted the idle and changed the jets right out of the box. runs good. i turn 7200 rpm at the top end.
That sounds just like my 750 DP... 74 front, 79 rear, 31 squirter front, 28 rear, 330 cams #1 in position 1. I will always remember those numbers, I tried others many times and always ended up back in the same state of tune. The engine turned up to almost 7k. Dave
You said 'internals unknown'. If you have aftermarket heads, lot of compression, lots of bump in the cam, the 750 may work fine. If not, 600-650 is probably correct. As the mechanic with the blue Mav above stated, most people oversize cam and carbs. Here's an interesting note. A Hi-Po 289 as installed in Falcons, and Mustangs in '65/'66/'67 with factory installed solid lifters, used a little old 480 cfm Autolite 4V carb. Shelby added a bigger Holley. But Ford got 271 HP out of the factory Hi-Po version of the 289 with 480 cfm's. Seth
Here Is What I Know It Is A 302 With A Edelbrock Torker Manifold,1"spacer Under Carb,mallory Unilite Distributor,heads Are Iron, I Think I Can Remove The Valve Cover And See A Casting # If That Helps..long Tube Hedders And A Big Cam It Runs Good After The Inital Stumble And It Stumbles In Any Gear When You Hit The Throttle But Only At First Then It Opens Right Up.........thanks For All The Info So Far..barry
I called Demon with my specs and the 750 Street Demon works GREAT on my built 306. I had the same stumble you are talking about with a 650 worked over Holley, stumble is long gone with the Demon. Todd
Sound like the accel pump linkage could use some adjusting, or you might experiment with squirter size. These are the things that affect tip in performance in every gear. Edit: Unless you are opening the secondarys manually or are running too loose a spring. If the secondarys are not properly adjusted, they will open too soon and come 'crashing' in and cause a hole in acceleration.
Ratio, I'm in Pensacola to and I have a few issues with my carb...or timing. I just replaced the plugs..gapped to .32, Holley was just rebuilt and fuel pump is new. Things were great until it started getting cold. Those few mornings when it was REAL cold. Tried starting the car for an hour and it finally came oo and it was fine. I then said the hell with it and replaced the holley with an edelbrock. The edel (right out of the box) took an hour to start the car. Now I see it's not the carb so I will be taking the edel back. I have the holley back on and it stumbles on acceleration now. Maybe the plugs are gapped wrong. Timing is set to 10. Before I replaced the plugs and points, the car would burn in 1st and 2nd from a dead stop. NOT now. Is it as simple as the plugs? Vaccum is steady at 18 from the manifold.
