My folks have 1973 Gran Sport, 455 Stage 1 Buick that runs 13.70's on street radials, and 13.30's with B.F. Goodrich Drag Radials in the quarter mile. MPH is just shy of 100 mph (99.8) with the street tires, 100.5 or so with the DRs. Where is my MPH? Here are the basic specs, and what I have done to try and solve the problem, if there even is one. The car weights 4400 lbs with me in it (I need to diet, but not that much!). .030" over (Buick) 455 with 9.1:1 compression and Gessler ported Stage-1 heads. Lunati ground flat tappet camshaft, 224 Intake, 230 Exhaust, .480" lift on a 112 L/S. Installed at 107 L/C. 800 CFM Holly DP, Edelbrock B4B with 1" open spacer, 1 7/8" shorty T/A headers and a 3" X system into 2.5" Dynomax Ultra-Flo mufflers and full tailpipes. 3.42 gears and a Turbo 400 with a 2600 stall ATI Converter. Ive picked up a tenth and 1 mph with the following: 1) Dropped the gas tank, tossed the nasty, 30 year old sock, installed a big filter and electric fuel pump to feed the engine mounted one. Ive checked the fuel feed and it puts out plenty of volume. 2) Tossed the older Stinger S4 and installed an MSD box with a new MSD billet distributor. Timing is 16 degrees initial, 35 total, all in by 2500 rpm. The car runs awesome. It starts with just the touch of the key, idles well and throttle response is incredible. It will shred the rear tires from a 20 mph roll. It has pulled away from many fast cars from a 45 mph roll... so all is well, except for the MPH at the track. It pulls hard to 5200 rpm in first and second, but seems to drive out the last couple hundred feet at the track in third. The engine is turning about 4600-4800 rpm through the traps. Each change we have made (shorty T/A headers, upgraded fuel and ignition system) make it feel even stronger in the mid-range and the 60 foot and 1/8 mile numbers improve a bit, but doesnt translate to better numbers at the end of the quarter mile. I am thinking along three lines: The carburetor is too small, the camshaft is too small or I am running through the converter at the top end of third. Any thoughts? Thanks! Dave
That's about the same mph my 71 GS455 used to run with 13.4's and 13.5's on sticky tires - very efficient 1/4 mile car. It had 5300 rpm shift points, probably less power, but a couple hundred less lbs. Only a few times did it see over 100 mph, and was usually 98.X or 99.X mph.
I have a 73 Regal that had a mild 430 motor that started out at 13.6 and after some changes to the motor, body, and suspension the best was 11.74 at 114.26 MPH. That motor was only 9.5 compression. I have now replaced the motor due to need for quicker E.T.s. My car also started out at 4100 Lbs but I put it on a major diet. If you would like to talk firther feel free in sending me an e-mail.
What are your 60 ft times? Your set up could just be slow off the line.i think that is a good time for a 3.42 geared 4400 lb car with 9 t0 1 commpression, so far the best i have got is 12.2's at 110 mph, 1.7 60 ft ,with my GS, i am 500 lbs lighter, 373 gears and a 332/346 cam, 11 to 1 comp. and run the stock fuel system with a stage 1 pump and 800 Qjet, recurved stock point distritor with electronic modual. i do have ported S1 heads, SP1 intake and 1 7/8 headers with a 2 1/2 system, 4000 S/P. hope this commparison helps.
What are your shift points? Experiment with them. I had a 224 - 234 @ .050 duration cam in my 70 455 4 speed convertible with 9.2 compression, small valves, stock manifolds and 255-60-15 radial tires. I was running 13.50 @ 102 mph shifting at 5300. I lowered my shift point to 5000 and then 4800 and ran 13.20 at 105 mph. I gained 3 tenths and 3 mph by experimenting with shift points. Each combination is different and each tach may read a bit different so experiment in both directions from your present shift point to see what works for your combination. I drove a 71 W-30 442 Olds for a friend. I did the same thing and dropped 2 tenths while gaining 2 mph by lowering the shift point to 4800. This car had a 224-234 cam with 8.5 compression.
Don't know but when I took my 850 CFM Thermo Quad off my 455 and installed a Osbourne 800 CFM Quadra Jet I lost 1 1/2 MPH in the quarter but the ET remained the same. What I gained was better idle, better fuel economy, better starting, and better part throttle operation. So my guess is not enough carb. Dave Berry
dave, when i raced mine, 4spd, nhra g/stock, i ran 13.2 at about 100mph. blueprinted motor, 4.56 gears and 29" tires. went thru the traps around 5800-6000. your in the ballpark with what you have. john
Thanks Guys! The car 60-footed 1.90 and 1.88 with the drag radials, and fairly consistently at 2.15 with the street radials. I can probably leave a little harder, as I haven't spun the drag radials yet, but I have only a pair of passes on them. The car does have Southside Machine Lift Bars. As you can see by my post total, I do a lot more lurking that posting - esp. considering Ive been a member here for almost three years - but I really appreciate all of your input. Unfortunately, a cam change probably wont happen as my folks are pleased with the way the car performs its mostly a street cruiser but I do think I am going to try a bigger carb and possibly a set of 1.65 rockers. I like the idea of the shorter shifting, as the reason I went through the fuel system in the first place was I thought the car was laying over in the top half of third. I am also going to be checking the valve springs, to make sure they still have the proper pressure. Thanks again guys, its good to know the coconscious is that I am not far off, if at all, with the combination in the car now. Edit: I forgot to mention - the car shifts at 5200 rpm 1-2, and about 5100 2-3. Dave
Dave, If you are currently running the 1.55:1 lift rockers (stockers) and lift is .480 with them, your lift with 1.65's will be around .511. That's too much for a stock Stage 1 spring, if that's what you're running. You may want to take that into consideration. What valve springs does it have right now? A 1.88 is decent, although you may have a little more in it. You may be able to bring that down a bit and cut your ET's too. But that may not have much of an effect on your mph.
I'm going to have to go through my papers, but the springs are from Lunati, to match the camshaft. I agree, they might not be enough for the 1.65 rockers. Thanks! Dave
according to the holley carb size calculator ( http://www.holley.com/HiOctn/ProdLine/Products/FMS/FMSC/FMSC.html ) 800cfm should just be sufficient for a worked (headers, porting etc, assume at least 85% VE) motor. specifically, they say you should have an 818cfm carb to run 5200 but i think i'm lowballing your VE.
Think John might be right on about your speed. I remember seeing on a suspension website that a properly set up NHRA stock type car that runs 100 MPH should run about 13.30 ET. So maybe your suspension is working so well (ETs)that it only seems that your MPH is slow. Dave Berry
i still feel your car runs good, i think you need more gear and stall to get out of the hole quicker, with your heavey car, unless you run alot more commpression to get more low end torque. a 800 CFM carb is all you need for 5500 rpm. i shift at 6500 some times with a 800 qjet and it still is pulling hard. if you went to a bigger cam you would get even slower 60 ft times and you would never make it up. just my 2 cents
2 points, 1st, i never had traction bars. car would hook no matter what the track condition was. strange car, only time it would run right was on sunday. would get my butt kicked the rest of the week!! 2nd, most of the stk or s/stk would/do run tall gears and tall tires. everybody here runs h/way gears. whats the theory??? john
