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#1
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Looking for better E.T. with bbduster
My 70 BB Duster runs a consistant 11.70 on 110 octane, open headers, at 113mph. The 60ft. times are typically 1.67. I ran this weekend on 93 pump gas and mufflers and averaged 11.98. I'm looking to pick up the e.t. to about 11.40-11.50 . I 'm told i cannot run a .590-.600 lioft cam with my 10:1 compression and 3800 stall. I currently run a .557 cam. It seems i have plenty of torque but need some top end. Is a bigger cam the answer? Or should i look at longer duration? Any input will help. additional info.. 4:30 gears, 28" tall tire, muscle motors bracket killer heads, M1 single intake, 850 holley, 6pak hood, 3200 lbs. I shift at 6500rpm. Thanks for input. Motor
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#2
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You need more converter stall and a 4.56 would help.
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#3
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Call Jim Doyle at Racer Brown he'll solve your problem.410-866-7660
You definatly need at least a STX 21 bump stick, Dynamic Convertor and a Denny's Driveline. I can't believe your not blowing the 28' tires off that thing 10:1 on 93 unleaded???? How do the plugs look, I would think there's some major detonation going on in that motor. I'd love to put an EGT gauge on that motor and get a readout at the stripe..I'll bet your making 1500-1800 degrees of meltdown on that 93 Octane......another 3 Mile Island waiting to happen. Try your fuel mix at 50/50 I'll bet you get your ET back. |
#4
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The actual compression is 9.7 to1, pretty close. I don't have any detonation problems. The exhaust does smell reaaly rich, i'm using a #79 at all 4 corners. The headers are hooker supercomp fenderwells with 2" primary. I know theres more in this motor, i'm just not sure how to get it out.
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#5
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You need to make some more power as at 113 mph you wont go much faster then 11.70's. Cam change may help some. Aslo how good do them heads flow? I know Jimmy Dow at Racer brown Cams as he is right here in Balt and he has some good cams. Convertor and more gear may help some as it depends on your power band. I would be looking for more power as it neds to pull about 116 mph at least to get solid 11.40's. Good luck , Ron
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#6
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The heads are supposed to flow up to a .650 lift cam. I've been talking with Jim at racer brown. I'm working on some fuel delivery problems right now. I ran a little better this past friday on the pump gas and mufflers. 11.92 with a crappy burn out. I switched to a borrowed holley pro series 830 and it slowed me down to 12.09. I did not make any adjustments to the carb as it is not mine. The owner says he put it on right out of the box with no changes. Anyone know what size jets come on these carbs?
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#7
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I read this a couple days ago, and it has been on my mind. What would I do? Am I right in assuming that this is a duel purpose vehicle(you ran it with mufflers). It is fairly easy to build a big or small block A body that runs low 12's high 11's and still drive it. After that you get into a new bag of worms. NOS , blower, still streetable, even a tunnel ram? A Cam change isn't the answer to your problem. You have to deside do I want to build a race engine and put it on the street or do I want a race car. High tech , light weight short block, aluminum heads, race induction, big cam, high stall converter, trans brake, and a whole race car to put it in. We have all reached this point at one time, what we have is maxxed out, and you have to start a whole new program. I am there with my car right now. 10.40's and there is nothing left but all of the above.
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#8
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This may be a dumb question but have you tried retarding your timing? I gained a few tenths and 3 mph doing this. The timing i was running on the street "felt good" with more low end torque but at the strip it was a different story! I also would wonder about the flow on those heads. I would check trap RPM before swaping out gears. But it seems more like your not making top end HP.
Your combo seems pretty well balanced IMHO, I think your close--just needs some more tweaking. |
#9
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Have you tried shifting this car a lot lower? My buddys big ole "C" body runs 11.20s, has similar rear gear/tires 3600 race wieght, 9.5 compression, edelbrock heads, and shifts at 6000 to 6200 with a DC .590 cam, open 2 1 /8 headers. Something is just not right, or the car would be faster, as the parts are there. Soooo, start checking a few things to make sure everything is up to snuff, like good ring seal, cam dialed in properly, ignition curve right, proper jetting, and a cold air package that has a good smooth air entry and a very good seal to the outside cold air. Then try it with the muffs off, and see if it flys!
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#10
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I found out accidentally that shifting at 5000 rpm resulted in the same e.t. as shifting at 6200-6500. I've settled for 5500. I'm in the process of installing an aluminum water pump and housing with the lower outlet on the driver side. I will now be able to see my timing mark more acurately. I'm planning on installing larger fuel line (1/2") to assure more volume. I would like to try the .590 cam in the future. Thanks for the input from all. motor
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#11
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I can tell you right now that 6500 shifts are not going to cut it !! your way out of you power band.... with a 557 cam and iron heads your done between 5800 and 5600 rpms ...my 496 indy head motor with a 708 roller only made power to 6500.... try bringing the shift points down to 5800 and make a pass then try 5600........Lee.....
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#12
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not like this has much relevance tpo the thread but i thought it was neat since your talking about dusters.....but i saw this duster that had a 340 street wedge.....and it ran 8 sec. quarter miles.
-jason |
#13
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Cam is perfect Modification now!
Motorhead 440,
That combo is begging for a better cam! I would reccomend an Ultradyne "Tightlash" solid, with thier aggressive ramps because these give a mild compression 440 what it needs..lots of lift, both under the curve and at the nose, without alot of duration at the bottom which bleeds off cylinder pressure. I think two would work great...the 282/582, and a new split lift/split duration design specifically for heavy car/ small converter combos like yours..it's 301/309, and .591/613. There Website is ultradyne.com. I wouldn't change any else yet...pehaps later I would try a 4.10 gear. DO NOT go to a lower gear..that will only cause traction problems!! One bit of advise: Any time a car goes faster on higher octane fuel, it was detonating on the lower octane fuel...PERIOD!!! any combo, any time!! If you must run 93 pump gas, pull timing back to 30-32. |
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