512 questions

Hello all My combos changed a little originally was going 432 now waiting on machine shop for my new 512 going to use same eldelbrock max wedge ported heads that flow aroung 315 at .700 compressions going to be about 11.5 for now when i can afford to update heads will bump to 13.0 and switch to e85 also running my ud 640 cam and a dominator going into a 3200 lbs duster with 14x32 tires couple things im worried about are the 4.88 gears even with tall tires i thinck its to much and also driveing through my 8 inch converter its a freshened fairbanks that flashed 4700 behind a fairly stout 383.any suggestions?Im thinking the power band is going to move down a bit what can I realistically expect this thing to run for carb using a pro sys dominator on a indy dominator intake.Thanks Dan

I'm running a 512 with OOTB Stealth ports, 13:1, and a solid roller cam with .630 lift. Running a Prosystems Dominator on an M1. Car weighs 3380 with me in it and has run a best of 10.39. This is with 3.73 gears and a 5500 stall 8" converter. I plan on stepping up to a 4.10 gear soon.

With your bigger ports I would imagine you would be in the high 9s. Not sure if the 4.88s would be too much, but I think your converter would be fine.

My 499 combo with large port heads, flowing about 310 unported went 9.30s at 3000 lbs. 12.5/1 compression, Methanol for fuel. Shifted it at 6800. You should be able to run the same shift points, and the 4.88 might be a touch on the high side. With rollout of 103, 6 percent slip, I come up with 7400 rpm through the traps at 140 mph. 7200 at 136 mph. So it should be real close on the gear, might need to drop to a 4.56 or 4.30. Ask your engine builder how many rpms he wants to see in the lights. If you have room, there are some slicks out there that go 106 roll out, would put you into a situation where you have lots of fresh tire, no gear change to do. A tire that will grow some in the lights like those with the 106 roll out will bring you down to 7100 rpm at 140, with 6 percent slip.

Sounds like the gear is going to be just a touch to much I do have some 33 10.50 tires I can put on it also I guess Ill start there and work my way down and keep my eys open for a 4.56 gearset

I am worried the converter will stall too high, slip too much with the larger engine. It can be reworked to tighten it up.

I also agree the 4.88 gear will be twisting it higher than desired in the 1/4 mile. I wouldn't run that UD solid lifter cam over 7000 rpm, since controlling the valves with those lobes gets tough and there is no reason to beat up the valve train. With only 315 cfm and 512 CID, the power will drop off in the higher rpm range.

Are those RPM or Victor heads?
It should run 9.90 or quicker, and that is at least 136 mph?
If/when you upgrade the heads, the mph will go up, so if you change gear keep that in mind.
RPM_ slip_ gear dia__ mph_____ rollout
7320 0.06 4.88 32.8 138.0 103.044239
7280 0.06 4.88 33.0 138.1 103.6725576
6850 0.06 4.56 32.8 138.2 103.044239
7010 0.06 4.56 32.0 138.0 100.5309649

thanks for info heads are rpm cnc max wedge ported by muscle motors that is a interesting chart figure with smaller heads should 60 like a monster and beat its oars on the water at finish line guess ill have to try it and see cn always go 1/8th mile racing this is total new car so im sure ill have much to sort think its a pretty good start what are your thoughts on converter

I have a pump gas 518 C.I. motor now, it was a 512 to start with( I changed the crankshaft from a 4.25 stroke to a 4.300 stroke to raise the compression from 9.25 to to 10.29 t0 1 I had switch the heads from a set of ported 906 to a set of MCH CNC ported Eddy RPM that flow almost the same as yours. I use a Comp Cams solid roller that is 260 @ .050 on the intake with .420 lobe lift and 266 @ .050 on the exhaust side with .409 lobe lift, 1.65 rocker ratio. The motor had a stock type low deck six pak on the Eddy heads, it would pull like gangbuster to 7600+ RPM in 1st and 2nd and cross the finish line at 6000 to 6200 RPM. It made peak HP on the engine dyno at 5600 RPM and peak torque at 4500 RPM I have switch the heads again to a set of Indy SR with M.W. ports and a Indy 400-2 intake with a single Holley 850 DP, it still pulls real hard above 7000 RPM, I have tried shifting it at 6000 RPM before but it runs the fastest shifting it higher BTW, I have ran 30 inch tall tires with 3.73 gears to 4.30 gears, the car ran the same best 60 ft. so far is in the 1.41 range on a good track in good weather Go try it and see what it likes, it will talk to you Write down somethings to try, change one thing at a time and have fun

Thanks Cab that is what I plan to do just hate not to be able to make a full pass was going to change to a 4.56 but let my buddy have those I do have some real tall tires.Been out of racing for a few years looking forward to getting behind the wheel again my 64 chevelle(yes im a reformed chevy guy) ran 10.90 in street trim this should hopefully get to low tens ultimate goal is running 10 flat heads up.

You might want to PM Maximus Wedges on the board here. He can give you some good info as your builds and cars are similar. He's running on E-85 on to small a carb, to much stall, to much gear and it still ran a 10.04. He's a pretty nice guy on top it all too. Dave

Thanks for info Dave Ill see if I can get ahold of him.....Dan