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Old 10-27-2009, 08:56 PM
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Crazy BBC Street Engine

All I ever hear is "no replacement for displacement" so for my 70 Skylark i decided to go BBC (i know im gonna hear some crap from the Buick guys) and after months of looking in local salvage yards craigs list etc. i gave up on finding a good 454 core that i didnt have to pay through the nose for. so i bought a 638 CID short block from these guys http://www.cnc-motorsports.com/produ...58&CtgID=22998 i would have just gotten a 502 0r 572 but this engine was only 500 more bucks well worth the money i think. So my question now is what i need to finish this engine. ive got a TH400 turbo and a currie 9inch to back this thing up with a 3.89 gear. this is strictly a toy just to cruise around surprise some folks on the street and maybe bolt some slicks on to go to the track. I figure with the cubes i wont need a ridiculus camshaft, i just want to make some stump pulling tire shredding tq. so what heads intake camshaft carb etc. do i need? I do know i want to go with an aluminum heads for the weights savings. Im new to the site will post pics of my car/engine soon.

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Old 10-28-2009, 08:42 PM
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none of you guys have any suggestions for me? im thinking about going with a hydraulic cam whether it be roller or flat tappet. wont this be alot easier on valve train components in a street driven vehicle over a solid cam?
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Old 10-28-2009, 11:45 PM
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While a motor of this magnitude is far beyond my experience and capabilities, it's still fun to play "what if" with the parts choices....
Brodix recommends these heads for that displacement...
These have double springs, 0.800" lift limit....
http://www.summitracing.com/parts/BRO-2021026/
These have triple springs, 0.800" lift limit....
http://www.summitracing.com/parts/BRO-2021027/
Brodix HV2005 single plane intake mounting 1150 Dominator.
Large tube headers through the mufflers.
I ended up with a mechanical roller marine cam to get the lift I wanted to take advantage of these heads. You will want to call up your favorite cam grinder and get them to spec a hydraulic roller cam for you. Most of the off-the-shelf cams that I have access to on the DynoSim, if they have the lift I was looking for, also have timing figures for a much higher static compression ratio than you will have. Therefore, the intake closing point of the cam that I ended up using will not be perhaps the best you could use with your SCR. That fact can be shown by the rather low volumetric efficiency and BMEP of this DynoSim pull. This combo should run all day on pump gas though.
http://www.compcams.com/Cam_Specs/Ca...?csid=505&sb=0
RPM HP TQ
2000 177 466
2500 259 543
3000 317 556
3500 409 614
4000 511 671
4500 602 702
5000 661 694
5500 701 669
6000 710 620
6500 684 553
Peak volumetric efficiency 91.8% @5500
Peak BMEP 165.9 @4500

Just out of curiosity, I played with the timing events on the cam. I'm not sure you could use less duration and still get the lift, but maybe you could with increased ratio rockers. Not sure, but at least we improved things with some different timing events. I only went as far as increasing the BMEP to the point that I still thought you could run pump gas with the motor. Your cam grinder will be able to tell you for sure about that.

The timing events on the 11-745-9 are 47-83-83-47. I changed them to 44-73-82-34. Here are the results of that change....
RPM HP TQ
2000 235 618
2500 308 648
3000 383 670
3500 481 721
4000 574 753
4500 647 755
5000 698 733
5500 716 684
6000 679 594
6500 579 468
Peak volumetric efficiency 94.0% @5000
Peak BMEP 178.3 @4500
The motor peaks earlier in the rpm range due to the decreased duration, but picked up 53 ft/lbs and 7 hp. Check out the torque change at 2000 rpm's!!!!

Last edited by techinspector1; 10-29-2009 at 12:17 AM.
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Old 10-29-2009, 12:34 PM
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haha, that place is hear in my town, brookings sd. they did all the machine work on my motor and i've become really good friends with all of them. good purchase.
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