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SBO buuild questions


Guest lostboys65
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Guest lostboys65

Have a nice 68 350 block with good nickel content and I sourced a 330 forged crank. I have a set of Edelbrock Aluminum Performer headers to use on a SBO build. There was a Power Block episode where they built a SBO with about 375 HP and 410 pound of torque. I want to emulate this build (Yeah, I know-Get a BBO) and this build had SBC rods and Olds pistons. They said to use Olds wrist pin bushing to get the two things to fit. I don't understand the logic of using a connecting rod with a .927 wrist pin with an piston with a .980 wrist pin opening. It would save me some money so I understand why they suggested this but now how to accomplish it. Can anyone explain?

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Well, you'll be "bushing-down" the hole in the piston to that of the smaller wristpin size (plus applicable clearances).

I believe you mean "Edelbrock Aluminum Performer HEADS", rather than "headers" (which would NOT be aluminum, but some sort of steel or stainless steel tubing).

You can probably watch the video of that episode on the www.powerblocktv.com website. They'll probably detail such things as: camshaft choice, intake manifold, carburetor, piston choice. You'll need to EXACTLY match what they do to get the same result--period! If they didn't use the same heads, carb, or exhaust headers, all bets of matching what they did are "off".

How did you determine the "good nickel content" of the block? Casting number, date code, other markings?

Hidden over in the www.wildaboutcarsonline.com website is a "race manual" for how to make Olds V-8s perform best, circa about 1969. It might take some digging to find it in the Olds literature section, but it might give you some insight into how to make things work best.

Now, for what you might have seen on PowerBlockTV, some of those builds look good and perform great. But without the exact same thing, in a different "real world environment", the resuslts CAN vary. Also, it seems they are only worried about "numbers" rather than how it might really run and perform in a vehicle with four tires that must successfully interface with the pavement to make the car move. For example, when does the torque curve come in? When does it peak? How flat might it be? And, of course, the fuel consumption factor! For example, back in the late 1960s when Edelbrock introduced their "optimized port flow per cylinder" Tarantula intake manifold, one of their test versions didn't make the top end power they were wanting, so it was in the scrap pile . . . to be removed and installed on a vehicle and raced later. THAT manfold later became Edelbrock's "Torquer" intake manifold. Not enough top end rpm power, but plenty of "real world torque" in useable power ranges with a 2-speed automatic.

If you want to play around with "horsepower" figures, you can find several programs to generate power/torque curves with various component combinations. Seems like CompCams has one on their website? The more involved the specs you have to input, the better the program might be, I suspect.

The KEY to engine power is in the cylinder heads AND how the combustion chamber and piston crown shape (and deepness in the cylinder at TDC) interact (which might explain the particular engine's power level!) in the "combustion dynamics" area. Then "enough cam" to need and effectively use the intake manifold flow AND an effective under-car exhaust system (2.5" seems like a good size for a higher power motor, to me), with sufficient carburetioin and ignition to help everything work optimumly . . . makes it all happen.

Personally, dyno "numbers" might be good for scientific comparisons, but getting all of that power "to the ground" is really what determines how quick the car will be on a race track. No sense in having a chassis capable of putting 300 rear wheel hp to the ground (tires included) and having a 400 horsepower engine up front! Tire smoke might look neat and "powerful", but it's really wasted forward energy that "goes up in smoke".

Please keep us posted on your progress.

NTX5467

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Guest lostboys65

Mr. NTX5467

Thanks for corrections on "heads". Can't type and think at the same time. I agree with your assessment about real world results vs. Perfect World results. I have a 68 Small Block with #2 Nickel content. Not sure how to go about "bushing down the hole" or how effective this would be. The pistons used in the build are from Probe and I called them and they said the rod mfr (Eagle) would have the bushing information. I am going to call them tomorrow. I can not get anyone from Power Block to reply so I may not pursue this much further but I have the crank at the machine shop and I need to decide how much to shave off the rod journals. Thought I could save a couple of $ but may not be worth the effort. I have a 455 that I could just as easily use but I would prefer something different and I have a fortified T-5 that I want to use and it will only hold up to 400 hp which is about where this engine will top out. BTY, the dyno testing was done at the end of the video and was impressive (about 375 HP with 410 FP at 5000 rpm as I recall). Not likely I will be winding this thing up that high but I need the overdrive gearing to get my highway rpms and gas mileage back into respectable range since I have installed a 3.73 rear end posi in the car recently. Will also be fortifying the suspension with Hotchkiss sway bars and upper/lower control arms in rear. Might even go so far as tubular upper/lower front suspension. Thanks for reply.

Well, you'll be "bushing-down" the hole in the piston to that of the smaller wristpin size (plus applicable clearances).

I believe you mean "Edelbrock Aluminum Performer HEADS", rather than "headers" (which would NOT be aluminum, but some sort of steel or stainless steel tubing).

You can probably watch the video of that episode on the www.powerblocktv.com website. They'll probably detail such things as: camshaft choice, intake manifold, carburetor, piston choice. You'll need to EXACTLY match what they do to get the same result--period! If they didn't use the same heads, carb, or exhaust headers, all bets of matching what they did are "off".

How did you determine the "good nickel content" of the block? Casting number, date code, other markings?

Hidden over in the www.wildaboutcarsonline.com website is a "race manual" for how to make Olds V-8s perform best, circa about 1969. It might take some digging to find it in the Olds literature section, but it might give you some insight into how to make things work best.

Now, for what you might have seen on PowerBlockTV, some of those builds look good and perform great. But without the exact same thing, in a different "real world environment", the resuslts CAN vary. Also, it seems they are only worried about "numbers" rather than how it might really run and perform in a vehicle with four tires that must successfully interface with the pavement to make the car move. For example, when does the torque curve come in? When does it peak? How flat might it be? And, of course, the fuel consumption factor! For example, back in the late 1960s when Edelbrock introduced their "optimized port flow per cylinder" Tarantula intake manifold, one of their test versions didn't make the top end power they were wanting, so it was in the scrap pile . . . to be removed and installed on a vehicle and raced later. THAT manfold later became Edelbrock's "Torquer" intake manifold. Not enough top end rpm power, but plenty of "real world torque" in useable power ranges with a 2-speed automatic.

If you want to play around with "horsepower" figures, you can find several programs to generate power/torque curves with various component combinations. Seems like CompCams has one on their website? The more involved the specs you have to input, the better the program might be, I suspect.

The KEY to engine power is in the cylinder heads AND how the combustion chamber and piston crown shape (and deepness in the cylinder at TDC) interact (which might explain the particular engine's power level!) in the "combustion dynamics" area. Then "enough cam" to need and effectively use the intake manifold flow AND an effective under-car exhaust system (2.5" seems like a good size for a higher power motor, to me), with sufficient carburetioin and ignition to help everything work optimumly . . . makes it all happen.

Personally, dyno "numbers" might be good for scientific comparisons, but getting all of that power "to the ground" is really what determines how quick the car will be on a race track. No sense in having a chassis capable of putting 300 rear wheel hp to the ground (tires included) and having a 400 horsepower engine up front! Tire smoke might look neat and "powerful", but it's really wasted forward energy that "goes up in smoke".

Please keep us posted on your progress.

NTX5467

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The use of Chevy rods in Olds motors is done for two reasons. First, the Olds rod bearings are larger, which leads to high bearing speeds for high RPM engines and thus premature bearing failure. Second, there is obviously a much larger selection of aftermarket SBC rods in different rod lengths, allowing a variety of stroker selections to be built. Usually this is done using Chevy pistons, which requires you to carefully select rod length and compression height of the piston to get the correct installed deck height of the piston. Obviously, you also need to have the crank cut down to the SBC rod journal size; usually it makes sense to offset grind the crank at this time to get a longer stroke as well.

Obviously this requires a lot of custom machining and parts matching to make it work. Can it be done? Sure, it's been done many times before (380 cu in is a common resulting displacement). The real question is, what are you trying to get out of this build? You're talking about a lot of custom machining and balancing, and that isn't cheap. Also, you'll get a better HP return on your investment by putting that money into the heads as opposed to the short block. Olds exhaust ports are especially restrictive, and simply changing the rods isn't going to overcome that problem.

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Guest lostboys65

Joe,

Thanks for information. I am following a build by Bill Trovato in one of his books. It will be a 374 stroker. I talked to Bill today and he explained that he uses CP pistons that will accommodate the SBC wrist pin dimensions of .927. The bore is to be 4.125 and stroke at 3.5. I have set of SBC Carrillo rods that I am going to use as well. The 330 steel crank is being machined to match the reciprocating dimension of the SBC. Have Edelbrock Performer heads with roller rockers from Mondello. Have a Performer RPM intake and will be going with a 750-800 cfm carb. Full length headers and 2 1/2 inch exhaust with X pipe. 3.73 posi in rear and fortified T-5 backing up the stroker. Wanted something different and this should be interesting. I am in total agreement with your stated concerns and aware that reality can be harsh master but hoping to have something I can drive on weekends and terrorize the local Honda tuners and my buddies who all drive 383 stroker Camaro's.

QUOTE=joe_padavano;1259921]The use of Chevy rods in Olds motors is done for two reasons. First, the Olds rod bearings are larger, which leads to high bearing speeds for high RPM engines and thus premature bearing failure. Second, there is obviously a much larger selection of aftermarket SBC rods in different rod lengths, allowing a variety of stroker selections to be built. Usually this is done using Chevy pistons, which requires you to carefully select rod length and compression height of the piston to get the correct installed deck height of the piston. Obviously, you also need to have the crank cut down to the SBC rod journal size; usually it makes sense to offset grind the crank at this time to get a longer stroke as well.

Obviously this requires a lot of custom machining and parts matching to make it work. Can it be done? Sure, it's been done many times before (380 cu in is a common resulting displacement). The real question is, what are you trying to get out of this build? You're talking about a lot of custom machining and balancing, and that isn't cheap. Also, you'll get a better HP return on your investment by putting that money into the heads as opposed to the short block. Olds exhaust ports are especially restrictive, and simply changing the rods isn't going to overcome that problem.

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