Gen 5 BBC Shortblock

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RevTheory
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Gen 5 BBC Shortblock

Post by RevTheory »

Hey fellas, I'm interested in the rpm and hp capabilities of the stock bottom end of a Gen 5 BBC. Also, are the factory hyd/roller lifters ok for your average Xtreme Energy, Voodoo style lobes in a 6,000 rpm, street build, depending on your comments regarding the shortblock?

I've kind of set the rpm limit based on not being able to get the compression ratio up enough to justify the duration needed to go beyond that. Life blew the hell out of the 496 plan but he's got a Gen 5 out of a motor home sitting in the garage with 20k miles on a rebuild (oh boy...) so now it looks like a top end/cam build just to get the damn car on the road.

Anything funky about the bottom end that would screw that up?
69top502
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Re: Gen 5 BBC Shortblock

Post by 69top502 »

Same block and bottom end I started with. Blocks are as strong as any standard MKIV or GenVI block. I believe all GenV’s are 4 bolts with forged cranks. The 502 blocks have the Siamesed bores. My GenV was not a roller block but did have the .300 inch taller lifter bores which are great for running a roller. I would think this would take anything you could throw at it at your intended rpm range. Oh and as a heads up, the GenV’s didn’t have clutch ball stud bosses or a provision for mechanical fuel pumps, and may need special head gaskets depending on the heads you run.
69 Corvette, 502 w/ solid roller cam, 653 hp Street/Strip.
RevTheory
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Re: Gen 5 BBC Shortblock

Post by RevTheory »

Right on, thanks!
rustbucket79
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Re: Gen 5 BBC Shortblock

Post by rustbucket79 »

If you're planning on using the shortblock "as is" make sure the intake valve reliefs are large and deep enough to work with your chosen heads and cam. Factory 454 cranks are cast and somewhat weak, but ok for a budget build.
RevTheory
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Re: Gen 5 BBC Shortblock

Post by RevTheory »

"As is" is the plan. I'm eyeballing Edelbrock 454-O heads with 100 cc chambers and 2.19/1.88 valves. He's going to pull the intake off when he gets back to see if we're dealing with a roller or flat tappet cam.

Damn, PTV on a stocker from the 90s is probably the last thing I thought I'd have to worry about. Off the cuff intake lobe probably 224 to 227* at .050 on a 103 intake centerline and 1.7:1 rockers. Think that may be in the danger zone?
pdq67
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Re: Gen 5 BBC Shortblock

Post by pdq67 »

RevTheory wrote: Wed Aug 08, 2018 7:32 am "As is" is the plan. I'm eyeballing Edelbrock 454-O heads with 100 cc chambers and 2.19/1.88 valves. He's going to pull the intake off when he gets back to see if we're dealing with a roller or flat tappet cam.

Damn, PTV on a stocker from the 90s is probably the last thing I thought I'd have to worry about. Off the cuff intake lobe probably 224 to 227* at .050 on a 103 intake centerline and 1.7:1 rockers. Think that may be in the danger zone?
FWIW, L-29 BBC heads are also 100 cc chamber sized. that have about 230 or so real large oval intake ports as well as heart-shaped chambers that might need the, "beak", trimmed back

They only come with the smaller valves in them, but bigger valves should fit fine.

The way older BBC -206 heads have a true bath-tub closed chamber that is down around 96.7 to 98 cc's.. They also are true large oval intake port heads again with the small valves in them..

pdq67
rustbucket79
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Re: Gen 5 BBC Shortblock

Post by rustbucket79 »

RevTheory wrote: Wed Aug 08, 2018 7:32 am "As is" is the plan. I'm eyeballing Edelbrock 454-O heads with 100 cc chambers and 2.19/1.88 valves. He's going to pull the intake off when he gets back to see if we're dealing with a roller or flat tappet cam.

Damn, PTV on a stocker from the 90s is probably the last thing I thought I'd have to worry about. Off the cuff intake lobe probably 224 to 227* at .050 on a 103 intake centerline and 1.7:1 rockers. Think that may be in the danger zone?
Mark 5 will be flat tappet. Not precisely apples to apples comparison, but a mark IV 454 needed flycutting on the intake valve reliefs to fit offshore rectangle port heads with a Comp 280 magnum hyd flat tapped cam. You'll need to check for sure. [-o<
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Re: Gen 5 BBC Shortblock

Post by RevTheory »

Can't have nothin' nice :lol:

Thanks for the input.
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