I'm Going To Build A 650 HP 496 With 781 GM Oval Port Heads

[Mark Jones]

My plan is to build this: A BBC with a 4.310 bore and a 4.250 stroke, 9.8 compression,

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ported 781 GM oval port heads 1.880/2.190 valves, 238/248/578/608/110 hyd roller cam, performer RPM air gap intake, 850 Holley carb. Some pictures.

 

[Mark Jones]

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[Turbo4whl]

Even the valves look pretty! I'm going to watch this thread.

 

[bucket]

I'm in for the read.

 

[hirschdalechevy]

I am in as well. Do we get to see a dyno sheet after your build is done?

 

[Mark Jones]

Of course, and a video as well.

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[Mark Jones]

More pictures

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[Paladin]

What block are you using as in Mark IV, Gen 5, Gen 6, Gen 40?? And pistons??

 

[82sbshortbed]

That sucker is clean. I'll watch.

 

[bucket]

What block are you using as in Mark IV, Gen 5, Gen 6, Gen 40?? And pistons??

It's a mark IV

 

[BigDaddy72]

Nice looking work as usual Mark, can’t wait to see it done, I love engine build threads!

Got a question for ya. The closest to me (engine dyno) dyno shop has broken the last 4 engines they have dynoed.

I would love to dyno the afr headed 496 I just finished for my wife’s truck, but this “rumor” has me extremely gun shy.

What or could would cause engine damage like that on the dyno.

Me personally I have never engine dynoed anything for fear of the horror stories I’ve heard.

What is your opinion or advice?

Sorry I guess this is off topic I don’t want to clog up your thread but I gotta know?

 

[Mark Jones]

I guess my advice would be to stay away from that dyno shop? Maybe find another dyno shop. More pictures.

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[bucket]

Did the block need clearance grinding for the crank?

 

[Mark Jones]

Yes, the picture above shows the clearencing.

 

[Mark Jones]

More pictures

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