BB mod - worth doing?

[Joe R.]

that is a distance below the deck .100" less than the measurement between the top of the piston and the top of the first ring. Make lines from that mark to the edges of traced areas on the deck then fill this in with bluing. Start grinding at the horizontal center of the blued area and grind until you reach the bottom of the vertical mark. After that, grind sideways each direction until the blued material is gone. Curt Hooker used a die grinder fitted with a carbide rotary file for this. The markings must be done carefully and the grinder operated with a steady hand. A serious mistake will cost you a block. Needless to say, Mr. Hooker is a big-block master and completed this with the greatest of ease."

What do you guys think about this mod?

Thanks,
Joe

[John H.]

Re: BB mod - worth doing?

What do you guys think about this mod?

Thanks,
Joe

Joe -

I think I wouldn't bother - here's the result of an amateur clearancing the bottom of a cylinder bore for rod clearance on a 383; bye-bye block.

[Clem Z.]

Re: BB mod - worth doing?

I read this on the Idaho Corvette web site (Big Block from Hell Part 1).

that is a distance below the deck .100" less than the measurement between the top of the piston and the top of the first ring. Make lines from that mark to the edges of traced areas on the deck then fill this in with bluing. Start grinding at the horizontal center of the blued area and grind until you reach the bottom of the vertical mark. After that, grind sideways each direction until the blued material is gone. Curt Hooker used a die grinder fitted with a carbide rotary file for this. The markings must be done carefully and the grinder operated with a steady hand. A serious mistake will cost you a block. Needless to say, Mr. Hooker is a big-block master and completed this with the greatest of ease."

What do you guys think about this mod?

Thanks,
Joe

this will also lower the compression ratio because you are increasing volume at TDC. if you want better breathing change to the open chamber heads and pistons.

[Ken A.]

Re: BB mod - worth doing?

I believe you would see a drop in HP on a dyno, because a BB likes compression gain, not loss. Plus, you couldn't tell any difference, other than making a big mess. Do the exhaust ports, first!

[Joe C.]

Re: BB mod - worth doing?

This is how it is done on a SBC. There is no danger of ruining the block, since there are no water passages up in those areas. Be judicious in metal removal............any relief will do some good, UNLESS you exceed the head gasket footprint. If you do so, the fire ring will burn off of the gasket and that's trouble. The reliefs you see here measured less than 1 cc each. If you need to, you can always compensate with thinner head gaskets.

I did these with a die grinder.

[Joe R.]

Re: BB mod - worth doing?

I don't think I would attempt to do it myself. I would take the block to a machinist. How much horsepower / torque could be gained if the mod was done right?

Joe

[Jack H.]

Re: BB mod - worth doing?

I'd keep in mind that many of these machinest's tricks came from wheel to wheel competition where cars are typically running at/near 100% WOT and component longevity isn't really a major consideration (make it last long enough to finish the race and win/place...).

Why those in our restoration/preservation circles are FOCUSED on trying to 'soup up' a classic high performance street machine for essentially weekend warrior use on public highways often leaves me questioning the logic! Aren't we really after the factory stock performance profile with as much longevity improvement as we can get?

[Joe C.]

Re: BB mod - worth doing?

I'd keep in mind that many of these machinest's tricks came from wheel to wheel competition where cars are typically running at/near 100% WOT and component longevity isn't really a major consideration (make it last long enough to finish the race and win/place...).

Why those in our restoration/preservation circles are FOCUSED on trying to 'soup up' a classic high performance street machine for essentially weekend warrior use on public highways often leaves me questioning the logic! Aren't we really after the factory stock performance profile with as much longevity improvement as we can get?

That is very true, Jack. In this case, however, longevity does not enter into the equation, at all.

There is only one "downside" if you will, to this modification, and that is, that once you relieve the block, you can no longer use a head gasket with a smaller bore diameter and/or relief size than the one which you used as your template. Any gasket overhang (area protruding into the chamber beyond both the block's bore and the head's valve relief area) will quickly succumb to deterioration due to exposure to excessive heat (flame impingement). This will compromise the end seals of the "rolled" stainless steel fire rings and cause subsequent gasket failure.

I respect your concern about originality as it exists "under the skin", although I don't agree with it. That concern is much the same as one involving obsolete paint surfacers/primers to be used underneath the color coat, and which will never see the light of day. I am not such a purist, and disagree with this line of reasoning on just the same durability issue that you stressed above. After all, is it not true that when ancient artifacts and priceless artworks are restored, that there is always a blending of old and new technology!

In restoration work, sweating the details is important. In engine building for maximum power production, every detail means more power, and not necessarily at the expense of durability.

GM used mass production processes in the 50's 60's and up until recent times which contributed to its near demise. One such example was their deck/oil pan mount flange broaching process which produced variations in thickness on the order of .010" and more! With that in mind, could you imagine the resistance the engineers would have met from the bean counters if they had specified an extra machining step of relieving the block's bores, for a minimal gain in horsepower! Quality was not an issue as much as it was to "get the crap out the door" and let the Service Department worry about it later.

My feeling is that if someone has enough interest and desire in "hand building" a precisely machined and "blueprinted" engine, then no detail should be left unexploited.

[Chris E.]

Re: BB mod - worth doing?

If you've got the engine apart enough to be able to do this, why not swap heads, cam and other components that will have a HUGE impact on power?




If you still want to maintain originality on the OUTSIDE of the engine, hog out the air passages for the heads and put a big cam in. Can you get stroker cranks for 427s? Don't know.

[Clem Z.]

Re: BB mod - worth doing?

the best improvement to a 427 engine is to install a 454 rotating assy as the .250 longer stroke makes for a lot more torque.

[Joe L.]

Re: BB mod - worth doing?

the best improvement to a 427 engine is to install a 454 rotating assy as the .250 longer stroke makes for a lot more torque.

clem-----


Absolutely!

[Joe R.]

Re: BB mod - worth doing?

Clem and Joe,

Would a judge be able to detect the 454 rotating assy in a 427 block during ops check or PV? For a 66 with stock size tires, I'm not so sure I can put more torque to the ground. What are your thoughts?

Joe

[Joe C.]

Re: BB mod - worth doing?

Clem and Joe,

Would a judge be able to detect the 454 rotating assy in a 427 block during ops check or PV? For a 66 with stock size tires, I'm not so sure I can put more torque to the ground. What are your thoughts?

Joe

Yes......idle vacuum.
The stroker will make more vacuum @ the same idle speed, all else being equal other than displacement.

[Clem Z.]

Re: BB mod - worth doing?

Clem and Joe,

Would a judge be able to detect the 454 rotating assy in a 427 block during ops check or PV? For a 66 with stock size tires, I'm not so sure I can put more torque to the ground. What are your thoughts?

Joe

you would have to have the rotating assy balanced for internal balance as the 454 was external balance and the damper would be a give away

[Patrick H.]

Re: BB mod - worth doing?

Yes......idle vacuum.
The stroker will make more vacuum @ the same idle speed, all else being equal other than displacement.

However, I've never seen a PV include an idle vacuum check.