GM 502 Gen VI Sonic Test
#1
Off the Radar
![](https://www.offshoreonly.com/forums/images/icons/platinum_member_star.gif)
Thread Starter
Join Date: May 2001
Location: Short Pump or Colonial Beach, VA
Posts: 1,097
Likes: 0
Received 1 Like
on
1 Post
![Default](/forums/images/icons/icon1.gif)
I was wondering how far I could bore a 502 block. Just by measuring the thickness of the cylinder walls through the water passages in the deck, it appeared that 4.600 was easily obtainable. I had my machine shop sonic test it for me and here are the results. This is a very thick block. If I was to bore it to 4.600, the minimum thickness in cylinder 3 would be .264.
With a 4" crank that would take a 502 to a 532.
With a 4.25" crank that would take a 502 to a 565.
565 sounds good. and just a tad more expensive than a 540. With a JE flat top piston the compression would be 9.4/1.
With a 4" crank that would take a 502 to a 532.
With a 4.25" crank that would take a 502 to a 565.
565 sounds good. and just a tad more expensive than a 540. With a JE flat top piston the compression would be 9.4/1.
#3
Charter Member #601
![](https://www.offshoreonly.com/forums/images/icons/charter_member_star.gif)
![Default](/forums/images/icons/icon1.gif)
Linster,
I have a Gen V block and a few years back I was looking to open it up.. My guy went to 4.520" which is oddball size, and had to do a lot of ring work because of it.. I was told at that time 4.530" was max on the standard production block.. we never did a sonic test. Problem being that when cylinder wall scoring happens, then the block is done. If you take it all the way to the limit, your gain in hp due to cu is minimal when you consider that you can get one more hone or bore to clean up a messed up cylinder bore.. Just my .02 on the subject..
Dick
I have a Gen V block and a few years back I was looking to open it up.. My guy went to 4.520" which is oddball size, and had to do a lot of ring work because of it.. I was told at that time 4.530" was max on the standard production block.. we never did a sonic test. Problem being that when cylinder wall scoring happens, then the block is done. If you take it all the way to the limit, your gain in hp due to cu is minimal when you consider that you can get one more hone or bore to clean up a messed up cylinder bore.. Just my .02 on the subject..
Dick
#5
Registered
Join Date: Jan 2004
Location: San Diego, California
Posts: 2,777
Likes: 0
Received 6 Likes
on
6 Posts
![Wink](/forums/images/icons/icon12.gif)
Linster:
My opinion and suggestion is to keep the block bore at 4.500" on overbore and use a bigger stroke crankshaft like 4.50" and that way you'll have bore left over for a possible future re-bore need and still have the big cubes needed for big torque. Its a "Triple Nickel" 555 cubic inch size BBC as we call them at 4.50" stroke and a great engine configuration. Also 4.50" piston sizes in standard strokes are many times shelf stock at piston houses as well as crankshafts and less expensive than custom bore sizes or strokes.
Best Regards,
Ray @ Raylar
My opinion and suggestion is to keep the block bore at 4.500" on overbore and use a bigger stroke crankshaft like 4.50" and that way you'll have bore left over for a possible future re-bore need and still have the big cubes needed for big torque. Its a "Triple Nickel" 555 cubic inch size BBC as we call them at 4.50" stroke and a great engine configuration. Also 4.50" piston sizes in standard strokes are many times shelf stock at piston houses as well as crankshafts and less expensive than custom bore sizes or strokes.
Best Regards,
Ray @ Raylar
#7
Registered
Join Date: Feb 2011
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
Sorry about that but i was researching what has been done in the past and was curious what he went with and if he was successfull in the new bore. I plan on upgrading mine next winter and am undecisive on exactly what I am going to do. I have a plan but not enough facts to base my decisions on yet.
#9
Registered
![](https://www.offshoreonly.com/forums/images/icons/platinum_member_star.gif)
Join Date: Mar 2008
Location: Vancouver BC
Posts: 1,181
Likes: 0
Received 0 Likes
on
0 Posts
![Default](/forums/images/icons/icon1.gif)
Linster:
My opinion and suggestion is to keep the block bore at 4.500" on overbore and use a bigger stroke crankshaft like 4.50" and that way you'll have bore left over for a possible future re-bore need and still have the big cubes needed for big torque. Its a "Triple Nickel" 555 cubic inch size BBC as we call them at 4.50" stroke and a great engine configuration. Also 4.50" piston sizes in standard strokes are many times shelf stock at piston houses as well as crankshafts and less expensive than custom bore sizes or strokes.
Best Regards,
Ray @ Raylar
My opinion and suggestion is to keep the block bore at 4.500" on overbore and use a bigger stroke crankshaft like 4.50" and that way you'll have bore left over for a possible future re-bore need and still have the big cubes needed for big torque. Its a "Triple Nickel" 555 cubic inch size BBC as we call them at 4.50" stroke and a great engine configuration. Also 4.50" piston sizes in standard strokes are many times shelf stock at piston houses as well as crankshafts and less expensive than custom bore sizes or strokes.
Best Regards,
Ray @ Raylar