I posted this in tech but I need more help quick .


My block is about to go in for an over bore because it blew up . It is 588" now . (supercharged) THats a 4.56" bore and 4.5" stroke . I jsut read in that "How to build a BB chevy" book that the GEN 4 motor is maxed out at 4.56" which is where I'm at now ! It says the GEN 5 & 6 can go to 4.6" . Is this a fact ? Please tell me no ! What else can I do ? Can I sleave the cylinders ?How will that afect it ? I would like to just bore it out another 20 or 30 thousanths and move on . Can I do that or not . I need to know facts . I guess I could have the block sonic checked to see if it can take it ???

Some one help ! I was going to send it today till I read that ! Thanks ,JOE

I think that DanL had a couple of those blocks that he was trying to unload cheap.

Jon

Thanks Jon , I'll call him tomorrow . I would rather fix mine but it may be cheaper to start from scatch . Thanks ! JOE

A regular gen 4 block can go to about 4.310" before getting to weak. If you are at 4.560" with a 4.5" crank and you have a GM block it must be a "bowtie" block and this can go to 4.600" without a problem. This will get you a 598" motor.

greg

Yes it's a bow tie block ,but I read that the gen 4 can't be bored as much as the gen 5 and 6 even as a bow tie block . I am wondering if that is true because aren't the gen 5's relatively new ? I know they have had big inch motors aroun dfor a while . THey must have used the gen 4 or some custom blocks .

boot
Is there a good engine shop in your area that you could call and ask the question? If not, call Tommy at CHIEF ENGINES in Ft.LAUD. I'm sure he has an answer for you.
954-587-3020
Robert

Boot-
The GM Performance Parts Catalog (1999) states that the GM Mark IV Tall Deck has a bore range of 4.495-4.560. The Mark V has a range up to 4.6

Hey...I've got a stupid question...

Is there a way to tell the difference between a Gen 4, 5 or 6 tall deck?