[chrisjk383]

Hello,

I am rebuilding a 564ci BBC and am trying to decide if it is worth the time and money to get the bores re honed/new cross hatching... The engine was machined and honed last year (A very high-quality job I might add) and since then the engine only has about 20-30 1/4 mile passes on it. I am rebuilding for street usage and going from a high compression N/A setup to an 8.5:1 10psi turbo setup which means I will be going from a 44.9cc piston DOME to an 18cc piston DISH which is the reason I am debating new cross hatching to achieve a better piston ring seal. The hold up is that the current cross hatch is still in excellent shape, and I would hate to put it on a machine if it's not going to gain me anything. (See image below). What would you guys do if this was your build?

Part 2 to this question if I dare - JE told me if I gave them the weight of my existing pistons that they could add material to make the new pistons the same weight... With this said - would you guys re balance the rotating assembly? Note that the previous balance was done by the same shop whom I have great trust and does great work.

Thanks guys,
Chris

 

[chrisjk383]

The block measures perfectly, this is not a question that will be answered with a torque plate. It is a matter of surface finish, not out of round

 

[chrisjk383]

Im quite surprised by these responses but im glad I posted the pic - I've gone to the same machine shop for probably 10-15 years and never had any issues at the track, but then again ive never tried doing a leak down test either with pressure or vacuum. I will this time around. Im going to be safe and just take the whole short block to a new shop and have it re balanced and honed per my new application. I did have a mysterious blue smoke issue at about 1000' down the track that was never determined, who knows could havwe been blow by this whole time! Any advice o what valiues are passable for a leak down test? I would like to test the assembled motor this time around... What are good vacuum numbers and over what duration of time?

 

[chrisjk383]

P.S. not sure if i mentioned yet or not but the new motor will be a 8.5:1 564CI BBC with 10psi of boost ~ Shooting for 850HP street car - not sure if this info will have any effect on responses or not