engine builder question

[fastford]

what do you consider the max tolerance for a out of round cylinder ? me and a fellow engine builder are having a dispute , all in fun , on how much you can allow , obviously none is the best , but a lot of folks cant bore every time and just getting by ....

[brad hibbard]

when i started in the crate world i certainly had to change my standards for out of round
crates cannot be bored or use any type of over-size piston or ring
it was (and still is) amazing to me how well these engines seal up with cylinders that are so far out of round.
when freshening these engies we have to find the happy balance between round and big
2 to 3 thou out of round is not uncommon and still seals just fine when broke in properly.

we have recently installed a permanent blowby meter as part of our dyno connection
it has helped us develop break-in procedures for this condition.
also the factory finish on new engines is not the most desirable and different break-in procedures have helped us do a better job with that condition also.

what I have learned since being stuck in the crate box and having to deal with less than perfect cylinder conditions is that initial start up and break-in is critical
the ring has to find it's happy home on that piston quickly and then mate itself to the cylinder wall---this all needs to happen in the very beginning of the engines life --

Brad
www.race-1.com