I am considering buying a camaro on ebay, the owner says the engine is a 402 BB ( casting # 3999290 ) and he said it has been bored out to a 427. Is it possible to bore a 402 out to a 427 ??? Next question, if it was bored to a 427 would it be likely to over heat ???

Ralph:confused:

I doubt it could be bored that far.There is one casting from 1965 and 66{#961) that was used for 396's and 427's,that casting will go all the way out to a 427+.100.A very select few of other 396 castings will go to standard 427 bore.This guy might have tried it.I know one of my machinists was talking about a guy who tried to make a 427 out of a 1971 402 and the block fell apart on the boring bar,but something must have made him think he could do it.The block you have is the less desirable block often used for 402's,and I dont think it is a thick wall block.I think the guy is full of crap about it being a 427,but if he did get away with it I wouldnt want to use that block.

From the Mortec website:
396 = 4.096" x 3.76"
402 = 4.125" x 3.76"
427 = 4.250" x 3.76"

The 65/66 396 block that could sometimes be overbored to 427 was the 962, not the 961 block. That is a whopping .154" larger hole to make the jump. Bear in mind, the 66 427 used the same casting.

The 402 in question would have to only make it .125" to grow into a 427. Possible? I'd say possible some of the time. Be on the lookout for a short fill of HardBlock filler in the water jackets to keep things rigid. Nearly 100% of the BBCs go .060" over, most will go .090" over, lots will go .100" over but not a lot pass the sonic testing to go .125" over. I am basing this on 454 blocks being overbored. Most will not bore a 396/402 block that big when 454 blocks are plentiful

I heard quite a long time ago that many vehicles marketed after 1970 with a "396" actually had the 402 casting , but 396 was more "marketable" due to its history??

I heard quite a long time ago that many vehicles marketed after 1970 with a "396" actually had the 402 casting , but 396 was more "marketable" due to its history??
:yes: Why change a well known, high identity, marketable item, because of a slight over-bore?

Thanks guys,first let me apologize , this car is a Nova not a Camaro. I guess I had my 68 Camaro on my mind. If I could get a couple of you to go to EBay item #( 250524134484 ) and check out the video link to youtube and hear the car run.He actualy has two videos , one idling and one road test. Please let me know your opinions.
Thanks
Ralph

The block that shared the same casting between 396 and 427 was the 961 block.The only difference was in the finished bore size.Some other 65 thru 67 396's are rumored to have been able to go to 4.250",but the later 290 blocks arent know for this.