Posted by roadrage (IP: 205.188.200.164) on May 24, 2000 at 07:31:25:
In Reply to: Re: 302/289 trick posted by Jim Glover on May 23, 2000 at 17:05:31:
: OK! One more time. First off 289 connecting rods are 5.155 long center to center and 302 rods are 5.090 center to center. Using the block of your choice and a 302 crank with a 289 connecting rod will get you a long-rod 302 inch motor,which makes more power because the piston hesitates at TDC longer to build more cylinder pressure. This will make the piston stick up out of the block about .060 inches, so you will have to machine down the pistons to acheive a zero deck(flush).
: Now the suggestion is to use a forged piston and all stock designed pistons(Ford,TRW,etc) have more than enough thickness and strength to allow you to do this and you will have a lighter piston as well(faster revving engine). Stock 289 connecting rods are plenty strong enough for most street and some strip applications, if they are properly reconditioned and quality(read racing type) rod bolts are installed(such as ARP brand).In all my years of experience, I've seldom seen an engine failure due to a smallblock Ford connecting rod. Most failures are related to cylinder block failure due to main bearing cap movement(a good case for a main cap girdle). My engine bored .030 with an .039 thick head gasket and a 54cc combustion chamber has about 10.5 to one compression.
: Use a reputable machine shop and you should be alright.
i consulted one of my friends who used this trick. he used forged 289 connecting rods, and bought 302 "pop up" pistons. he had to have the pistons shaved down 0.60, and cut eyebrows in the tops of he pistons.
he did say that there were several manufacturers who already made the pistons for anyone interested in doing this conversion.
i will find out just who does sell these parts and who you can purchase them from.
will be back soon with that info.
RR