Mar 20th, 06, 8:14 PM
i recently bought a 454 motor. im tearing it down and rebulding it i want to put a set of speed pro dome pistons in it, but i cant figure out the bore. i had a machinest measure my piston head with an outside micrometer. he told me its "standard bore" the speed pro pistons say - Piston specs: Compression@.030" bore, .210" dome, 2 valve relief, also Std, .020, .030, .040, 060,.100. piston #'s are like greek to me. i know each number is a bore size whats "standard bore" for 454 with #'s 361959. the compresstion is the only thing i understand about them. i need to determine my "standard" bore so i can buy the right pistons. can anyone help?
Mar 20th, 06, 8:48 PM
Standard bore size for a 454 is 4.250".
Mar 20th, 06, 9:04 PM
i asked him that: "so its like standard bored 40 over?" he said "no its just standard bore, standard!" so do i order pistons "standard" or....?. the block has never been moded outside the factory, all original. im lost!
Mar 20th, 06, 9:16 PM
the numbers .020 .030 etc just means the pistons are 4.250 (std)+.030 so they will be 4.280 you need to talk to the machinist to find out how much taper is in the bore. basically its bigger on the top than the bottom thats why you can feel a ridge where the piston rings stop at the top. the machinst will measure and figure the minimum over bore to true up the cylinders. it may have to go 30 over 40 over or 60 over. basically if you go with the minimum bore you leave enough metal for another build at a later date. Jim
Mar 20th, 06, 9:47 PM
oh, i see, i get it now. yeah, the machinest looked in my cylinder walls and said the ridges are small and will hone it with a honing stone. so i should probally go with std size piston heads?
Mar 21st, 06, 12:30 AM
talk to the machinist if he thinks a hone job and new pistons will work for you. sounds like your going for a performance rebuild. for the price of new pistons and rings you may want to spend the extra and have it bored and honed with torque plates. probably get more longevity out of the motor to make it pay for itself. Don't forget there are open and closed chamber heads and you need the correct dome for the head your using. Good luck.
Mar 21st, 06, 1:30 PM
Jim Mac is correct! Just as important as the bore of the cylinders in choosing a piston is what heads you have and the cc of them. This is critical in determining what piston to buy so that you can run an optimum compresssion ration for the octane fuel you choose to use ( I would assume 92-93 pump gas..so about 9.5-10:1). And again as someone else mentioned...while its tore down and out of the vehicle...no way I would spend money on new pistons and put them in a block that has miles on it and run, only hone the cylinders....get a bore on those cylinders finished up with torque plate hone! According to your post, your machinist feels the bore is ok and standard.... I personally would order a .030 over set of pistons, and tell him to bore the block. By the way you only want to run a domed piston if you need it to achieve compression with an large open chambered head, otherwise flat designed pistons are more efficient. On the top of the head there are going to be several casting numbers. One group typically is 6 digits long and the last three digits indicate the casting series of the head. Very common heads if the motor came out of a mid seventies and up car are 781 and 049 heads. Do a search on here on how to identify your heads and you will figure out what casting they are and what cc they are. From there the piston manuafacturers can usually help you choose a piston for that head to get you a good compression ratio, and then of course if your block bore is standard 454 now (4.25") you will want to go .030 larger that that on the piston too.
When I was a teen doing my first motor I made lots of mistakes that were costly to the pocket. Nobody on here can educate you on all the variables in one post. My recomendation before you start building is to spend a few weeks reading threads on this site to educate yourself more; and buy a couple of books. You will make better decisions for your motor, make fewer costly mistakes, and will be overall more happier with the motor. Then my suggestion would be to maybe find online a build of the same motor you have and duplicate it for your first build......at least then there is no guessing in a proven combination that someone else has already done the homework on. JMO....good luck