what is involved in switchign a motor to accept unleaded fuels? is it just teh valves and valve seats? or are there more changes that need to be made?
i just got a great runnign 71 455 pontiac motor and i plan to use it as is until i cna afford a really nice rebuild. it woudl jsut be nice to not have to play with lead aditive in the freezing cold if i can avoid it wiht a head swap or a little head work.

thanks
tim

 

Have some hardened valve seats installed, a valve job, and a good general mag&pressure check (preferably before you spend any money). Then you will be good to go.

-Mindgame

 

Your '71 motor should be compatable with unleaded fuel. That is the first year of the lowered compression. Some of the earlier ones did not have the hardened seats but you can go a long time without that. Is the motor that you have an HO? If it is it is a very desireable motor with lots of potential. have fun

 

thaksn for the help guys.
i am nto sure which motor it is. i was told that it is the 325hp rate motor. i do not know a ton about the car. the basic story is i got tired of driving my POS 84 cavy and then i saw a for sale sign on a co-workers car. it si a 71 Grand Prix Model SJ.
i did soem research on gp's from 71 and i found out that the model sj is pretty rare. i am planning to use the car as a driver and soem light towing(jet ski, dirt bikes...etc). i just gotta make soem minor repairs to get it through a new jersey inspection.

thanks again for the help.

later
tim

 

If the motor is pretty fresh, you should be ok. Running a motor designed for leaded gas with unleaded really becomes a problem if you're doing a lot of high rpm blasts. That's what will cause the valves to recede unless the hardened exhaust seats are installed. You should be fine driving it and it probably already has the unleaded heads anyway.

 

i got teh low down on hte motor and ran all the codes for the heads and stuff.
the motor is a factory 455/4bbl. heads are #66's. that is a big chamber/big valve head for unleaded gas. compression is only around 8.1:1, not much, but hey, i can run more timing that way
teh factory cam is a #67, sorta small, but it seems to have good torque, so i don't mind. teh factory hp rating is 325. not sure at what rpm or anything, from teh look of the cam prolly around 4000-4500rpm at most.

thanks again for your help guys.

later
tim