Hey,

I was recently looking at B&M 144 Powerchargers for my 327. I asked the previous owner and then did the test to back it up and found out I have 9.5 compression. Thats seems high to run a blower with. So I looked into it and they say the ideal compression is 8-9. So now im trying to find out ways to lower my compression or put on the blower anyway without playing around with the heads on my engine. Lets just say Im now going to mess around with the lower end of my engine. I have had to many negative experiances in doing so. So the question is...IS 9.5 COMPRESSION TO HIGH TO RUN WITH A BLOWER WITHOUT HAVING TO WORRY ABOUT OVERWORKING/OVER REVING IT AND POTENTUALLY SEVERLY DAMAGING MY ENGINE??? Your help is greatly appreciated...

Regards,
Brian

Do a search on this site and you will find that this question has been asked a lot lately.

Can you run a blower with 9.5 compression w/o worries?

In a word, no.


IS 9.5 COMPRESSION TO HIGH TO RUN WITH A BLOWER WITHOUT HAVING TO WORRY ABOUT OVERWORKING/OVER REVING IT AND POTENTUALLY SEVERLY DAMAGING MY ENGINE???

yes


Basically, this is a receipe for not having much fun. You'll end needing to run an underdrive pulley setup, you'll end going through all kinds of gyrations trying to keep the pinging down so it won't knock the top off a piston. First time you get a tank of bad gas the motor is history. Sorry, I'd like to give a more favorable opinion, but it's just not there. Does your engine have TRW or better forged pistons in it?

Tom

do you have Aluminum heads?
the reason I ask is with aluminum heads you can get away with up to a whole point better compression ratio with the same octane gasoline as you would with cast Iron heads.
general rule of thumb with about 6-7psi boost is
no more than 8.5:1 on cast iron heads
no more than 9.5:1 with aluminum heads.

my daily driver Thunderbird has 9.3:1 compression and I run 9psi boost on it and suffer NO issues with 91 octane gas. Its got factory Aluminum heads on a cast iron block.

keep the ignition timing mild and fuel ratio rich (Like 11.5:1 WOT) and you shouldn't have problems.

As above, with a centrifugal blower 9.5 is fine for a street deal. With a roots type blower like the B&M it isn't ideal, won't be able to run much boost.

Jody