To Run or Not to Run High Compression

cobralee · #1 (**permalink**) 08-09-2004, 10:32 PM

Just need some feedback from you guys. I'm runnng a 427 T.O. in my Cobra, stock motor with 10:1 compression. Cruises great, fast enough, reliable, etc. I'm considering rebuilding it with 11:5 to 1 or even 12:1 pistons. To me, nothing beats the sound or performance of high compression. I know I'll need to buy high octane gas. I need someone to tell me why I should or shouldn't do this. Will I be sorry after 6 months of the high comp?

Thanks,

Ron

Excaliber · #2 (**permalink**) 08-09-2004, 10:41 PM

I'm running 12.5 to 1 427 side oiler. It's a love/hate thing. The sound and power are awesome. When I ran 11.90 at 121 mph at the drag strip on the FIRST NIGHT I ever ran a drag race in my life I was blown away. Man this car is FAST. Got a big cam too, love the wicked rump rump idle. It's everything a bad ass Cobra is supposed to be.

Hate the 8 mpg (maybe thats because of the dual fours?). And it's a tempermental engine, don't DARE even THINK about "lugging" that engine. You got to WORK at keeping those rpms up, which might mean cruising in 3rd if traffic is going slow.

On a bad day I find myself wishing it wasn't quite so "radical". Then I go for a drive and when the loud pedal hits the floor and it moves out I think, "Damn, I wouldn't have it any other way. This thing rocks!"

cobralee · #3 (**permalink**) 08-09-2004, 10:52 PM

Hey Slick-

Thanks for the information. Thats sort of what I wanted to hear. I only drive my car usually on weekends, so I don't anticipate much bumper to bumper traffic. Can you email me directly, I'd like to ask you some questions about the specs of your cam, etc. I also have tons of family in Oahu, who you probably know. My dad was from there, lived on Judd St. My email is cobralee1@aol.com.

Ron

CobraEd · #4 (**permalink**) 08-10-2004, 05:35 AM

Compression doesnt affect drivability. Only cam and intake does. High compression adds torque across the board. All the new performance cars are near or at 11:1

Ed

vettestr · #5 (**permalink**) 08-10-2004, 07:24 AM

Yea Ed, and the evilness of spoons did not cause Rosie O to become large !! Next you will be saying guns kill people........
Ed, Just kidding. Sorry I am in one of my moodes. Think you will agree that higher compression is rarely built into the engines in our Toys without the other common items like big cams and high CFM intake systems and tons of timing. I do not consider 11/1 as high C/R but is getting there. Heck I am running an engine built for alky now converted to gas and love life.
The down side to high C/R is gas price, limited run distance due to amount of gas I can haul and quirks of the normal set up with high C/R. I would not do it differently but am building second car with near stock engine so we can have best of each world. May go off the deep end and install stereo, AC and hard top.
Take care all. jeff c

Cracker · #6 (**permalink**) 08-10-2004, 07:26 AM

My 427 was run at 11.5 and on PUMP GAS ONLY. Everything works fine but the timing had to be pulled back to 32 total. The advantage however is IF I had wanted to go radical and pump up the timing and pour in race fuel I found an extra 30 hp!!!

Through the KCR test we are reducing the compression to 11:1 so the timing can be advanced a little more with standard 93 pump gas but anything less with aluminum heads is just throwing away potential (not that I know anything about this though - I thought that sounded good!) Best wishes and YOUR RIGHT about high compression revving and idleing - nothing beats it!