Thread: Just dynoed my 396 BBC...how to get more HP?

Tweet

Oh and 0-100 in 10 seconds is close to your calculated ET of 108 in 12.7... Like I said you should get more power with some tuning... If you're at 9:1 on ~95 octane you could use a lot more timing (read your plugs to get timing right... You can probably add 4-5 degrees) and lean out the mix some you'll shave 3 to 5 tenths or so off that time... Good luck

-Chris

Originally Posted by skids72

Well, in short standard atmospheric pressure at sea level is 14.7 psi so if your cranking compression is 160psi your dcr is 160/14.7=10.88:1... Just math... So it seems one of these numbers ain't right... That's why I mentioned it because you would be detonating with pump gas... I would expect a normal cranking compression to be in the 120-130psi range for a hot street motor... If your scr is closer to 9:1 you should be around the bottom of that range... I would also be very surprised if you could get 1.25 hp/ci out of a 9:1 motor... If you can post all the motor specs I can run it through desktop dyno for you but it sounds you've already done that... Keep in mind dd won't account for accesory drive (water pump alternator etc) which can amount to about 20hp... I'm not trying to beat you up or anything... The numbers just don't sound right.

-Chris

I know you're not trying to beat me up... I'm not a math whiz but my 2-stroke dirtbikes putting out 8.5-9:1 static make 175PSI and I run them on premium gas. I know people that run them on 87 too. 110PSI is when they are just about dead, and need a cylinder, piston, and rings...140-150PSI is when I do a topend on them.

Thanks for the info, I will get it tuned up. It just seemed low to me. I guess if I was losing 20% through the tranny and rearend which is possible I'd be at 430HP 430TQ which is believable.

Well my 10.9:1 motor cranks about 125psi but the air is thinner up here... It will run on 91 but I use 100 at the track so I can run more timing = more power... I use 20% rule of thumb for auto trans (and 17% for altitude here). You will have more loss in 2nd gear than drive but not a huge amount... All said I think your power is in the ballpark of what I would expect... Get her on the strip and after some tuning you'll see low 12s which is great for a streetable ride... I had similar motor similar cam (but hydraulic) similar car abou 3500lbs ran 13.2s at altitude which would be low 12s at sea level 10.2:1 but air is thinner

Oh ok. I am at 200 feet above sea level. Cars run pretty good down here.

hey if you ever make it up to Denver I'd be happy to challenge you to a race

Or if I ever get down to SJ I might find out what it's like to drive a 10s car

-Chris