Printable View
I have a rebuilt 390 That does not run strong/pull any help would be appreciated this is were I'm at bore is .080 Silv-o-lite pistons PN# 1138 Comp.Height 1.66 compression ratio(s) 10.3 crane cam 941 Edelbrock performer manifold holley 650 DP headers Mallory unilite dist. At 750 rpm idle vacuums 14 Compression tested 140 low 150 high my question is that enough compression? also if not what is the best way to raise compression?
The compression is fine. What do you have your timing set at?? Is the carb in good condition??? What are the cam specs??
This is the cam spec. Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 1 BTDC 35 ABDC 107 216 °
Exhaust 51 BBDC (3) BTDC 117 228 °
Lift: Intake @Cam 3027 @Valve 533 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 3200 @Valve 563
Rocker Arm Ratio 1.76
Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 25 BTDC 67 ABDC 272 °
Exhaust 75 BBDC 29 ATDC 284 °
Also I decreed the cam and it is right on the numbers
Sorry I have had the timing all over I advance to fastest idle and back off a little just so the ping goes away.and the Holley is new.
I noticed your profile sez Denver, from my drag racing days I remember how tuff it was to run the numbers at Bandemeire. Do your plugs read good??? What kind of gear ratio are you running behind it??? The cam looks like it has a ton of duration in it. I'm not a cam expert at all, I usually do the tech data sheet on the motor and let the cam company do the reccomendation. Hopefully someone will be along with a more definitive answer.
it sounds like your advance isnt working vacuum or mechanical could be stuck or sticking
Dave plugs look good! and gears 4.56 This thing just has no balls I spent my high school drag racing days with a 70 chevelle SS396 really a 402 3.73 posi and that thing would tear the skin off your face! I was hoping this 390 would run close to it but it's a turd! I away thought FE engines liked high compression 180-190 range?
Atlas went down that road too! 3rd dist I have had in it, at this moment there is a mallory unilite mechanical advance,That is smooth as anything out there.But thanks you guy's keep them coming I hope someone can help or this thing will be on E-BAY soon!