knock under load

[jballa]

I have a 92 Mustang coupe, 331 stroker w/ 10:1 compression and 5-speed Tremec (N/A). The motor was professionally done and only the block was reused. I upgraded to 30#injectors, 190gph fuel pump, msd coil, bbk ssi intake, cold air, cc 1.6 roller rockers, World Windsor Jr. iron heads, chip, shorty headers, deleted smog, high flow cats, flowmasters, 70 mm TB, 73mm MAS, SRP forged pistons, 5.4” H-beam rods, 4340 steel crank, balanced @ 28 oz, billet steel flywheel, etc.

Lunati Custom Cam 110/118 lobes, .548" lift, 230/237 dur. @ .050

Under load, especially at lower rpm/low gear (1500/5th @ 1/3 throttle) you can hear a knock and at higher rpm (W.O.) it blows fuel out the exhaust occasionally knocking like hell! I set the fuel pressure @ 45psi by checking the AP24's after a hard run. If I turn the initial timing down to 10, no problems but no power... I'm running the timing at 12 now and its still low on power. I pulled the chip and it made the power worse so its reinstalled. I'm looking to make about 400 HP and it feels more like 300-330 and would like to run 14+ init. timing.

I’ve already checked for basic things like cap/rotor/wires, vacuum/exhaust leaks, and such. B/c of the intake design, the EGR valve vac. line is not connected but shouldn't matter. Someone mentioned that I may need to run race fuel mix? Maybe an upper intake spacer to cool charge air? Any ideas?

 

[BK_CAULEY]

i know fuel is getting high but try running a higher octane gas or maybe an additive. gas companies these days will sell you anything so watch where you get it from. and if you ever see a fuel truck at a gas station stear clear of it for a few days because all of that gas there pumping in is sturring up sediments in the holding tanks and you ar emore likely to get ahold of bad gas. just a thought.

 

[jballa]

They don't sell higher octane in my town

Thanks for the response.

93 is the highest they sell here... I've been putting a can of 104+ outlaw ($10/tank) in addition to the 93 and it helps some but that 14deg. still ain't happening!

By the way, anyone ever have this problem when running 10% ethanol? My car REALLY hates that crap, its mandatory now in VA east of I-95.

 

[BK_CAULEY]

i just saw (read over it the first time) where you have 10:1 compression. is that accurate or a guess. because the compression I.M.O is the culprit but not at 10:1 you should be able to run 87 with no problems. i have 10.5:1 and i hear a light knock with 89, a really noticable knock when running 87 and 93 works perfect.