So 'm hoping for some advice/help. I put together a nice 383 combo, Eagle forged rotating assemble aprox 9.43 Static CR, 7.90 dynamic CR. It's got a RPM intake, Edelbrock Etec 170's 454 Tbody bored to 54mm, EBL, Comp 260XFI cam, 1:6 Comp Gold Magnum Rockers, Stainless Headers, Open element air cleaner ect.... I'm getting alot of knock counts , I can't hear ping or what not because the engine and exhaust are so loud. I've looked at the plugs and don't see any residue from the pistons which is a good thing. I've used a really conservative spark map, double checked base timing. I went and bought a gallon of Torco race mix and mixed it with 20 gallons of 93 pump gas giving me around 110 octane. Still getting counts however less. I get counts when revving in neutral which leads me to think the cam at 59IVC@.006 I gulping to much air which I have read that DCR is a number however intake flow effects that also and it breathes very well. Once again advice/help would be greatly appreciated. This build is similar to a ZZ383 that runs 9.6 static cr and recommends 92octane. Any other things I should consider I don't think the plugs are to hot they look good.

 

Here's some screenshots to help out.

 

your quench distance is critical to prevent "knocking". I believe it should be somewhere around .035.

 

I used Pat Kelley's DCR calculator and my quench should be .064 based on a .0250 piston to deck clearance and .039 head gasket. I'm trying to post the images from photobucket however it's not working out I'm trying to figure that now.

 

since i didn't know what quench distance was i looked it up .i'm not thread jacking but i'm posting a link on a very informative sight i found .
http://www.irday.com/html/Engine%20f...0413/9142.html

 

I'm not a quench expert at all, all I know is what I learned from this site when I built my 383, It's just common practice to put in a thicker head gasket to reduce compression. I wanted to do the same thing until I did some searching and discovered that the quench is more important than the compression ratio. I also have aluminum heads so I can tolerate a higher compression ratio. I think .064 is a little much. Hopefully someone with more insight will chime in.

 

Thanks Freaky,
That is a very good read with extremely useful information. I just got back lowered spark map to 18 degrees total everywhere above 1600rpm even went to 12 degrees after that and same thing on the Torco gas the problem is I can't hear any knock or ping because like I said before the engine is to loud, forged pistons are a lot louder than hyper's. Anyway one again great read and if anyone else reads this post check out the above link.

I also checked the compression again and it's 162 this time which should be ok for pump gas. Here's a 10 minute run and the knock counts captured. I hope I'm not chasing gremlins I really doubt it though because I can trigger the knock by holding the brake while driving and having it in PE watching Wideband (12.5) and push the pedal a bit and ding knock count- so it seem with rpms increasing rapidly cylinder pressure increases with exhaust scavenging big gulp of air to much DCR, or like a read in that link a quench problem.

 

LOL pulled of the freeway this afternoon still chasing the gremlin and my brand new 700r4 tranny would not shift out of first, governor screwed. So I'll be chasing the gremlin next week

 

So I finally got it back from tranny shop Friday. I ran the torco mix out and put premium back in. I also went ahead and put the normal spark table back, I'll attach an image. Of course I'm still getting counts, even though I can't hear anything. So one thing I noticed today is that when free revving engine if I raise the throttle/rpms slowly I get no knock, If I blip throttle or fast rev I get all kinds of count / retard. So this may actually be a tuning issue, perhaps. Any more suggestions before I head over to the tune forum?

Thanks,
JDUBB