I posted this earlier today probably in the wrong forum (DYI) and only got one response, so I'm doing it here.

Anyway, here's the scoop:

383 SuperRam, 10.5 compression, Sportsman II iron heads, custom CompCam roller cam [218I, 224E duration at .050, lift .525I (1.6 roller rocker), .502E (1.5 RR)], in a 70's era 010 block. Have gone thru valve adjustments out the wazoo trying to make sure they aren't rattling as the cause, don't think that's it.

Problem is it runs like dung. Base timing is set at 6 BTDC, and Datamaster is cycling through 256 detonation counts in like 4 or 5 seconds. No known exhaust leaks, but I'm using SLP Tri-Y headers so they're loud to begin with. All emissions (AIR, EGR, etc.) is hooked up. This is a T-5 manual setup, and I'm getting these counts while sitting in neutral sitting in the driveway.

I'm about to give up on this one.....

I'm using a brand new 350 knock sensor for a 1991, but this was a 305TPI car before the swao 2 weeks ago to me 383.

Any suggestions or ideas on how to address this problem? What can cause this type/level of detonation counts?

 

ttt for ya...

Curious as to how you know it makes 400+hp/500+lb-ft if it runs so bad.

What octane gas are you using? What is quench?
10.5:1 on iron heads is pushing it?
Have you calculated your DCR?

 

Is one of the headers slapping hitting something. Mine did that. Takes that straight up the header to the head and the knock sensor.

 

Those are the flywheel numbers from Desktop Dyno 2K using the actual flow numbers the engine builder got from his heads on a flow bench, and the cam specs Comp Cam gave me with the hyd roller conversion custom cam (using small diameter headers for the simulation exhaust) and an 850 CFM TPI induction system. The numbers actually came out as 413 HO and 529 ft-lbs, but I realize from what I found in the archives it will probably be a little lower in real life, but hope the 58mm BBK and SuperRam make up for it a little bit.

Now, as for it running so badly....

The 350 memcal I was using was not actually for a 91 as I originally thought. I got chip number off it and tracked it down as being an 89 MAF memcal, which was totally off kilter for my 91 speed density system. Just discovered this last night I think it was (maybe the night before). I posted that finding in the DIY forum, and got concurrence there that would be a definite problem. Some folks even expressed surprise it ran at all. As soon as I get the chip fine tuned a little bit it will be going on a dyno for some more tuning runs, then I guess we'll see what the real world HP and TQ numbers ar the rear wheels are. Since I think I heard a 10% drop for a manual transmission is fairly common, I'm hoping for a 350 HP reading there. - that would be outstanding but is probably too optimistic. But only time will tell.

To answer your other questions, I am using 92 octane premium gas, I have NOT calculated my dynamic compression ratio, and I don't know what the quench is. I guess I'm not that smart, sorry.

So, I found the knocks problem to be a stupid wrong memcal/chip choice to put on the piggyback board. My Bad. Now we'll proceed with the first tuning logs and get it ready for it's first dyno pull in a few weeks to really tune it right.

Thanks for all the inputs and responses. Have a Great Day!

- Vern