natural breather ignition timing help

[turbo3.8monza]

I built up a 3.8l for my Monza the specs are as followed
bored .03" over
ported 8445 heads with 1.77"/1.5" valves
9.5:1 compression
TA performance C110 cam custom ground for the v6
.455"/.465" lift
218/224 duration @ .050"
110 lobe separation
port matched Kenne Belle single plane intake
600 CFM edelbrock carb
custom made almost equal length headers (took me forever and a day to make)
the trouble I'm having is I can't find a good initial timing point, I can get it to idle nice but anything past 2500 rpm it detonates and if get it to rev good it struggles to idle. I'm running a HEI dist. with Mr. Gasket advance kit with the light springs. I'm still pretty new to Buick game any help would be appreciated

 

[charlief1]

Back your initial timing down. You need to set the timing at max rpm with an adjustable timing light. Did the heads and block get cut? If so you may be running to much compression now and it's causing the det issues.

 

[turbo3.8monza]

the heads and block where cut just enough the make them flat not for increasing the compression. I'm only running about 9.5:1 static compression.
I have the timing at 12 degrees it revs very quickly and clean. the idle is almost acceptable, it idles like it should for the most part but every so often it shudders

 

[mikestertwo]

With that cam you have to run a lot of initial timing. Put heavier springs on the weights to slow the curve down.

 

[charlief1]

Yes it does need more initial timing, but as I said you need to set total timing to make sure to eliminate detonation issues. How much is "just enough to clean up" by the way. .030 off the heads and block with a dished 8:1 piston on a 3.8 will bump you up to almost 10:1. If you started with a 9.5:1 piston and did a .010 cut off the heads and block you're over 10:1 now. Try switching to to a much higher grade of gas like racing gas and see.

 

[turbo3.8monza]

I don't remember the exact measurements of my deck clearance and combustion chamber size but with .020" head gasket I'm right at 9.52:1. I have 93 octane in the tank right now if I could get me hands on some race fuel I would try it to eliminate another variable. I'll also try putting a heavier set springs in the dist. to see if that helps

 

[unboostedV6]

34 deg total is where I ended up at 10.5:1 on pump gas back in the day. The light springs bounced around too much to get steady timing even when rev'd up. GB

 

[turbo3.8monza]

well I put the medium springs in the dist. seems to be working better, finally got my mufflers in so i can finish ther exhaust and tune the motor right with a*s chewing from the neighbors. I would be nice to get this running right to shut up my friends with small blockitis!