Large rpm drop

Charlesvolare said
It was just a thought, I have many of those as I'm sure you do too

Something wrong with science? Lol I'm not using it to tune my idle, just stating that's where it was landing, adding to info that may help. Not gonna completely disregard the second law of thermodynamics, but I'm not too concerned how rich it needs to be to idle decent. If I can lean it out some and good, if not oh well kinda deal.

Plugs look good, I can pull and take a picture of I need to

Some calculators put it at 10.8:1 if it makes you feel any better. I'm not sure what to say, I can send to my build sheet. Put it together myself, I'll swear on all I've got the measurements are correct.

It's an amazing cam, zero complaints at all- very streetable and plenty of power.originally I thought it was around 9:1, so we speced the cam for that. Had detonation problems running timing anything I've 32* on 93 octane. Butted rings and broke a ringland, pulled and rebuilt. Made sure to measure everything like I did putting it back together.

What cam would you have gone with?

Autolite 3923

If it's pulling fuel from the main jets you'd see it. Fuel would be coming out of the boosters.

An O2 sensor can and will lie to you. Not all O2 sensors read the same. Different fuels require a different A/F ratio so tuning to a number is not correct. As I said, put it away until you get everything else correct and then hook it back up. Really, if you can't data log it, and overlay it with RPM, MAP and throttle position, you are still really guessing except at idle and WOT.

I'd love to see a picture of your plugs, preferable a couple of plugs with the shells off.

If you didn't actually measure the volume of the piston at say .500 down the bore, it's still a guess. How did you account for the valve notches?

You showed very little info on your cam. What I was able to see was what is most likely a slow ramp, wide LSA early intake closing cam. If you are at 11:1 and you didn't call someone and tell them what you are doing, the cam will always be wrong.

A faster ramp lobe (doesn't need to be an outrageous lobe) would allow the cam timing to be more agressive (what the cylinder actually "sees") while not giving up driveability.

IMO, you are at least 6 degrees too small on duration and I'm not sure why it's a dual pattern cam. Comp love that stuff but mostly, it's a gimmick.

You might be a range too cold on your plug. It's hard to tell without looking at an Autolite plug catalog. Getting Autolite to send me a catalog has proven futile up to this point.