I run champion rc9yc in my high c small block .
So what heat range/ plug should I be looking at? I didn't do much research when purchasing the original plugs so I wouldn't trust my starting point.
Yes, it can be to loud to hear the ping. IMO, you'll be OK on 93.I do have an O2 sensor and gauge, and a high flow water pump. Will look into a new fan and shrowd and possibly a 6 pack hood scoop to get cooler air intake.
So you guys think I'll be safe running 93 octane gas with 10.2:1 compression and iron heads, with 280 duration cam assuming I can keep it cool?
I've got pretty loud exhaust. Is it possible to not hear the pinging? Is there a good way too test?
The larger cam bleeds off some compression making it easier on octane requirements and pinging issues. But not by much between the two cams.Did it run cool?
Looks like the MP280 cam has slightly more duration at .050 lift 238 vs 230. Not sure if that makes a big difference.
Maybe I'm more concerned than I need to be. I had always heard 10:1 or higher was dangerous with open chamber iron heads.
Often that is what you will read and I say it a lot as well mostly because there is a bit of truth to it but, BUT, it is combination dependent. I say it because it is a dead safe area to do much with.From what I read 9.5 was the limit for open chambered iron heads and medium cam. I'll give it a shot as is with a better radiator fan and hopefully a closed air system hood scoop with race gas/ premium gas mix and just keep lowering the octane until it becomes an issue...
Tuning a carbs mid rpm lean spot can be a huge pain. The smaller carb is only giving up 10hp or so. It's not a huge thing.I'm running an Edelbrock 650 which might be a bit small, but my Holley 750 vac secondary has a flat spot at part throttle (lean per O2 sensor) and I don't want to risk it with the high compression.
What actual AFR readings are you getting at this so-called 'lean spot' and at how much is the 'part-throttle' condition? 14-15 is fine at cruise and light throttle.I'm running an Edelbrock 650 which might be a bit small, but my Holley 750 vac secondary has a flat spot at part throttle (lean per O2 sensor) and I don't want to risk it with the high compression.
The explanation from mderoy340 is right and your conception is right. His advice is to start with no vacuum advance and then work it in after the mechanical advance is all set; sounds like a good plan.That's the first time I've considered the vacuum advance coming into the equation. I figured it only upped the timing where there was little to no load, which is usually a safe zone for detonation. Is that not the case?
Plugging up the hose is super easy, just trying to better understand the science here.
When people shoot off with "I run bla bla bla plug in my small block"... immediately put them on ignore... jk but seriously, to hell with THEIR small block, this about YOUR small block, RIGHT??
Try one heat range cooler, in YOUR case IF you find you can't quite tune it out with a timing adjustment.
Good luck, I still think a little more coolant flow at low speed and 2-3 degrees timing taken out will be enough, if needed.
The engine hiccups and the O2 gauge would spike. Didn't matter how hard or light I stepped on the peddle, happened off idle. Drove me crazy so I pulled the carb.What actual AFR readings are you getting at this so-called 'lean spot' and at how much is the 'part-throttle' condition? 14-15 is fine at cruise and light throttle.
People get all hung up at keeping an AFR around 13 all the time and it is just a waste of fuel; at part throttle, the cylinder filling is only partial and the cylinder pressures are much lower so pinging and detonation is very hard to have occur unless the timing is waaaaaay wrongly advanced. FYI, the Chrysler Lean Burn system would run up into the 18 range for AFR.
The O2 sensor is a great tool; just don't let things like this fool you.
What are the cylinder pressures at sea level?
OK, not just a lean spot, like the air or fuel jet was off but sounds like an accelerator pump or progression circuit issue.The engine hiccups and the O2 gauge would spike. Didn't matter how hard or light I stepped on the peddle, happened off idle. Drove me crazy so I pulled the carb.
Understandable. I'll run out and borrow a compression test kit from one of the auto part stores around here this weekend and report back.Everybody's guessing until you know these figures. You might not have to do much. Or you might need to do more than tuning and spark plugs. A simple compression test will tell you where you're starting point is.
Exactly. Rebuilt the carb, played with accelerator pump adjustment, and switched around some jets. Next step was bigger squirter diameter and possibly putting small holes in the butterflies to help with off idle transition. Strang thing was the accelerator pump was shooting plenty of fuel...OK, not just a lean spot, like the air or fuel jet was off but sounds like an accelerator pump or progression circuit issue.
Exactly. Rebuilt the carb, played with accelerator pump adjustment, and switched around some jets. Next step was bigger squirter diameter and possibly putting small holes in the butterflies to help with off idle transition. Strang thing was the accelerator pump was shooting plenty of fuel...
Knock sensors are piezo-electric sensors that respond to vibrations in a certain narrow frequency range.
All you will get is a quick electrical pulse out of them, so you would need a small circuit to detect a pulse over a certain level, and then 'latch' it (in the electronics sense of the word) to light an indicator. It could also be set to not latch in a fault (knock) on one or a few knocks, to avoid nuisance indications. So, yes, doable for sure.
Well lookie here: Caspers Electronics Knock Gauges 102003
Naw, I can still come up with all sorts of excuses LOL!With one of those and a wideband O2 AFR readout there would be no excuse not to get your car tuned perfectly.
Agree. Most folks with AFR gauges lean the idle to 14:1 and carb motors need to be rich at low rpm high load (coming off idle). Fully warmed up with airgap manifold my motor needs 12.5 at idle in gear to transition properly. Don't use the gauge to set idle mixture, give the motor what it needs to run properly.I found an online PDF of tuning instructions for my 750 Mighty Demon from the manufacturer, not exactly the same as a Holley but similar enough. In those instructions it pointed out that unless the transition-slot opening is set correctly (throttle plate position), the accelerator pump squirts fuel AS SOON AS the throttle is touched, AND the idle mixture is sufficiently rich, it WILL produce an off-idle bog or flat-spot. Tried it myself, leaned out the idle mixture not even that much (it still idled smooth) and all of a sudden it was hiccuping every time I touched the gas off idle. I gradually richened it back up and miraculously the stumble was completely gone and throttle response was instantaneous.
Agree. Most folks with AFR gauges lean the idle to 14:1 and carb motors need to be rich at low rpm high load (coming off idle). Fully warmed up with airgap manifold my motor needs 12.5 at idle in gear to transition properly. Don't use the gauge to set idle mixture, give the motor what it needs to run properly.
So I did a compression test today. Sorry for the delay, the rental tool kit I got was shot so I ordered a new compression test kit online.Everybody's guessing until you know these figures. You might not have to do much. Or you might need to do more than tuning and spark plugs. A simple compression test will tell you where you're starting point is.
So I was able to get all the plugs back in and warmed it up before doing the cranking compression test again. This time everything came back pretty close to 155 PSI.You need to warm it up and then do a compression test.