[hal101]

Originally Posted by tom s

Your lucky you can get by with the 100,you have to be way over 11-1 if the block has been decked and any over bore.Tom

the block has not been decked but it is .040 over

i dont know the actual comp ratio but it runs very well on 100 octane race gas

[wbnapier]

With 100 octane, at WOT, I hear a crackling sound, which I assume is pinging. I don't know the details of my engine, other than block, heads, and mild build circa 1991.

Originally Posted by tom s

Your lucky you can get by with the 100,you have to be way over 11-1 if the block has been decked and any over bore.Tom

[PunchT37]

After 62 posts, either lower the idle speed, reduce cyl. pressure, reduce cyl. temp., all the above, or raise octane.

[commanderpilot]

Originally Posted by Navy Horn 16

Why not just buy 100LL and mix it at 30%. WAY cheaper.

I don't trust additives at all. You don't really know what they are putting in it, and all you know it is that is making your gas less volatile.

Commanderpilot:
Hate to say it, but the availability of 100LL is hanging by a thread due to EPA's pressure and the fact that the only source for the tetraethyl lead is a single manufacturer in Europe. It's become a "boutique additive." Believe me, piston powered plane owners are very concerned about this because burning anything else would require FAA approval (assuming the refiners come up with a no-lead 100 octane fuel). Nobody is likely to go through that given the high cost to certify a new fuel and the (relatively) low demand for the 100LL to begin with. I believe it accounts for only 2% of all gasoline sales in the USA.

[shaker455]

Originally Posted by PunchT37

After 62 posts, either lower the idle speed, reduce cyl. pressure, reduce cyl. temp., all the above, or raise octane.

X2 Wade!

[STEELCITYFIREBIRD]

Originally Posted by PunchT37

After 62 posts, either lower the idle speed, reduce cyl. pressure, reduce cyl. temp., all the above, or raise octane.

X3....might I add tighten up the squish, might be easy as some thin head gaskets.

Attempting to be a fuel Alchemist can have disastrous results during the learning curve.

[dataway]

Speaking of squish ... I am at about .043 ... .004 in the hole and the .039 Fel-Pro gasket. I had wanted to be about .035 .... is there a gasket option to lose a few .001s without going to solid copper?

[dataway]

Originally Posted by wbnapier

With 100 octane, at WOT, I hear a crackling sound, which I assume is pinging. I don't know the details of my engine, other than block, heads, and mild build circa 1991.

A "lean miss" can sound like that sometimes. Once had a holley 450 cfm carb on my GTO ( when I was 17) ... at about 4000 rpm it would start crackling. Luckily I corrected the situation before I melted a piston.

[STEELCITYFIREBIRD]

Originally Posted by dataway

Speaking of squish ... I am at about .043 ... .004 in the hole and the .039 Fel-Pro gasket. I had wanted to be about .035 .... is there a gasket option to lose a few .001s without going to solid copper?

Cometic MLS, not cheap, your close enough from what I know.

[wbnapier]

Originally Posted by dataway

A "lean miss" can sound like that sometimes. Once had a holley 450 cfm carb on my GTO ( when I was 17) ... at about 4000 rpm it would start crackling. Luckily I corrected the situation before I melted a piston.

How did you correct it? I had a dyno test done and I was a little lean at WOT, so I increased the jetting. I redid the dyno thing and no change. Strange. Timing is 12 initial 32 total.

[dataway]

Not saying that is definitely your problem ... it was obvious in my case that the carb was too small .... installed a larger carb and was done.

The sound is actually a bit more like you would imagine a .22 caliber machine gun might sound.

Lean enough to cause a lean miss would have surely been spotted on the dyno so I doubt it's your problem.

["QUICK-SILVER"]

Originally Posted by dataway

Not saying that is definitely your problem ... it was obvious in my case that the carb was too small .... installed a larger carb and was done.

The sound is actually a bit more like you would imagine a .22 caliber machine gun might sound.

Lean enough to cause a lean miss would have surely been spotted on the dyno so I doubt it's your problem.

Not the carb too small. Carb just wasn't jetted/calibrated right for the application. Carb too small and engines run like they have govenors. Runs fine, just wont rev high and make power. Like the difference between running a 2bbl and 4bbl.

Clay

[wbnapier]

Originally Posted by dataway

Not saying that is definitely your problem ... it was obvious in my case that the carb was too small .... installed a larger carb and was done.

The sound is actually a bit more like you would imagine a .22 caliber machine gun might sound.

Lean enough to cause a lean miss would have surely been spotted on the dyno so I doubt it's your problem.

Thank you for the reply. I've been struggling with compression / octane issues. The previous owner doesn't remember / have the engine build details, and I am new to the automotive hobby. The only thing I know for sure is that on 91 octane the engine diesels substantially, which doesn't happen on 100 octane. The sound of engine pulling is better with 100 octane as well. I don't know what really pinging sounds like, and I am unsure what the crackling sound at WOT is.

On the dyno, I was 1 point lean at WOT. We up-jetted the end carbs, and it didn't move the number. We also advanced the timing from 12/32 and the hp / torque didn't change. All this is contrary to accepted doctrine.

One day, I may pull the engine, re-gasket, aluminum heads, etc... It's just so expensive, so I just pay $9 / gallon in race gas until then.

[dataway]

Originally Posted by "QUICK-SILVER"

Not the carb too small. Carb just wasn't jetted/calibrated right for the application. Carb too small and engines run like they have govenors. Runs fine, just wont rev high and make power. Like the difference between running a 2bbl and 4bbl.

Clay

Yep, that sounds right ... when I think about it CFM limit is just that, can still be rich or lean. The 450 CFM carb was probably jetted leaner as it wasn't a "performance" carb by any means.

However .... throttle response was fantastic