retarding the cam from 4 degrees to straight up

[Tom68]

That is a new one for me. What does BSFC have to do with squish clearance?

Stan

Efficiency.

[Stan Weiss]

That is a new one for me. What does BSFC have to do with squish clearance?

Stan

Efficiency.

Yes, if you get the squish correct you will see an increase in efficiency which should show as lower BSFC. But looking at an engines BSFC how does that tell me if the squish is correct and if not what I need to change to get the squish correct?

Stan

[Tom68]

That is a new one for me. What does BSFC have to do with squish clearance?

Stan

Efficiency.

Yes, if you get the squish correct you will see an increase in efficiency which should show as lower BSFC. But looking at an engines BSFC how does that tell me if the squish is correct and if not what I need to change to get the squish correct?

Stan

Well at least it'll tell you you're off when you have good baseline data, or even a target, it can't tell you how to fix it, that's the dream and error testing. Dream up a fix, try it and hopefully it wasn't an erroneous dream.

[digger]

So the crappier the chamber the less it matters?

[JES]

[quote=digger post_id=935295 time=1674195889 user_id=6525]
So the crappier the chamber the less it matters?
[/quote]

Yes.

[rgalajda]

Bigcheif632 wrote
 Compression was 11.5:1.  And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. 

91 octane with 11.5:1 compression?

[Bigchief632]

Bigcheif632 wrote
 Compression was 11.5:1.  And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. 

91 octane with 11.5:1 compression?

Yep. Actually we usually use BP 93 premium ethanol unleaded,
But they run on 91 premium ethanol unleaded too. Actually tried race gas/pump gas mix in it, made more power on straight pump gas. Which is usually the case if it doesn't need the octane.

[ClassAct]

Bigcheif632 wrote
 Compression was 11.5:1.  And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. 

91 octane with 11.5:1 compression?

It’s done all the time. I’m at 11.77:1 and I’m going to 12:1 on my next build. With iron heads.

[skinny z]

Alright then. Two possible scenarios.
Target compression ratio is 10.4:1.
DCR ~ 8:1
Presently, with parts on hand as they are:
357: 4.04" x 3.48" ( shortblock assembled so no decking possible)
Piston .008" below deck
5cc piston
65.4 cc Vortec chamber (iron)
.026" x 4.100" gasket
Net .034" quench.

I may rework the chambers and then mill the heads again to restore the 10.4:1 CR.
For the sake of this discussion, let's say I end up with a 60cc chamber which would require a .050" gasket for 10.4:1.

Am I better off with the now .058" quench for a pump gas track only car?
How would that translate to a streeter?

Or would the difference be un-noticable given a 450 HP, 6500 RPM example?

[rgalajda]

Bigcheif632 wrote
 Compression was 11.5:1.  And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. 

91 octane with 11.5:1 compression?

It’s done all the time. I’m at 11.77:1 and I’m going to 12:1 on my next build. With iron heads.

What percentage of ethanol? How much camshaft duration?

[ClassAct]

Bigcheif632 wrote
 Compression was 11.5:1.  And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. 

91 octane with 11.5:1 compression?

It’s done all the time. I’m at 11.77:1 and I’m going to 12:1 on my next build. With iron heads.

What percentage of ethanol? How much camshaft duration?

Whatever comes out of the pump. It says up to 10% but I’ve never verified that. 282/255 @ .050 so nothing outrageous. It’s on a 105 LSA so according to the experts it’s all wrong.

[Bigchief632]

Alright then. Two possible scenarios.
Target compression ratio is 10.4:1.
DCR ~ 8:1
Presently, with parts on hand as they are:
357: 4.04" x 3.48" ( shortblock assembled so no decking possible)
Piston .008" below deck
5cc piston
65.4 cc Vortec chamber (iron)
.026" x 4.100" gasket
Net .034" quench.

I may rework the chambers and then mill the heads again to restore the 10.4:1 CR.
For the sake of this discussion, let's say I end up with a 60cc chamber which would require a .050" gasket for 10.4:1.

Am I better off with the now .058" quench for a pump gas track on
How would that translate to a streeter?

Or would the difference be un-noticable given a 450 HP, 6500 RPM example?

I think you're over thinking this. Don't create more expense for yourself for +/- .-2 of a compression ratio. The difference you'll see, is virtually un detectable. Your talking +/- 5hp with however you slice it. Send me a pm. I'll evaluate your combo, and I promise you, if you listen to my advice, you'll make 20-30 more hp than you thought you could. Maybe more.

[Bigchief632]

Bigcheif632 wrote
 Compression was 11.5:1.  And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. 

91 octane with 11.5:1 compression?

It’s done all the time. I’m at 11.77:1 and I’m going to 12:1 on my next build. With iron heads.

What percentage of ethanol? How much camshaft duration?

According to the pump, 10%. I've never measured it. But I have e85, and that varies A TON!

[skinny z]

Alright then. Two possible scenarios.
Target compression ratio is 10.4:1.
DCR ~ 8:1
Presently, with parts on hand as they are:
357: 4.04" x 3.48" ( shortblock assembled so no decking possible)
Piston .008" below deck
5cc piston
65.4 cc Vortec chamber (iron)
.026" x 4.100" gasket
Net .034" quench.

I may rework the chambers and then mill the heads again to restore the 10.4:1 CR.
For the sake of this discussion, let's say I end up with a 60cc chamber which would require a .050" gasket for 10.4:1.

Am I better off with the now .058" quench for a pump gas track on
How would that translate to a streeter?

Or would the difference be un-noticable given a 450 HP, 6500 RPM example?

I think you're over thinking this. Don't create more expense for yourself for +/- .-2 of a compression ratio. The difference you'll see, is virtually un detectable. Your talking +/- 5hp with however you slice it. Send me a pm. I'll evaluate your combo, and I promise you, if you listen to my advice, you'll make 20-30 more hp than you thought you could. Maybe more.

I think you missed the point of my question Chief.
The CR stays the same but the quench goes up from .034" to to .058".
What am I giving up or gaining if anything?

[Bigchief632]

Alright then. Two possible scenarios.
Target compression ratio is 10.4:1.
DCR ~ 8:1
Presently, with parts on hand as they are:
357: 4.04" x 3.48" ( shortblock assembled so no decking possible)
Piston .008" below deck
5cc piston
65.4 cc Vortec chamber (iron)
.026" x 4.100" gasket
Net .034" quench.

I may rework the chambers and then mill the heads again to restore the 10.4:1 CR.
For the sake of this discussion, let's say I end up with a 60cc chamber which would require a .050" gasket for 10.4:1.

Am I better off with the now .058" quench for a pump gas track on
How would that translate to a streeter?

Or would the difference be un-noticable given a 450 HP, 6500 RPM example?

I think you're over thinking this. Don't create more expense for yourself for +/- .-2 of a compression ratio. The difference you'll see, is virtually un detectable. Your talking +/- 5hp with however you slice it. Send me a pm. I'll evaluate your combo, and I promise you, if you listen to my advice, you'll make 20-30 more hp than you thought you could. Maybe more.

+/- 5hp. If you want to spend a bunch of time reworking the chamber, then paying a shop $100+ dollars to mill the heads to get back what you lost, that's what you're looking at. 6 of one, half a dozen of the other.
I think you missed the point of my question Chief.
The CR stays the same but the quench goes up from .034" to to .058".
What am I giving up or gaining if anything?