Fuel and compression questions

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12valve

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Here is my combo:
'75 360 block, square decked, line honed, bored .030 over
KB107 pistons at zero deck
Scat forged I beam rods with ARP bolts
2.02/1.6 J heads, ports untouched with stainless valves, cc'd at 66
Lunati 60403 cam (.494/.513;268/276 adv dur; 226/234 @.050)
Crane Gold 1.5 rockers
Eddy rpm air gap intake
FBO ignition with MSD rev limiter
Dougs headers into 2.5" TTI X-pipe exhaust
Milodon road race pan with windage tray
A833 4spd with 3.23 gears in 8.75 rear (eventually 3.55's when $$ allows)
Looking at Cometic headgaskets; 4.040 bore and .060 compressed thickness, haven't purchased yet but used them for comp calcs.

Question #1: Can I use 91 octane fuel with a static compression of 9.95 if the dynamic is 8.54?

Question #2: I have a Holley 750 DP from my circle track days that has no choke tower and a PV plug in it along with .037 squirters and 50cc accel pumps in it. Since I will be putting this on the motor on initial fire, what would be a good place to start for jetting and PV? I plan on backing the squirters down to .031 and backing the pump cam off a little but I am more concerned about where to start with the jetting.

Motor will end up in my 67 bcuda fastback, and will be used to make me giggle like a 16 year old again.

Your input is much appreciated, thanks, Jason
 
I think you will have problems IF (!) that is the correct dynamic comp.
Usually, some where in the mid 7's would be more appropriate for pump gas.
most important thing to determine dynamic compression would be the intake closing point. Most cam manufacturers supply this. Another tip; if the cranking compression goes over ~170, you will be out of the 91 octane range (unless you really have things "sorted out). So, bigger cam, wider LSA or retard the cam all could help.
I would think that cam would have less dynamic than that, Are you sure that is the correct number?
 
as far as the 750 holley..

I would use the stock jetting..and a 6.5 pv....

I would also get rid of the 50cc pumps..
 
omahamoparguy said:
I think you will have problems IF (!) that is the correct dynamic comp.
Are you sure that is the correct number?
Click to expand...

I used the formula on Keith Black's website and the intake closing point from the cam card is 39* ABDC plus 15 gives you 54. That's how I came up with my numbers.

However, I have been wrong before so if you have a different method I would be interested in knowing it.

Thanks again, Jason
 
12valve said:
I used the formula on Keith Black's website and the intake closing point from the cam card is 39* ABDC plus 15 gives you 54. That's how I came up with my numbers.

However, I have been wrong before so if you have a different method I would be interested in knowing it.

Thanks again, Jason
Click to expand...


Other calculators use the advertised closing point ABDC (rather than @.050 plus 15 degrees) so there's some latitude there. It would give a closing point of 60 degrees ABDC and about 8.1 dynamic. But this is just playing with numbers.

However, I'd question the use of those thick gaskets -sure you'll reduce the compression but you'll also increase the quench distance. You may end up with more problems from lower compression but poor quench.

With a slightly bigger cam you could go with a thinner gasket and shoot for 10.3 to 1 static. JMHO
 
From what I have gathered here, I was under the impression that quench didn't come into play with open chamber iron heads, so I wasn't planning for that.
 
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