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ok, workin on getting info ready for the bbc stroker ready so i can talk to the cam guys. i am dead set on the edelbrock performer heads. heres what i found out. one im sticking with an eagle rotating assy. i talked to them and they told me to go with the 11011 kit or the 11012. the 11 kit has a 9.0:1 compression and the 12 about 11.0:1 nothing in between with the 110 cc combustion chambers. which one should i go with. this car is street drivin but i want it to go and have serious big block power and sound! i want it to have good maners. but is 11.0:1 to high or what should i do? if i dont do the stroker and just do a 454 than i can get a better compression but it dont cost all that much more to stroke. what do you guys think?

thanks al.
 

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I ran 11.1 with a iron head 350 for over 10 years using 94 sunoco ultra pump gas and sometimes 92/93 every summer day and it was fine even with 16 degrees inital timing, but i also had a 10" convertor, 4.10 gears and a hydralic cam with a 106 LSA. conv/gears took load off the engine and tight LSA bled down cylinder pressure at low rpm's. You on the other hand are using aluminum heads and that alone will allow you to run 1 point higher cr for the same octane. so 12 to 1 cr is possible using 94 and at 11.1cr 92/93 should be fine. so i say go for it as long as you buy the eddy heads and dont go higher than 11 to 1 cr. Just a FYI i love the 496 combo, the torque will be super brutal so i hope you have a good trans and rear.
 

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I heard that the performer heads can be had used for $1000. is this true?

I like the lower compression myself so you are good to go if you ever want to turbocharge/supercharge it
 

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You can adjust your compression a little with the head gasket. A thinner gasket on the 9:1 pistons will increase the compression and a thicker gasket on the 11:1 pistions will decrease your compression.
 

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i think you would be fine. it might not want all the timing on pmp gas as it would on say some 110 but if your driving it on the street you shouldnt need it. for the past ten years ive been running 91 oct on a 355 with 11.4-1 CR. never had a problem. but when i go to race it i put 110 in it mainly cause i hit it with a little N2O.:yes:
 

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....tight LSA bled down cylinder pressure at low rpm's.....
I really wish people would quit perpetuating false internet theories and myths.

Narrowing the LSA does not lower pumping pressure. With no other changes, tightening the LSA increases pumping pressure by causing the intake to close sooner. Over lap doesn't "bleed down" pressure either because the overlap period occurs at exhaust TDC not compression TDC.

here's two examples using a generic 9:1 350:

  • 218/[email protected]" 106 LSA; 102 ICL; intake close: 71 degrees ABDC;
    pumping pressure = 165 psi
  • 230/[email protected] 114 LSA; 110 ICL; intake close: 85 degrees ABDC;
    pumping pressure = 135 psi
In case you assume it's caused by duration here's the same cam on 106 LSA:
  • 230/[email protected] 106 LSA; 102 ICL; intake close 77 degrees ABDC;
    pumping pressure = 152 psi
Gaining or losing pumping pressure is closely related to intake close, not overlap or LSA.
 

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I really wish people would quit perpetuating false internet theories and myths.

Narrowing the LSA does not lower pumping pressure. With no other changes, tightening the LSA increases pumping pressure by causing the intake to close sooner. Over lap doesn't "bleed down" pressure either because the overlap period occurs at exhaust TDC not compression TDC.

here's two examples using a generic 9:1 350:

  • 218/[email protected]" 106 LSA; 102 ICL; intake close: 71 degrees ABDC;
    pumping pressure = 165 psi
  • 230/[email protected] 114 LSA; 110 ICL; intake close: 85 degrees ABDC;
    pumping pressure = 135 psi
In case you assume it's caused by duration here's the same cam on 106 LSA:
  • 230/[email protected] 106 LSA; 102 ICL; intake close 77 degrees ABDC;
    pumping pressure = 152 psi
Gaining or losing pumping pressure is closely related to intake close, not overlap or LSA.

Paul, do you have a program that predicts cranking compression? I have a 9.98-1 static compression ratio 468 that I plan to run a voodoo 60234 solid roller cam in- any idea what the cranking compression will be? http://www.summitracing.com/parts/LUN-60234?part=LUN-60234&autoview=sku
 

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It's basic gas law physics but most people get it wrong because they don't account for T1 T2 (self heating from compression) and the DCR is usually calculated wrong because people use intake "closing" values that are still "open".
I have it all programmed into my HP48 calculator and it assume sea level conditions and low leakage. High altitude and higher leak down values will give lower compression pressure.

I need all the usual CR specs:
Bore diameter
Stroke
Rod Length
Piston CH
Dome volume
Gasket thickness
Actual combustion chamber volume
Block height
Deck height
The hard part is Cam actual intake close at 0 lift (not .050" or .006")
It's possible to estimate it if I have the cam card, but when I setup my own engines I use a degree wheel and dial indicator.
By advancing and retarding the cam you can vary the intake close.
 

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My 496 came out to 11.2 to 1 with my Eagle stroker kit and 049 iron heads. It runs good 93 octane. I just bought a barrel of 110 octane and mix it w/93 now. Now it runs REALLY good, definetly likes more octane, but had no problems on pump gas. Just couldn't afford aluminum heads at the time, which would have made it a little easier on pump gas.
 

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Most tight lobe center cams have more duration than a typical 114 lsa 350hp 327 cam. A typical 234/244 @ .050" 106 lsa cam will reduce the signal to the carb up to a certain rpm. once the engine gets into the powerband, the VE (Volumetric Efficiency) will be better than with the wide lobe center cam. So, cylinder pressure is reduced above and below the intended powerband vs. the wide lsa cam. This is the effect most people refer to when stating close lobe center cams are better for pump gas. Problem is, most of these engines have increased cylinder pressure at the torque peak and have detonation trouble. The type which you cannot hear, but show up as specs on the plugs, hammered rod bearings and main cap walk.
The DCR calculators can be used to get you in the ball park, but it isnt an absolute guarantee the engine will be knock free. For example, you wouldnt run the same intake valve closing point on a 400 sbc with a set of vortecs and a 600 holley, vs. a 400 with AFR 227's and a 1050. Even if both engines ran 10-1 compression. If you did, you would limit the rpm capability of the 227 headed engine by using the optimum closing point for the mild 400.
 

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so, what is the difference between 9:1 and 11:1 in a bbc 496?

10-15 hp? and a whole lotta trouble if you ever decide to boost it?
 

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What Camgrinder is talking about is the pressure increase from inertial ram effect. It's possible to have VE (cylinder filling) over 100% due to the supercharging of the cylinder from inertial ram effect. This is different then the mechanical air pumping of the engine but still needs to be considered.

Under certain circumstance, detonation is most likely to occur at maximum VE. Peak VE usually occurs around peak torque not peak HP. Some maxxed out engines we'd have to tell the driver to go light on the throttle until it gets past a certain rpm.

Most street engines don't come close to 100% VE so inertial supercharging isn't a big factor.

It's an interesting advanced topic but unfortunately most questions we get here are along the lines of "How's my engine going to sound with cam 'X'? " :rolleyes:
 

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I really wish people would quit perpetuating false internet theories and myths.
Paul im sure you are 100% wright on the LSA theories and am not at all discrediting your knowledge, but my engine ran this way proving it can work in the real world using a 106 LSA with 16 degrees inital. first cam had a 110 LSA and 9.7 cr with smog 76cc heads and .100 dome pistons, would run on 92/93. next i changed heads to 64cc camelhumps giving 11.0cr ran on 94 and spark knock with heavy loading unless i mixed 110 in or a booster. Next changed cam to 106LSA because of lift issues, and was back to running 94 only. Last change was same cam and +.030flat tops with sportsman2 heads and 10.5 cr and back to running 93. I used to drive my nova everyday for years with these combos and tried everything to not run racing gas. During this time i found lots of people doing this in magazines back in the early 90's and running 12 to1 on 92/93 octane. This is all effected on weight, convertor, gear and weather too, but i drove heavy 78/74 novas everyday with the same convertor and gears.
 

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I don't dispute your anecdotal evidence that you changed a number of variables and the engine ran on lower octane. What I am disputing is your explanation for why this was so. What are the cam card specs for both cams?
Did they have the same or different duration, ICL and Intake close?

What was the measured chamber volume on the heads and pistons? Did you even measure the volumes? If not, then how do you know that the CR difference wasn't greater than 1/2 a point?

In any event I am 100% confident your explanation is incorrect.
 

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Al,

I don't know if you are still tracking your thread but here is something to think about.

http://www.carcraft.com/projectbuild/ccrp_0703_more_horsepower_for_less/index.html

Here's the port velocity comparison (feet per sec.)
int/ex
AFR 305's CNC - Edelbrock oval ports

.3= 190/205 - 176/177
.4= 236/253 - 212/215
.5= 271/286 - 229/247
.6= 289/303 - 233/270
.7= 289/318 - 235/288

Note that the AFR heads out flow the Eddys from .300 lift right up through to .700 That's good street usable torque!!!
Get the higher compression assembly and go to E-85. I thing you would be knocking on 740 HP. :D

Jim
 
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