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Old 02-12-2014, 07:57 PM
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ccracin ccracin is offline
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Can I just first say, I LOVE THIS STUFF! Ok, here we go:

Quote:
Originally Posted by Ron Sutton View Post
Hi Chad,

The key to optimizing restricted engines is to not leave anything on the table & take nothing for granted.
Every little bit matters. 10.8 compression is better than 10.7 ... 510 cfm is better than 500 cfm … a few ounces here & there … etc, etc.


A. The 034 bowtie head is the best of those options hands down. I think it flows around 215 cfm, which isn’t anything astounding but it’s the best cast iron GM SBC head.

B. A big deal in these engine is the getting the "squish band" to the optimum number of .035". This means "cold" the piston has .035" clearance to the head surface. This is achieved with a combination of head gasket thickness & block decking.

As an example,

If they run a .041" FelPro gasket, the piston needs to stick out of the block by .006" ... putting the top of the piston at .035” from the head.
If they run a .039" FelPro gasket, the piston needs to stick out of the block by .004" ... putting the top of the piston at .035” from the head.
If they run a .031” FelPro gasket, the piston needs to be down in the bore by .004” ... putting the top of the piston at .035” from the head.

While we’re on head gaskets, run the smallest diameter bore you can. If the engine bore is 4.040”, try to get a head gasket bore around 4.080”. To achieve the optimum squish band, you’ll need a gasket .035” or thinner to meet the "no piston above the deck rule". There are several around .031” See if you can get them with the 4.080” bore. That would be a good gasket for this app with the small 64cc chamber. When I was running we had a 10.5:1 rule and I ran zero deck with a .035 steel shim gasket, so I had this in mind

C. If the track doesn’t tech carbs with a gauge, there is 30 precious cfm with some TLC. If they do, see if they tech the butterfly shafts. Milling them is worth 10cfm. If the carb has to be 100% gauge legal, it still needs to be reworked. They have a No-Go for the throttle shaft and plate combo, I will try to get that size and see if there is anything we can gain there.

D. K&N Filters designed a racing filter with a profiled top & bottom that flat out flows more air. Since every CFM matters, you’ll want to use the K&N “Flow Control System” on their 2-barrel. Run the 4.5” tall version & pick the correct one if the carb has the choke horn still on or not.Believe it or not they have outlawed that filter housing. you can run a 3x14 K&N element but that's it. No flow control devices at all. The best we can do is the spun aluminum setup from Speedway with the o-ring seal.

E. Too bad you can’t switch manifolds. The Edelbrock Victor Jr 2-BBl … is the best mid range Intake manifold I have found through testing. In fact, with our 587HP 2-barrel 410” engines, we went away from it to kill some mid-range (and gain upper end.) But it sounds like a performer it is. Do the rules allow you to run the air-gap version? Negative on the air-gap. 2101 only.

F. I see they do not allow methanol for fuel. What about E85 or “Ethanol”? If they allow E85/ethanol, that is your best choice by far. If they require it to be a certain percentage of ethanol, the best strategy is to mix Ethanol & racing gas. Ethanol will flat out build more top end power, so in the 4000-6300 rpm range they’re have an advanatge.No alchohol or E85. Must by fuel at the track. VP 110 They will do a specific gravity test.

G. Back on the carb again, if they allow E85, I’ve got a guy I worked with that together we developed some good pieces. Ugh

H. Comp Cams has some new-ish solid lifter lobe profiles that have more area under the curve while still allowing standard .842” solid lifters. The mistake too many racers make on restricted engines is under-camming them. They think well there is less airflow, so I need to make all my power down low. This is not optimum. When these are the rules, the racer that builds the most total power under the usable rpm curve … and specifically the last 1500 rpm of powerband … will have a faster combination.I ran a custom Comp Cam that used the MA Solid Flat Tappet Lobes for .842 lifters. I gave the cam card to them, but I believe it was the 244/248 at .050 on 115 deg. center line. It ran very well with the combo I had.

Two keys to cam selection is car handling & driving. If we have a poor handling set-up car that can’t carry as much mid-corner speed without pushing … or a driver that parks it in the corner … we can’t optimize the engine. We have to band-aid the engine to build more low end torque to get the turd out of the corner. So 3800 rpm matters more. On the other hand, if we have a well set-up car … with good front end geometry that allows higher mid-corner speeds … and the driver knows how to get optimum corner speed out of the set-up … we don’t have to worry about the very bottom of the rpm curve. We can build a rocket that is “good” at 4200 … but doesn’t blow the tires away … and is “mean” from 4700-6300. I'm not sure where he will be honestly. Once he learned the tires, he ran well through the corner. Once I convinced him to use the brake and throttle together in the corner rather than using the engine to brake in the corner he picked up a lot of time. They now have another new tire, the Hoosier Commanche. In my opinion he has the capability of getting there. I would shoot for "maybe" to "mean" from 4700-6300. Make sense?

I have three cams in mind, depending on how good you think they are with corner speed.

I. Header & exhaust design are critical here. For optimum power throughout the range, we need step headers & a crossover. Before I make any specific recommendations, I need to know what cam strategy we land on … and if there are any sound decibel limits we need to meet at the track(s) they run. Sound Limits are 100db at 100 feet. I know he doesn't run crossovers. I did, but he didn't want to pay for the exhaust system when I sold the car. My system was Howe crossovers, 1 5/8" stepped to 1 3/4" with 3" collectors and a 3' to 3" Y and 3" Dynomax Bullet Muffler It worked very well.

J. Gear ratio. If we build the “mean” engine that builds better power up top … and less power down around the corner exit rpm … we can run a step more gear in the rear. This is faster. A lot of guys think if two engines put out the same power at different RPM’s … then they can just gear the car to the power band & they will be equal. Not true. Agreed. The top cars are running a 4.86 and hitting the chip just as they lift for the corner. Although we will have to see what the tire sizes will be as compared to last year to verify this will remain the same. When he ran last year he was topping out between 6 and 6100

K. Ignition timing will be more critical with the 10.8-1 compression. I’d start at 37° with this combo. Don’t mess around with advance curves. Ideally in race engines, you want to have full timing at idle. Just use a retard feature for starting it. For these engines I like the MSD E-Curve billet distributer. You can set it up to retard the timing 24° to start … then it goes to full timing at idle once the engine is running. It runs smoother, doesn’t load up, gets rolling easier, gets around the pits better, and handles low speed caution flags better. The rules state "No electronic timing controls" not sure if this distributor falls in this category.
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