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Discussion Starter #1
Well its been a while since last post. For many reasons had I to scrap the 496, but good news is it forced me to build a 505 Stroker (454 2 bolt base).

Although I reused a lot of the same parts here is the new build sheet.

-AFR 290 Heads
-Custom Carrillo Pistons
-Forging 542
-Weight 585
-Dome 0.125
-Custom Cam
-Advertise 303/309
-Lift 643/60
-Sep 108
-Adv 5
-Stealth Manifold
-950CFM Quick Fuel Carb
-MSD Ignition

Engine was Dyno on a Stuska Depec W/ ADL load control

-605 TQ @ 4300
-568 HP @ 5400
-11.98 Air/Fuel
-Timing 36

All of that translated to 461 TQ and 423 HP on the chassis dyno (Don't know which Dyno Type)

Any comments/ thoughts /advice would be appreciated.

To note the original 496 measured on a Super Flow SF-8902, without the custom cam or pistons

-611 TQ @ 4400
-593 HP @ 5400
-13.6 Air/Fuel
-Timing 30


Have not yet driven the car yet, installing sub frame connectors and close ratio steering box. Should have it on the road next month when the weather breaks
 

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25.52% parasitic loss through the drive train lets me guess you have a 4,200 RPM stall converter and a nine inch rear end.

The increase in initial timing over the 496 and the loss of horsepower indicates that this isn't a very efficient combination. I am of the opinion that your heads are a little on the small size for an engine with this displacement (I probably would have gone with the 315 cc CNC AFR head for this size motor; if I were buying new heads).

I am also assuming you increased the bore on your old 496 build as opposed to going to a longer stroke crank. The thinner cylinder bores also contribute to your horsepower drop as you are loosing more heat to the coolant (which will put a further strain on your cooling system). Cast iron is a lot worse at conducting heat compared to a metal like aluminum, but as you thin it down the then the heat can flow through it at a faster rate as the metal thickness decreases. It also becomes more flexible which will upset your ring seal.

My final comment is on the carburetor. A 4500 series carb makes a BBC a lot happier than the same size (cfm) 4150 series carb. People say you can not run a 4500 on the street (I did it for years), but I would point out that most cars built to this level are not considered daily drivers. I prefer the added performance over the look of originality with the smaller carb throats with a shinny open element air cleaner and a 396 decal on it.

Big Dave
 

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Discussion Starter #3
Dave,
Thanks for the feedback, I appreciate it. I am actually running a dual disc Macleod back to a M22,12 bolt with 3:73s.

You are correct rebored with same crank and connecting rods. I get the heat issue just have a hard time believing its causing that large of a overall power loss given the blueprinted pistons and upgraded cam.

I also agree with the heads 290s are at the limit for the 505s and if I was buying new heads would have went with something a little larger. I also wondered it the 950 CFM was little under sized.

The other thing to note is that all 3 dynos (engine and chassis) were done by different people and different machines. Its a street car but might just have to take it t the strip to see what it can do.
 

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Different dyno,s give different numbers so I would not worry about that. Only advice I can give is make sure your tires are up to the job, no sense having all that power to just burn rubber(although that is fun but expensive).
 

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Dynos vary from each other (eddy or water brake), and the same dyno will yield different results on different days just due to changes in the weather. I only use a Dyno to tune as it offers easier access than leaning over the fender of a car at the track.

I don't really care what the ultimate number is as it is far too late once it is built to worry about it. I just take the info and add it to my note book which gives me direction for my next build (back then I was building a motor or two a week, so it was an ongoing learning experience). In retrospect, my memory was failing even twenty years ago which is why I wrote everything down (very important when you have to read what you wrote down were on different parts that are often fitted together a number of times). I caught an oil pump I thought from memory that I had torqued for final assembly; but my records indicated it had only been hand tightened (no record of being checked off on assembly build sheet with a torque value).

Big Dave
 

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Im only 44 and have to keep records. I keep a notebook on carbs, jetting and engine size. I downloaded an engine assembly sheet. You have built WAY more engines than I have but things tend to get blurry when your trying to remember what you did months or years ago. My bracket engines are running 3 years.
 
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