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Old 08-12-2009, 11:19 AM
oldbogie oldbogie is offline
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Quote:
Originally Posted by Doc Hawk
I am building my first small block Chevy and I would appreciate the guidance and input from folks who have gone down this path before me. I can build you a Nissan L6 motor that puts out double the stock HP with my eyes closed, but I want to try something new and I'd like to get it right the first time.

Project
I will be dropping a 350 block into a 1972 Datsun 240Z. 010 block from 1973.

Intended Use
75% street/ 25% road course. Spirited street/canyon driving "for fun" (not a daily driver), non-competitive high performance driving events on road course race tracks.

Power Goals
It would be nice to have 400 HP for bragging rights, but I think if I am anywhere in that area it will feel pretty darn good in a car that weighs 2400 lbs.

Budget
The idea is to show how much power can be put down by the venerable Chevy V8 without spending much money. I can wind the heck out of an L28ET and get 500 HP very reliably... for about $10K, done right. I believe I can put 400 HP in a SBC for under $2000.

Why a SBC in a 240Z?
I already have a very high strung 240Z that is 20% street/80% race (bad idle, obnoxiously firm suspension, very grippy racing clutch), so this car is intended to be more streetable. I figured the V8 motor will give me a much smoother powerband than the I6 does when it is built for 250+ HP.

Planned Build
Edelbrock Performer 750 carb
Edelbrock Performer RPM Intake
ProComp PC3003S Aluminum Heads (64cc/210cc, straight plug)
Custom valvetrain and head work from my machinist
1.6 Roller Rockers (mfg. not selected yet)
Hydraulic roller lifters (mfg. not selected yet)
Hooker Super Comp Block Hugger headers (to clear stock steering in my 240Z)
Whatever hydraulic cam the smart people at COMP recommend with this setup
Stock bottom end w/ stock forged, dished pistons

Discussion
Will this work? I am choosing the cam last as I figure that is what the cam help line is for; they know their products after all.

Will the large runners on the 210cc heads match up with the intake? Any special gaskets I need to think about? Is that too much intake volume for 350 ci?

Any idea what CR this combo will yield? Looking to run California's lousy 91 octane at most; I don't want to have to put race gas in here all the time. 87 wouldn't be bad, either, because I'd love to beat my import buddies using Regular Unleaded.

No need to bash the ProComp heads in this thread. They are dirt cheap and my engine builder has put them in several race cars. Some of those race cars are winners, both in drag and dirt. He likes the 3rd gen ProComp head at the price, and he's willing to do the machine work to make them pretty. He says he refuses to use their assembled heads as he's seen too many assembly issues and doesn't trust their valvetrains. I trust the guy and he's always given me good motors, so...

What else? Will she make power?

Thanks all,
David
I think the port size of the heads you're thinking about using are too big for the engine and the RPM band needed to make 400 hp. Getting 400 HP out of a 350 is at the edge of a no-brainer; a set of Vortec heads and a comp 268 cam with a 650 cfm 4 barrel and 1-5/8's tube 36 inch headers will get you there with space to spare and run nicely on California premium.

Given it doesn't take a Whomper-Stomper cam to grind out 400 hp from a 350, you won't need to rev the motor to the moon to get power, so that's why I'd recommend port sizes more like 170-180cc to keep the velocity up and use what the engine will make tons of which is mid range torque. But I'd stick with aluminum heads as you're looking at as they take 50 pounds off the engine, which is off the front axle as well, so this will help handling. The aluminum head lets you push the compression another ratio or more than cast iron which will add to the engine's ability to avoid detonation on 91 octane fuel. Given you car is very light, you might push the comp ratio another point and get away with around 11 to 1 but certainly half again above 10 at 10.5 would be safe since you can't really bog this engine down with a ton and a quarter car.

I also don't think you need a 750 cfm carb, again it's too big for what little a 350 needs to get 400 horse, large begets more RPMs on a 350 say above 6500 and with a 268 cam a 350 just isn't going there 'cause it doesn't need to.

Chevy engines are very dependent upon the piston for compression selection and proper squish/quench. You need to pay attention to the crown height as many aftermarket pistons assume the block will be zero decked (cut .020-.025 inch) and these have a shorter pin to crown distance. If used with a standard height block, these pistons end up way down the hole .040 inch or so plus gasket, as a result compression, squish and quench go in the trash. A flat top with proper compression height is best with a small chamber head, but if compression needs to be trimmed to hit 10 to 10.5 to 1 then the next best choice is a D shaped dish as this keeps a flat piston surface against the head's squish/quench deck for very good anti-detonation characteristics and keeps the major mixture density jammed up against the spark plug for a fast burn, this lets you get by with less spark advance so the engine gains energy otherwise lost trying the drive the piston back from whence it came with excessively early ignition that open combustion chambers or circualr dish OEM style pistons need.

If you've never dropped an SBC or SBF into an old Z-car before, head on over to Jags that Run http://www.jagsthatrun.com/Pages/Datsun_Z_V-8.html and check out Mike Knells book on Chevy to Datsun swaps. It'll save you some bucks and sweat in the long run.

Bogie

Last edited by oldbogie; 08-12-2009 at 11:30 AM.
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