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Old 09-21-2011, 04:22 PM
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Got a SBC on my hands; trying to ascertain what I have (HP, RPMs, Carb sizing)

Hi all. I am now an owner of a new rod project; well at least a 'rod' project to me. I purchased a rough looking '73 Datsun 240Z with a SBC V8 for $1200. Trying to get her sorted and I have a mountain of receipts/notes but this is my first American V8 experience since I owned a Mustang when I was 16 years old.

The worn out 600 CFM Holley is just not cutting it and I am in need of a new carb and am trying to figure out; A) what size carb I need? B) What kind of max RPM I should be running (this is a factor in terms of how many cfms my carb should be pushing)? C) What kind of power/power curve do you think I would be getting out of this thing?

Here are the specs taken from the receipts and notes that came with the car.

- LT1 4 bolt 350 block (3970010)
- Trickflow G2 Aluminum heads. Compression is either 10:1 or 12.5:1.
- 350/350hp cam, hydraulic lifter
- Keith Black Pistons (again either 10 or 12.5:1 compress)
- 6" H beam race rods
- Polished Steel crank
- Edelbrock intake
- Headers
- Flowmaster
- Stock ignition
- (And again) currently Holley 600cfm w/ KN air filter

Brought it by a shop that does some work on old Chevys and the owner recommended a 700-750 dual feed. That seems a bit large to me, but again I'm a novice when it comes American V8s and Holleys, my experience lies with Euro cars and Weber carbs. I would love to, and the ultimate goal is to, put 4 pairs of dual barrel Webers on there IF I can come across a kit for less than what I paid for the car, haha! The car itself weighs around 2200lbs and likely has a higher ratio rear-end so perhaps I can get away with something larger than typical. The car will see some steet and track driving.

So....? Any suggestions on carbs, what I should rev this thing to, idea on how ponies this thing may be turning?

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Old 09-21-2011, 05:08 PM
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Years ago I built 2- 240 Z's with 355" chevys. One was an automatic and the other was a 4 spd. First off, your 010 block is not necessarily an "LT1 4-bolt". The infamous 3970010 came in just about every Chevrolet known to man and was available in 302 327 and 350.....2 and 4 bolt main. You easily could have a 2 bolt 327 as well.....and most likely NOT a 302.

You say you have either 10 or 12.5 compression...BIG difference in which type of gas you run and the associated parts for a 12.1 engine. What you really need to do is find out exactly what your engine is and what kind of internal parts are in there....DON'T take the sellers or anyone else's word for it. If you really want to know pull the pan to see 2 or 4 bolt, condition of rod and mains, rod bolts, which oil pump. You should be able to see through the spark plug hole if you have domed or flat top pistons. If it turns out to be a 350 then a Holley 3310 750 cfm carb may work.

You also need to do a lot of research on sbc engines, get acquainted with the performance aspect and just what a good combination of parts will work for a good reliable engine. Who knows on the rpm and hp, first things first, this engine, whatever it is has probably had the chit ran out of it and may be ready to grenade itself. Better take a look and see what you really have in there.

Last edited by 327NUT; 09-21-2011 at 05:22 PM.
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