How much horsepower?

[Fasted]

I have a 340 with 360 heads. Specs as follows:

Block 2780930-340-5 3m340 0424 22

Heads3671587-7

Crank 3462387

Pistons TRW L2385 .040

Forged 8.4:1 (w/65cc chambers) Deck height .001 down

Rods 3418645 full floating

Cam Isky 3901-28 TZ282 13P 07 273 280 HL HYD

Per Isky .465 lift, 280 Dur, 108 Lobe ctrs

Edelbrock Rpm manifold

Longtube headers

1. What is the stock cc for these heads?

2. What is the approximate horsepower for this combo?

3. What rear gears for street/hwy daily driving?

4. What carburator/size is correct

This will be in a street driven 72 Duster, 727 Auto trans, 8 3/4 Rear, 255/60-15 BF Goodrich Radial T/A's

Thanks

[DartGT66]

Basically a stock rebuild with small CR, smallish cam and hi perf intake & exhaust.

Stock cc's, no one knows without measuring A guess is 72cc, but it may be a few cc's off.

'72 340 was rated at 245 hp, I would say you are between 250 and 300, with good fortune maybe even a bit over 300.

Gears depend of what you want, is acceleration mroe important than low rpm at highway? If the highway use is more important, then a gear ratio starting with 2's, if you want good aceleration and don't care about rpm on the highway, 3.91 or 4.10. 3.55's are a good compromise with your tire height. What about the converter? With your parts, even the stock 340 converter should work decently.

Carburator size, 600-650 cfm, I would pick a holley.

[valiant64]

I agree W/ dartgt here, mostly. I would think 3.73/3.91 gears would work well with your rear tire diameter of approx. 27", and to help w/ torque with the low compression, unless youre doing lots of highway miles @ speeds above 60-65 mph. Otherwise 3.55/3.73's. 3.55 gear @ a minimum. As far as carbs go, I'd say 700-750 cfm with the lower gears. Also, I'd stay with vacuum secondary carbs on the street with A.T. Carb make is up to you, but I prefer Carter. Either will work fine, but it is fun to watch people on here argue about who makes the best carb. It all depends on the combo, and your preference.

[rumblefish360]

1. What is the stock cc for these heads?

Stock should be @ 72 cc's but can varry. More like 72cc's than not. You can do the cc job yourself.

2. What is the approximate horsepower for this combo?

If the heads are stock with 1.88 intakes, I wouldn't predict more than 300 - 320 hp.
The real key for this is low lift hi flow abilty, back cut the valves with good seat work, If you port the heads out some, bowl work and you can wack a good 60+ hp out of them easy.

3. What rear gears for street/hwy daily driving?

With the said cam, a good converter can have you use a gear set as low as 3.55's and it will be able to run and drive just fine.
If you were looking to run light to light type of gears, you could step up to 4.10's and do well.

4. What carburator/size is correct

street 650
strip 750
The difference is about 10 -15 HP on the big end while getting the revs up quicker and easier with the bigger carb. It is doable on the street, the secrect to it all is just tune tune tune.

Question to you...are you sure the pistons are down the hole .001?

[Fasted]

thanks everybody. This is great. Yes-I measured the pistons myself!

[DartGT66]

In that case, your CR should be higher, or are the pistons dished? Assuming 5cc valve reliefs and 72cc chambers, you should be at around 9.2:1. That should wake the engine up. Like Rumblefish stated, some head work is really a big +, a good valve job and at least a bowl port job will make a big difference.