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Old 06-08-2010, 08:18 PM
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My first BBC build. Help wanted.

My engine is finally in the machine shop and I would like to get some opinions on the build.

'67 396 2 bolt main block and rotating assembly punched .030

39117215 heads- was told these are small port and chamber, 96.4cc from the factory

Edelbrock dual plane intake w/ q-jet (750 cfm iirc)

Recommended by the builder:

21cc dome pistons for a static CR 9.7:1

Lunati cam 268H

HG .025-.040 to fine tune CR for 93 octane

I'm pretty new to all this, so please bear with me. My biggest question mark is the heads, is it worth getting $700 worth of work done for new valve seats, machine work, etc, or should I pony up for new ones? If I ditch these I can spend up to $1400 on a set of heads, what kind of power difference should I see? Everything at this point is variable, but the sooner it's all hammered out the better.

This is very budget oriented. My goals are reliability and power somewhere 400-450, but I'd prefer to overbuild and cam it down than do it wrong and have to spend more when I want to go faster later. Hopefully this is not a pipe dream. Let me know if you need more info. Thanks!

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Last edited by my_wayward_son; 06-14-2010 at 03:32 PM. Reason: Typo
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Old 06-08-2010, 08:44 PM
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The 3917215 heads (one too many "1"'s) are the oval port (not peanut port) heads, chamber volume is likely larger (109 cc nominal) than what you've referenced- cc them to know what you have, do not rely on published figures for volumes.
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Old 06-08-2010, 08:55 PM
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Zero deck, 0.030" over bore, 0.041" quench, using your dome and chamber volumes, the CR is 10.7:1. Even w/the piston 0.025" down the hole, your CR is over 10:1.

With "my" chamber volume, all else same as 1'st example above, the CR is about 9.5:1.

"Adjusting" for CR by differing the gasket thickness is OK to a point- but you don't want to get too far away from the "ideal" quench.
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Old 06-08-2010, 10:04 PM
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Quote:
Originally Posted by cobalt327
cc them to know what you have, do not rely on published figures for volumes.
Agree. Do this now, before you do anything else. You have to know where you are before you can figure where you're going.
http://www.summitracing.com/parts/SUM-911581/

Although I pieced mine together over 40 years ago, I have the same thing shown at Summit and it still works first time, every time. If you enjoy cc-ing heads, offer to cc a set of V8 heads for 35 bucks, 4-banger head for 20 bucks, 6-banger head for 25. Let the word get around and you'll have the cc kit paid for in no time.

Use Vaseline to seal the valves to their seats, the spark plug threads and the Lexan to the head surface.
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Old 06-08-2010, 11:00 PM
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Get a copy of the June super chevy and check out the 454 build . Low buck is the idea . I checked ebay for the heads they used and it is worth looking at. If I had my motor apart to do agian I would order them up.
Quote:
Originally Posted by my_wayward_son
My engine is finally in the machine shop and I would like to get some opinions on the build.

'67 396 2 bolt main block and rotating assembly punched .030

39117215 heads- was told these are small port and chamber, 96.4cc from the factory

Edelbrock dual plane intake w/ q-jet (750 cfm iirc)

Recommended by the builder:

21cc dome pistons for a static CR 9.7:1

Lunati cam 26814

HG .025-.040 to fine tune CR for 93 octane

I'm pretty new to all this, so please bear with me. My biggest question mark is the heads, is it worth getting $700 worth of work done for new valve seats, machine work, etc, or should I pony up for new ones? If I ditch these I can spend up to $1400 on a set of heads, what kind of power difference should I see? Everything at this point is variable, but the sooner it's all hammered out the better.

This is very budget oriented. My goals are reliability and power somewhere 400-450, but I'd prefer to overbuild and cam it down than do it wrong and have to spend more when I want to go faster later. Hopefully this is not a pipe dream. Let me know if you need more info. Thanks!
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Old 06-09-2010, 09:26 AM
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can't find that cam even on lunati website.????

Be careful with BBC's. They don't tolerate compression ratio as well as small blocks. better too little cr than too much.

bbc's are hard on lifters and cam lobes. use an oil additive to make up for todays emissions oil. www.zddplus.com. use at break in and at each oil change.

furthermore, you need to build the engine to match the car it is going into. what gear and stall are you going to use??

finally, the engine bearings on BBC's need to be set up on the tight side if you want to maintain oil pressure when warm. I set mine up in the 0.0015 to 0.0020" range. 0.0025 to 0.00030 on the rear main.

Last edited by 454C10; 06-09-2010 at 04:10 PM.
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Old 06-09-2010, 04:08 PM
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Thanks for all the replies guys!

Quote:
Originally Posted by 454C10
can't find that cam even on lunati website.????
I was just looking it up too. No luck.

From a little bit of web surfing it looks like the 215s are okay heads, and so far no one has said otherwise

I was planning on reusing the stall that came with the engine. The previous cam was a hot street cam that had a serious lope, it didn't tug much when put in gear. I don't think having too low a stall will be an issue; slightly too high is livable.

I'll contact the builder tomorrow. Things to address:
1) ccing the heads
2) finding out which cam he meant

Again, thanks for the help so far. I'll keep you posted.

Last edited by my_wayward_son; 06-09-2010 at 05:57 PM.
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Old 06-14-2010, 03:50 PM
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Some clarification:

The Cam recommended is the Lunati 268H
Specs- Intake/Exhaust
Duration 268/276
Duration at .050" 227/233
Lift .542/.554 (w/ 1.7 rockers)

LSA 112
Intake opens 5.5 BTDC, closes 41.5 ABDC
Exhause opens 52.5 BBDC, closes .5 ATDC

Part# 30299VLUN
Grind# VBDC-268

Last edited by my_wayward_son; 06-15-2010 at 05:30 PM.
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Old 06-14-2010, 04:13 PM
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Quote:
Originally Posted by my_wayward_son
Also, my builder says these heads usually cc out around 100.
If "usually" is good enough, you're all set AFA combustion chamber volume goes. But if you care how well this engine is going to go together, you have to actually measure them.

There are large variations in production castings. Add to that the distinct possibility the heads have been decked at some point(s) in their life (they're going on 40-plus years old, after all) and it becomes obvious that they're going to need to be measured, if you want to accurately calculate the CR.

Just because I own a set of 215's that measure 108cc w/dirty chambers isn't proof positive yours are that size too. And, hey- after all- it's your build...
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Old 06-14-2010, 10:57 PM
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Quote:
Originally Posted by my_wayward_son
My engine is finally in the machine shop and I would like to get some opinions on the build.
Cobalt has strongly suggested that you cc the heads. I have strongly suggested that you cc the heads. Yet you resist and seem content to take the word of your machinist who has not measured them. That's what makes participation in this forum so damned maddening. When you know that you are giving the best possible advice and the OP disregards it altogether.

Do whatever you want to. I'm done.
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Old 06-15-2010, 07:16 AM
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with 100cc heads, 21 cc domes, 402 cid, 0.040" gasket, and a piston -0.015" below deck, then the cr will be 9.94:1. I think that is too high for a BBC with a cam of only 268 degrees on the intake.

from my BBC experience with pump gas. I would use 9 to 9.25:1 max with 268 degree cam, 9.25 to 9.5 with a 280 cam, and 9.5 to 10.0 with a 290 degree cam. Like I said earlier, bbc don't handle as much compression with the same octane as small blocks.
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Old 06-15-2010, 02:23 PM
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Sorry guys, I didn't mean to annoy any of you. I'm working through this as budget allows. The builder will cc the heads, but it's not going to happen for a while. They are with him and not sitting in the garage so I can't go do it myself. I guess I should have waited to post, I just wanted to let those of you who were wondering about the cam know what it is.
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