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Discussion Starter #1 (Edited)
Hey everyone:

My father and I figured the winter would be a good time to begin building the motor for our '69 project. It's not going to be a track car, but we do want it to have some go, and will have a TH400 and 12-bolt with 3.73's behind it. We don't have much experience with blueprinting big blocks and wanted to ask for some expertise.

What we've got so far: A 1968 block bored 0.030 over, stock steel crank, and a set of TRW L2240N forged pistons (which have a bit of a dome on them). We'll be picking up a set of rods soon to get the rotating assembly balanced (either GM Dimple Rods or Eagle I-Beams, opinions on these?)

As for the top end, we are considering the BBC Top End Kit that Edelbrock puts out. Does anyone have experience with these, and will the pistons I have work with them?

Any information is appreciated.

Thanks!
 

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If you want 500 hp look to a SBC 400 not a 396. First thing is pistons are a consumable, once used you throw them away or sell them on e-Bay along side the i-Pod with the smashed screen. TRW hasn't even made that piston since the sixties. It was used in a closed chamber 350 horse power 396 as a stock replacement back when TRW was the OEM supplier.

Since Edelbrock is the current OEM supplier of big block heads for Chevy you are going to get a stock head to bolt onto your 350 horse 396. So if you are looking for 500 horsepower think instead of AFR heads sitting on top of a 496. That will make 500 horse on pump swill all day long. The 396 is the 305 of the big block family. It's bore is too small to make power because the valves actually hit the cylinder walls unless a notch is cut in the block to clear the valve. But it still obstructs flow as a third of the vale is looking at the scenic side of the cylinder wall.

The ONLY reason the 396 was used in the Camaro and the Chevelle was due to the moronic 400 cube restriction placed on GM cars (which evaporated the second Ford released a 428 Mustang. All other vehicles were using the 427 instead of the 396 in 1967 when the 427 was released. Of course you couldn't give away a 427 in 1970 after the 454 was released as everyone wanted the bigger more powerful motor.

A big block is a horrible street motor. It was designed to operate at wide open throttle as a race car engine or as a truck motor. As a car engine it is a dog in the lower RPM range encountered in street driving. Which is why the SBC 400 will eat a 396's shorts every time on the street. At wide open throttle the 396 will start to pull away once you wind it up because the SBC has smaller heads and weaker rods. The BBC can rev higher and has the strength to stay together in a race that back before chrome moly rods, ARP bolts and chrome moly cranks for the small block would have resulted in carnage.

Big Dave
 

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What we've got so far: A 1968 block bored 0.030 over, stock steel crank, and a set of TRW L2240N forged pistons (which have a bit of a dome on them). We'll be picking up a set of rods soon to get the rotating assembly balanced (either GM Dimple Rods or Eagle I-Beams, opinions on these?)

As for the top end, we are considering the BBC Top End Kit that Edelbrock puts out. Does anyone have experience with these, and will the pistons I have work with them?
Those pistons are for a 396 ?

I would start over and build a 454 or 496. JMHO. Or you can use that crank to build a 427.

Scat makes the best rods that are affordable ($300).

A 496 stroker kit with a 454 block will save you $$ in the long run. It's easy to make 500 hp with 496 cubes.
 

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Go 454 with edelbrock topend kit , all I did was gasket match intake and exhause but used a higher lift can and ut dynoed at 650 hp , edelbrock heads are very good
 

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We're looking for at least 500 horsepower
Budget Build
Cleaned up set of OEM 049's or 781s
Hyd Roller camshaft and lifters
Air Gap Intake Manifold
850HP Carb
Will make 500. Just did a chevelle board members 468 with 781s and a hyd roller and it made 530HP

3500 budget
AFR265s
Hyd Roller and lifters
AirGap Intake
850 CArb
Will make over 575HP.
 

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Budget Build
Cleaned up set of OEM 049's or 781s
Hyd Roller camshaft and lifters
Air Gap Intake Manifold
850HP Carb
Will make 500. Just did a chevelle board members 468 with 781s and a hyd roller and it made 530HP

3500 budget
AFR265s
Hyd Roller and lifters
AirGap Intake
850 CArb
Will make over 575HP.
Great advice as always. :yes:

Does the "3500 Budget" mean it costs about $3500 more than the budget build ?
 

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Since Edelbrock is the current OEM supplier of big block heads for Chevy you are going to get a stock head to bolt onto your 350 horse 396. So if you are looking for 500 horsepower think instead of AFR heads sitting on top of a 496.
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Edelbrock heads have been dynoed against Brodix and AFR and usually lose out by 10 hp in the upper rpm ranges. They use smaller valves and smaller chambers which tend to shroud the valves more. They are good heads; much better than stockers.
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A big block is a horrible street motor. It was designed to operate at wide open throttle as a race car engine or as a truck motor. As a car engine it is a dog in the lower RPM range encountered in street driving.
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Are you talking about the 396/375 hp with rectangle port heads ? That was not a great street engine.

A BBC with matched oval port heads will blow away any SBC of the same size because the canted-valve heads breathe better. It's been proven on the dyno.

I personally owned a Chevelle with a 427 that got 13 mpg with no OD- just a muncie 4 speed and 3.55 gears. And it was wicked fast.

.
 

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If you want 500 hp look to a SBC 400 not a 396. First thing is pistons are a consumable, once used you throw them away or sell them on e-Bay along side the i-Pod with the smashed screen. TRW hasn't even made that piston since the sixties. It was used in a closed chamber 350 horse power 396 as a stock replacement back when TRW was the OEM supplier.

Since Edelbrock is the current OEM supplier of big block heads for Chevy you are going to get a stock head to bolt onto your 350 horse 396. So if you are looking for 500 horsepower think instead of AFR heads sitting on top of a 496. That will make 500 horse on pump swill all day long. The 396 is the 305 of the big block family. It's bore is too small to make power because the valves actually hit the cylinder walls unless a notch is cut in the block to clear the valve. But it still obstructs flow as a third of the vale is looking at the scenic side of the cylinder wall.


The ONLY reason the 396 was used in the Camaro and the Chevelle was due to the moronic 400 cube restriction placed on GM cars (which evaporated the second Ford released a 428 Mustang. All other vehicles were using the 427 instead of the 396 in 1967 when the 427 was released. Of course you couldn't give away a 427 in 1970 after the 454 was released as everyone wanted the bigger more powerful motor.

A big block is a horrible street motor. It was designed to operate at wide open throttle as a race car engine or as a truck motor. As a car engine it is a dog in the lower RPM range encountered in street driving. Which is why the SBC 400 will eat a 396's shorts every time on the street. At wide open throttle the 396 will start to pull away once you wind it up because the SBC has smaller heads and weaker rods. The BBC can rev higher and has the strength to stay together in a race that back before chrome moly rods, ARP bolts and chrome moly cranks for the small block would have resulted in carnage.

Big Dave
DING DING DING! A first, I think. A first time I've disagreed with Dave, anyway.:D
In my entire life of driving my BBC's I've not lost a street race to a SBC. Not even close Dave. In fact, I've not lost a street race to another BBC with my 396 375hp BBC. But those didn't really happen because they're illegal, right.;)
 

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If you already have the block and pistons, I see no need to start over.
Chris provided some great advice.
I am assuming the pistons are new, not used. First question: are they really vintage TRW forged pistons? If so, you need quite a bit of clearance because those expand quite a bit. There is a modern version going under the same part number, made by speed pro. They are a completely different alloy which does not expand as much and therefore does not required the same clearance.

I believe the clearance on the vintage trw piston is .005. Pretty high by today's standards.

Also assuming the final hone was done with deck plates to get the proper clearance AS SUGGESTED BY THE PISTON MANUFACTURER. That is where to start for blue printing. Second, make sure to get the quench down at least to .040, which is living on the edge, I admit.

Third, buy rings that will require filing to fit exactly as recommended by the manufacturer.

If I am wrong, and the pistons are vintage AND used, measure CAREFULLY. Old TRW pistons can take a lot of abuse, but run hot and the skirts can collapse.

Follow Chris' guidelines and rec on a camshaft and you can make 500 horses easily with a 396.
 

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Discussion Starter #12
Thanks for all the advise guys! We bought the block and pistons as a package. The previous owner had it machined and then he ended up not building it. The pistons are new, and they are TRW, not sure of how old they are but they are spotless. We have a new set of rings so I'll have to check those out as well as all the measurements to at least get a short block going.
 

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Brand new pistons; no reason to NOT use them if the block checks out OK.

Just to be sure, your pistons look like this one (except this one is .020) correct???:

http://www.ebay.com/itm/L2240F-PISTON-FORGED-TRW-020-OVER-SINGLE-396-CHEVY-/311097526422?pt=Motors_Car_Truck_Parts_Accessories&hash=item486edb8896&vxp=mtr

Just looked in my vintage Chev Power book and it calls for .0065 clearance measured at the center line of the wrist pin hole, perpendicular to the pin. That is even more than I was thinking. Guess the big block with the bigger slugs requires more clearance than my LT-1. I got mine at .005 and have zero piston slap even stone cold.

If I were building this motor, I would use Chris' recommendation of AFR heads. I would also use whichever hydraulic roller he recommends, and follow his directions exactly.

575 hp will be lots of fun.

Good luck.
 

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Discussion Starter #14
Yes, they do look like that one. I believe they are about 20 years old and the original box says that they require a minimum of 0.001 clearance at the skirt.

As far as heads go, I do also have a set of the stock 215 oval ports. From what I can gather from above the 396/375 hp motor with the square ports was not a very good street motor. Wouldn't I have the same problem with the AFR's?
 

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From what I can gather from above the 396/375 hp motor with the square ports was not a very good street motor. Wouldn't I have the same problem with the AFR's?
I would sell the 396 block and pistons and start over with a 454. You will be down 60 hp before you even start if you go with the 396.

JMHO but building a 396 for a fast street car makes no sense unless it's a restoration or you're shooting for better gas mileage.

The 454 is better because it's bigger; it's easier to get 10-1 compression with a smaller piston dome and the bigger cylinder bore breathes better.

And for the same reasons a 496 makes a lot of sense too.
 

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Yes, they do look like that one. I believe they are about 20 years old and the original box says that they require a minimum of 0.001 clearance at the skirt.
That means .001 clearance per inch of bore. Minimum
 

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I would sell the 396 block and pistons and start over with a 454. You will be down 60 hp before you even start if you go with the 396.

JMHO but building a 396 for a fast street car makes no sense unless it's a restoration or you're shooting for better gas mileage.

The 454 is better because it's bigger; it's easier to get 10-1 compression with a smaller piston dome and the bigger cylinder bore breathes better.

And for the same reasons a 496 makes a lot of sense too.
Yep Anne, those are the reasons time passed by my L78 in 1968. That's when I bought my 427, a year before the car in '69. (427 is a 454, just not stroked yet)
 

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"There is no replacement for cubic inch displacement" as far as NA goes. Every extra cid equals 1 extra hp (relatively speaking) when you go for 1 hp for every inch of displacement.

That's why I have a 454 in my 67...
 
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