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Old 10-28-2008, 11:49 AM
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74 454 bbc build qustions?

Hi i recently picked up a 75 impala with a 454 under the hood, We brought it home filled the carb with gas, threw a battery in it and she fired right up . So im gonna be putting it in my 78 stepside truck. Torque will be key with this motor so would like some suggestions for this build. It has the 079 heads and i read that with some porting they should handle what i want to do. Im gonna run 9:1 comp, dualplane intake and was looking at this XR264HR roller cam, according to camquest thats puts me a 600 ft pounds with edelbrock performer heads . Not shure if thats so true but any/all suggestions apriciated, Thanks Jake

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Old 10-28-2008, 02:34 PM
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Looks like you are heading in the right direction with this build.

Roller cams are a good idea in Big blocks because of the different angles between the intake and exhaust lifters. The early BBC's were kind of notorious for chewing up cams, but that usually isn't a problem with todays materials.

I am not sure of the specs on the "079" heads but most oval port heads with 2.06/1.72 valves are capable of supporting 450-475 HP with some porting. If you really want to open them up then install 2.19/1.88 valves. Which is what the higher performance heads came with from GM. These oval port heads will support closer to 550 HP with porting and large valves.

9.5:1 compression is about the limit for a BBC on pump gas. So make sure you limit it to the 9:1 you spoke of.

All those cubic inches will soak up a lot of lift and duration and what most people would consider "too radical" for a small block will be just fine for a big block. If I were you I would go two sizes larger with the cam. Especially with a roller. I had a solid roller in a big block with .660 lift and 254 dur @.050 and it idled nicely and had no bogging problems at 9.3:1 compression. There is a video of it idling in my photo section.

I would doubt the 600 ft/lbs is accurate but 525 would not be unreasonable
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Old 10-28-2008, 04:10 PM
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Check that casting number again. 99% of the mid 70's BBCs came with 049s. If you have 049s, don't touch them. They already have large ports that will support well over 400 hp. There is no need to port them and make the ports any bigger. If you're building for torque, leave them in their beautiful natural state.

Keep the domes tiny and flat. Try to get your compression with head gasket and piston height instead. Domes kill flame fronts which further degrades detonation tolerance on an already sensitive engine.

The 264HR is a great cam. I'd say 500-525 lb-ft as well on stock heads. Edelbrock heads will make a little more torque, but at about 500 rpms higher
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Old 10-28-2008, 07:30 PM
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Alright so i got mixd up with heads, i have the 781 casting heads, are these large oval aswell or are they small and with they support this engine? Also i have a chance to buy some 396 heads, not sure of the casting, but if there closed chamber what would they raise the compression to on this motor? Thanks, Jake
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Old 10-28-2008, 09:06 PM
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the 781 heads were never good 396 a little better that motor wont make the torque your after youd be better off to go with a motor with a longer stroke like a 427 then you might be on your way to 400 ftlbs of torque if that.
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Old 10-28-2008, 09:31 PM
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From my understanding the "781"s are very close to the "049" heads . They quit making "049" s in '73 and replaced them with the "781"s ."781"s/"049"s work great with flat top pistons and mild hydraulic cams for what you are describing . The 396 heads are mostly closed chamber heads and will cause some shrouding of the valves and subsequent air flow through the head . Go with the 781s, with or without the 2.19/1.88 step up in valve size , flat tops or .100 dome pistons to get your 9.1 CR and a mild hydraulic flat tappet with around 224- 230 degrees duration at .050 and .530-.540 lift at the valve . Don't rule out Marine grind cams , they are all about TORQUE . We have used several in street cars with BBC and they perform well. Rollers are great, but are three times the cost of flat tappet cam set-ups. Sounds like a great find on your blig block .

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Old 10-28-2008, 10:00 PM
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Quote:
Originally Posted by chevyeater
the 781 heads were never good 396 a little better that motor wont make the torque your after youd be better off to go with a motor with a longer stroke like a 427 then you might be on your way to 400 ftlbs of torque if that.

I disagree... the 780s ARE basically 049s with smaller chambers. Even better. They flow in the neighborhood of 240 cfms at .600" lift.
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Old 10-29-2008, 09:41 AM
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Quote:
Originally Posted by chevyeater
the 781 heads were never good 396 a little better that motor wont make the torque your after youd be better off to go with a motor with a longer stroke like a 427 then you might be on your way to 400 ftlbs of torque if that.
I also disagree. the 781/049 is a great street head, they also do respond well to larger valves, however, by the time you spend the money on machine work & parts for the larger valves, some of the aftermarket heads start looking better & better.
Longer stroke like a 427 ? he said he has a 454
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Old 10-29-2008, 11:40 AM
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Thanks for the replies, i think i'll just stick with the 781's and do a little porting but leave the valves. I'm trying to keep this build cheap so ill do the work myself and just upgrade cam/bearings and possibly pistons. I have a bbc book here and it says that the 73-74 454 had 9:1 compressio is this true? Thanks,Jake
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Old 10-29-2008, 05:00 PM
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BBCs in full size cars were low compression. Reportedly there were some hi-po options, but I've never seen them. They came in two versions; a 215 hp and a 245 hp. They would be X and Y in the VIN, respectively. The 215 was a single exhaust and the 245 was a dual exhaust. There was a 235hp option, but it was monte carlo.

Both were advertised at something around 8:1.
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Old 11-02-2008, 12:28 AM
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Agreed, the 049 heads and 781 heads flowed the same the only difference being that the 049's had a combustion chamber of 122cc's and the 781's were 118cc's.

And mortec claims these flow in the 255 CFM range.
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