396 to a 427 Need more HP - Team Camaro Tech
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post #1 of 12 (permalink) Old Jul 23rd, 15, 06:01 AM Thread Starter
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Bruce
 
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396 to a 427 Need more HP

Built my 69 C-10 short/wide in the early 90's to tow my 69 Camaro vert to the shows. It has been outside and used for hauling projects and has about 10k miles on the BB engine. Time to be restored again and this time will be garaged. I would like more power from the engine without a full rebuild as it runs fine. The engine is from a 68 Camaro (it doesn't care) a 396 bored to a 427 with standard 427 pistons, 9.5 to 1 compression, Original oval heads with hardened valves and roller rockers. The engine builder installed a "RV" cam. for towing. Edelbrock Performer intake, 800 DP Speed Demon, headers with 2.5 Flowmaster, GM HEI, 700 transmission, 373 posi, PS, PDB, AC. lowered. I am thinking a cam change and Aluminum heads and less carb. Your thoughts. Oh the engine was already bored 60 over and no pistons were available then, so I was told, so it was bored further to accept standard 427 pistons.
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post #2 of 12 (permalink) Old Jul 23rd, 15, 07:05 AM
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Dave
 
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Re: 396 to a 427 Need more HP

If you bore a 396 block out to a 427-454 bore size, and you haven't hit water yet; I would install a 496 rotating assembly instead of building a 427. The factory dropped the 427 for a reason. Longer stroke motor builds a lot more torque and that is what is going to accelerate your C-10 trailer and load. Now if you want to run the high oval at Daytona then I would be considering a short stroke engine, but for the street, bigger is better.

By the way if the block doesn't crack after a few heat cycles, it will run a LOT hotter than a 454 block will because the thinner cylinder bores allows the heat of combustion to travel through the thinner cylinder walls at a faster rate. So more of the heat of combustion goes to heating your coolant (and the air under the hood) than in pushing your vehicle combination down the road. You may have to add a second full size radiator in the bed of the truck with an electric fan just to keep your new motor in it's normal operating range. Higher heat under the hood results in a greater chance of detonation.

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post #3 of 12 (permalink) Old Jul 23rd, 15, 07:26 AM
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Re: 396 to a 427 Need more HP

Quote:
Originally Posted by The Camaro Guy View Post
I am thinking a cam change and Aluminum heads and less carb. Your thoughts. Oh the engine was already bored 60 over and no pistons were available then, so I was told, so it was bored further to accept standard 427 pistons.
I would try switching to a quadrajet style carb like the new street demon 750 before doing anything else.

It's a great carb and has a lot of improvements over the quadrajet. The tiny primaries should give a lot more torque up to 2500 rpm ; right where you need it for towing.

Here is a video of the 625 street demon; the 750 is built exactly the same :

https://www.youtube.com/watch?v=IHWJpZCmUAk

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post #4 of 12 (permalink) Old Jul 24th, 15, 05:43 AM Thread Starter
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Bruce
 
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Re: 396 to a 427 Need more HP

Great comments. I too am surprised how the old engine has held up. It has the widest 4 core radiator that fits in the truck and has always ran at the thermostat temp even while towing with the AC on. I don't plan on towing anything as I have gotten out of the trailer queen business and just drive to the few shows I go to with my Camaros. Any suggestions or comments on what and if a change of heads would be to any benefit?
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post #5 of 12 (permalink) Old Jul 24th, 15, 09:35 AM
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Re: 396 to a 427 Need more HP

Quote:
Originally Posted by The Camaro Guy View Post
Built my 69 C-10 short/wide in the early 90's to tow my 69 Camaro vert to the shows. It has been outside and used for hauling projects and has about 10k miles on the BB engine. Time to be restored again and this time will be garaged. I would like more power from the engine without a full rebuild as it runs fine. The engine is from a 68 Camaro (it doesn't care) a 396 bored to a 427 with standard 427 pistons, 9.5 to 1 compression, Original oval heads with hardened valves and roller rockers. The engine builder installed a "RV" cam. for towing. Edelbrock Performer intake, 800 DP Speed Demon, headers with 2.5 Flowmaster, GM HEI, 700 transmission, 373 posi, PS, PDB, AC. lowered. I am thinking a cam change and Aluminum heads and less carb. Your thoughts. Oh the engine was already bored 60 over and no pistons were available then, so I was told, so it was bored further to accept standard 427 pistons.
What kind of power do you want out of the combo?

Chris

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post #6 of 12 (permalink) Old Jul 24th, 15, 09:56 AM
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Dave
 
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Re: 396 to a 427 Need more HP

If you have a set of 1969 BBC oval port heads they are the best you can use at the moment. They can be improved with much bigger valves and a minor pocket port. They are heavy but unless you are thinking of drag racing your truck it isn't worth worrying about the added weight.

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post #7 of 12 (permalink) Old Jul 24th, 15, 11:02 AM
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Doug
 
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Re: 396 to a 427 Need more HP

It is not worth putting money into the 396 engine. Sure you can get more hp out of it but the cost would be too much. You would be better off finding a 454 engine (rebuildable) and purchasing a 496 rotating assembly. You will need to make sure the 454 head casting numbers are 781 or 049 as these are the best open chamber heads for the 454. Using 2.19/188 valves and a little pocket porting, gasket matching these heads could handle 600 hp. A roller camshaft with a 240+ duration and the 496 rotating assembly would put you around 550 or more hp. BTW you don't have to use forged parts unless you want them. I would clean the block, bore and hone with a torque plate, and align bore for using studs. Here is an idea of the cost for a 496 rotating assembly. http://www.cnc-motorsports.com/engin...e-pistons.html
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post #8 of 12 (permalink) Old Jul 24th, 15, 01:04 PM
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Re: 396 to a 427 Need more HP

Quote:
Originally Posted by Cdminter55 View Post
Here is an idea of the cost for a 496 rotating assembly. http://www.cnc-motorsports.com/engin...e-pistons.html
That is a great 496 combo.

For a truck I would use a hydraulic roller cam like the ZZ502 cam : 224/232 with ~.540" lift.

Aluminum heads are expensive but hold their value. Brodix race-rite 270's or AFR 265's would be ideal.

That truck would be a real torque monster.

Chris Straub can help advise on an ideal combo and might save on getting everything thru him : www.straubtechnologies.com

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post #9 of 12 (permalink) Old Jul 24th, 15, 01:50 PM
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Re: 396 to a 427 Need more HP

Is there a partial VIN on the 396 from the Camaro? Can you send me a picture of the engine pad at the front of the passenger side head if there is?

Oh, not sure, but I doubt that 396 will accept a stroker crank to go to 496. At least not without grinding/clearancing and filling back with epoxy, and that is not worth it when 454 blocks are readily available.

You could sell the bored out 396 and then go to 454 or larger but that would be your decision.

68 Camaro SS 396 - 468 BBC now, M21, 12 bolt 3.73 coded housing but w/ 3.31 gears.
Looking for 68 Camaro with body number NOR 181016
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post #10 of 12 (permalink) Old Jul 24th, 15, 02:34 PM
DT
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Re: 396 to a 427 Need more HP

Go 454 !!!

1969 X66 396 LeMans Blue, M20, 373 (Sold)
1969 Convertible LS3 TKO 600, 373
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post #11 of 12 (permalink) Old Jul 25th, 15, 05:47 AM Thread Starter
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Bruce
 
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Re: 396 to a 427 Need more HP

I think the 454 route is the way to go. Thanks for all your input.
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post #12 of 12 (permalink) Old Jul 25th, 15, 06:53 AM
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Re: 396 to a 427 Need more HP

Why not do something like this:
http://www.superchevy.com/how-to/pro...ottom#cxrecs_s

Keep the costs down by ditching the belt drive for the cam.
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