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Old 09-04-2012, 10:47 PM
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454 cam info

I currently obtained a rebuilt mid 70's 454 with factory flat tops and 781 heads. compression is to low so I am getiing a set of early 396 heads 702 castings and using a head gasket shim and head studs. I am figuring the compression should be somewhere in the area of 9.5 to 10.0 to 1 and will be running an rpm intake with a 750 hp carb. I have a 3500 stall and am looking at the xe284 cam and would be okay going solid, dont plan on going higher than 5500 to 6k rpm. Dont have $ for a roller set-up so any input would on this would be appreciated. Need info on head work and cam, not as familiar with bbc's as I would like this is my 1st build on one

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Old 09-05-2012, 07:23 AM
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454 cam info

Ok, a word of advice. The 781's you have is one of the best oval port heads that were produced. These are open chamber heads. Here's a suggestion you can do some research on. Have a good valve job and shave the heads to 118cc. Have the valve springs, retainers, and locks for the cam you are going to use. Get a set of KB207 -25.5 dome pistons, .041 head gaskets. Have the block bored .030 over and zero decked. This will give you .041 Quench which is good for pump gas. Get the Comp Cam 11-676-4 XS268S solid lifter cam. With this setup your compression will be 10.2 and the DCR 7.521.
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Old 09-05-2012, 10:05 AM
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454 cam info

The bad thing about the 702's is they are called the bathtub chambered head. Look them up. As any closed chamber head, they will need to be upgraded to 2.19 I and 1.88 E valves. Then the valves will have to be unshrouded. This enlarges the chamber so you would have to have them shaved. By the time you are finished you will have the same amount of money that a pair of aftermarket iron heads cost. A pair of World Products cast iron heads w/ 2.300 x 1.88 valves for a solid lifter cam is $835. Please do not use steel shim head gaskets on a big block just have the block squared and decked to .000 this way the quench is perfect at .041. If you do decide to use closed chamber heads find the 3904390's 98cc. Install 2.19 or intake valves and 1.88 exhaust valves. The chamber shape is not the bathtub shape.

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Old 09-05-2012, 05:54 PM
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The engine has a fresh rebuild on it and is currently std bore. I'm interested in working with the set up I have not interested in tearing into a good short block, I know there are other routes to go. I cannot fork out the money at this time or I would. I can do different head gaskets though seeing that I have the heads off at this time. I am not out to get 600hp out of it but would like 550ft of torque with a flat curve and hp in the mid to high 400's with a nice idle and dont need to go with the 3500 stall, I am looking for useable power up to no more than 5500-6k. I know the old ls-6 grind needed 11.0 to 1 to run correctly but what about the comp cams version of it the rpm cam or the xe274, they have a broad power band? Thanks for your advise

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Old 09-06-2012, 08:10 AM
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454 cam info

Hi, I found an article on the same build that you are doing. 69 Camaro Project Part 2: Big Block Chevy Rebuild - Minneapolis American muscle car | Examiner.com. The motor made 450hp and 515 lbs. of torque. The cam they use was the XE274. The higher the duration moves the hp and torque into a higher rpm range, something you didn't want. Here is a link to the head gasket you want. Mr. Gasket 1131G Mr. Gasket Steel Shim Cylinder Head Gaskets When installing these gaskets use the Permatex copper spray. Be sure to re-torque all the head bolts after cam break in. Good luck with your build. Be sure and order the valve spring kit for your cam so you don't have problems wiping cam lobes.
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Old 09-06-2012, 10:21 AM
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Thanks this is what I was looking for, according to the build I should be in the area of 9.0 to 1 compression. I also noticed the cam was changed to a 112, other than idle quality and broader power band would I be better running on a 110 or 108
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Old 09-06-2012, 12:06 PM
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454 cam info

Here is cam specs on Xe274H. It has a Lsa of 110. 11-246-3 - XTREME Energy. Here is an article on testing cams with different variables. Camshaft Variables Basics - Tech Article - Chevy High Performance Magazine. The way I understand if you take the XE274H and lower the LSA (108) you would lose low end torque and moves peak torque to a higher rpm range. With higher LSA (112-114) would lose hp and Torque all through the operating range. All that would be gained is some engine vacuum. Now I ran your numbers through a compression calculator on KB piston site. I used 100cc Head Volume. I came up with a static compression of 8.941 and a DCR of 6.427.
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