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Old 11-17-2018, 03:32 PM
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Building a Big Block on a Budget.

It would appear that my Rat motor is smoked (literally).....all indications are that I have a ring problem, and if that is the case I am going to run through the motor. I need some advice on parts to get, parts to re-use, etc.

I have a 1968 Camaro with a Mark IV block (361959). The heads are 67ish closed chambers, oval intake/square exhaust (3904390), that appear to have had some work done, and they are part of the question...rebuild or replace. I have a new Holley 750 carb, Edelbrock performer II manifold, and 2" Hooker headers. Summit Racing distributor/ignition system. Muncie 4 speed, 3:55 rear end. 280/520 comp cam.

I would like to see 500 HP out of this motor, so I guess the question comes down to the heads and the pistons (and probably a variety of other things I am missing, because I am not a mechanic...I only pretend to act like I know what I am talking about around my friends who have no idea). So....I am thinking about aluminum heads, but is that necessary? I have been told they do not make closed chamber aluminum heads, so if I went open chamber I would have to change my manifold (which is fine....not a huge expense). I have basically zero room for additional clearance with my headers. I had my valve seals replaced and was told that I had some "ears" broken off on the heads (not the slightest idea what that means, and nobody else seems to either). If the heads can be reworked will they help me to my HP goal? Lots of questions and a long post....thank you for hanging in there to this point. Your advice is very much appreciated!

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Old 11-17-2018, 03:42 PM
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500 is within reach. Before making any purchases or choices, buy David Vizard's book about Building BBC on a Budget. Read it - multiple times if you have too and then ask questions. Book is about $25-$30 - but you'll not regret spending it on your project.
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Old 11-17-2018, 03:52 PM
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thank you for the suggestion.....went on Amazon and downloaded to my ipad for 12 bucks!
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Old 11-17-2018, 04:55 PM
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Hopefully in your new book he talks about the need for a roller cam.
Big blocks eat flat tappet cams at an alarming rate.
Something to consider in your budget.
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Old 11-17-2018, 05:28 PM
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that is interesting....I have not heard that before. I suppose a cam in this situation is a small investment, although I want it to be streetable like the rest of the car. Do you think the size cam I have in now is sufficient to do the job?
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Old 11-17-2018, 06:10 PM
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Changing head to an open chamber doesn't mean you have to change the intake manifold....the only thing that would have to change is the size of the dome on the piston.
Only reason the intake would have to change is if you swap to a rectangle intake port head....although there are quite a few guys who successfully use an oval port intake on rectangle port heads....it improves velocity of the incoming mixture, the port mismatch is in a direction that doesn't hurt and can actually help with fuel shearing.

Headers won't need to be different, unless you choose a head with raised exhaust ports...and then it still depends on how much they are raised.

Your cam is fairly small for a Big Block...it is still pretty small even in Small Block terms. A pretty "average" cam, the good old 280°/.480" lift small block or 280°/.520" lift Big Block hydraulic flat tappet has been around forever.

Read Vizard's book, you'll likely go back through several parts a dozen or more times to fully absorb it...it's a good read.
I believe he talks about the Flat tappet problem, big blocks tend to trash flat tappet cams and it has only gotten worse now that no OEM's use flat tappets anymore, the quality control and material oversight just isn't there, and the removal of ZDDP from most motor oils hasn't helped either.
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Old 11-17-2018, 06:18 PM
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On re-using your current heads, the fact they are closed chamber is strike one in my book, but its up to you.

I know that in the Small Block world, both Chevy and Ford, when it comes to rebuilding heads, it has now become either cheaper, same cost, or only a few dollars more gets you into an aluminum performance head vs reworking old tired iron castings that can't make the same performance without a ton of work.
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Old 11-18-2018, 02:24 AM
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Where do you want peak torque?
How high do you NEED the engine to rev?
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Old 11-18-2018, 05:22 AM
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Quote:
Originally Posted by Colin68 View Post
that is interesting....I have not heard that before. I suppose a cam in this situation is a small investment, although I want it to be streetable like the rest of the car. Do you think the size cam I have in now is sufficient to do the job?

What is the cam part number or a link to it? (Not that I can advise you about the cam, but so I can compare it to mine.)
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Old 11-18-2018, 05:43 AM
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both good questions....not sure about peak torque? I would probably have to do some research to see what is optimal for the type of driving I will do. As for the RPMs, I have read that somewhere in the 5500 range is fairly normal, but I am not sure.
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Old 11-18-2018, 05:47 AM
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the cam part number is CL11-208-3. At the time I felt like this was a good option for the driving I would do. I live in Texas, the land of bigger is better, so If I need to change it, I will.
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Old 11-18-2018, 06:26 AM
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Here’s a link to your mild cam.
https://www.jegs.com/i/COMP-Cams/249...208-3/10002/-1

That’s a real mild cam for a 454.
Specs close to a 350 hp 396.
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Old 11-18-2018, 06:35 AM
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Here's a link to the cam specs.
11-208-3 - Magnumâ„¢ Hydraulic Flat Tappet Camshafts
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Old 11-18-2018, 02:56 PM
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Quote:
Originally Posted by Colin68 View Post
both good questions....not sure about peak torque? I would probably have to do some research to see what is optimal for the type of driving I will do. As for the RPMs, I have read that somewhere in the 5500 range is fairly normal, but I am not sure.

You can build your engine to make neck (and drive train) snapping power off the line all in at 3000 rpm with the thing falling on it's face at 4000rpm torque wise. Or you can have the rat built into a screamer that can rev up to 7000 with peak torque around the 5500 area.

In my experiences the faster a v8 engine spins the more expensive it is to build to withstand the increased stress of spinning that fast. As you can imagine where you put that peak torque influences everything which is why I asked about it before ever talking about a cam or heads.
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Old 11-19-2018, 10:36 AM
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Howards makes a lot of nice roller cam kits. This is one I have saved for my pending BBC project on eBay.

https://www.ebay.com/itm/HOWARDS-BBC...53.m1438.l9372


Another example with more stuff in it.
https://www.ebay.com/itm/HOWARDS-BBC...53.m1438.l9372
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