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Old 03-08-2011, 10:43 AM
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406 cam

this is the cam I want to use.

http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT

I will have RHS 200cc heads and be running a 10.2:1 compression ratio.
I see that this cam requires a 9:1 compression ratio. Is this a minimum compression ratio, or a required compression ratio.

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Old 03-08-2011, 08:52 PM
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9:1 is the minimum recommended compression ratio.

Just a little note...Catalog suggested rpm ranges for SBC cams are based off use in a 350 cube engine as the "standard". The cam you have linked will have an actual powerband of about 1500-5800 rpm in a larger 400 cube engine. Just a little FYI.
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Old 03-09-2011, 06:26 AM
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thank you! that is actually good news.
The engine will be going in a 4x4 and I would like to have more "usable" horsepower and torque at lower rpm's. And the roller lifters I bought are maxed at 6500 rpm's.
These: http://www.summitracing.com/parts/HRS-91164-2/

While I have you all on the line, do you think RHS 200cc heads are to big for low end torque? I don't mind having the power come in at 2500 rpm's. I find it fits my driving style just right.

P.S. Manual tranny.
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Old 03-09-2011, 06:48 AM
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My favorite small block, the 400 . Eats up cam duration without losing low end torque because of its large size(compared to a 350), and the same with intake runner volume.

You won't lose any low end to speak of with the 200cc head. Its a great fit on a 400.
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Old 03-11-2011, 09:32 AM
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OK, the cam card says .507 lift with 1.5 rocker ........ So, .338 lift at the cam?

Then with a 1.6 rocker the lift should be...... .541?

FYI
I am building the engine FOR propane. From what I have read on here, I would want a compression ratio of ~13:1.

I bought a Scat 9000 crank with Scat I beam rods (bushed), and KB129 pistons.

I have not bought the heads yet. I am thinking I need a large camber head to help with flow (less shrouding). Should I be concerned with this? KB129 pistons are a dome type piston.
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Old 03-11-2011, 10:42 PM
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Your math on the valve lift is correct.

If you are going to use an aftermarket head the closed chamber (basically 64cc) is opened up around the intake valve more compared to old factory closed chamber heads, so flow isn't a problem. you will need to use a 64cc head to get a 13-1 compression ratio, an open chamber head(usually 76cc) drops compression to 11.2-1
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Old 03-12-2011, 06:27 AM
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Thank you ericnova72.

I will post some pics and data when I start bolting things together.

But, this is my first "blue print" type built, so it will take a while. I want everything to be perfect. I ordered a ton of tools to get the job done correctly.
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Old 03-31-2011, 01:30 AM
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I need more advise/help. Today I had my pistons and bore meassured for piston to wall clearance. The machinist says that I have .003 clearance. (KB piston ask for .002 to .0025 clearance) Yet the piston skirt has NO play in the cylinder at all. I can get it to move up and down the bore but it is tricky.

I was under the impression that the skirt will lock up in the bore before any thing else, not so much the ring area. Am I wrong?
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Old 03-31-2011, 02:36 AM
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How are you checking?? If you are just putting a piston in the bore by itself, by hand, it is very easy to tip it slightly and make it feel tight. At the small .003" clearance, you will not be able to "rattle" the piston in the bore by hand, there will seem to be no play at all.

The clearance is measure at a specific position on the skirt, roughly the same height as the pin IIRC on the KB piston.

Pistons are smaller at the top for expansion room due to heat, will be .020"-.030" smaller than the bore at the top, only the recommended clearance(.003" in your case) at the measurement point, and maybe .002-.007" at the very bottom of the skirt.

You can check clearance by putting the piston upside down 1/2 way in the bore, then use a .002-.003" feeler guage slid in between the skirt and the bore. Otherwise you will need a 4-5" micrometer and a snap guage or dial bore guage to take actual measurements.
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Old 04-04-2011, 02:07 PM
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I know this thread is getting a little long in the tooth, but newbies like me need to know this stuff.

Over the weekend I did the feeler gage test.........
I could not get a .002 feeler gage between the cylinder wall and the piston.
So, today I went to another machine shop and had them mic the pistons and bore. Clearance was.........0.......
The bore and pistons are the same size!

Guys, if it doesn't seem right it usually isn't.

So, I just lost 300 bucks do to poor workman ship....
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Old 04-04-2011, 07:22 PM
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You should just be able to have a shop you trust hone the needed .002" clearance out of the bore size you have now. At least your not totally screwed, like if they honed it for .005" clearance with the hyper piston.

I would suggest you have it done with a torque plate, on the 400's bigger bore the head bolt holes are real close to the bore and will distort the top 1" or so of the bore in 5 places, right adjacent to each bolt.
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Old 06-26-2011, 11:30 AM
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I'm getting things going on the 406. The 406 will most likley end up in the 1981 Scottsdale. But I am also building a 1984 Jeep Scrambler!
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Old 06-26-2011, 11:46 AM
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Main bearing clearance is 002. Rod bearing clearance is 0015. The rotating assembly rotates smoth as silk. BUT, did have cam to rod "issues". I had to file the corners of 4 rods.
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Old 06-26-2011, 01:40 PM
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http://www.youtube.com/watch?v=V0zcz...t=HL1309113550
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Old 06-28-2011, 04:58 AM
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Quote:
Originally Posted by nathon001
o that loooked so beautiful.. I cant wait to start on mine. good luck
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