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350 cam selection help
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oregonchevelle
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PostPosted: Sun Mar 12, 2006 10:40 am    Post subject: 350 cam selection help Reply with quote

Hi guys. Took the intake off the motor yesterday and saw what looked like oil and gas sitting in my heads. Valves looked pretty carboned up too. So looks like the heads are coming off and going to get new seals and maybe guides. I took the intake off to try and seal a nasty leak by the distributor I had. Well since I took it off I figured I would replace the intake and carb as well. Then I decide I might just put on an aluminum water pump too. Well all this leads me to the fact that I am looking to replace the cam now too since it is all coming aprt anyway. So what I am looking for is what you guys would put in for a cam and an intake and crb to go with it. The car is a 3600lb chevelle with a Richmond T-10 Manual 4 speed transmission. Rear gears are 3.08 but will be changed to 3.73s or 4.10s as soon as I can get the rearend from a buddys car. Motor is a 350 bored .030 with aluminum Trick Flow heads. 2.20/1.60 valves and 64cc Combustion Chamber. Pistons are 12 or 15.7 dished. Present cam is 454 lift and 216 duration with a centerline of 112. While I have all this stuff off which cam would you suggest I replace it with or would you leave it alone? This is a street/strip car that sees twon driving in the summer and 5-6 trips to the track in the summer.
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Big Dave
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PostPosted: Sun Mar 12, 2006 3:22 pm    Post subject: Reply with quote

I would throw a CompCams 12-246-3 (XE274H) at it. This is an Extreme Energy hydraulic flat tappet cam with advertised duration of 274/286 and 230/236 at 0.050" lift, the valve lift is 0.490"/0.490" and it has a 110 LSA. This should work with your prospective gear and heads, though if it were me I would buy the K (complete) kit with SPRINGS to have piece of mind. You may not have enough static compression to take full advantage of the power this cam offers. It is similar in performance potential of the factory 300 horse 327 mechanical flat tappet cam.


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af2
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PostPosted: Sun Mar 12, 2006 8:31 pm    Post subject: Reply with quote

FYI I wouldn't be too fast on pulling the heads. I have had many intake gasket leaks from the bottom that caused the exact same problem you are experiencing. You can't tell because it is acting like a PVC valve but sucking oil like crazy. You can check the valve situation with the heads on. Check the intake seals first then you can move the valve back and forth to quickly check the stem wear. they shouldn't move too much( a few thousandths) Then you can determine if you have to pull the heads. I have had many small blocks have this problem not just mine. Good luck
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jonny_b
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PostPosted: Sun Mar 12, 2006 8:51 pm    Post subject: Reply with quote

I used to have a Luinati .480/.480 230/230 cam in my 350 w/TFS heads and I liked it alot. very good street performance/bracket racing cam. Also in the future moving up to 1.6 rockers will bring it up .512 lift and the heads definatly like the more lift. But now i'm going to more race than street so I have switched it out for a comp cam 294S with my 1.6 rockers is .560/.560 lift, still hopeing for some streetable drivability though.

But I would deffinatly recomend the same as Big Dave, the comp cam XE274H is probably the best choice out there.

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oregonchevelle
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PostPosted: Sun Mar 12, 2006 11:39 pm    Post subject: Reply with quote

Now I am pretty much a novice at this stuff so... What do I need to do to check the heads while they are still on the motor? Do I remove the rockers first?

Thanks for the help

Perry

P.S. If I do remove the heads how thin of a head gasket can I safely go with? I want to up the compression as much as I can. right now I have .038 gaskets on it.

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af2
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PostPosted: Mon Mar 13, 2006 12:19 am    Post subject: Reply with quote

[quote="oregonchevelle"]Now I am pretty much a novice at this stuff so... What do I need to do to check the heads while they are still on the motor? Do I remove the rockers first?

Thanks for the help

Perry

P.S. If I do remove the heads how thin of a head gasket can I safely go with? I want to up the compression as much as I can. right now I have .038 gaskets on it.[/quote]

Perry everything you check is with the heads on! You have to remove the rockers to get access to the valves. Forgetting that part if you want to pull the heads you need to see if the block has been 0 decked or how far the piston is below the block at top dead. If the block is stock it will be .025 below. other wise use the given .040 for a 4" bore. You can figure out thickness from that equation. The point is you can't assume. you have to know. If you're block has not been touched the steel head gaskets will work.
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oregonchevelle
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PostPosted: Mon Mar 13, 2006 1:05 am    Post subject: Reply with quote

accorrding to my build sheet form summit the deck is -.001. Does that make sense?
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af2
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PostPosted: Mon Mar 13, 2006 10:24 am    Post subject: Reply with quote

Don't go any thinner on the head gasket. You have the perfect squish now without worrying about parts colliding.
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coppergmc
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PostPosted: Mon Mar 13, 2006 2:51 pm    Post subject: Reply with quote

That's 2 votes for Comp's XE274 cam. Try the Air Gap intake and a 650 or 750 dp Holley if you are going to spend the money.

I did the math on the compression and came up with 9.583:1 with 12cc dish and 9.225:1 with the 15.7cc dish. That's pretty good compression. Your car should hall when you get the gears in. Good luck. Copper
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af2
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PostPosted: Mon Mar 13, 2006 4:31 pm    Post subject: Reply with quote

I also agree with the XE274 cam choice. Professional Products sells an air gap they call Cross Wind for about $140.00. I run one on my 331 Vortec head motor and it is impressive.
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oregonchevelle
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PostPosted: Mon Mar 13, 2006 8:28 pm    Post subject: Reply with quote

Professional Products? I don't think I have heard of them. You think they have good stuff though huh?
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coppergmc
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PostPosted: Tue Mar 14, 2006 11:10 am    Post subject: Reply with quote

For the money, you can't beat the proffessional products intake. Also, I found a cam and lifter kit in the Doug Herbert book yesterday for $109.00 that should be pretty good. I think it's CLC4N. 228/234 @.050 with .480/.497 lift on a 106 lobe sep. Not a bad price and should work well if you are looking for more power and that choppy idle. Copper
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oregonchevelle
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PostPosted: Tue Mar 14, 2006 12:07 pm    Post subject: Reply with quote

Yes those do sound like good prices! As for the sound? I don't really care as long as it gets it going in a hurry when I press the long skinny pedal. Also, anyone care to explain effect of lobe seperation to me? I get the duration and lift bit but the seperation is still a bit puzzling to me. As I understand it a larger seperation will make it idle more "friendly" and the shorter will be a bit more "choppy" So I would venture to guess a larger lobe seperation would probably also give you a better vacuum. I thik I read somwhere that a larger lobe seperation will also have a broader torque curve? Feel free to clear any of this up and correct my mistakes as I am assuming on some and trying to remember on the rest.
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coppergmc
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PostPosted: Tue Mar 14, 2006 2:18 pm    Post subject: Reply with quote

Try this sight: http://www.webcamshafts.com/cam_glossary.html#flank
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clay
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PostPosted: Tue Mar 14, 2006 8:47 pm    Post subject: Reply with quote

Very good website for summarizing cam stuff. If you are a reader, another good thing to do is start with David Vizards book on Building Small Block Chevy's on a Budget. It is an excellent book covering basically everything from air cleaners to mufflers. He also has some specific books on heads, cams and valvetrains, intakes and carburetors and bottom ends I believe. Very interesting reading and a wealth of information. Clay
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