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  #16 (permalink)  
Old 08-10-2013, 09:50 AM
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Originally Posted by jokerZ71 View Post
That's why it's important to give all the details.You said a mostly stock or mild rebuild.That cam is not really radical.It's just that stock heads wouldn't accommodate that much lift.If your heads are already set up for a high lift cam & your springs & parts are good,that's a different story.I'm not familiar w/ the specs on a 292.Do you know the specifics of your heads?Casting#,have they been decked,etc.What compression were you running?Were your previous pistons also dish?Do know off hand the specs of your previous cam?
Thanks for your input joker it is definitely appreciated. I called my builder after your last reply to make sure. The heads are bone stock and are the 76cc crap heads that came on the 71 400 originally. I bought the camaro used and this engine was already in it. The guy said it was freshly rebuilt but the bore is stock right now. From what we can see this guy put new rings and bearings and threw a radical cam in it. There is no work done to these heads, still has stock springs. The cam that cam out was a 292 with 518 lift at 244 duration at .050. I ran this for about 6 months then sold to brother n law and after 2 months he put a zz4 engine in camaro. He then gave my 400 back. As far as compression I know stock my engine has 8.5 My builder said he will deck my heads and upgrade parts and springs and retainers. If me and him didn't have a deal it would have been much better to buy better aluminum heads but it is no cash out of pocket for me using stock heads.

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  #17 (permalink)  
Old 08-10-2013, 10:03 AM
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stock heads and pistons,close the intake valve early.
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Old 08-10-2013, 10:24 AM
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Originally Posted by vinniekq2 View Post
stock heads and pistons,close the intake valve early.
Sorry. I don't know what that means to what I am trying to find out here. Basically I want to know if my setup will make engine die or fall on its face on acceleration. Or won't run smooth are something of that nature. I have a 305 in it now and I am sure a bone stock 400 will be night and day difference in my elcamino. But I would just like a little extra over stock.
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Old 08-10-2013, 10:37 AM
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If you use stock pistons that are low compression,you need to use a small cam,IE: short duration with higher lift. close up the intake centerline to a low number like 102. The heads flow fair and with a short roller,750 cfm carb,decent intake,1 5/8 headers,3 inch exhaust system,that engine should make very good power to 5500 RPM and be a tire shredder,,,,
high 13s easy
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  #20 (permalink)  
Old 08-10-2013, 10:40 AM
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Originally Posted by gmtony55 View Post
Sorry. I don't know what that means to what I am trying to find out here. Basically I want to know if my setup will make engine die or fall on its face on acceleration. Or won't run smooth are something of that nature. I have a 305 in it now and I am sure a bone stock 400 will be night and day difference in my elcamino. But I would just like a little extra over stock.
The point that the intake valve closes(IVC) determines how much cylinder psi & your effective CR.The XE274 you have has an IVC of 64*,which is rather late.This let's the cam bleed of cylinder psi.You could install the cam advanced to make IVC sooner,but,if you need more than 3 to 4*,you have the wrong cam.You would be better finding a cam w/ an earlier IVC,or using different piston,head chamber volume to raise compression.The 274 says it needs 10.5:1 CR.This is due to the late IVC which is gonna lower your actual CR.A cam w/ an earlier IVC will help your stock heads,pistons retain a better CR..I may not have explained this very well.Vinnie or some of the others can prolly do a better job explainin it.
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Old 08-10-2013, 11:02 AM
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Originally Posted by vinniekq2 View Post
If you use stock pistons that are low compression,you need to use a small cam,IE: short duration with higher lift. close up the intake centerline to a low number like 102. The heads flow fair and with a short roller,750 cfm carb,decent intake,1 5/8 headers,3 inch exhaust system,that engine should make very good power to 5500 RPM and be a tire shredder,,,,
high 13s easy
So if I am reading this correct. My .490 lift is ok but I need less duration one that opens sooner? Please recommend a cam. I don't have carb yet so I can always get what I need. I don't need 13's high 14's would be fine.
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  #22 (permalink)  
Old 08-10-2013, 11:03 AM
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Quote:
Originally Posted by gmtony55 View Post
Thanks for your input joker it is definitely appreciated. I called my builder after your last reply to make sure. The heads are bone stock and are the 76cc crap heads that came on the 71 400 originally. I bought the camaro used and this engine was already in it. The guy said it was freshly rebuilt but the bore is stock right now. From what we can see this guy put new rings and bearings and threw a radical cam in it. There is no work done to these heads, still has stock springs. The cam that cam out was a 292 with 518 lift at 244 duration at .050. I ran this for about 6 months then sold to brother n law and after 2 months he put a zz4 engine in camaro. He then gave my 400 back. As far as compression I know stock my engine has 8.5 My builder said he will deck my heads and upgrade parts and springs and retainers. If me and him didn't have a deal it would have been much better to buy better aluminum heads but it is no cash out of pocket for me using stock heads.
It's hard to believe that your heads are bone stock if those are the specs of your current cam.That's a lot of lift for an unaltered stock head.I'm guessing you prolly have #882 heads.
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  #23 (permalink)  
Old 08-10-2013, 11:12 AM
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this is what I built for a friend years ago
stock 400 long block
sig erson TQ-20 cam (much better available now)
street dominator intake
625 carter
1 5/8 headers
with 2.73 gears the 86 Monte Carlo ran 14.1s
with dual exhaust hooked up and non posi diff.
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  #24 (permalink)  
Old 08-10-2013, 11:27 AM
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113215-08 NA 270 278 217 225 .495 .500 108 104 Hyd. Hyd
a cam like or close to this would make power to 5k
217 intake duration, .495 lift.would have to calculate intake closing time to see if this is good? maybe same cam with 102 icl or advance the cam,,,
depends on final results wanted,piston deck height,combustion chamber CCs after resurfacing
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Old 08-10-2013, 11:27 AM
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Originally Posted by jokerZ71 View Post
It's hard to believe that your heads are bone stock if those are the specs of your current cam.That's a lot of lift for an unaltered stock head.I'm guessing you prolly have #882 heads.
To make sure I went get the cam and u really won't believe this. I was wrong,the stamp on the end is CCH-296-2. Isn't that even more lift? This is 100% the cam that cam out of this engine.
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  #26 (permalink)  
Old 08-10-2013, 11:28 AM
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Quote:
Originally Posted by gmtony55 View Post
So if I am reading this correct. My .490 lift is ok but I need less duration one that opens sooner? Please recommend a cam. I don't have carb yet so I can always get what I need. I don't need 13's high 14's would be fine.
If you are wanting to stay with the Xtreme Series line of cams,the XE262H is a decent cam for a mostly stock SBC.You need a cam that closes the intake valve sooner than the 274.
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  #27 (permalink)  
Old 08-10-2013, 01:18 PM
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Quote:
Originally Posted by vinniekq2 View Post
stock heads and pistons,close the intake valve early.
That goes back to what I said earlier: Advance the cam

This does nothing to change the duration or lift or LSA. It just changes the phasing of the cam with the crankshaft. By advancing it, it causes the valve events to happen sooner than they normally would. Intake opens sooner. It also closes the valve sooner. Did you read that link I sent you in my first post? It explains all this stuff. The sooner the valve closes, more PSI is built in the cylinder, and thus less compression ratio is needed.

The opposite is true too. The later the intake valve closes, the more compression ratio you need.

I think the XE274H is going to be a great cam for a 400ci engine.
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Old 08-10-2013, 01:57 PM
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With his 76 cc heads & a stock 8.5:1 CR,his DCR is gonna be really low with the 274.Just barely above 7.5.Even if he advances it 4*,I don't think it's gonna allow a good enuff CR & cylinder psi to make good power.He's gonna need a minmum of 9.5:1 SCR to even get above 150 psi on cylinder psi with late IVC of that cam.With better pistons or heads it would prolly be fine.The 274 is going to be totally different in his engine I think than in yours.You have a smaller bore,less stroke,& better heads,pistons.However,i'm thinking his heads are not completely stock if he was running the cam he currently has.It's hard to imagine over .500 lift on a stock SBC head.
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  #29 (permalink)  
Old 08-10-2013, 02:03 PM
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The only thing that limits stock heads to under .5oo lift is the screw in studs and spring pressure combo. If the heads are plained then maybe the CR is ok,depending on deck height.
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Old 08-10-2013, 03:14 PM
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Even if you end up using the dish pistons,be sure you use 1 with a 1.56" compression hgt & don't let them cheap out on ya & use a 1.54" Rebuilders piston that will put you .020 farther in the hole & lower CR even more.
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