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nonsensekid20 Member
Joined: 30 Sep 2010 Posts: 490
1991 Chevrolet Camaro RS
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Posted: Mon Feb 18, 2013 2:37 pm Post subject: Power adders |
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So I've had this question before, but I haven't really brought it up. So I have a rebuilt chevy 350, 4 bolt main, 2 piece rear seal, holley 670 carb, 221/224 cam, and stock iron heads. What I'm wondering is what can I do to build more than 221 HP/276 TQ? It seems like with the cam and carb I should be running a lot higher than that. Maybe jetting? |
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Alphius Peanut
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Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Mon Feb 18, 2013 3:48 pm Post subject: |
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What compression is your motor?
Head casting and valve size?
Need more specs on the cam as well. Max lift, LSA, Adv. duration, etc.
What intake manifold are you using?
What about your exhaust setup?
Given that I used to run a pretty similar carbed setup on pretty low compression, I'd say your numbers are not too far off. Is this through an automatic as well? _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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nonsensekid20 Member
Joined: 30 Sep 2010 Posts: 490
1991 Chevrolet Camaro RS
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Posted: Mon Feb 18, 2013 6:15 pm Post subject: |
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IIRC compression is around 9:1.
Valve lift: .470 intake .470 exhaust
Duration at .007 tappet lift 270in 270ex
Valve timing - Open: 29* BTDCin 69 BBDC Ex. Closed: 61 ABDC ex 21 ATDC ex
Duration at .050 Int: 224, Ex: 224
Lobe Lift: .3130 Int, .3130 Ex.
Rocker Arm ratio: .00
lobe seperation 110.
Grind # CS 270H-10
IIRC heads are 76cc chambers.
Intake manifold I believe is stock replacement. This was just a long block built by Paul at Bowtie.
I've got Hedmen headers w/ 2 1/2" collectors that meets up with a Y-Pipe to lead back 3" exhaust into the Flowmaster 40 series and back out with dual 2 1/2s.
And this is through stock rear end, stock t5. |
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Twilightoptics Hardcore (12sec Club)
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Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Feb 18, 2013 6:41 pm Post subject: |
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Put some 64cc aftermarket heads and enjoy 280-300hp with a decent intake.
Your cam is marginally small, but your heads are crap, your compression is crap, and your intake is crap. You're doing well at 221hp. Your torque number is good and is a direct indication of the small intake/heads. _________________ A redline a day keeps the carbon away! |
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nonsensekid20 Member
Joined: 30 Sep 2010 Posts: 490
1991 Chevrolet Camaro RS
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Posted: Mon Feb 18, 2013 7:14 pm Post subject: |
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Should I go aluminum or stay with iron? And should I go with an air gap intake and take off the carb spacer I put on? Vortec? If I'm changing the heads I can switch to vortec heads and intake.
Found these, don't know if they're good or not. Comments or speculation? http://www.summitracing.com/parts/tfs-30400003-m64/overview/make/chevrolet |
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Alphius Peanut
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Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Mon Feb 18, 2013 7:29 pm Post subject: |
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Yeah, I had almost the same build except I had a little bigger split pattern cam and a Qjet on an OEM aluminum intake. I made like 243RWHP IIRC with that combo through a T5 and 3.23 gears.
Switching to fuel injection with a Holley Stealth Ram and a MegaSquirt and a new exhaust and matching the cam to my heads a little better I made 274RWHP. Also switched back to 3.73 which helped acceleration a lot.
Switched to aluminum 64cc heads (10.3:1 CR)and made 310RWHP with a bad tune and lots of room for improvement. Then I broke my engine and put an LS1 in.
Probably a pretty cost effective route is going with a set of worked over iron Vortecs and seeing what that gets you. IMHO if you can get around 300WHP that's pretty solid fun for a street car. It starts getting more and more expensive to build for more power above and beyond that with an SBC.
If you do this, you need to measure your engine specs (deck height, dish volume, head volume) while you have it apart and build for a specific compression ratio and quench area. This will help you make good, reliable power. _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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Twilightoptics Hardcore (12sec Club)
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Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Feb 18, 2013 7:40 pm Post subject: |
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Trick Flow makes good heads. If you're spending that kind of coin, go Brodix or at minimum AFR.
Budget means iron heads. Go with something that has a heartshaped chamber: RHS, Vortecs, etc
IN the middle, rock the GM Fastburn heads. Fastburn heads and the LT4 hot cam (which you can't do unless you go retro roller) makes 300+ easy and it's NICE power.
Air gap is a bad ass street manfiold with easy 300HP yields and good street manors since it's still a dual plane.
Gabe is right, 300RWHP in a thirdgen is a great go fast, streetable combo. Start going beyond that and other things become sacrifices.
You need to know your piston CC, your actual bore, and your deck height. _________________ A redline a day keeps the carbon away! |
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Twilightoptics Hardcore (12sec Club)
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Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Feb 18, 2013 7:42 pm Post subject: |
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Also factor in hardened pushrods, guide plates, and a set of rockers than can handle it all. _________________ A redline a day keeps the carbon away! |
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nonsensekid20 Member
Joined: 30 Sep 2010 Posts: 490
1991 Chevrolet Camaro RS
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Posted: Mon Feb 18, 2013 8:19 pm Post subject: |
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I noticed on my dyno sheet that my power line looked like a tweaker drew it. It was a smooth line besides the shallow up and down movement, some people said it was because my valve springs weren't strong enough and I was beginning on valve float. So with that said, I've heard great things about cost effectiveness and performance out of GM Fast Burn heads, but the highest CC is comes in is 62cc. Probably close enough right? And the more important question, should I get the unassembled set and get my own push rods and rockers? And what do you mean by hardened guide plates, push rods etc? |
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DBL_TKE Member
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Joined: 28 Feb 2007 Posts: 1505 Location: Aloha, OR
1991 Chevrolet Camaro Z/28
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Posted: Tue Feb 19, 2013 6:21 pm Post subject: |
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You all really think that's what it should be at? that's only 5 more hp and the exact same torque that my stock LB9 puts out at the wheels... |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Tue Feb 19, 2013 6:50 pm Post subject: |
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Your engine has better heads, better quench, and higher compression. It is also running a reasonable tune.
IMHO His car being untuned is leaving horses on the table but, as Paul and Gabe have already pointed out, the heads and intake are the limiters for him. |
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Alphius Peanut
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Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Tue Feb 19, 2013 6:51 pm Post subject: |
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DBL_TKE wrote: | You all really think that's what it should be at? that's only 5 more hp and the exact same torque that my stock LB9 puts out at the wheels... |
Two things:
1. Dynos all read different.
2. You're not factoring in the low compression and terrible head flow, combined with a little too big of a cam and probably not optimal carb tuning.
nonsensekid20 wrote: | I noticed on my dyno sheet that my power line looked like a tweaker drew it. It was a smooth line besides the shallow up and down movement, some people said it was because my valve springs weren't strong enough and I was beginning on valve float. So with that said, I've heard great things about cost effectiveness and performance out of GM Fast Burn heads, but the highest CC is comes in is 62cc. Probably close enough right? And the more important question, should I get the unassembled set and get my own push rods and rockers? And what do you mean by hardened guide plates, push rods etc? |
Honestly that sounds pretty much normal. Post up the graph and we'll tell you if it looks funny.
Don't bother with the fast burns, find a used set of Vortecs and get bigger valves installed. You'll be money ahead for suspension mods and still make good power. The only thing better than power for having fun is good handling.
Only you can tell if 62cc is big enough by measuring the current specs of your motor as Paul and I said before and doing some math. _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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izcain 9sec Club
Joined: 09 Sep 2006 Posts: 1306 Location: Port Angeles WA
1983 Chevrolet Camaro Z/28
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Posted: Fri Feb 22, 2013 8:30 am Post subject: |
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Do you know what total timing and AFR you were running when putting the readings down. Im not saying you are going to magically pick up a ton but if it is off there is free hp laying there ready to be picked up.
If you want considerably more time to tear into it! _________________
1983 Z28 383 + 201ci more = New Heart for this season!
9.17 @ 148 |
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nonsensekid20 Member
Joined: 30 Sep 2010 Posts: 490
1991 Chevrolet Camaro RS
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Posted: Fri Feb 22, 2013 11:05 am Post subject: |
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Alright here are my two dyno sheets. One is a 3rd gear pull, the other a 4th gear pull.
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Alphius Peanut
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Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Fri Feb 22, 2013 11:33 am Post subject: |
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Looks about right to me except it is too lean. Richer would probably help smooth that graph out. Maybe getting a little predet too? Any idea on total timing?
I wouldn't expect too much more from that engine with those heads and cam. Like izcain said there is probably a little more to be unlocked but not a ton. _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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izcain 9sec Club
Joined: 09 Sep 2006 Posts: 1306 Location: Port Angeles WA
1983 Chevrolet Camaro Z/28
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Posted: Fri Feb 22, 2013 12:55 pm Post subject: |
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Alphius wrote: | Looks about right to me except it is too lean. Richer would probably help smooth that graph out. Maybe getting a little predet too? Any idea on total timing?
I wouldn't expect too much more from that engine with those heads and cam. Like izcain said there is probably a little more to be unlocked but not a ton. |
Totally agree, looks like it could use some more fuel. There is more in it from that graph you put up. Would be interesting to know what the timing is. _________________
1983 Z28 383 + 201ci more = New Heart for this season!
9.17 @ 148 |
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nonsensekid20 Member
Joined: 30 Sep 2010 Posts: 490
1991 Chevrolet Camaro RS
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Posted: Fri Feb 22, 2013 4:26 pm Post subject: |
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IIRC I have it at 8* when I set it with the line on the harmonic balancer. Since then I've turned my mix screws out 1/4 turn. Couldn't really tell much of a difference. But you think I need to change the cam? I like the rump it gives. ![Cool](images/smiles/icon_cool.gif) |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Fri Feb 22, 2013 5:08 pm Post subject: |
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nonsensekid20 wrote: | I have it at 8* |
nonsensekid20 wrote: | I've turned my mix screws out 1/4 turn |
..and there's the problem right there. ![Laughing](images/smiles/icon_lol.gif) |
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91RSVert Member
Joined: 16 May 2007 Posts: 2736 Location: AR
1991 Chevrolet Camaro RS
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Posted: Fri Feb 22, 2013 8:16 pm Post subject: |
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I'm still learning carbs, but shouldnt it have more timing, and also isnt out "leaner"? |
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Twilightoptics Hardcore (12sec Club)
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Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Fri Feb 22, 2013 9:51 pm Post subject: |
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Out is richer at idle only. 8 at idle tells us nothing. We need total timing without vacuum.
Depnding on the curve should be closer to 12-14 at idle wihout vacuum advance. _________________ A redline a day keeps the carbon away! |
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