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my87Z is right on the money with his suggestion of 9.5:1 to 9.8:1 static compression ratio. Here's the roller cam I might use with that SCR
9.5:1 with this cam will produce a dynamic compression ratio of 8.399:1 9.8:1 with this cam will produce a dynamic compression ratio of 8.660:1 Either of these DCR's are easily compatible with pump gas if you build the motor with a tight squish (0.035"-0.045"). You see, what you have to understand is that you will be BRACKET RACING, so your E.T. and TRAP SPEED are unimportant. Build the car so that it's a pleasure to drive on the street and then just live with what times you post at the strip. You'll be bracketed against faster and slower cars, so it won't matter what speed and e.t. you go. The only thing that will matter is your reaction time and running consistently on your dial. |
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But at the target you have for power, there's no need to use race gas gas. Better to go w/around 9.5:1 CR like mentioned above that matches the cam you need to make the power you want. It's all interrelated. By not pushing the limit on compression, you have a cushion against detonation caused by a bad tank of fuel or something causing the engine to run hotter than normal. |
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Thanks a lot for the info everyone. Think I'll be going with a setup that runs the 10:1 "starting line ratio" for gears/trans. I definitely want a mild/slight performance roller cam(I'm looking for power in the 1600-6000 rpm range) with 1.6 rockers on intake at least; probably 6" rods. 9.5 CR with a typical 0.035-.045 squish seems to be my ticket for what I want.
I'm not too keen on heads and I will be changing them, a suggestion for 195-200 cc intake runner range was made and I'm not sure what valve size to go with either...I'm looking into a 750 cfm carb and I know this depends on the combustion chamber/piston size too. I have a better idea what to get with the other components in terms of a kit, but I am a little concerned about piston weight/balancing, etc. when it comes to forged and "hyper" pistons...just trying to find the right balance |
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as seen as this is a build you'll be doing down the road..
I'd see if you can come across a 1987 up block as they are roller cam ready.. and the 100.oo you'll pay for it is cheap compaired to the 800.oo+ retro fit roller cam kit to go roller cam in that 1976 block.. if moneys tight. this might be the best 100.oo you spend before you start machining the block.. If not going roller.. then forget this post.. |
| The Following User Says Thank You to gearheadslife For This Useful Post: | ||
techinspector1 (11-14-2012) | ||
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This is a general statement.Torque is = to E.T.,the first 60' to 330' and MPH is = to HP. If you want to bracket race you should for both a street vehicle and a bracket racer a engine that is more slanted towards torque. Have I ever been beat by being MPH'ed??. Yes I surely have,but those times are rare. My averages early on racing where won in the first 60' to 330'.
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Vinnie-A Honda with turbo and a small c.i. engine in a relative light wt car doesn't have a power curve the same way a bigger heavier BBC does.But both cars are relying on the torque curve.The Honda has to buzz high because the smaller engine doesn't develop any power until the later in the RPM range.And then it transitions to HP faster to create the MPH it ends up getting.
My suggestion is two fold.He dials on a E.T. for the car to bracket race and the torque is surely going to help him get to the dial or goal he has in mind for that and the torque curve that is low enough in the RPM range he'll get to use and enjoy more often driving the car on the street.Would be more effective in some street light to street light racing with the right cam/head/T/C,gear combo/tire size. |
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383 build
Check out this 383 Scat rotating assembly. This rotating assembly is used in a 2pc rear main seal block. It is external balanced and comes with a balancer and flexplate. Scat Engine Rotating Assemblies 1-90355BE - SummitRacing.com. This assembly is for using 64cc chambered heads for a compression ratio of 9.7. Here is a 383 Scat rotating assembly for a 2pc rear main seal block. It is also external balanced and comes with a balancer and flexplate. SB Chevy 383 Scat Rotating Assembly Kit, 3.750 Stroke 5.700 Rods 9.8:1 Hypereutectic Keith Black Dish Pistons - 383 Kits with 5.7' Rods - 9000 Series Kits - Small Block Chevy - Scat Rotating Assembly kits - Rotating Assemblies | CNC Motorsports | Car. This kit also uses 64cc chambered heads for 9.8 compression ratio. Since you are going to have a stick shift transmission I also looked at this 383 Scat rotating assembly. It has 6" rods and Keith Black Hypereutectic 18cc Dish Pistons. This is an internal balanced assembly by CNC Motorsports. The balancer and flexplate (which is not needed) does not come with an internal balanced kit. It also uses 64cc chambered heads for a 9.8 compression ratio. SB Chevy 383 Scat Rotating Assembly Kit, 3.750 Stroke 6.000 Rods 9.8:1 Hypereutectic Keith Black Dish Pistons - 383 Kits with 6.0' Rods - 9000 Series Kits - Small Block Chevy - Scat Rotating Assembly kits - Rotating Assemblies | CNC Motorsports | Car.
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| The Following 2 Users Say Thank You to cdminter59 For This Useful Post: | ||
Camaro R/S LT (11-15-2012), techinspector1 (11-15-2012) | ||
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flat top or dished pistons: pros/cons?
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if heads are already sourced then use what gives you the compression you need/want.. if heads are not already on hand and need to be bought.. flat top 99% of the time is the better choice.. and use the heads chamber size to get the compression you want... no always possable ..but mosttimes you're not reinventing the wheel.. and the parts needed are out there.. of cource I'm talking n/a, boosted is a totally different animal |
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http://www.strokerengine.com/383Combos1.html |
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Those combos and their power numbers seem a little optimistic for the parts used but either of those set ups (15-17) should easily produce 430-460hp and be a real nice street motor with some fun strip time.
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So 2 question: What kind of difference is there between 1.5 roller rockers and flat-tappet? AND I'm leaning towards Comp Cams XR288HR. One thing I don't like about this cam is that the RPM Range starts at 2500. I want something closer to 1600-2000. Is there a better cam? Last edited by Camaro R/S LT; 11-17-2012 at 08:54 PM. |
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