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304 on the dyno

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jcisworthy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jcisworthy Quote  Post ReplyReply Direct Link To This Post Posted: Mar/06/2019 at 5:58pm
This is an automatic 700R4 trans 354 gear, 26" tire and a mild converter application. 

With this cam I called Bullet to order and told him what I had for lobes and LSA, ICL then he recommended a slight change and I told him to go for it so he did. 

Typically, I order a cam with the lobes I want from the Bullet master lobe list. I choose LSA and ICL based on the customers desire for the engine then adjust compression for cylinder pressure. 

So far it has been working out well. 

Of course cylinder heads and intake play a large part also. 
Specializing in engine building and cylinder head porting

https://www.rbjracing.com
Phone Number 518-915-3203
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Trader View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Mar/06/2019 at 8:21pm
Thanks
And rightly so, you cannot look at a single aspect but the entire combination of engine components, transmission, gearing, application, customers plans,  etc.
Likely people being the hardest part of the equation!
By the math I'm using:
Just for your interest, take it or leave it, from 2000 to 4500 RPM a 304 has the highest torque at 22° and a 401 at 24°.
The drop off power curve puts the exhaust open at 70° BBDC on a 304 and 68° BBDC on a 401 assuming your using the 111° separation angle and 107° ILC.
These numbers seem very static unless there is a drastic change. A torker intake vs a dual plain being a big one.  The torker likes lots more overlap by the numbers I'm using.
Look forward to your next build!
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Sonic Silver View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Mar/06/2019 at 9:02pm
Originally posted by Trader Trader wrote:

Thanks
And rightly so, you cannot look at a single aspect but the entire combination of engine components, transmission, gearing, application, customers plans,  etc.
Likely people being the hardest part of the equation!
By the math I'm using:
Just for your interest, take it or leave it, from 2000 to 4500 RPM a 304 has the highest torque at 22° and a 401 at 24°.
The drop off power curve puts the exhaust open at 70° BBDC on a 304 and 68° BBDC on a 401 assuming your using the 111° separation angle and 107° ILC.
These numbers seem very static unless there is a drastic change. A torker intake vs a dual plain being a big one.  The torker likes lots more overlap by the numbers I'm using.
Look forward to your next build!
I'm trying to understand this, but I need some help. When you say "the drop off power curve puts the exhaust open at 70* BBDC", etc., what does that mean if the exhaust opens before that or after that? Also, what do you mean by the 22 or 24 degree number for max torque between 2,000 and 4,500 rpm?

   What is the number for a 360 engine, if the 304 is 70 BBDC and the 401 is 68 BBDC? If the exhaust valve opens before this, do you lose some cylinder pressure and torque? If it opens too late, what happens, detonation? Thanks.

Edited by Sonic Silver - Mar/06/2019 at 9:18pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Mar/07/2019 at 5:42am
I will explain best I can as I don't have the excel knowledge to graph this.
The intake closing, cylinder diameter, stroke and cylinder velocity all contribute to charging the cylinder. There is a peak period for the intake to close to obtain the highest gas charge.
The timing and detonation of the charge at a set RPM will dictate the crankshaft angle with the most power to the crankshaft. This is a lot more like a spike then a curve compared to a valve opening curve.
As the spike starts down the cylinder pressure is dropping but there is a point that pressure vs calculated torque fall off very quickly.
Everything seems to be a compromise. In a perfect world, a low RPM engine will use all the available power. The higher up the RPM you set the goals.  Typically 3000 RPM to use 80% to 85% of the available power. This can be calculated to the exhaust valve opening point. This in turn sets your degrees of duration, overlap ...
So now you have numbers for intake open, close, exhaust open, close.
Type of valve train drive will dictate how aggressive you can make these points and also how much lift.
Then you can take your valve sizes, lift, head flow, intake flow, exhaust flow and calculate the charge and pressure to get a torque/HP number.

And no I have not calculated a 360 as it takes still over an hour to come up with one engine combination.
  
 
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austinsamx74 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote austinsamx74 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/16/2019 at 8:55am
Did you use early 304 heads too get your compression or custom piston .Thanks just curious
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jcisworthy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jcisworthy Quote  Post ReplyReply Direct Link To This Post Posted: Mar/16/2019 at 1:00pm
086 castings with a custom 5cc piston set at zero deck

3.8" bore with Cometic 3.810 bore .040 compressed MLS gaskets
Specializing in engine building and cylinder head porting

https://www.rbjracing.com
Phone Number 518-915-3203
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