086 castings with a custom 5cc piston set at zero deck

3.8" bore with Cometic 3.810 bore .040 compressed MLS gaskets

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Did you use early 304 heads too get your compression or custom piston .Thanks just curious]]>

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.

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! |

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]]>

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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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.

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I cannot get an off the shelf cam for that price!

Just out of curiosity John, I plugged the 304 build into my obscure formulas;

I get your build for a 4200 RPM center, and this produces a maximum torque (cylinder pressure) at 22 degrees ATDC.

By no means knocking your work, I wish I had the knowledge, experience and TOOLS!

Your intake open and close match closely to my calculations for best cylinder charge.

My calculations bring me to reducing the duration of the exhaust by 4 degrees, showing it would pick up 4 ftlbs of torque and 6 to 8 HP. This is of course on paper and not the real world.

Would very much like to see how you came up with your custom grind!

Are you calculating by peak cylinder pressure and fall off pressure number?

Am I also correct in that this is for an automatic transmission with a higher then stock stall converter?

Edited by Trader - Mar/06/2019 at 4:52pm]]>

203 plus shipping for a typical American V8 iron flat tappet cam ]]>

John, how much is a custom hydraulic flat tappet cam from Bullet? Just as a reference point for everyone.]]>

Very kind words, thank you

I am not going to lie, there is a customer or two where the communication was lacking and things did not go as well.

Probably not a good thing to say about myself but I would be lying if I said things always work out perfectly.

One thing I can say is, in every case a top notch product was delivered in the end.

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