Getting Stroked now what?

347HO · Feb 8, 2008

5spd GT said:
If I was to build a 347, I would go with a AFR 205 head. But, there is a reason why I did not suggest it.

The stock block...

I would hate to spend 2k on put it on a stock block.

You bring up a very valid point. Yes, the stock block has it's weak main webs but it's asset is it's very lightweight.
I have to de-tune my engine combo, yet I still have more power at the wheels than most people of equal cubic inch.
I'd accept if "you" called me a dumbazz for my choice in block... but I as well as many others before me have proven a stock roller block can make big power with upper moderate rpms and survive.
Exact machining and attention to detail matter here.

And getting to the camshaft... a custom is the REAL value here and the most bang for your dollar. When matched to your setup/combo, it makes everything work the way you want it, when you want.

5spd GT · Feb 9, 2008

347HO said:
No offense taken.

The restriction on an engine whether carburetor or a throttlebody is the the throttle blade. As you've already mentioned... the larger TB's advantage is at wide open. Also mentioned was the camshaft events, and that's so true. What I'm getting at is what is the air column doing from the back of the valve to the throttle blade at any position? With a well setup cylinder head, custom camshaft, get that air column into the cylinder with as much pressure as possible. I believe the larger area of the 90mm throttle blade allows atmosphere pressure to enter the intake plenum, runners and cylinder head ports quicker than the said 70mm with less speed and more pressure.
So yes, I agree the application pertains more to wide open and drag racing, but at any other throttle position... they both are restricting airflow.

Bernoulli's principle...

Air sits in the plenum for a short time before being "rammed" down the pipe with the harmonic intake tuning accounted for, so this is why I do not believe the engine is going to notice the difference in a positive or negative way at this point. From what I have followed with the aire requirements of the engines here, I see the 70mm and 90mm both "keeping up" here Not all cylinders are getting air in, due to the different cycle points of each cylinder.

It is the throttle body that lets us apply the air we need to the engine to do what we want it to do. After all, it is just a valve that lets air in and out, right?

70mm - 8.65" of area (squared)
90mm - 9.85" of area (squared)

5spd GT · Feb 9, 2008

347HO said:
You bring up a very valid point. Yes, the stock block has it's weak main webs but it's asset is it's very lightweight.
I have to de-tune my engine combo, yet I still have more power at the wheels than most people of equal cubic inch.
I'd accept if "you" called me a dumbazz for my choice in block... but I as well as many others before me have proven a stock roller block can make big power with upper moderate rpms and survive.
Exact machining and attention to detail matter here.

And getting to the camshaft... a custom is the REAL value here and the most bang for your dollar. When matched to your setup/combo, it makes everything work the way you want it, when you want.

The builder is huge factor for sure Since I did not know who his builder was going to be, I hated to advise the larger head, although deep down I wanted to.

347HO · Feb 9, 2008

5spd GT said:
Bernoulli's principle...

Air sits in the plenum for a short time before being "rammed" down the pipe with the harmonic intake tuning accounted for, so this is why I do not believe the engine is going to notice the difference in a positive or negative way at this point. From what I have followed with the aire requirements of the engines here, I see the 70mm and 90mm both "keeping up" here Not all cylinders are getting air in, due to the different cycle points of each cylinder.

It is the throttle body that lets us apply the air we need to the engine to do what we want it to do. After all, it is just a valve that lets air in and out, right?

70mm - 8.65" of area (squared)
90mm - 9.85" of area (squared)

Benoulli's theorum has been a huge factor in my old job for over 20 years... and have gotten very intimate with his science.
I agree with you and Beroulli in almost all respects... but if/when you ever have the chance to run a 70mm tbody and then remove and reinstall a 90mm tbody, I'm 99% sure you'd drop some ET if conditions were equal. I doubt you'd gain HP, my point is you'd gain acceleration.
I'm not sure if "everyone" would experience this... I believe you would, due to what I believe is your experience with engine tuning, engine operation, and level of been there/done that which would ensure it's done correctly.
I am assuming here... you do sound competent to me, and I'm not patronizing or trying to insult you. I can only go on what I read from your posts and translate that with my experience.

drews87stang · Feb 10, 2008

So if i want in the future to get a turbo or something will I have to change the heads? When i bought the car it came with nitrous but not hooked up. Should i hook it up? Im probably going to sell that and eventually get a turbo or a supercharger. But thats going to be years from now.

iwashmycar · Feb 10, 2008

i was gonna say 'clean up and say thanks'.....

347HO · Feb 10, 2008

drews87stang said:
So if i want in the future to get a turbo or something will I have to change the heads? When i bought the car it came with nitrous but not hooked up. Should i hook it up? Im probably going to sell that and eventually get a turbo or a supercharger. But thats going to be years from now.

Drew, the cool thing about Boost, whether turbo or supercharger... it pressurizes your air charge. Your cylinder heads don't have to change for that to work. Your camshaft most likely will, but not your cylinder heads.
Here's a small example, and I won't go deep into it either.
During your intake stroke, air rushes in at atmospheric pressure and fills the void caused by the negative pressure of the piston going down the cylinder. The camshaft events can assist this air column for more performance, but you're still only operating with atmosphere or Barometric pressure.
With a Turbocharger or Supercharger you increase the air charge's pressure many times over that of atmosphere, so now when the intake cycle or stroke starts... the air column is pretty much crammed into your cylinder on the down stroke. And again, the camshaft can manipulate the aircharge to allow for more performance.

5spd GT · Feb 10, 2008

347HO said:
Drew, the cool thing about Boost, whether turbo or supercharger... it pressurizes your air charge. Your cylinder heads don't have to change for that to work. Your camshaft most likely will, but not your cylinder heads.
Here's a small example, and I won't go deep into it either.
During your intake stroke, air rushes in at atmospheric pressure and fills the void caused by the negative pressure of the piston going down the cylinder. The camshaft events can assist this air column for more performance, but you're still only operating with atmosphere or Barometric pressure.
With a Turbocharger or Supercharger you increase the air charge's pressure many times over that of atmosphere, so now when the intake cycle or stroke starts... the air column is pretty much crammed into your cylinder on the down stroke. And again, the camshaft can manipulate the aircharge to allow for more performance.

Spot on...

This is why you see boosted cars well above 100% VE. It multiplies the atmospheric pressure (14.7 psi).

Getting Stroked now what?

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