408 or 351 with Vic Jrs ?

2

2002BLGT

Well-Known Member

Dec 18, 2003

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Feb 22, 2007

#1

• Feb 22, 2007

• #1

friend of mine is debating on building a 408 or a 351 and using a set of Vic Jrs , the cam he has picked out is a hydraulic flat tappet with duration of 284 int /292 exh 241/249 at .050 and lift of .560 int / .582 exh

he wants to keep compression in the 10-11 range with a forged flat top piston


so the question is , to stroke or not to stroke , gonna be using either a vic jr or performer RPM intake as well , what would you guys suggest ??

 

Jason 302

10 Year Member

Aug 9, 2003

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Newark, Ohio

Feb 22, 2007

#2

• Feb 22, 2007

• #2

Go with more cubes. The Vic Jr's probably wouldn't be the optimum head for a 408, they would be better suited for a 351, but they also should be a head that has plenty of material for porting. If you already have the heads, use em and maybe someday have them professionally ported. If not I would save up for some CNC Twisted Wedges or some AFR 205/225's.

 

J

jaredgoodwin

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Sep 29, 2004

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Feb 22, 2007

#3

• Feb 22, 2007

• #3

408, won't be able to use flat tops though.

 

2

2002BLGT

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Dec 18, 2003

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Feb 23, 2007

#4

• Feb 23, 2007

• #4

jaredgoodwin said:

408, won't be able to use flat tops though.

Click to expand...

why wont you be able to use flat tops if the valve reliefs are cut ?

 

FORCED2DV8

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Jun 6, 2005

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Feb 23, 2007

#5

• Feb 23, 2007

• #5

You can use flat tops if the valve reliefs are cut, Some companies probably make a piston for that 408 combo, with a 10 to 1 comp ratio. Youll just have to search for them. Or take the ones you have and have them cut.

 

vristang

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Mar 31, 2005

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Feb 23, 2007

#6

• Feb 23, 2007

• #6

Won't take too much effort to find flat top pistons for the 408w.
I have some from Probe for my 410w.


jason

 

8

86bluecobra

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Dec 20, 2004

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Feb 23, 2007

#7

• Feb 23, 2007

• #7

I like the vic jr's i have on my 351w. I have always wanted to build a 408 stroker. The vic jr is a great head. Yes the AFR 205 would be a better head but the vic jr's can flow just as much with a little work. They will be able to support the power you will see with either combo.

 

Jason 302

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Feb 23, 2007

#8

• Feb 23, 2007

• #8

A flat top piston will give you too much compression with a stroker motor. More cubes = more compression. Usually a flat top piston with a 393/408 with adequate valve reliefs and zero deck will give you 11+:1 compression, a dished piston will bring it down to a more pump gas friendly 9 or 10:1.

 

J

jaredgoodwin

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Sep 29, 2004

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Feb 23, 2007

#9

• Feb 23, 2007

• #9

Jason 302 said:

A flat top piston will give you too much compression with a stroker motor. More cubes = more compression. Usually a flat top piston with a 393/408 with adequate valve reliefs and zero deck will give you 11+:1 compression, a dished piston will bring it down to a more pump gas friendly 9 or 10:1.

Click to expand...

Exactly. Most combustion chamber sizes will require a dished piston for your desired compression ratio. There is nothing wrong with a dished piston, I was just pointing out that you probably wouldn't be using flat tops.

 

J

jaredgoodwin

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Sep 29, 2004

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Feb 23, 2007

#10

• Feb 23, 2007

• #10

vristang said:

Won't take too much effort to find flat top pistons for the 408w.
I have some from Probe for my 410w.


jason

Click to expand...

How much compression are you going to run? Aren't TW's like 60cc chambers?

 

vristang

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Feb 24, 2007

#11

• Feb 24, 2007

• #11

jaredgoodwin said:

How much compression are you going to run? Aren't TW's like 60cc chambers?

Click to expand...

Not sure yet Jared.
I pick up the block and heads tomorrow morn.
The heads have been shaved twice since the last time they were cc'd (they were 72cc). Once for a leak/warp, and a second time to fix the Sh@# job that was done the first time.
I think it should be between 10.5 and 11.

If I have to swap the heads, I won't be too upset. The TW's are a little small anyway

jason

 

M

Matts89LX5.0

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Feb 24, 2007

#12

• Feb 24, 2007

• #12

how do you pick out a cam before even picking out a motor????

 

2

2002BLGT

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Feb 26, 2007

#13

• Feb 26, 2007

• #13

the cam is a mild cam should make good torque under the curve , the idea is not not have to spin it to 7500 to make power and that cam I picked out should work good with a 351 or a 408 especially given the nature of these heads not being quite as good as the afr 205s