To Supercharge or not

M

mylostclub

New Member

Oct 9, 2006

3

0

0

Feb 16, 2007

#1

• Feb 16, 2007

• #1

Hey guys,

Got a '71 Mach I with 351C that has been mildly built. I beleive right now it is running about 11:1 compression, with forged pistons, good valves and a strong bottom end.
I was thinking about one of two options - either adding a supercharger/blower to this motor, or getting a 429 to put in the car. I want something that will push about 600hp, but I heard that you cant put a blower on a motor with high compression. Is this correct, and is there any other concerns I should have?

 

302 coupe

Founding Member

Mar 2, 2000

1,952

3

36

Macon, Ga.

Feb 16, 2007

#2

• Feb 16, 2007

• #2

What's your budget?

I wouldn't consider a 429, unless you already have one. 460's are cheaper usually, but a 514 can be made cheaply out of either. You can never tell the difference by looking at them, if thats a concern. A set of the new super cobra jet heads or trick flows, or Kaase P51's will have you making 600hp easy, not to mention gobs of torque. You can make well over 500hp with ported stock heads. Plan on changing to a big block trans and beefing up the rear end. Don't forget headers, mounts, front accessories, all that little stuff that adds up. Maybe have 4-5K in the engine, 2-3k in everything else, unless you already have parts laying around.

As for keeping the 351C, if you have 11:1 comp, you need to change pistons to get it down to around 9:1. If you're gonna do that, you might as well freshen up the entire short block. Add the supercharger and make whatever fuel system mods you need, custom cam, and nice headers..no problem getting 600hp there either.

 

M

mylostclub

New Member

Oct 9, 2006

3

0

0

Feb 16, 2007

#3

• Feb 16, 2007

• #3

Thanks for the info. I am aware that Ican use the 460, or other block instead of the 429. Cost is not really a factor (I have a budget for around $10K).
From the sound of it though, it woul;d be easier to pull my motor out, put new psitons in and the blower, and let it rip. Car already has a built C6 in it that would handle power, as well as the rearend.
And, if I am correct, the motor mounts for the 429/460, aren't they the same as for the 351C?

 

302 coupe

Founding Member

Mar 2, 2000

1,952

3

36

Macon, Ga.

Feb 16, 2007

#4

• Feb 16, 2007

• #4

I think clevelands share mounts with the windsor family, not the 385 series big blocks. I've been wrong before though, once, lol. I think keeping the cleveland would be cheaper too. 429/460 use a different bolt pattern on the bellhousing, so you'd have to change to a big block C6, your small block C6 wouldn't bolt up.

 

67Dylan

New Member

May 11, 2006

259

0

0

Phoenix, AZ

Feb 16, 2007

#5

• Feb 16, 2007

• #5

If you have 10k$ for a budget then why pass up on a 514? That motor will make the power you want and LOTS O' torque. Good heads, custom cam, big headers, and you probably won't push the motor near it's limits = more reliable motor.

If you want to build the 351 for boost.... go turbo. I have a friend that went from SC to turbo and swears he would NEVER EVER go back. Plus, turbo's don't take power to run them as SC's do. Which is another thing to think about; the SC will be a constant 'strain' on the motor. I think the costs will be close, the turbo set up costing a little more, but once it's running and tuned you will be happy you went that route.

It's your $$$ and your car, but thought I'd throw those ideas out to ya'.

 

M

mylostclub

New Member

Oct 9, 2006

3

0

0

Feb 16, 2007

#6

• Feb 16, 2007

• #6

Well, that makes my decision easier the. I will just keep the cleveland, and lower the compression and then put the blower on. Any thoughts on what I would need to lower it to, or what I dont want to go above compression wise? Anything else I need to consider for a blower? Thanks

 

classic boost

Founding Member

Feb 3, 1999

709

0

0

canton, oh

Feb 16, 2007

#7

• Feb 16, 2007

• #7

i vote the bb route (500+ ci). simpler, more reliable.

 

M

mustangdave

My rearend needs a stud and two nuts.

Founding Member

Feb 26, 2002

2,976

1

56

North Carolina

Feb 16, 2007

#8

• Feb 16, 2007

• #8

No on the big block: having ro buy all new brackets, pullies, dizzy, lttle parts... will go over budget. New pistons, blower, fuel system upgrades will eat up that 10 grand quick enough. Look for 8.5:1 to 9:1 on compression.

 

1

10secgoal

Active Member

Dec 1, 2003

2,801

3

49

San Diego

Feb 16, 2007

#9

• Feb 16, 2007

• #9

paul302 said:

i vote the bb route (500+ ci). simpler, more reliable.

Click to expand...

Oh, blower cars are reliable. As long as you don't try for 700hp on a stock block.:SNSign:

 

latamud

Founding Member

Oct 22, 2002

791

2

19

Tampa, FL

Feb 17, 2007

#10

• Feb 17, 2007

• #10

Swapping for open chamber heads will lower your compression if you don't already have them. I have -22 dished pistons. 60cc combustion chambers with my engine give me 10.4:1 but with 76.2cc I get 8.9:1. My answer to wanting to run 15lbs of boost on a 408w was to build it as clevor. If your 351c already needs a rebuild then mind as well build it with lower compression pistons. I don't like to tear down a perfectly good running engine.

 

Travis77

Member

Oct 1, 2004

153

0

16

Baytown, TX

Feb 18, 2007

#11

• Feb 18, 2007

• #11

If it were me I would also stay small block, but be conservative on the stroke, and add a turbo. Having a huge amount of torque with a big block would great, but I would rather feel the hp higher in the rpm range with 10-14 lbs of boost. On the other hand, if I was building a truck, I would love to go the 460 route with the Kaase heads.