Keeping Compression Down In A Motor?

1

1993 Mustang

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Jan 29, 2006

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Feb 9, 2006

#1

• Feb 9, 2006

• #1

In the near future I want to go with a 347 motor and I have been seeing in the threads about keeping compression down to 8.5:1 to 9:1 for naturally aspirated motors and a compression of 10.5:1 is too high for supercharged motors. My question is how is compression brought down for engines for N/A or supercharged engines?

 

D

Daggar

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Jul 19, 2004

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Feb 9, 2006

#2

• Feb 9, 2006

• #2

How far towards the top of the cylinder the piston travels as well as the entire travel of said piston, the chamber size of your heads, the dish of pistons (or lack thereof), ummmm.... what else am I forgetting.... head gasket thickness.... what else....

 

1

1993 Mustang

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#3

• Feb 9, 2006

• #3

So, the larger chamber size of heads and thicker head gaskets I will be ahead of the game- not a headache to upgrade. But the pistons in a already put together block will that hamper my compression problem?

 

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Daggar

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#4

• Feb 9, 2006

• #4

A better question would be:

What is your static compression now
--and--
what are you trying to get to?

 

3

304billet

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Sep 16, 2005

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#5

• Feb 9, 2006

• #5

My old 347 stroker had SRP 10.3:1 flat tops and the engine builder who bought it flycut the pistons to 9.75:1 and ran 15lbs of boost from a s-trim and put down 550rwhp on a stock block. pulled back the boost to 12 lbs and now runs about 500rwhp.

If u have a NA motor with 10.5:1 and u want to reduce the comp u can go with a 70cc head and a cometic head gasket. Tht usually reduces it about 1/2 a point to a point. or u can get the pistons flycut.

But it really depends on what ur trying to do. My engine builder and dyno tuner runs 11:1 dish pistons in a R331ci stroker and 25lbs of boost from a YSi trim and puts down 780rwhp in a drag car. He has to run C114. It's all in the tune

 

1

1993 Mustang

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#6

• Feb 9, 2006

• #6

Well, I am looking to get the Ford Racing Motorsport 347 Forged Stroker Short Block Part No. M-6009-C347 in the Ford Racing Catalog and in another forum it was posted that this block has a compression of 10.5:1 which was said that it is too high for supercharged applications. I am only running 12-14lbs. of boost and not going any higher. I have my eyes on the Victor Jr. Heads which have a 75cc exhaust port and some thick head gaskets. But if anyone would look at the internals of the shortblock and give some feedback on the pistons I would gladly appreciate it.

 

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Daggar

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#7

• Feb 9, 2006

• #7

If I remember correctly, the pistons are hypers. If you're going to order this block new, then call them and ask them what it would cost to upgrade the pistons to forged and tell them that you'd like to be in the 9:1 range.

I remember seeing somewhere that parts could be substituted for a fee.

 

1

1993 Mustang

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#8

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• #8

For the year 2004 the shortblock came with all FORGED parts it is part no. M-6009-C347 (FORGED STROKER), the one with the hypereutectic pistons is part no. M-6009-B347. The forged shortblock is with forged aluminum pistons.