How much will compression effect this combo?

9

9 Deuce GT

Member

Dec 10, 2003

550

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16

Geneva, NY

Aug 10, 2004

#1

• Aug 10, 2004

• #1

I hope you guys can help. I am in the process of swapping a 351w into my '92 GT. I got a great deal on it, ($150), so I want to just slap it in there. It is a recent Jasper rebuild with approx. 30,000 miles. Everything looks good with the internals. The engine is already bored 40 over. Here is the combo I plan to use:

351w bored 40 over
AFR 185's (purely a street car and emmisions are a concern)
TFS 351w intake
1.6 RR
75mm T/B
Biggest mass air meter I can find
24#'ers
AFPR
190 lph pump
1 3/4" longtubes
Not sure on cam-looking at TFS stage 2

I know the engine was built with a Full size econo van in mind, and I believe the setup with 69cc heads produced 8.2 - 8.5:1 compression. I hope to be near 9.0:1 with 60cc heads. What would the real world difference be in this combo with 9.0:1 compression compared to the same setup with 10.5:1 compression? I guess I am asking how much of a difference does compression make in HP/TQ?

 

bluevenom867

I will have images of molesting stuffed animals in

Dec 15, 2003

1,704

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St.Petersburg,FL

Aug 10, 2004

#2

• Aug 10, 2004

• #2

In that motor it's the diffence between runing 12's and runing 11's.
My 351 is almost 11:1 comp and kicks butt.If it were only 9.5:1 I would HAVE to run a blower/turbo or it would be terrible slow.

 

bluevenom867

I will have images of molesting stuffed animals in

Dec 15, 2003

1,704

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0

St.Petersburg,FL

Aug 10, 2004

#3

• Aug 10, 2004

• #3

Oh I've also head that 1 point increase in compression = +4% total power.

 

408stroker5.0

The world would be a better place if all males jus

Mar 10, 2004

639

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16

Bonnyville, Alberta, CANADA

Aug 10, 2004

#4

• Aug 10, 2004

• #4

Quick Sum Up:

More Compression= More Power
More Compression=More chance's of Detonation if not tuned and driven proparly.
More Compression=Higher Octane Gas $$$$

 

5.0 HOtrain

Founding Member

May 20, 2001

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New Hampshire

Aug 10, 2004

#5

• Aug 10, 2004

• #5

I would go with 30#'s.

 

T

tjm73

Founding Member

Aug 3, 2000

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48

Rush, NY

Aug 10, 2004

#6

• Aug 10, 2004

• #6

I second the call for at least 30# injectors.

Also if emissions are a concern, your choice of camshaft will be critical if your state tests tailpipe emissions. If they only test that the sytem is functioning, and nothing else, then it's much less critical from an emissions stand point.

 

9

9 Deuce GT

Member

Dec 10, 2003

550

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Geneva, NY

Aug 10, 2004

#7

• Aug 10, 2004

• #7

This is what I was thinking, although it is probably way off base, but:

My stock 5.0L is only 9.0:1 compression, and with the mods I have, It is deffinetly making power. If I can get the 351w up to 9.0:1 compression, I would hopefully be happy with it for a few years until I save up enough money to stroke it (after buying a house and having my girlfriend beat me for spending more money on my car). And heres the question that everyone hate to hear- do you guys think I will see anywhere near 400hp with this set up?

As far as the cam and emissions, right now NYS is not tailpipe testing cars 1995 and older. But who knows what will happen in the future. If they decide to do something different, I cam change a cam easier than a lot of other things to make the car smog legal.

 

9

9 Deuce GT

Member

Dec 10, 2003

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Geneva, NY

Aug 10, 2004

#8

• Aug 10, 2004

• #8

Hey ****ers, how about a little help! lol

 

Stang8URMPRT

Active Member

Dec 28, 2003

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38

Daytona Beach, FL

Aug 11, 2004

#9

• Aug 11, 2004

• #9

I dunno, but I've heard if emissions are a concern, an engine swap to a non stock motor isn't emissions compliant.

Nick

 

IndyBlk5.0

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Nov 24, 2003

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New Whiteland, IN

Aug 11, 2004

#10

• Aug 11, 2004

• #10

No one really answered his question...
Put it in this way, how much hp gain for .5 of a compression point on average?

 

9

9 Deuce GT

Member

Dec 10, 2003

550

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Geneva, NY

Aug 11, 2004

#11

• Aug 11, 2004

• #11

ttt

 

mustangsquared

Founding Member

Jun 8, 2002

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new bern nc

Aug 11, 2004

#12

• Aug 11, 2004

• #12

Here is a link to a calc that will let you play with Comp ratio and see the results of changes YOU make.

http://www.bgsoflex.com/crchange.html

hope this helps...

 

Grn92LX

Fidanza Man!

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Jan 14, 2001

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Aug 11, 2004

#13

• Aug 11, 2004

• #13

IndyBlk5.0 said:

No one really answered his question...
Put it in this way, how much hp gain for .5 of a compression point on average?

Click to expand...

1/2 point compression increase? About 5hp gain. Without knowing what pistons are in it, you cant really fnd out compression. Like what compression those pistons equal with 'xx' cc head. If your looking for a decent shelf cam, i'd look at the comp 282 cam. I agree with the guys telling you to get 30's.