How much will compression effect this combo?

[9 Deuce GT]

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]

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]

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

 

[408stroker5.0]

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]

I would go with 30#'s.

 

[tjm73]

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 Deuce GT]

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 Deuce GT]

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

 

[Stang8URMPRT]

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]

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

 

[9 Deuce GT]

ttt

 

[mustangsquared]

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]

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

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.