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Re: how much more power with a compression bump?
[Re: mshred]
#1095841
10/17/11 10:50 AM
10/17/11 10:50 AM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
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Az
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I know this doesn't answer your question, but raising compression has deminishing returns. You will get more of a HP return going from 8:1 to 9:1 than from 12:1 to 13:1, etc. I would say the range you are looking at would still have good returns HP wise. To come up with an actual # would be a guess on anyones part IMO.
Fastest 300
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Re: how much more power with a compression bump?
[Re: mshred]
#1095843
10/17/11 01:51 PM
10/17/11 01:51 PM
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Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem
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My opinion 1.5 compression numbers will only gain you 15 to 18 hp. You need 40 to 45. I would bump the compression to 10.5 with a bigger 254/264 ish cam .620/.600 ish lift with 108ish LSA.
Those two things should get you there. A step header 1 5/8 to 1 3/4 might be a great add on without giving up any bottom end. (or 1 7/8??) if you can afford CNC porting that will add even more.
I don't feel a 230 duration cam will get you there.
The better quench of a 0 deck piston should help some more for sure!
Last edited by Dodgem; 10/17/11 01:57 PM.
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Re: how much more power with a compression bump?
[Re: Dodgem]
#1095847
10/17/11 07:43 PM
10/17/11 07:43 PM
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Joined: Oct 2007
Posts: 4,208
New York
polyspheric
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Posts: 4,208
New York
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Jennings pointed out 35 years ago that the volume in the squish band does almost nothing - it burns too late, and burns with lower efficiency than the remainder of the chamber volume, which adds to emissions.
That's why the chamber on 452 etc. RB heads is recessed - to get that volume exposed to the flame front at the right time, and reduce emissions.
If you have a 10cc band at .080" now, reducing the band to .040" and 5 cc not only suppresses knock, etc. but also adds 5cc to engine size.
Boffin Emeritus
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Re: how much more power with a compression bump?
[Re: gregsdart]
#1095849
10/18/11 12:03 AM
10/18/11 12:03 AM
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Joined: Apr 2009
Posts: 3,415
Toronto
mshred
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OP
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Joined: Apr 2009
Posts: 3,415
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Quote:
Give Brian a call. He built it, right? Sharp guy.
yes, Brian spec'd the heads and cam for me and did an awesome job
This thread was more of me just trying to learn the effects of compression....I know Brian is a busy guy and I didnt want to call him to discuss this since i wasn't sure yet how it all even works (not to mention my schedule has been way to hectic to get a chance to call him during the week).
To everyone who replied, there is alot of good info here, some of it i have and have not heard before
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Re: how much more power with a compression bump?
[Re: Brian Hafliger]
#1095850
10/18/11 12:08 AM
10/18/11 12:08 AM
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Joined: Apr 2009
Posts: 3,415
Toronto
mshred
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Quote:
Quote:
Hey guys,
Just curious how with everything else being the same how much more power my engine could pick up with a compression bump from just under 9:1 up to about 10.5:1? The current configuration has the pistons below the deck about .083". So with the new compression I would be zero decked with about .040" quench. Here is a mild run down of the engine...best time is in my sig...guessing at about 320hp at the wheels
1991 360 Roller block
Bone stock bottom end
9:1 compression
RHS heads prepped by Brian at IMM engines
custom ground hydraulic roller from Brian at IMM with specs as follows:
Gross Valve lift with 1.6 rocker arms- 577 int., 569 exh.
Duration at .050”- 230/230
Lobe Separation- 106
Cam installed at 101 Intake Centerline (5 degrees of advance ground into cam)
Topped off with an Eddy air gap, Holley 750HP, 1-5/8's headers, 3" exhaust
So how much more power can I expect to make? If i can get this engine to e/t the car to a high 11 on the motor I would be super happy.
With Kb 107's at zero deck, if your heads were 62cc that'll be 10.6:1 so I would back the cam up so it's straight up. That will pick up power in the upper end while the compression will pick it up in TQ everywhere.
Then zero lash the rockers and rev it to 6500 and that should be close to where you want to be.
Then work on the chassis...
Hey Brian, I was looking at a forged offerring in pistons, possibly from probe. My biggest thing was with the compression bump and the fact that I would create quench by zero decking and using the appropriate head gasket, how much more power would I make? Im not sure im comfortable taking the stock lifters to 6500rpms considering my prior luck with them this past summer, but I do trust you. I really wouldnt mind getting a different cam ground either if it is the best way...I was going to eventually call you about this, but was just trying to get an idea of what the compression bump would do...Ideally I want to do a stroker, but not sure if its in the cards financially, so just exploring my other options. I would also be spraying the heck outta this thing if i kept it a 360 with forged pistons, so that may change cam stuff up a little
So far the chassis on my car is working pretty good....Reason I don't want to rev the car higher also is because I would need to up my rear gear ratio, and with the 4.10's its already a huge compromise. Only crossing the stripe at 5500rpms in 4th gear with the current combo, so I would definitely have to gear up
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Re: how much more power with a compression bump?
[Re: Crizila]
#1095851
10/18/11 12:11 AM
10/18/11 12:11 AM
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Joined: Apr 2009
Posts: 3,415
Toronto
mshred
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OP
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Joined: Apr 2009
Posts: 3,415
Toronto
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Quote:
I know this doesn't answer your question, but raising compression has deminishing returns. You will get more of a HP return going from 8:1 to 9:1 than from 12:1 to 13:1, etc. I would say the range you are looking at would still have good returns HP wise. To come up with an actual # would be a guess on anyones part IMO.
this is something I have heard before which is part of why I was asking the question to begin with...wasn't sure how far up on that scale I was with the compression im at right before the increase of cr has diminishing returns
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Re: how much more power with a compression bump?
[Re: Dodgem]
#1095852
10/18/11 12:15 AM
10/18/11 12:15 AM
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Joined: Apr 2009
Posts: 3,415
Toronto
mshred
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Joined: Apr 2009
Posts: 3,415
Toronto
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Quote:
My opinion 1.5 compression numbers will only gain you 15 to 18 hp. You need 40 to 45. I would bump the compression to 10.5 with a bigger 254/264 ish cam .620/.600 ish lift with 108ish LSA.
Those two things should get you there. A step header 1 5/8 to 1 3/4 might be a great add on without giving up any bottom end. (or 1 7/8??) if you can afford CNC porting that will add even more.
I don't feel a 230 duration cam will get you there.
The better quench of a 0 deck piston should help some more for sure!
As far as cams go, I dont really want to increase duration because I figure im going to have to rev it more? My car is street/strip and im already in need of more gear with my 4.10's and 28" tires, but I drive it to the track, and 2 hours at 3000rpms isnt fun, so i cant really go more...I don't mind getting a totally new cam to work with the setup, and I have no doubts Brian will set me up nice...I just don't want to overcam it..I mean with my current combo things were so simple and the cam was nothing radical yet it worked real well to squeeze every last bit out of my engine.
As far as headers go, I thought the 1-5/8's I have would be good for producing torque, which I thought is what I need considering im using a short stroke low tq motor
I was also hoping that the bump in CR and the quench factor would work well together... I should also look into CNC porting, though im not sure that is offered on the RHS castings?
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Re: how much more power with a compression bump?
[Re: Dunnuck Racing]
#1095853
10/18/11 12:16 AM
10/18/11 12:16 AM
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Joined: Apr 2009
Posts: 3,415
Toronto
mshred
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Quote:
I have a truck/towing build in the truck section I have been working on. It is on my dyno now,a 440 with factory closed chambered heads. When I recieved it,it had KB quench style pistons but was set up with too much quench clearence.
I took the .053 head gaskets out and went to a .020 steel shim gasket to tighten up the quench,that gained me just over a half point of compression.
With the quench fixed and the small bump in compression,it gained roughly 30 hp. The best part was that it really helped the power hang on for a lot longer than before.
Keith
Now that is some promising info right there 
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Re: how much more power with a compression bump?
[Re: 451Mopar]
#1095854
10/18/11 12:16 AM
10/18/11 12:16 AM
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Joined: Apr 2009
Posts: 3,415
Toronto
mshred
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Re: how much more power with a compression bump?
[Re: SomeCarGuy]
#1095856
10/18/11 02:40 AM
10/18/11 02:40 AM
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Joined: Jan 2003
Posts: 5,486
SoCal
Brian Hafliger
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SoCal
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If you don't mind changing the cam, we can pick up the power you want with pistons and cam...no problem!
Brian Hafliger
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