Compression Ratio and Whipple 2.9l,
Thread Starter
Staging Lane
Joined: Dec 2015
Posts: 71
Likes: 2
From: Roy, Utah
Compression Ratio and Whipple 2.9l, Hello all,
I want to build a stroker LQ4. I have the stock 317 heads with a fresh setup. I have contacted Tick about the stage 2 blower cam. I like the sound of this cam. I have a built 4l80E, 3600 stall and 4.10 gears. The car is a 68 Chevelle. I want it to be street friendly and pump gas friendly. I called Whipple today and the guy on the phone told me I should shoot for a build with compression in the 10.5-1 to 11-1. I said really I need can build my motor with that high of compression on pump gas? He stated yes they have found the LS to love compression on boost. He said run 10-12lbs and you will make mid 800hp at the crank. I would be happy with 700rwhp. I am not sure if a 408 and Whipple can do this on pump gas.
Have you heard of anyone running this high of compression? This goes against all the detonation rules. But maybe the Whipple keeps IAT down so low its ok. With 10-15lbs of boost what compression on pump gas? I do not want to run meth. One more thing to worry about.
Any advice at all relating a 408, Whipple, Ticks Blower Cam, and trying to make 700rwhp?
Thanks everyone
I want to build a stroker LQ4. I have the stock 317 heads with a fresh setup. I have contacted Tick about the stage 2 blower cam. I like the sound of this cam. I have a built 4l80E, 3600 stall and 4.10 gears. The car is a 68 Chevelle. I want it to be street friendly and pump gas friendly. I called Whipple today and the guy on the phone told me I should shoot for a build with compression in the 10.5-1 to 11-1. I said really I need can build my motor with that high of compression on pump gas? He stated yes they have found the LS to love compression on boost. He said run 10-12lbs and you will make mid 800hp at the crank. I would be happy with 700rwhp. I am not sure if a 408 and Whipple can do this on pump gas.
Have you heard of anyone running this high of compression? This goes against all the detonation rules. But maybe the Whipple keeps IAT down so low its ok. With 10-15lbs of boost what compression on pump gas? I do not want to run meth. One more thing to worry about.
Any advice at all relating a 408, Whipple, Ticks Blower Cam, and trying to make 700rwhp?
Thanks everyone
Last edited by redtacoma31; Sep 9, 2016 at 10:32 PM. Reason: Laptop posted topic before I had typed it out.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
There is almost nothing to lose from playing it safe with CR, and little to gain pushing and keeping it high.
Perhaps even more so given the nature of the boost with such a blower and the torque it will produce. But keeping high CR's is the current fascination with many although most are using E85 with it too so no concerns.
If you never intend to push any harder than 10psi or so, 10.0:1 should be perfectly safe.
Perhaps even more so given the nature of the boost with such a blower and the torque it will produce. But keeping high CR's is the current fascination with many although most are using E85 with it too so no concerns.
If you never intend to push any harder than 10psi or so, 10.0:1 should be perfectly safe.
TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
There are many different factors to consider, but I would think that 10:1 with a 10psi should be relatively achievable on pump gas.
Do not lose any sleep over thinking about static compression ratios with or without boost. Your dynamic compression ratio is what is going to matter most, and that is dictated by the valve events/cam.
If your Chevelle has A/C, you can actually get kits that actively cool your intercooler water with the air conditioning coolant loop. Pretty nifty closed loop system that keeps your IAT's at or below ambient outside temperatures. Such a system is perfect for top mounted superchargers.
Honestly, with an LS motor, I wouldn't ever drop below 10:1 compression, simply because these aren't Ford motors, the days of lowering compression for boost are behind us. Just make sure you have a spot on tune.
I really cannot stress that last part enough. Get a good tune and enjoy.
Do not lose any sleep over thinking about static compression ratios with or without boost. Your dynamic compression ratio is what is going to matter most, and that is dictated by the valve events/cam.
If your Chevelle has A/C, you can actually get kits that actively cool your intercooler water with the air conditioning coolant loop. Pretty nifty closed loop system that keeps your IAT's at or below ambient outside temperatures. Such a system is perfect for top mounted superchargers.
Honestly, with an LS motor, I wouldn't ever drop below 10:1 compression, simply because these aren't Ford motors, the days of lowering compression for boost are behind us. Just make sure you have a spot on tune.
I really cannot stress that last part enough. Get a good tune and enjoy.
TECH Fanatic
Joined: Jun 2014
Posts: 1,533
Likes: 12
I run a sbe ly6 with a whipple 2.9 .I think it's 9.6:1. on 10 lbs boost it is outrageous . Even on a very safe tune, it is a torque monster. If I bang 2nd gear , 60 ft of rubber easily on drag radials( my car is an auto) if it were me, I would keep the cr reasonable. Why push it? There's no need really.
You might be ok in Utah at 10.5-11.0 cr with boost, but I would feel much better overall at about 9.5 cr. I don't see the need to push the limits of pump gas detonation when you already have the tire frying instaboost of a PD blower. If this were an oversized turbo with a lag problem, I would be much more inclined to take my chances on higher compression. As was mentioned earlier, however, high compression boost builds seem to be the new fad.
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Have you heard of anyone running this high of compression? This goes against all the detonation rules. But maybe the Whipple keeps IAT down so low its ok. With 10-15lbs of boost what compression on pump gas? I do not want to run meth. One more thing to worry about.
Any advice at all relating a 408, Whipple, Ticks Blower Cam, and trying to make 700rwhp?
Thanks everyone
As other have said playing it safe with compression can save you a motor but cost you a few horse power, not a huge deal imo.
Heat soak yes, any positive displacement supercharger will get hot, I have a larger supercharger running 15psi and it heatsoaks. Heat, timing, and high compression is not a good mix.
I was so against meth, but for the price of a kit and the safety it adds I am now using it. You will find there is a reason most guys on pump gas are using it.
408 is so touchy, I was told stay shorter stroke because its less side loading on the cylinder walls, and on an iron stroker motor the piston will actually come out of the wall just a little every stroke. Guys do it everyday but I feel longevity is compromised.
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On The Tree
Joined: Jun 2009
Posts: 139
Likes: 1
From: Scottsdale Arizona
I run a sbe ly6 with a whipple 2.9 .I think it's 9.6:1. on 10 lbs boost it is outrageous . Even on a very safe tune, it is a torque monster. If I bang 2nd gear , 60 ft of rubber easily on drag radials( my car is an auto) if it were me, I would keep the cr reasonable. Why push it? There's no need really.
Im thinking about the 2.9L whipple instead of a 76mm turbo on my L96/LY6. What do you have done to the motor and what are you putting down power wise? Have you dynoed it?
I love instant power and laying rubber but this is a street race car and on the street races are won and lost out of the hole. Im no *** roll racer. To me thats not even racing. Thats for guys who cant drive and also cant set up their car right as well.
Im wanting at least 600 rwhp MINIMUM because thats what i need to run into the 9s.
Thx
MS
It would be pushing things, but you could probably get 600rwhp out of a junkyard 4.8 with a 2.3L whipple. I'm not sure why you are worried about somebody's ultra safe low boost combo if you want to win races. Sounds like Jimmyg has a fun street ride.
On The Tree
Joined: Jun 2009
Posts: 139
Likes: 1
From: Scottsdale Arizona
LY6 /L96 2.9L Whipple So your saying that the 6.0L L96 @ 9:6:1 with a 2.9L whipple and a decent cam is going to make way more than 600 rwhp if a lowly 4.8 or 5.3 can muster 600rwhp on a 2.3L PDSC? We have 91 here in AZ but we do have plenty of E85 stations and one 1 mile from my house thank you.
So your saying that the 6.0L L96 @ 9:6:1 with a 2.9L whipple and a decent cam is going to make way more than 600 rwhp if a lowly 4.8 or 5.3 can muster 600rwhp on a 2.3L PDSC? We have 91 here in AZ but we do have plenty of E85 stations and one 1 mile from my house thank you.