Change the pistons and get a blower cam.
How much boost could I run??
Thread Starter
Burning Brakes
Joined: Mar 2005
Posts: 1,139
Likes: 0
From: Salina Kansas
How much boost could I run??
I am thinking about getting a Vortech blow through centrifugal blower next year and am wondering approximately how much boost I could run with a 10.5:1 CR 427 sb? It looks like the standard Chevy sb kit would bolt right up, maybe even with the tall valve covers I have. The CS144 alternator and power steering pump might be a problem though. It also has a 111 LS 250/258 solid roller cam.
I have heavy enough injectors at this point that I could simply bolt it on and retune it, run low boost and pick up some hp until I was ready to pull the motor and set it up for a high boost setup.
What do you all think?
I have heavy enough injectors at this point that I could simply bolt it on and retune it, run low boost and pick up some hp until I was ready to pull the motor and set it up for a high boost setup.
What do you all think?
Advanced
Joined: Jan 2007
Posts: 67
Likes: 0
From: Sindal Jutland
I am thinking about getting a Vortech blow through centrifugal blower next year and am wondering approximately how much boost I could run with a 10.5:1 CR 427 sb? It looks like the standard Chevy sb kit would bolt right up, maybe even with the tall valve covers I have. The CS144 alternator and power steering pump might be a problem though. It also has a 111 LS 250/258 solid roller cam.
I have heavy enough injectors at this point that I could simply bolt it on and retune it, run low boost and pick up some hp until I was ready to pull the motor and set it up for a high boost setup.
What do you all think?
I have heavy enough injectors at this point that I could simply bolt it on and retune it, run low boost and pick up some hp until I was ready to pull the motor and set it up for a high boost setup.
What do you all think?
I have done many forced induction setups and I would say that you are asking for trouble when going forced with more than 10:1 in static compression, especially with the typical design of a SB combustion chamber. You will properly need to keep it under 5 Psi and at the same time retard the ignition curve so much that your gain will be even less - Most modern turbo cars run less than 9:1 in compression and seldom boost harder than 7-10 Psi. Keeping intake air temperatures down is another very important factor, even more on a high compression engine. A combination of a good intercooler and some Methanol injection would be a necessary security.
I'm going forced myself with a C38-81 Rotrex compressor on a 406 SB engine running 8:1 static and planning on aprox. 15 Psi as max boost. That should bring me up in the 600-700 hp range and more than enough to spin the tires
Regards from Denmark
Karsten
Instructor
Joined: Mar 2005
Posts: 104
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From: Perkasie PA
Check this very handy chart from BDS that illustrates the actual compression ratio by taking the static ratio and adding in the pounds of boost. Anything over two pounds and you need race gas.
If you want more boost but do not want to go into your bottom end you could use early iron heads (60s - early 70s) with 76 cc chambers. Assuming you are using 64 cc now you could lower your cr by about a point. Others may know the exact amount. Also use the thickest Fel-Pro gaskets to increase chamber volume. Last but not least you could use Manley valves that have a recessed head that adds 2 cc to the chamber.
The cam should help avoid detonation down low because it will blead off boost.
http://www.blowerdriveservice.com/techcharts.php
If you want more boost but do not want to go into your bottom end you could use early iron heads (60s - early 70s) with 76 cc chambers. Assuming you are using 64 cc now you could lower your cr by about a point. Others may know the exact amount. Also use the thickest Fel-Pro gaskets to increase chamber volume. Last but not least you could use Manley valves that have a recessed head that adds 2 cc to the chamber.
The cam should help avoid detonation down low because it will blead off boost.
http://www.blowerdriveservice.com/techcharts.php
Burning Brakes
Joined: Oct 2007
Posts: 816
Likes: 107
All good points....I agree you have tooo much compression right now to even make the time and money worth it. Also wanted to add that you will be limited on how much boost you can run on pump fuel, no problems on race gas but if you want to avoid $7 a gallon fuel you may want to look into a good intercooler kit and meth injection.
I do not have a blower on my vette but I do have lots of work done to my Grand National. I can currently run about 14 psi safely on 93 oct but with the meth injection I can run 20 plus psi.
Since you are fuel injected I would definitely look into a meth injection kit, it will save you money on fuel and save your engine from detonation.
I do not have a blower on my vette but I do have lots of work done to my Grand National. I can currently run about 14 psi safely on 93 oct but with the meth injection I can run 20 plus psi.
Since you are fuel injected I would definitely look into a meth injection kit, it will save you money on fuel and save your engine from detonation.
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Verdad Gallardo
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I'd get used to driving what you have first.
I was reminded again on sunday that I didn't have my road racing slicks on!:o
I was doing the max "G" big two lane 270 degree on ramp to a 5 lane freeway in 4th gear. just as i was coming out of the turn I floored it. My big rear 315's came around and I let off the gas while cranking the steering to full lock into the slide. I was passing the few cars out on the freeway sideways at 90 mph. I got it straight just like I knew what i was doing.
This guy in a late model camero caught up to me and gave me the thumbs up smile.
These 600+ hp 427+ ci motors are dangerous in the wrong hands!
I was reminded again on sunday that I didn't have my road racing slicks on!:o
I was doing the max "G" big two lane 270 degree on ramp to a 5 lane freeway in 4th gear. just as i was coming out of the turn I floored it. My big rear 315's came around and I let off the gas while cranking the steering to full lock into the slide. I was passing the few cars out on the freeway sideways at 90 mph. I got it straight just like I knew what i was doing.
This guy in a late model camero caught up to me and gave me the thumbs up smile.
These 600+ hp 427+ ci motors are dangerous in the wrong hands!
Thread Starter
Burning Brakes
Joined: Mar 2005
Posts: 1,139
Likes: 0
From: Salina Kansas
Yeah, your right George. I'm getting mine tuned again Saturday with the new intake setup I think, so I'm definitely going to drive it for awhile. I'm just thinking ahead...Frankly, the Tom's rearend will be the next upgrade anyway, so I can drive it hard with some slicks.
Thread Starter
Burning Brakes
Joined: Mar 2005
Posts: 1,139
Likes: 0
From: Salina Kansas
That is a good idea, except I have the 75 cc AFR heads planed down a bit, not the 64 cc heads. So that option is out for me it looks like and I am stuck with looking at new pistons and all the work that goes with that.