Alright, I know that this question cant be given a definate answer(since cam overlap and such play such a big part, but would like to at least get an idea. I am wondering about what boost levels can be run on 93 octane with what compression.

Here is the scenario. I am getting ready to build a 406, which will probably be N/A for a year or so. I have ported sportsman II's w/ 64 cc chambers I will be running. I am wanting to run around 10:1-10:3:1 right now. I am also planing on saving up for a supercharger(been looking at the vortech YS carb kit) and a set of AFR(probably 210's) w/ the 76 cc chambers. I figured that if I am running a dish that will equate to 10.3:1 w/ .015 shim head gaskets, that when I go to the 76 cc chambers and go to a normal thickness head gasket that I would be down to around 8.75.

Obviously, I am going to have to refresh the motor and change ring gaps accordingly if I add a power adder to it, but would like to be able to use the same rotating assembly if possible.

So, if I have 8.75:1 compression w/ aluminum heads and a pretty good sized cam, what kind of boost could I aim for. How about with or without intercooler. How much of a diff in possible pressure is there? I have looked at the mondo cooler, but dont know that I will be able to fit it. Does anyone know how tall it is?

Also, if I were to run a 3.875 stroke, which would make it a 420, that would actually allow me to make the same power at less boost correct since the supercharger could pump the same amount of air and not create as much pressure. Then could I get away with a reasonable amount more power at a lower boost level, or am I better of to stay w/ the 3.75 stroke so I have the taller piston compression height?

By the way, my goal is eventually to get into the single digits just to give you an idea. If you dont think that that is realistic on 93 octane let me know. Also, if that compression isnt low enough, I may be willing to lower the compression on my N/A setup for the future benifit.

Ben

 

i dont have your anwsers but i would like to hear how it all goes ... 8.5 is about right for 5 or 6 pounds of boost but im not sure about alum. heads you might check with gail banks turbos they are about the best ... IMO ... good luck ... make it happen ...tao

 

I used to run 9.5:1 CR on my 9lb boosted intercooled 355 on pump gas.
Now i run 9:1 with 16lbs but I haven't done a pump gas tune yet.

 

Why can't you guys run more boost on such low compression. With forged internals and 8.5 compression, I'd be able to run like 30 psi. Are your pistons not forged or something?

 

not on pump gas

 

I'm running 15-16 on stock internals that include 9.1:1 pistons right now on pump gas.

 

Give it a few months.. then ask your muffler how your ring lands taste..

 

I know it's a turbo but on pumpgas(93 octane)my boost stays right around 19-20psi with 8:1 compression and iron heads, and of course an intercooler.

HTH,
Steve

 

It said after 5 years, they're still fine.. Ugg.

8.96:1 cr here. NON intercooled, 10-12psi boost. 26d total timing under boost.

If your gonna run 8.75:1 on alum heads, get a bigger blower than an S-trim..

With the alum heads, I'd aim for more in the 9.5ish range or even a little higher.


-- Joe

 

Lack of tuning mainly.. 30's a bit excessive but..

People forget vortech, ati, etc makes these kits for stock 9.5:1ish motors. Then they spend 10k building a super low compression alum headed motor, and wonder why stock LS1's go right by them.. duh!


-- Joe

 

I run 93 octane with 9:1 compression and 6lbs of boost

 

.

 

yeah everybody... go build high CR and high boost stock bottom end motors.. The local machine shops need the work...

LOLOLOL

Ill stay WRONG and slow with my 8 to 1 motor... living in fear that 1 day you will bring your higher compression stock bottom end beast to my town to teach me a lesson..

 

Erm. Ok.

 

well what about 10.5:1 compression????? alumnium heads of course

 

Well In fear of being laughed at by "lololololrotflmaololololzololz!" or anything from @aol.com, I'll just say look at the compression ratio of an LT1, then visit some of the web sites selling blowers for stock LT1 cars.

-- Joe