turbo 6 bangers post here
Perfect info thank you. My new question then is at what point do you suggest mechanical secondaries open on a boosted system. Should I only have them open under full boost?
68 valiant is the car I am actively seeking and the plan is as stated around a 300hp engine and i plan on lightening the car in as many ways possible so my HP to weight should end up in a pretty cool spot once its all said and done. I also noticed you suggested 340 valve springs in a different post. Do you think I would see benefit in my system if plan on stock heads, and cam?
Thanks
Joel
Please understand one thing, here: I am JUST LIKE YOU, in that I am building my first-ever turbocharged car and my first-ever slant six.
When you read my comments on your project (which, BTW, I think is a VERY cool one!!!) keep that in mind; I am NOT
any kind of an expert on this stuff, and most of what I have learned about slant 6's and turbos, I learned right here, just like you're doing.
That doesn't mean I don't have opinions, unfounded though they may be. What I DO have that may give me SOME insight into this buisness, is a lifetime of hands-on, hot rodding experience in trying to make things go fast. I am 73 years old, so, the term "a lifetime" does mean something... LOL!
Insofar as your 4bbl question, I really don't see the need for a 4bbl carburetor on that car in any way, shape, or form. I think it's an unnecessary complication added to an already complicated-enough problem, and is more expensive to boot. On top of all that, I can't see it making a bit more horsepower than a Holley 2-bbl would, especially, at the boost levels you are going to run. The carburetor is more expensive, the manifold is more expensive, and the mods to the carb will be more expensive. And, for what?
Why would you want to do it???
The 340 springs are a good alternative valve spring for this engine, yes, but let me tell you another thing I have learned about these engines by listening carefully to the guys who actually KNOW what they're talking about: A turbo'd slant six doesn't run well above 5,500 rpm. None of them seem to. Even the really powerful ones that seem to make 500+ horsepower are all done by 5,500 rpm.
That means that heavy valve springs in a low-boost engine such as yours are a waste of time, money and energy. I don't see any sense in increasing the load on your cam by putting heavier springs than what is needed on your engine. It's going to make its power for the most part, below 5,000 rpm, and as long as you leave your stock cam in place (which should work fine with the turbo,) stronger valve springs probably won't benefit you at all, and could put your cam at risk.
Spend that money on a Snowperformance Boost Cooler. THAT is something you really DO need...
Next time, we'll talk about ignition. Since there are no high-rpm issues, there's not a lot of upgrading to do there, but limiting the advance is a very important item! Boosted engines don't need nearly as much spark advance as normally-aspirated ones. It seems as how the flame front travels much faster under boost. Those 500hp engines only run a total of 18 degrees, I am told... and that's not much!
Good luck!!!:smile:
Bill