Is it worth it to get an air to air intercooler for a low boost Carb application? I have heard the carb acts sort of like a mini intercooler for one thing. Also I plan on only running 7 PSI of boost, and i have heard intercoolers can almost be parasitic at such low boost #'s. Thanks guys

Seth

 

bttt anyone?

 

it depends on the intercooler design/efficientcy, the engine compression, compressor efficientcy... at that low a boost a non optimized setup will hurt you, OTOH, a really good setup (assuming that you're comparing 7psi intercooled to 7psi non intercooled) could give you up to about 30% more power.

 

So say on a 9.1:1 motor with a P1SC pushing 7 pounds of boost with a holley 650 double pumper, do you think an intercooler would be useful or just a pain. I was hoping to get away without having to run one for now.

 

Well, there's still a lot of variables out there that could make a big difference. What heads and cam are the biggest.

Big duration cam, aluminum heads and good exhaust, you might have no issues without an intercooler. Iron heads, stock cam and exhaust… no way, you’ll probably be borderline detonating on pump gas without the blower (my stock L98 will ping at the track without 93 octane in the tank with 9.3:1 compression), you’ll absolutely need it to get a reasonably streatable package, but it might be fine on some race gas.

Most likely you’re someplace in between, meaning that you could probably get reasonable performance on pump gas with an intercooler or some timing retard…

 

Make a cold can for the fuel lines and retard the timing a bit and it may be livable. It all depends on what your static cr is.

 

RIG UP a cold air induction system for the blower, don't just hang the filter over the header...

 

So here is my motor basically:
9.1:1 hyper. pistons
Nodular Cast Iron Crankshaft
PM Steel Connecting Rods
Cast Iron 64cc Chamber Vortec Cylinder Heads with 1.94'' Intake and 1.50 Exhaust Valves
Cam- Lift: .435'' Int. / .460'' Exh., Duration @ .050: 212° Int. / 222° Exh. 1.5 Ratio Rocker Arms

So if I were running an air to air intercooler, what would you guess the max boost i should run would be as opposed to not running an intercooler.

 

What's the advertized duration and LSA of the cam? those have a much bigger impact on cylinder pressure then .050 numbers.

9.1:1 pistons, but what is the actual compresson? If you don't know, what head gaskets are you using (bore and compressed thickness would make it easier), how far in the hole ar the pistons installed and how big are the valve reliefs/dish/dome on the pistons? Quite often, compression ends up significatly different then the advertized compression of the pistons.

hypereutectic pistons and boost don't work well together. Hypereutectic pistons are stronger then cast, but are also the least tolerant of detonation, they shatter with any sign of detonation, so you'll probably want to go very conservative with the boost no matter what the rest of the numbers predict...

 

its a crate motor rated at 9.1:1 compression, so i would imagine that is what it is. as for the other cam specs, i have no idea what the advertised duration is on the cam, it is a corvette cam from the 60's converted to dual pattern that GM puts in them, the LSA is 112 i believe.

 

Well, doing some guessing on the cam timing, it looks like you should be able to tolerate about 6-8psi without an intercooler and about 8-12 with assuming really good tuning.

Considering the hypereutectic pistons I don't think that i'd really shoot for more then the bottom of those ranges unless you consider the engine disposable...

 

So 7 psi wouldnt be crazy? Also, what have you heard about the vortech carb kit?

 

Just that the major mags seem to like them, which usually means that vortech is throwing a lot of money, free stuff... at them, and about 50/50 that it might be as good as it sounds.

 

lol no kidding. so do you think maybe a 100-125 shot of nitrous would be a better solution for me than spending the $2500 for a supercharger setup that I wont be able to run run a ton of boost on?

 

donno, depends on your goals. No matter what you do that engine will be happier with 100-150hp spray rather then a blower, but if the engine is getting long in the tooth and you'd really like a blower...

Really, unless you've got something to prove or have a specific goal in mind I'd go NA. There is a certine charm to NA power and you'll be much less likely to learn how little detonation hypereutectic pistons will tolerate. But geeze, that's still a tough one, since you've kinda backed yourself into a corner with the vortec setup, not many choices for better heads... you could go fastburn or edlebrock I guess, bigger cam and vic jr vortec intake...

If you really want to go all out with a power adder then I'd pull the engine appart and spend the $500 on some forged slugs, either dished for a blower or flattop for the spray. But at that point you're opening a can of worms.

If you go with a blower and decide you need to run more boost you could always get some 76cc heads (will put your CR at around 8.1... good for iron+ blower, maybe 70cc aluminum unless you plan on running A LOT of boost) and matching intake... but you've still got the pistons.

Of course, there will be a bunch of people that will tell you that 9.1 is plenty low to run a blower on... I'd rather be safe so I can play harder on 92 octane then have to rebuild the first time I push it to the limit without race gas.