I haven't really set a limit on boost yet. My long-term goal is 500whp (650ish at the crank) at ~6-65000rpm on an interia-style chassis dyno. The bottom end is currently a 20-30k mile stock rebuild so I'm going to crawl into boost, rev limit to around 5800rpm and settle on lower power until I can put a set of forged pistons with some nice, beefy ringlands inside and maybe a 393 or 408 storker crank to help the turbo spool.
Based on previous turbo projects, I used a recent machine shop check of my heads as an excuse to put down a set of Cometic MLS gaskets and ARP head studs. I doubt I will need them just yet but both parts will be reusable when I go through the short-block.
For my larger goal, the boost required to get there is going to depend on how well my heads, intake and cam are matched and how well my charge piping and exhaust piping are sized/plumbed (among other things like charge density). My plan was to use my stock 2v heads (new guides, seats, springs match to cam, stainless 1-piece valves, unported) as a baseline to see if I can hit my number on pump gas. If I can't, the injectors and fuel pump are sized for and compatible with E85. Switching to that will give me better detonation resistance and a massively improved latent heat of vaporization. Plus, it's cheap race gas in the midwest. I'm running a -10 supply and -8 return which should be overkill at my power goal, even when a conservative BSFC for a turbocharged E85 application is used.
After I find out what the 2v heads can do, it was my intention to switch to a better flowing aluminum head. My hope was that I would gain improved detonation resistance and hopefully hit the same power/torque numbers on lower boost. Area under the curve is another story. I've accepted the fact that after all the A3 effort, the 2v heads might still be a better fit for my mostly street car application.
I am actually working on the intercooler support brackets right now. Since a restraint I set was not cutting the car's chassis (no shock tower delete and Mustang II suspension swap), I decided to go the air-to-water route. I couldn't make the 2.75" OD tubes that I calculated necessary fit in front of the radiator without some convoluted piping arrangement that snakes under the radiator. Moreover, any air-to-air core that I managed to make fit would have to be undersized or very thick because there is not much room vertically or left to right.
The heat exchanger I chose is a crude looking, cheap aluminum core shaped like a shoe box. The brand (Frozen Boost, ChiCom stuff) has excellent reviews from folks on theturboforums, yellowbullet and others. It is alleged to have a ~0.2psig drop at its 600hp rating (I'm skeptical and plan to test with PTs and thermocouples).
Static CR is not precisely known. The engine was rebuilt when I was a snot-nosed teenager with more car ego than knowledge or experience. I found the original machine shop build slip but even they didn't know what the CR was. The pistons they chose were Sealed Power 30-over replacements for a stock H-code Cleveland. They are cast which makes them a time bomb. My assumption based on the minimal decking needed for the block and heads is that I am probably no higher than 8.5:1 based on my head castings and '73 h-code specs (8.0:1).
Dynamic CR is another matter. I wasn't content with the Crower Baja Beast cam that was originally installed so I swapped it for an Ultra Beast (220/226 dur, 0.529"/0.540" lift) before I committed to turbocharging this engine. I think the overlap is too much for my static compression and might lead to reversion issues with my turbo. It was a boneheaded choice on my part but I still want to see how it does. A mild hydraulic roller will be in the final setup.
Right now the car has a stock FMX and set of 3.89s with a PowerTrax locker. The locker is awesome for laying even stripes but as a middle aged guy, I can no longer stand the clicking around corners. It's being replaced with a Traction Loc or aftermarket LSD.
I was going to go back to milder gears with a built 3-speed auto (probably not an FMX) but I am now leaning towards keeping them and swapping to a built 4R70W with a Baumann controller. Converter stall speed is still an unknown. Transmission tech isn't my strongest suit. I'd like it to be electronically locking if the two-piece input shaft will allow at my target power level.
Sorry for the novella. I love talking about this stuff and I know from years of lurking on this forum that you guys are a very knowledgeable set.
quote:Originally posted by Panterror:quote:Originally posted by Looftie:
I am in the process of buying a virgin set of A3 heads for a mild turbo/EFI 351C that I am building for my 1973 Mercury Cougar convertible.
How much boost? Intercooled? What static CR are you targeting? Automatic (what stall) or stick? What rear end gear?
Best,
Kelly