TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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The only reason I went with a 52mm is because I just wanted a new TB and I've always wanted a BBk piece. To be honest, you will never need a 58mm TB unless you are making HUGE power. The point has been made several times that GM's Ramjet 502 motor makes 500+ hp and it still uses a 48mm TB. I think 52mm is ok, I probably would have been better off with a 48 in the long run, but 58mm is just too big for most people making less than 500hp, and even then.
Nah! This has been disproved years ago. Going larger increases the responsiveness and usually bumps the hp across the rpm. I went from a 52 to a 58 on my current 355 and absolutely loved the difference. It was worth just a couple more ponies and the responsiveness is just amazing. 58's are now commonly used period. I used to advocate the larger TB's are not necessary, until I seen many tests and eventually tried it myself. When your starting from a 48 and your ready to buy, get the 58. It'll pay off in the long run. Your engine looks like it will be a torque monster! Keep us up to date!
All XFI cams will pass smog. It's all about how to tune it.
Tuning can make or break passing smog(tailpipe) tests, but to say "all" is a stretch. I don't see the 280 and 292XFI cams passing, but you CA guys are always pushing the limits of emmissions, that's for sure!
what valve covers are you runnin on the motor i want a pair
They are GMPP cast aluminum valve covers. I always liked the covers and I got a set last christmas. IMO they are the nicest valve covers for a SBC out there.
Nah! This has been disproved years ago. Going larger increases the responsiveness and usually bumps the hp across the rpm. I went from a 52 to a 58 on my current 355 and absolutely loved the difference. It was worth just a couple more ponies and the responsiveness is just amazing. 58's are now commonly used period. I used to advocate the larger TB's are not necessary, until I seen many tests and eventually tried it myself. When your starting from a 48 and your ready to buy, get the 58. It'll pay off in the long run. Your engine looks like it will be a torque monster! Keep us up to date!
I will give you responsiveness (larger throttle blades give more area from fewer degrees of rotation, you would do the same thing by moving the pivot point on the linkage to open the stock throttle body quicker) more power NO. I personally do not like larger throttle bodies because thy are harder to take-off with in the rain and tend to jolt forward. If the 48mm is flowing enough air it is not going to gain you a single horsepower to put a 58mm on it. This is where the MAP sensor will not lie. My TBI setup made 380 RWHP with a 50mm (2") 454 TBI unit and without an air cleaner was within 2 kpa of barometric pressure at peak HP and above. I ran out of engine before I ran out of airflow.
My current TPI engine has the stock TB on it, with nothing more than a flow straightener. It works GREAT for my use. I am only pulling 4 KPA restriction through the entire intake tract. Its over 300 hp at the wheels.
Tuning can make or break passing smog(tailpipe) tests, but to say "all" is a stretch. I don't see the 280 and 292XFI cams passing, but you CA guys are always pushing the limits of emmissions, that's for sure!
