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I didn’t get to do my gear swap over the holidays due to gas tank issues, that seems to be fixed ( for now) and of course now I can’t do anything as work is going nuts! So what does one do in the evening when all energy is spent???
why, he sits on the sofa and buys shiny things!!!
if anyone recalls, I have a set of heads and an intake out being ported, it’s about a 4 week turn around, so can’t do anything any engine stuff now regardless, but when I spoke to the porter, he suggested bigger injectors and a 58 mm throttle body( versus the stock 48)
sooooooo….. It’s so pretty…. 36 lb injectors , up from 24lb stock injectors All this , plus the rear end will require a retune, but above what I am comfortable fiddling with, so will be reaching back out to the guy that did my original tune!
Last edited by Darrenmb; Jan 11, 2022 at 07:35 AM.
The problem with the 58mm is that even a small amount of throttle movement passes a lot of air so the car becomes harder to control and drivability suffers. You loose lots of throttle resolution with larger TB's. The 52mm is better for a mild 383 or stout 350. I was running a 406 with a matching 7k RPM manifold so the 58 was needed and I hated the loss of throttle resolution so ... so what to do? I ended up extending the moment arm of the throttle linkage about 1/2 of an inch. This gives less throttle movement for a given amount of pedal travel and worked great to restore the drivability.
Last edited by icsamerica; Jan 11, 2022 at 04:23 PM.
I have read about the 58 being too big, also read better throttle response also read. Lost a lot down low, but it’s what was specified by the porter ,Lloyd Elliot, he’s supposed to be the lt1 guru, if I have issues I will send out the factory 48 to be bored to 52, and keep the 58 for when I have saved enough to build. The 383 I really want!
Darren,
Icsamerica laid it out very nicely on the 58mm vs 52mm issue. BBK makes a 52mm, part #1543.The 350ci engine just doesn't have enough air volume, in reasonable builds, to create an air flow that let's the engine react comfortably for non-race driving. Big flat spot off-idle. The 36lb injectors are way too big for anything except all-out racing. On the street, they will wash down the cylinders from over fueling and make your eyes water when you stand behind the car. Non existent gas mileage is a given, you can't tune that much fuel in a mild to moderate 350ci engine. 24lb injectors flow enough gas to support 400hp.
The porter is in business to port heads/manifolds for people who are building their engines for big HP gains. Big HP gains are almost always made with higher RPM and a loss of performance at lower RPM. Don't let yourself head down the path labeled "if bigger is better, then too much is just right".
I am still iffy on the throttle body, but like I said, I can get Stock one bored out, so that’s not really a big deal, the injector sized is really a non issue, as once the new injector size is put in the tune, it will reduce the pulse width as therefore flow less, will only make a difference up top when it can keep up with demand, although the 24 lb injectors can support 400 hp, it put them at over 80 percent cycle time, which isn’t good for them, also i will be making about 400 at the wheels, which is a bit more at the crank, so injectors should be fine! As a side note, the lt4 rated at 30 more horsepower than the lt1 had 28 lb injectors from the factory as they felt 24 weren’t bug enough . Like I said earlier, my only real concern Will the be throttle body, being as I currently have 2 48 mm ones and a 58, sending mine out isn’t a massive ordeal either, still a couple weeks out on heads anyways, plus I still want to get gears done before the heads show up, would be nice if work slowed down a little to give me some down time!!!
New bits….
